Some changes are obvious and you have heard of, like morning sickness and sudden cravings.

Others are far less visible, including the microbial communities that live in and on the mother-to-be.

What exactly happens to the microbiome during pregnancy? And why does it matter for a healthy pregnancy and birth?

Let’s take a closer look.

How the immune system keeps track of what to attack and what to tolerate

One of the main roles of the immune system is to fight off anything foreign. At first, a mother’s immune system also sees the baby growing inside her as foreign, even an enemy.

But rather than fighting or even eliminating it, the body has preventative mechanisms built in: so-called immune tolerance. This mechanism locks immune cells into a non-responsive mode.

Imagine immune cells as immigration officers at an airport: they check a person’s details to see if they match the passport. Similarly, immune cells check every cell inside the body for proteins on the outside. Some of these proteins activate the immune cell’s danger system, meaning the cells then eliminate the foreigner.

Yet the immune system needs to be mindful. Immune cells need to correctly distinguish disease-causing bacteria from commensal bacteria, such as Lactobacilli that generally live in the vaginal tract.

Similarly, immune cells recognise and tolerate the growing foetus. Proteins on its surface prevent immune cells from activating. I like to think of them as ‘don’t eat me’ signals. In scientific lingo, they’re called non-classical MHC class I isotypes HLA-E and HLA-G.

On the other hand, pathogenic fungi like Candida albicans are examples of how both the immune system and beneficial bacteria work together to keep us healthy. The commensal bacterium Lactobacillus competes with Candida and normally keeps it from overgrowing.

But when there are not enough Lactobacilli to protect us, our second layer of protection, the immune system, steps in. When Candida infects us, it damages some of the body’s inner walls, which activates other players in the immune system. Eventually, immune cells, like natural killer cells and neutrophils, come in and kill the fungi.

Finally, the placenta plays another important role. The placental barrier limits mixing of maternal and foetal blood, and thus immune cells. In this way, maternal immune cells will not come into contact with the foetus, so they won’t get activated.

Roles of the microbiome during pregnancy

The immune system does not do this job alone: throughout pregnancy, microbial communities, particularly in the vagina and gut, support the health of both the mother and the baby.

The vaginal microbiome changes according to age, race, sexual intercourse, smoking, contraception, lifestyle and diet. Swabs taken from pregnant women showed that while Lactobacillus was dominant, the vaginal microbiome as a whole was stable.

The main role of Lactobacillus is to create an acidic environment (pH < 4.5) by breaking down glycogen. Vaginal epithelial cells store glycogen, from which Lactobacillus produces smaller sugars and, ultimately, lactic acid. This makes the vaginal flora more acidic and prevents dangerous microbes from growing. At the same time, lactic acid is a signal for the immune cells to stand down, or to switch into a tolerogenic mode.

In pregnant women, hormonal and genetic differences also shape which Lactobacillus subspecies mainly reside in and on them. In particular, hormones like oestrogen influence how much glycogen is deposited in the vaginal walls. This affects the amount of Lactobacillus species and, as a result, the entire vaginal microbiome.

Moreover, pre-term births were also associated with higher levels of inflammatory signals. These activate immune cells, which change the microbiome. Instead of Lactobacillus, Prevotella and Sneathia amnii become dominant.

Infertile women also had a low prevalence of Lactobacillus. However, this raises a chicken-and-egg scenario: whether inflammation initially causes microbiome disruption, or whether vaginal microbiome dysbiosis initiates inflammation, this mystery remains unresolved (for now).

Either way, some researchers suggested using the microbiome as a predictor of successful pregnancy. This may become an important tool for in vitro fertilisations.

The vaginal microbiome changes throughout pregnancy

During pregnancy, the vaginal microbiome helps protect against foreign pathogens by maintaining a Lactobacillus dominance and thus an acidic environment.

The microbiome adapts to various factors, such as diet, hormones, obesity, genetics and age etc. These factors can change the microbiome for better or worse. However, we do not have a complete picture of how these factors work together.

Diet plays an important role in maintaining a healthy microbiome. To understand whether there is a link between the vaginal microbiome and diet, researchers compared vegetarian and non-vegetarian diets.

Indeed, women following a vegetarian diet had a more complex vaginal microbiome. Although it remains unclear how or which nutrients are responsible for this diversity.

One initial suggestion to increase estrogen levels and help Lactobacillus survive was to be on a high-fat diet. However, when this hypothesis was tested, they found that high-fat intake was associated with severe bacterial vaginosis.

Unfortunately, maternal obesity is another risk factor that has been on the rise recently, and now there have been associations with obesity and pregnancy complications. Obesity alters the microbiome and promotes the growth of harmful gut bacteria.

These move toward the placenta and disrupt the placenta’s stable immune environment. Moreover, children of mothers who were obese during pregnancy have an increased risk of obesity and type 2 diabetes later in life.

However, diet goes both ways. While having a high-fat diet is associated with complications, it can also be improved. Diets rich in fibre, plant-based proteins and omega-3 fatty acids are beneficial for both the mother and the baby.

Can microbes support a mother’s and a baby’s health?

Based on these preliminary results, researchers are exploring ways to support a healthier microbiome during pregnancy. Some experimental approaches, such as vaginal microbiome transplantation, aim to transfer beneficial bacteria from healthy donors to people with vaginal dysbiosis.

More traditional approaches, including oral or vaginal Lactobacillus probiotics, are also being studied to see whether they can help during pregnancy. However, these strategies are still under investigation and are not approved so far.

As you could see here, pregnancy is not just an adventurous story of hormones and cravings. Also a mother’s microbiome goes on a little adventure.

A mother’s immune system needs to learn to tolerate the growing foetus while still policing potential threats. Microbes in the vagina and gut support this mission by keeping acidic conditions stable and signalling to immune cells.

While we do not yet fully understand the links between commensal microbes and pregnancy outcomes, we do know that certain factors can shift microbial communities. Let’s see what research reveals next on how to support a mother-to-be and her baby.

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Consider the scent of a ripe cheese or a glass of wine—these aromas come from bacteria and other microbes. Even less pleasant odours, like old sweat, smelly feet or a mouldy apple, are thanks to molecules produced by microbes.

Let’s explore the fascinating world of bacterial smells, their origins and what we can learn from them.

Microbial smells come from volatile organic compounds

All microbes produce volatile organic compounds as part of their metabolism. These molecules are generally gaseous and vaporous, allowing us, animals and even plants to smell and react to them.

Depending on their environment, the substrate they use, pH, salt concentration and temperature, microbes produce various volatile organic compounds. These can range from simple gases like carbon dioxide or ammonia to organic acids such as isovaleric acid or large and complex steroid derivatives.

For both microbes and us, volatile organic compounds serve as a means of communication and information. As we’ll see, these small compounds play crucial roles in microbial communities and their survival. On the other hand, for us, certain volatile organic compounds signal to our brains that bacteria are present, indicating that something may not be safe to eat or drink.

Some bacterial odorous molecules have a dual nature: indole, produced by gut bacteria from food, gives faeces its characteristic odour. Yet, at low concentrations, indole has a flowery scent and is even used in perfumes.

Bacteria attract animals with earthy smells

Do you recall the scent of fresh rain? That earthy, musty smell comes from a molecule called geosmin, produced by bacteria of the Streptomyces family.

Streptomyces live in the soil, where they produce soil material and form long thread-like filaments. To survive and spread, they use the volatile organic compound geosmin.

When these bacteria release their spores into the soil, they cover them with both antibiotics and geosmin. While the antibiotics protect the spores from other microbes, geosmin attracts small insect-like animals. These creatures eat the spores and distribute them in the environment.

In this case, geosmin signals a food source to the animals as the spores nourish the animals. At the same time, the spores use the animals for transport to new areas. Once conditions improve, the spores develop into bacteria and start forming their filaments in the soil.

Also mosquitoes are attracted to the smell of geosmin in ponds and waters. Here, cyanobacteria produce the molecule, so the mosquitoes decide to lay their eggs here as the bacteria are food sources for the larvae.

Bacteria produce characteristic food smells

Other pleasant and unique bacterial smells come from the fermentation of fruit, vegetables or milk. During this process, bacteria produce compounds that give food not only their characteristic tastes but also aromas.

As an ancient fermentation product, vinegar has a very characteristic sour smell due to volatile organic compounds produced by microbes. Mainly bacteria from the Lactobacillus and Leuconostoc families and some yeasts degrade the sugars of cereals or fruits to produce acids and alcohols.

Also, the fine aromas of wine and cheese come from the many volatile organic compounds bacteria and yeasts produce during fermentation. They include alcohols, aldehydes, ketones, lactones, esters as well as many other classes of chemicals. As you probably know, depending on the origin of the grapes or milk, the ripening temperature and the microbes added, the resulting product can taste and smell entirely different.

However, the unpleasant smell of rotten foods is also due to bacterial metabolic activity. Meat, fish and eggs contain molecules like choline and trimethylamine oxide. Over time, bacteria break these down into trimethylamine. Your brain likely recognises this off-flavour as a sign of food decay, triggering you to reject rotten foods to protect your health.

Bacteria create your unique body odour

Interestingly, your body odour changes based on what you eat and which microbes and bacteria you introduce into and onto your body. Depending on your diet and health, your body secretes different mixes of sweat—generally a watery mixture of minerals, amino acids, fats, urea and antimicrobial substances.

Although your skin produces odourless sweat all over the body, some areas are more hospitable for bacteria and microbes than others. Consider your armpits, where your main body odour originates: They contain more sweat glands and slightly different hair follicles, making them moister and more enclosed. With more water and nutrients available, your armpits are very microbe-friendly.

Consequently, the microbial communities in your armpits can differ completely from the rest of your body. Here, three bacteria—Corynebacterium striatum, Corynebacterium jeikeium and Staphylococcus haemolyticus—have special strategies to survive the high salt content of sweat and even use the urea in sweat as food.

They break down the molecules in sweat into volatile organic compounds that together give each person their unique body odour. For example, sulphur-containing compounds, often with strong onion-like smells, are produced by Corynebacteria.

Our sweat also contains lactic acid and glycerol, from which Staphylococcus and Propionibacteria produce acetic and propionic acid. These molecules directly impact your body odour as they evaporate leaving a pungent smell or supporting the growth of other bacteria. But our smelly sweat has advantages too: After eating citrus fruits, people’s sweat contains limonene, a mosquito-repellent possibly generated by skin bacteria.

Bacteria are responsible for smelly feet

Another significant area of your body directly impacted by bacteria and their smell-creating superpowers is your feet.

Our feet actually contain the highest variety of microbial communities, with Staphylococcus, Corynebacterium and Brevibacterium being the most common. These bacteria feed on skin particles, urea and the amino acids in sweat.

For example, Staphylococcus epidermidis, a normal resident of human skin, degrades the amino acid leucine into isovaleric acid. Unfortunately, this molecule has a powerful, rancid cheese-like odour—the reason for smelly feet.

Fortunately, other bacteria, like Brevibacterium, Micrococcus and Kytococcus, can completely degrade both leucine and isovaleric acid, thus preventing the unpleasant smell. As usual, it comes down to having the friendly bacteria around.

Bacterial smells in your life

As we’ve seen, the world of bacterial smells is fascinating and complex. From the earthy smell of rain to the rancid odour of sweaty feet, bacteria play crucial roles in creating the smells that surround us.

These microbial odours are not just curiosities; they have important functions in nature and human biology. They can act as communication signals between microbes, influence animal behaviour, make our food smell delicious and even impact our unique body odour. So, embrace the microbial world with all its facets, colours and smells!

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Whatever it was, chances are high that part of your food was fermented by microbes. As exceptionally healthy and tasty as fermented foods are, these would not exist if it weren’t for microbes and their fermentation superpowers.

Yet, microbial fermentation is a lot more than processing food and giving it a new taste or aroma. Indeed, depending on who you ask, microbial fermentation means slightly different concepts.

For once, fermentation is a metabolic pathway in some microbes and organisms. It is an energy-saving way to degrade and metabolise substrates and produce complex and energy-rich fermentation products.

Secondly, microbial fermentation describes the process of preserving food based on the fermentation pathway. For this, we let microbes break apart and ferment food in a controlled manner, eventually producing well-known fermented foods, like yoghurt, beer and chocolate.

Lastly, the industrial process of growing microbes in big cultures is often called microbial fermentation. The goal of this process is for microbes to produce a specific product – and often they do so through the fermentation pathway.

As you can see, the different definitions for microbial fermentation are grounded on the same principle: microbes degrading substrates and making fermentation products from them. Here, we will look closer at the biochemistry of microbial fermentation and explore some examples of where this microbial superpower naturally occurs and how we make use of it.

The biochemistry of microbial fermentation

From the view of a biochemist, fermentation is first of all a metabolic pathway to conserve energy. Most organisms gain energy from opening chemical bonds of molecules. This releases the energy-rich electrons that are bound within the bond. They then save these electrons in other molecules or fuel cellular machineries.

Most microbes have one preferred substrate for their metabolism. For many, this is glucose, the same sugar that our cells preferably burn and degrade. By degrading glucose, they (and us) produce several intermediary products, the most important one being pyruvate. This degradation process sets free several electrons, which microbes save in a molecule called ATP. ATP is the main fuel for microbial growth machines, swimming motors or transporters.

Sometimes microbes find themselves in environments with an excess of their preferred substrate. In this case, setting free all the energy would produce a lot of heat, damaging or even burning the cell. Hence, as an alternative, energy-conserving pathway, they switch to fermentation metabolism.

During this pathway, they degrade the substrate only partly, thus not extracting all available electrons from it. Instead, they use one of the intermediary products and bind it to another molecule in an energy-neutral reaction. This conserves the electrons and energy within the fermentation product.

What makes fermentation so fascinating: Many species have unique fermentation pathways. Depending on their genes, they branch off the fermentation pathway at any intermediate and produce different molecules.

For example, from pyruvate, some microbes produce ethanol, which we use for beer or wine production, and others produce lactic acid, like for yoghurt production. Other microbes ferment substrates like citrate or succinate and produce complex molecules like caffeine or colourful biopigments.

By conserving the high-energy electrons in the fermentation products, microbes produce fewer ATP molecules. Hence, they have less energy available at that moment. But if they need energy later, they can break down the fermentation product to extract the electrons. Often though, their energy levels are so high, that they even export the product to get rid of it.

Fermentation is thus a way for microbes to process molecules and conserve energy. Gladly, we learned to make use of this pathway as microbes help us convert energy-rich substrates into beneficial products.

Microbial fermentation for food preservation

One source of energy-rich substrates are carbohydrate and fibre-rich foods, which is why these are some preferred environments for microbes. By fermenting fruits, vegetables, milk and grains, microbes can grow and spread on seemingly any plant-based substrate.

Gladly, we learned to grow microbes and ferment food in controlled environments, making food fermentation one of the oldest human technologies. Throughout history, many cultures have optimised different fermentation processes and created all kinds of products.

Food fermentation can include adding so-called starter microbes to the food or using those microbes that naturally live in the foodstuff. These microbes break apart the carbohydrate component of the foodstuff to fuel their fermentation pathways.

The resulting fermentation products can be beneficial vitamins, antioxidants or molecules that change the aroma, taste, texture or stability of the foodstuff. The degradation and modification of the food itself and the accumulation of fermentation products, over time, make our well-loved cheeses, coffee, bread, chocolate, beer, wine, kombucha, yoghurt or kimchi.

For example, thanks to microbes, cheese and yoghurt taste and smell differently than the original milk. Coffee and chocolate get their complex and unique aromas only thanks to the microbial fermentation of coffee and cocoa beans.

During fermentation, many bacteria produce strong acids from the original substrate. Thus, the resulting food becomes acidic and sour, which prevents other microbes from growing and spoiling the food. That’s why food fermentation became an efficient way to conserve food. Many vegetables, like cabbages, pickles or olives, are thus preserved into sauerkraut or kimchi, sour pickles and olives, and the like. Also making kombucha, kefir or cheese are ways to preserve the original tea or milk.

When fermenting cereals, yeasts mainly produce carbon dioxide or ethanol. Carbon dioxide, for example, in sourdough bread makes the bread rise. In the beer-brewing and wine-making processes, yeast produces ethanol as well as several beneficial and aromatic molecules that give beers and wines their tasteful and diverse aromas.

About the microbes involved in food processing

Each fermented food has a unique community of microbes that changes with the fermentation process over time. With the rise of one microbial species, the pH of the food might change or a certain substrate becomes available, which might kill one species or feed and thus help another one grow.

In many vegetable-based fermentation products, lactic acid bacteria, such as Leuconostoc, Lactobacillus and Weissella, are the primary microbes. They produce acids which prevent food-spoiling microbes from growing. The acids also give the resulting kimchi and sauerkraut their sour and acidic tastes. On the contrary, in alkaline-fermented foods of Asia and Africa and in bean-fermented foods, such as tempeh, miso or natto, Bacillus bacteria are usually responsible for the fermentation process.

In milk fermentation, bacterial cultures are of two types: Lactococcus, Lactobacillus, Leuconostoc and Streptococcus bacteria that acidify the milk. This denatures the milk and produces yoghurt-type products, such as yoghurt, buttermilk and kefir.

As a second step during the cheese-making process, Brevibacterium, Propionibacterium, Debaryomyces, Geotrichum and Penicillium are added. These bacteria and fungi produce more complex molecules and give the ripening cheese its unique flavour, texture and aroma.

For cereal fermentation, yeasts are the most widely used microorganisms, producing beer, sourdough bread, sake and whiskey. For bread-making, the principal yeast is Saccharomyces cerevisiae. Other Saccharomyces species, as well as Torulaspora, Hanseniaspora and Pichia are responsible for fermenting most cereal-based drinks.

How the human body benefits from fermentation

As we’ve learned above, many fermented foods are full of microbes – as long as the food was not heated or pasteurized. Hence, when eating fermented foods, you also take in the microbes in and on the food. And these are ready to settle in your body, feed off your food and do some more fermentation.

After arriving in your gastrointestinal tract, the microbes start digesting part of your food too. They degrade the plant cell structures of vegetables, fruits, cereals, seeds and nuts as well as non-digestible fibres. This releases sugars which gut microbes ferment to short-chain fatty acids and gases, like methane. These fermentation products have beneficial effects on your digestion, mental and gut health as well as your immune system.

Hence, by eating fermented foods you gain beneficial microbes – some of them are the so-called probiotics. And by eating plant-based foods you give your gut microbes the appropriate food to ferment, which is what makes some of them prebiotics.

But this is not the only place where microbial fermentation takes place in your body. For example, Lactobacillus bacteria are the key players within the vaginal microbiome and their fermentation activities influence the health of women.

Within the vaginal tract, host cells provide Lactobacillus with glycogen. From this, the bacterium sets free glucose and ferments it to produce lactic acid and hydrogen peroxide. These molecules decrease the pH creating an acidic environment within the vagina. This acidity kills some pathogenic microorganisms directly and prevents others from growing. Hence, by feeding residential Lactobacillus bacteria, the body helps them grow and in return they protect it.

Microbial fermentation as a pillar of industrial production

The more we learn about microbes, bacteria and their fermentation pathways, the better we can use their metabolic superpowers for our own good. Especially the biotechnology and food industry are making great use of microbial fermentation.

We now grow microbes in big batches and harvest fermentation products, like bioethanol, lactic acid or vitamin B12. In many cases, microbes grow on plant-based products or even ferment waste into usable and, thus, green products. As you can guess, food fermentation based on appropriate starter cultures is taking place on large scales to produce many of our beloved foods.

As such, microbial fermentation is an essential part of our lives. Not only as a fundamental process in cellular metabolism and thus human health, microbial fermentation has become a key pillar in food production and preservation as well as industrial production.

As a sustainable tool to produce plant-based foodstuffs, pharmaceuticals and fuels, microbial fermentation may even play a crucial role in our journey towards a greener and more resilient future. Just another reason to be grateful to microbes and their fascinating superpowers.

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

But have you ever asked yourself where yogurt comes from and how it is made from milk? Do you know why yogurt tastes so sour and yet delicious?

What if I told you that yogurt only tastes like this thanks to bacteria and their superpowers?

Yes, bacteria not only produce delicious chocolate, wine, beer or bread. But it is also bacteria that make yogurt from milk.

Here, we will look at which bacteria produce yogurt and what makes it so creamy, sour but also healthy.

What’s in your yogurt?

Yogurt would not exist if it wasn’t for our bacterial friends. Interestingly, it only takes two bacterial species to create this white creamy dream that we call yogurt. These two bacteria are Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

Within milk, these two bacteria live in a symbiotic relationship. This means they help each other grow and survive. And together, they produce delicious yogurt.

These two bacteria make many molecules that give yogurt its characteristic flavor. These include lactic acid and other acids like acetoin, acetate, acetaldehyde. Because of all these acids, yogurt tastes quite sour.

Also, our two bacteria produce exopolysaccharides. Generally, bacteria use these to make biofilms. But in this case, the exopolysaccharides with their long sugar chains make the yogurt creamy and viscous.

Thanks to bacteria and the milk content, there are also a lot of healthy molecules in yogurt: proteins that are rich in energy, calcium, and vitamins B2, B6 and B12.

How is yogurt made?

It seems that all we need to make delicious yogurt are milk, our two bacterial species Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus and the right temperature. We call these two bacterial species the yogurt starter cultures.

But before their superpowers produce yogurt from milk, the milk needs to be prepared. This is basically to get rid of all the other stuff that we don’t need.

So, to kill all other microbes that might spoil our yogurt, the milk is heated to 95 °C. You might know this process as pasteurization.

After the milk cooled down to about 40 °C, our two starter bacteria are added. Next, the mix is filled into cups and sealed. The cups are then stored in a warm room – something researchers call incubation. During this incubation time, the bacteria can get to work and use their superpowers.

This means that our two bacteria start a process called microbial fermentation. They break down the milk sugar lactose and produce lactic acid and other acids.

Due to all the acids, the pH of the milk drops and it becomes sour. Now, the acids denature the milk proteins – this is the same process that you see when you heat an egg: it becomes harder and loses its fluidity. The milk becomes more viscous and gets a gel-like texture and creaminess.

Why is yogurt good for you?

We already saw that yogurt has a lot of good stuff and some studies showed that it is healthy for us because of all these molecules. But how do these vitamins, proteins and short-chain fatty acids impact our health?

For example, yogurt stimulates the immune cells that are in our guts. This improves our immune system so that it can better fight bad intruders.

Our two starter bacteria also break down some of the milk proteins and produce so-called bioactive peptides. Our guts like these peptides a lot. Hence, it transports them into our bodies where they have health benefits.

Also, the sugars in yogurt are prebiotics. This means they are the right food for other bacteria that live in our guts and that keep us healthy.

Plus, yogurt is full of protein that our bodies need to grow muscles and stay strong. Interestingly, yogurt protein has two important fractions: whey and casein protein.

The whey protein is considered a “fast protein”. This means, our body digests this type of protein faster which gives us energy immediately after eating yogurt.

The other fraction is casein or the “slow protein”. This type of protein clots in our stomach because of the acids. But our body can digest this protein clot only slowly. Hence, the casein protein gives us energy even up to 7h after eating yogurt. Like this, yogurt helps with satiety so that in general we need to eat less.

Lastly, the short-chain fatty acids in yogurt have lots of health benefits for us. They regulate the blood glucose level, insulin resistance and inhibit our appetite.

Now you have a lot of reasons to include yogurt in your daily diet plan!

What is probiotic yogurt?

Researchers found that the two starter bacteria Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus do not survive the acidity in our stomachs. Hence, they do not arrive in our guts and have no impact on our gut microbiota.

However, yogurt is a great vehicle to transport other probiotic microorganisms into our bodies. Probiotics are organisms that “when administered in adequate amounts, confer a health benefit on the host”. Also, probiotics need to be safe, well-characterized and stable while the yogurt is waiting on the shelf to be eaten.

Hence, many yogurt companies now add beneficial probiotics to yogurt. These are bacteria like Lactobacillus casei, Lactobacillus acidophilus or Bifidobacterium.

These bacteria have beneficial effects on our digestion and immune system. They help the right bacteria in our guts to grow, meaning they keep our gut microbiota healthy.

For example, in one study, researchers added a Lactobacillus casei species to yogurt and gave it to children with acute diarrhea. After a few days, these children had fewer symptoms and less abdominal pain thanks to the yogurt mix.

Is (probiotic) yogurt on your diet plan yet?

Here, we looked at two new superhero bacteria that produce the fermented creamy white dream. Even though they might not survive the passage into our bodies, they produce a lot of healthy molecules for us. Hence, they have an indirect health benefit on our bodies.

Plus, yogurt is a great vehicle to transport other probiotic bacteria into our bodies. And it seems that by eating yogurt regularly you can indeed change your gut microbiome and bring in some helpful bacteria.

So, thank bacteria for their superpowers and for providing us with this delicious food!

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Microbes are necessary for many of our favorite foods, such as bread, cheese, and chocolate, and the beverages we wash them down with, like beer and wine!

With the holidays fast approaching, let’s look at how microbes play a central role in the holiday menu.

Microbes Help Make What You Eat

Microbes are everywhere, including your food. Not only known for food spoilage, but some microbes also help preserve and add flavor to foods. In a process called microbial fermentation, microbes convert sugars in foods into different compounds, such as alcohols or acids.

Bread

Microbes are also necessary to produce our foods. Many holiday meals include special bread that depends on the microorganism yeast. Bread making usually uses the yeast Saccharomyces cerevisiae to eat the sugar in bread dough to make carbon dioxide (CO₂) bubbles that expand and rise the bread.

Microbes can also give bread some of its flavors. Sourdough bread gained popularity during the COVID-19 pandemic because of the ease of culturing the sourdough yeast, called a starter. Sourdough’s unique flavor comes from the starter’s mixture of yeast and lactic acid bacteria. These Lactobacillus bacteria ferment and produce lactic acid, which gives sourdough that ‘sour’ taste and helps to prevent the bread from going stale.

Cheese

After making your holiday loaf, you will need to put something on those slices. Cheese is one of my favorite bread sidekicks and appears on many holiday menus.

Like bread, cheese requires a starter culture of bacteria to convert the sugars in the milk into acids such as lactic acid. Next, during cheese ‘ripening,’ added secondary microbial cultures give each cheese its unique flavor and texture. These secondary cultures can include bacteria, yeast, or even mold, like in the case of blue cheese, and all help produce those much-loved flavors.

Microbes Help Make What You Drink

Bread and cheese are delicious, but they are even better when paired with a nice beverage. Luckily, microbes help make some delicious drinks as well.

Beer

One of the oldest microbially-made drinks is beer. Beer dates back over 5,000 years, though recent evidence suggests people first fermented beer over 13,000 years ago! Like today’s beer, ancient cultures ground grains in large vats and exposed them to yeast that would eat the sugars and ferment it into alcohol and CO₂.

This process adds flavor to the drink as well as many nutrients and essential B vitamins. Most importantly, the alcohol kills possible contaminates and makes the water safe to consume. Adding hops aids its antimicrobial activity by inhibiting Gram-positive bacteria.

While the first beers relied on wild yeast strains naturally found in the air and dust, today’s brewers add specific strains of yeast for desired alcohol and flavor profiles. Or they might add bacteria. Many Belgian ales have Brettanomyces yeasts to produce their notable sour flavor, while German Berliner Weisse beers are fermented by Saccharomyces cerevisiae and Lactobacillus bacteria.

Wine

If beer is not your thing, possibly you will want a nice glass of wine this holiday season. You can thank microbes for that too.

Wine is produced when yeast ferment grapes, yielding both alcohol and CO₂ like for beer. Microbes are important not only for fermenting grapes, but specific yeast, fungi, and bacteria are important for keeping grapes healthy.

Additionally, some fungi are critical to produce specific wines. Botrytis cinerea is a fungus that helps to dry out and concentrate the sugars of a grape through a so-called ‘noble rot’. These grapes produce a sweet dessert wine called a botrytized wine. However, if Botrytis cinerea infects grapes during moist conditions, this ‘gray rot’ destroys the grape crop. Thus, having the right microbiome is important for agriculture just as it is for humans.

Kombucha

If you don’t like beer or wine, you can always try kombucha. This non-alcoholic beverage is produced from acetic acid bacteria and yeasts called a “tea fungus” that ferment tea. The bacteria and yeasts live symbiotically in a biofilm clump called a scoby (“symbiotic culture of bacteria and yeast”). Here, microbes work together to convert the sugars into acids that give the tea a nice tart flavor.

And don’t forget dessert!

Cakes, candies, and cookies are all staples of the holidays. These sweet treats would not be the same without microbes to add flavor and rise.

My favorite sweet, chocolate, comes from cacao beans that are initially fermented for many days by wild yeasts and bacteria. This process breaks down the beans and leads to the production of those oh so yummy chocolate flavors. Just another reason to love microbes!

Welcome Microbes to Your Next Meal

Microbes are vital for giving us so many of the foods and flavors we love. From foods like bread, cheese, and chocolate or drinks like beer, wine or kombucha, microbial fermentation plays an important role in many of our favorite dishes. Fermented foods give us flavors, vitamins, and additional food preservation.

These foods can also help maintain healthy digestive systems. Yoghurt, which is another fermented milk product, contains beneficial bacteria that can help maintain a balanced microbiome.

Not only do microbes help save the planet, but they also save our meals and our health too. So this holiday season, remember to incorporate microbial dishes into your menu.

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

No, but this is pretty much what happens there.

Okay, they might not sit at a table with napkins in their laps and fork and knife in hand. But bacteria do share food with each other and even feed each other with their leftovers. 

Not sure, how that might work? 

Read on to find out!

What’s in your plant food?

If you are like most people and eat a healthy balanced diet, you will probably eat a lot of plant products, including vegetables and fruits.

But think about what plants are actually made of: Their cell walls are extremely rigid and sturdy because plants need to be stable to withstand different weather conditions. So, to stabilise a vegetable or fruit, they have complex walls that we can barely digest.

And yet, they are some of the best foods you can eat…

While our own digestive system is struggling to break down plant material, we can always rely on the microbial friends in our guts. They have the necessary tools and superpowers to break up plant material, digest plant food and help us get the best from it.

But none of them can do it on their own. Also, bacteria work together and share their food to achieve that.

Let’s look at how food-sharing works between bacteria and which plant components they are digesting for us.

Arabinogalactan – a complex glycan from plants

To stabilise plant cells and make them sturdy, long and complex molecules are part of most plant cells. These are often glycans that are complex polymers with one main chain and many different side-chain branches. 

And one of these complex plant glycans is arabinogalactan – or short AG.

AG consists of very long main chains made of the same sugar molecules. And each sugar molecule consists of a ring of 5 carbon atoms. Now, these carbon atoms link to carbon atoms within the same sugar but also to carbon atoms in the next sugar.

So, within the main chain, the sugars are all linked to each other via the so-called 1,3-bond. This means, that the carbon atom at position 1 links to the next sugar molecule via the carbon atom at position 3. And between these two carbon atoms sits an oxygen atom. 

Okay, so far for the main chain.

The side chains consist of different sugar molecules. Hence, the bonds between them are different. 

Plus, the side chain is connected to the main chain via a different bond – the 1,6 bond. This means, that the carbon at position 1 from the sugar molecule of the side chain binds to the carbon at position 6 of the sugar molecule of the main chain.

Since these side chains have different lengths and lots of branches, the structure of the AG gets so complex. This is what ultimately makes it so difficult for our digestive system to break them down. We just don’t have the tools for that.

Enter our microbial friends in our guts.

Bacteria degrade complex plant polymers

Since this complex AG polymer is basically in every plant cell, we are eating a lot of it. And somehow we seem to be able to digest it. So, researchers were curious about what happens to this glycan in our guts.

And they knew already, that bacteria in our guts have really cool tools and scissors to break up complex plant sugars and glycans.

This scissor sits on the outside of a bacterium. Here, it directly chops off a piece of sugar when it comes into contact with a plant polymer.

And directly next to the scissor sits a transporter. This immediately takes the chopped off sugar molecule and imports it into the bacterium. Now, the bacterium uses this piece of sugar for energy and growth. 

One of the bacteria that break down AG in our guts is Bacteroides cellulosilyticus. Let’s call this one the Bacell-bacterium. 

These Bacell-bacteria have special scissors that cleave off the side chain of AG from the main chain. Plus, they have another set of scissors to chop off the last sugar molecule from the side chains.

However, they cannot break up the rest of the side chain. Hence, this leaves some valuable sugar chains lost in the deepest corners of our guts. 

But gladly, other bacteria pick up these yummy sugar sources and are grateful for that share of food.

Bacteria get their share of food

Researchers found that the bacterium Bifidobacterium breve uses these released sugar chains. Let’s call this bacterium the Bif-bacterium. 

Generally, the Bif-bacterium does not have these advanced scissors to break down complex glycans. But it can pick up and degrade released sugar chains from other bacteria. 

Researchers found that when they fed the Bif-bacterium with AG, it did not grow alone. However, they then added the Bacell-bacterium and fed them with AG. Now, the Bif-bacterium was growing.

This meant that the Bacell-bacteria break down certain pieces of the AG and share the leftover food with the Bif-bacteria. Since Bif-bacteria have the right scissors to break down smaller sugar molecules, they can use these now and grow.

Next, the researchers looked at what both bacteria produced from the AG.

Bacteria share food with each other and keep us healthy

They found that the Bacell-bacteria alone produce some short-chain fatty acids from the AG. These short-chain fatty acids are very helpful for our body and keep us healthy.

Yet, when the Bif and the Bacell-bacteria grew together with AG, they produced even more diverse short-chain fatty acids. This meant that the interaction between the Bif- and the Bacell-bacteria itself can be understood as a probiotic – they are healthy for us. And it also means that AGs are prebiotics – they feed healthy bacteria.

Interestingly, also other bacteria get their piece from this interaction: The probiotic bacterium Lactobacillus reuteri (Lacto-bacterium) also plays a role in sugar degradation in our guts.

The Bif-bacterium produces a molecule called 1,2-propanediol from AG. Now, the Lacto-bacterium can pick up 1,2-propanediol and make more short-chain fatty acids from it. And this also helps the Lacto-bacterium grow and keeps our gut healthy. 

So, when bacteria share food with each other, everyone wins!

Help your bacteria share food and you keep yourself healthy

From this little story, I hope it became clear again, that you are what you eat. By giving your bacteria the right food, they can feed each other so that they grow. And when the right bacteria grow in your gut, they will defend you against harmful pathogens and keep you healthy. 

So, yes, keep being nice to your bacteria! ?

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Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

So, you probably know that high cholesterol levels can have dangerous effects on your cardiovascular system and your heart.

But what if I told you that some of the good bacteria have can help you reduce your cholesterol levels? And that these bacteria would have another great benefit on your overall health.

Looks like another cool bacterial superpower to me!

Read on to learn about how bacteria in your gut can reduce your cholesterol levels.

Where does cholesterol come from?

Each cell in your body is surrounded by a membrane to keep the cell and all its content together. And most of these cell membranes have cholesterol in them to stabilise the membrane. Also, your body produces some hormones, vitamin D and bile acids from cholesterol. So in general, cholesterol is essential for us. We need it to survive.

The cholesterol in your body can have two origins. Either you take it up when you eat animal products or your liver makes cholesterol. 

Independent on where the cholesterol comes from, it all lands in your intestinal tract. From here, the cholesterol is transported into the plasma or it is degraded into the inactive molecule coprostanol.

When a lot of cholesterol is circulating in your plasma, it can be bad for your health. This is why researchers have been looking for ways to lower the amount of cholesterol in the plasma. 

And now, luckily, they found some special bacteria that can reduce the cholesterol in your gut.

Linking gut bacteria and cholesterol levels

As we’ve seen above, cholesterol passes through your gut. And we know that our guts are full of helpful bacteria. So, researchers thought that maybe bacteria have something to do with the varying cholesterol levels in our plasma. They just didn’t know how cholesterol levels and gut bacteria are linked.

A previous study looked at the Asian dish Tapai, which is fermented cassava or rice. A special Lactobacilli strain from this dish has probiotic effects in rats and can degrade cholesterol.  

Now, a new study used a fancy technique called metagenomic analysis to find new bacteria that reduce our cholesterol levels. For this, the scientists took data from previous stool samples. And they analysed the levels of coprostanol in these stool samples and which genes they could find in those samples.

Luckily, with this metagenomic analysis, they could detect ALL genes in a sample. And these genes could come from any organism: the person from whom the sample comes from, but also bacteria, fungi or viruses.

So, they found that the samples with higher coprostanol and lower cholesterol levels had some unique bacterial genes. Genes, that they did not find in other samples.

They then worked their ways back and tried to name the bacteria to which the genes belonged. Apparently, in these stool samples lived bacteria that produced a lot of coprostanol from cholesterol. 

But most of these bacteria were unknown. This means the scientists had never seen them before. Plus, they had no idea how to grow these bacteria in the lab. 

Yet, they found one bacterium, that the scientists already knew. And they’ve seen in other studies that this bacterium is somehow linked to cholesterol degradation.

This bacterium’s name is Eubacterium coprostanoligenes.

Meet your new superbacterium – Eubacterium coprostanoligenes 

With this new super bacterium showing up, the scientists obviously wanted to learn more about it. 

The scientists showed that Eubacterium coprostanoligenes degrades cholesterol. For this, they grew the bacterium in the lab in similar conditions as the gut environment. And so they learned about every step of how Eubacterium coprostanoligenes degrades cholesterol.

Interestingly, the scientists also showed that Eubacterium coprostanoligenes is related to the bacteria Faecalibacterium prausnitzii, Clostridium leptum and Ruminococcus bromii. And these are some of the friendly bacteria living in our gut.

Gut bacteria reduce cholesterol levels

After the scientists learned about which bacteria are our new superheroes, they wanted to prove that these gut bacteria can indeed reduce our cholesterol levels.

So, they used fresh stool samples and covered them with lots of cholesterol in the lab. After 4 days, in some of these samples, the cholesterol was degraded to coprostanol. And they found bacteria that had the same cholesterol-degrading gene that Eubacterium coprostanoligenes uses to degrade cholesterol.

But they also found that some samples had higher amounts of cholesterol. In here, now bacterium degraded the cholesterol. And similarly, scientists did not detect that gene and thus no bacteria that degrade cholesterol. 

Lastly, the scientists needed to check whether cholesterol degradation also means lower cholesterol levels in the plasma of a person. For this, they looked at data from other studies. And yes, they found that people with lower cholesterol levels in their serum have bacteria in their guts that degrade the cholesterol. 

So, with these data, scientists thought that some people carry special bacteria in their guts. When we eat cholesterol, it lands here as well. The bacteria then degrade the cholesterol so that less cholesterol is transported from the gut to the plasma. Therefore, these people have lower cholesterol plasma levels. 

Now we know that certain bacteria can degrade cholesterol and produce coprostanol. However, we do no know yet what happens to the coprostanol. But I am sure they will find out soon.

Be nice to your bacteria – they reduce your cholesterol

As I cannot state it enough: Be nice to your bacteria. 

They might help you in ways you did not even think about before. Now, we know that bacteria maybe even impact our health by keeping cholesterol levels low. This would generally improve our cardiovascular systems.

So thank your new friend Eubacterium coprostanoligenes and start being nice to it too!

Who knows when you might need it?

The post How bacteria reduce your cholesterol levels appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

We are completely surrounded by them and we surely would not be the same if it was not for our microbial friends.

Unfortunately, every once in a while, we read and hear negative news articles about certain players of the microbial world. And then we forget that many other microbes and bacteria are actually very helpful to us, our health, the environment and food production.

But the goal of the BacterialWorld blog is to remind you how colorful and interesting the microbial world is.

20 interesting microbes everyone should have heard about

The microbial world consists of many interesting players: bacteria, viruses, phages, fungi, protozoa, unicellular eukaryotes and microscopic animals. And together, they all make the microbial world such a diverse and fascinating environment.

So, here, we assembled a list of common and interesting microbes. Some of them you might find delightful, others you rather want to avoid and that is okay.

We want you to be aware that there are many more cool microbes and bacteria out there than what you hear in the news.

And that thanks so research, we know a lot about how to use these microbes or how to avoid them if they are dangerous.

For this list, I got help from microbe lover Rachel and her GIANTmicrobes which she introduced during the #MicrobesinMay challenge on Twitter.

Ready to learn about the microbial world and interesting bacteria and microbes?

1. The bacterium Escherichia coli

Escherichia coli is rod-shaped and can have flagella all around its cell. 

Most people have heard of Escherichia coli because of contaminated food or lakes. However, most strains are harmless and this bacterium is actually super important for your digestive health.

This is also why Escherichia coli is by far the most intensively studied and best-understood organism on the planet.

Escherichia coli serves as a model organism for microbiology and biotechnology. It is helping scientists to learn about everything DNA-related, as well as protein production and cell growth. In most research labs of biological or life sciences, scientists use this organism every day to produce proteins, produce gene fragments or use it as a vehicle for plasmids and vectors.

2. The Influenza virus

The influenza virus is an RNA orthomyxovirus that causes respiratory infections, which you may know as the ‘seasonal flu’. Luckily, there is a vaccine against the flu that you should get every year if you are able to.

Influenza is an RNA virus that contains 8 genetic segments. Generally, RNA viruses are prone to mutate a lot; this happens during so-called antigenic drift and antigenic shift events. These “shifts and drifts” can change the structure of the virus’s surface proteins. Unfortunately, this change makes it harder for our immune system to recognize and respond to the virus.

Because the flu virus is ever-changing, you should help your immune system to recognize the new antigens. You can do this best by getting the new FluShot every season. But be aware that each virus is different and a FluShot will not protect you against other viruses.

3. The fungus Saccharomyces cerevisiae

You may encounter this fungus – almost on a daily basis. Saccharomyces cerevisiae is also known as the common yeast.

We use this yeast to make beer and bread. Like many other microorganisms, Saccharomyces cerevisiae performs microbial fermentation. This means it eats sugar and turns it into alcohol in beer and CO2 for bubbles in beer and bread.

We cannot state enough that the yeast Saccharomyces cerevisiae is a fungus and not a bacterium. It produces rounded cells and researchers use it as a model organism for eukaryotes. This means its DNA is enclosed in a membrane and not swimming around freely as in bacteria. Humans are also eukaryotes, so lots of knowledge of human cellular and molecular biology comes from yeast research.

Saccharomyces cerevisiae also plays a role in biotechnology. Some strains produce biofuels while others produce recombinant proteins that we use as therapeutics.

4. The bacterium Lactobacillus acidophilus

Lactobacillus acidophilus gets its name because it produces lactic acids from sugars, which usually makes its surrounding very acidic.

Lactobacillus acidophilus cells are rod-shaped and usually grow in pairs or chains. This bacterium lives in our mouths and guts where it prevents the growth of other bacteria by maintaining a healthy microbiota.

This bacterium also helps make yogurt, since it breaks apart milk sugars to make acids and other healthy molecules. This is why Lactobacillus acidophilus is also a probiotic, meaning a microbe that promotes health. There are many claims out there promoting its use to increase health, but more research is needed.

5. The Rhinovirus

The Rhinovirus may look cute but it is one of those nasty viruses that you may not like. It causes the common cold and we all know how we feel not cute with a cold. There are more than 100 different varieties of rhinoviruses and together they cause almost half of all colds.

Rhinovirus is an RNA virus in a 20-sided capsid. They are some of the smallest viruses and can spread by aerosol or direct contact. The virus replicates best in temperatures slightly cooler than body temperature, like in the nose. In fact, “rhino” means nose in Greek.

Currently, there is no vaccine against Rhinovirus. And since it’s a virus, antibiotics won’t work against it.

The best way to protect yourself is good hand hygiene and physical distance from people with a cold.

6. The microscopic water bear

One of the most interesting and cutest microbes is definitely the water bear.

But what exactly are water bears?

Hypsibius dujardini are microscopic creatures, classified as the Tardigrada phylum.

As the name suggests water bears resemble bears and walk on eight tiny legs. Tardigrade means “slow walker”. So if you imagine a slow-walking bear through water, this is kind of what water bears are!

Besides being adorable, water bears can survive extreme conditions and they are found worldwide in diverse environments. Many species live in water or around moss. To survive in any habitat, water bears enter a state of cryptobiosis where it dries out and stops its metabolism. In this state, they can last several decades.

Water bears can live in hot springs, polar ice, mountains and deep in the ocean. In fact, researchers found that water bears can even survive the vacuum of space! That’s good since a capsule containing some crashed on the moon in 2019.

Learn more about what tardigrades look like under the microscope.

7. The microscopic rotifers

To us, Rotifers are certainly one of the most interesting and cutest microbes. These microscopic animals are almost all female and can reproduce without the involvement of males.

Rotifers are tiny free-living creatures found mostly in freshwater. Rotifers have a cylindrical body and a ring of cilia around their heads. When the cilia move, it appears as a wheel (rotifer means “wheel bearer”). This movement pushes food into the animal and helps them move through the water.

Rotifers are sexually dimorphic and the males are much smaller and usually do not live long.

Reproduction of this microbe is rather interesting: Unfertilized eggs grow as clones within their mother. But studies have found genetic differences without sexual reproduction. It is now just a question of how?

8. The bacterium Porphyromonas gingivalis

The bacterium Porphyromonas gingivalis causes bad breath and gum disease, so make sure to brush and floss regularly to keep it in check.

Porphyromonas gingivalis cells are rod-shaped and live in our mouths. They are anaerobic, so they don’t need oxygen to grow. This may seem odd since we should have oxygen in our mouths all the time. However, many different microbes grow in our mouths where they form biofilms. These are layers of almost no oxygen, in which the bacteria settle.

In the oral biofilm, the dental plaque, Porphyromonas gingivalis lives close to the gum line where oxygen is depleted. Here, the bacteria can infect the gum and cause erosion called periodontitis.

9. The Rubellavirus

The “little red” Rubellavirus is known to produce red rashes on children’s arms and faces. Luckily, there is a vaccine to prevent infection.

Rubella is an RNA virus in a 20-sided capsid wrapped by a lipid membrane. Also called German measles because it was first identified in Germany, rubella was once a common childhood disease causing rash, fever and sore throat. While it posed minor risks to children, rubella could be deadly for the unborn in the womb.

Today rubella is very rare because of the MMR vaccine, which protects against mumps, measles, and rubella. Thanks to scientific research and vaccination, many countries could be declared “free of endemic transmission of rubella”.

10. The morbillivirus

Separately, the virus that causes the measles. This virus leads to red spots all over the body and can be deadly. Fortunately, the MMR vaccine prevents infection.

Morbillivirus is a spherical RNA virus. Measles is very contagious and spreads by personal contact and contaminated surfaces. It infects the respiratory system and causes rash, fever, cough, running nose and red eyes. Measles can cause serious complications and be deadly for kids.

Today, morbillivirus is still responsible for more than 100 000 deaths yearly, down from more than 2 million deaths annually. This is due to the introduction and widespread use of the MMR vaccine.

11. The bacterium Shigella dysenteriae

If you’ve ever experienced Shigella dysenteriae, you would remember! This bacterium infects the intestines and causes shigellosis, which is incredibly painful and uncomfortable. Antibiotics treat this disease, but hygiene is the best prevention.

Shigella dysenteriae are rod-shaped bacteria. They have a biological needle with which they fire the so-called ‘Shiga toxin’ into our gut cells. This leads to stomach pain and watery diarrhea.

This bacterium travels through the fecal-oral route, from contaminated food or hands. It is very contagious because it needs only a few cells to make someone sick.

What’s the best way to protect yourself? Always cook food thoroughly to kill all bacteria. And wash your hands to prevent spread!

12. The human papillomavirus

This virus may look cute, but human papillomavirus has been linked to certain cancers! The human papillomavirus is a common virus that infects many. Thankfully, there is a new vaccine to prevent high-risk infections.

The human papillomavirus is a DNA virus surrounded by a circular capsid. This virus is very common and in most cases, one may not have any symptoms while the body clears the virus.

Sometimes, the virus causes small tumors called papillomas that appear as warts. If left untreated, those tumors can become cancerous.

The human papillomavirus spreads by direct contact and is one of the most common sexually transmitted diseases worldwide. A vaccine is available to prevent infection from the major cancer-associated human papillomavirus types.

13. The bacterium Anabaena

Anabaena, known as cyanobacteria, are photosynthetic bacteria, even though they resemble eukaryotic algae. These helpful bacteria contain pigments that give Anabaena the blue-green colour.

Commonly found in aquatic environments, cyanobacteria use their pigments to convert light into energy. Using that light along with CO2 and water, they convert it to sugar and oxygen. In fact, cyanobacteria are a major source of oxygen in our atmosphere today!

The bacteria are even more interesting since some of their cells have special superpowers. These so-called heterocysts can “fix” nitrogen.

Heterocysts have extra thick- cell walls to exclude oxygen that otherwise harms nitrogen-fixing enzymes. The heterocysts then share the fixed nitrogen with surrounding cells.

14. The bacterium Clostridium botulinum

Clostridium botulinum produces a neurotoxin known for causing botulism. But that same toxin is also a component of Botox. Just another way we use microbes for good.

Clostridium botulinum is a rod-shaped, spore-forming, anaerobic bacterium. Found in soils, it can enter the food supply as spores. Under correct conditions, like in canning, spores germinate and produce the toxin. Thus, food should be processed with high heat and pressure to kill spores.

The botulinum toxin is the most toxic substance known and causes paralysis. While botulism is serious and can be deadly, scientists found ways to use the muscle-paralyzing function of this toxin. In small doses, the toxin treats muscle disorders such as spasms. Also found in Botox, the toxin paralyzes muscles that lead to wrinkles.

15. The varicella-zoster virus

Remember those itchy spots caused by chickenpox? I do! But now many children don’t have to experience the results of the varicella-zoster virus because of the chickenpox vaccine (lucky them!).

The varicella-zoster virus is a highly contagious DNA herpesvirus. As a primary infection, the virus causes so-called varicella. You might remember this as body rash and itchy blisters that last a few days.

Yet, the varicella-zoster virus actually can remain dormant in our nervous system (called latency) and reactivate later in life. This secondary infection can then lead to herpes zoster, also called shingles.

While chickenpox is usually a non-serious childhood disease, shingles affect adults and can have serious complications and pain. That’s why there is a separate shingles vaccine, too. No one wants to be itchy or in pain, so make sure to get the vaccine!

16. The bacterium Borrelia burgdorferi

Borrelia burgdorferi is a spirochete bacterium shaped like a corkscrew with flagella at both ends. These bacteria live in ticks and can infect humans when bitten by an infected tick.

These bacteria cause Lyme disease, a zoonotic disease where the pathogen jumps from an animal to a human.

Lyme disease is best known for causing a bull’s eye rash. But it also causes fever, headaches and fatigue. Some cases of Lyme disease are asymptomatic and if left untreated can lead to serious neurological or heart issues. Make sure to protect yourself when going hiking and camping.

17. The bacterium Listeria monocytogenes

This bacterium has made headlines, but not for anything fun. Listeria monocytogenes has led to many food recalls because of contamination concerns. It can grow at 0°C, so even refrigerated food can be infected.

Listeria monocytogenes cells are rod-shaped and covered with flagella. This food-borne pathogen causes listeriosis that may result in sepsis, meningitis, or death. It’s especially dangerous for immunocompromised and unborn, which is why pregnant women shouldn’t eat soft cheese or uncooked meat.

Listeria monocytogenes is found in environments where food grows. Contamination can occur during food harvesting and processing. Once inside a human cell, they manipulate it so that the cell propels the bacteria into the next cell.

18. The Epstein-Barr virus

Did you know that the Epstein-Barr virus is one of the most common human viruses? It causes the commonly called kissing disease because we transfer the virus by saliva and bodily fluids.

The Epstein-Barr virus is a DNA herpesvirus with a lipid envelope. Most infections occur in childhood and are asymptomatic or with only mild symptoms. Roughly 90% of adults have antibodies against Epstein-Barr, which means they were once infected with this virus.

When infecting adults for the first time, the Epstein-Barr virus can cause mononucleosis. Symptoms include fever, sore throat and extreme fatigue, lasting weeks to months. You can prevent the spread by not sharing utensils or drinking cups.

19. The bacterium Staphylococcus aureus

One of the best-known bacterial warriors is Staphylococcus aureus and its methicillin-resistant super brother MRSA. These two can infect almost all parts of the human body with their arsenal of virulence factors.

Staphylococcus aureus cells are round-shaped and form grape-like clusters. Most people have this Gram-positive bacterium in their nose or on their skin.

Unfortunately, with certain triggers, this harmless bacterium can become a pathogen. Then, Staphylococcus aureus produces virulence factors, such as toxins, enzymes, and antibody-inactivating proteins. These bacteria can also form biofilms on medical implants.

What about MRSA? Those are strains of Staphylococcus aureus that are resistant to the antibiotic methicillin (Methicillin-resistant Staphylococcus aureus). Antibiotic resistance occurs when bacteria acquire ways to inactive antibiotics and has become a worldwide health crisis.

20. The protozoan Toxoplasma gondii

Love cats? Well, those cats might have a ‘friend’: Toxoplasma gondii. This parasite can be carried by cats and is one of the most common parasites in the world. The infection causes toxoplasmosis which is an important zoonosis.

Toxoplasma gondii is an obligate intracellular parasite. It can reproduce sexually only in cats (called the definitive host) or asexually in any warm-blooded host (such as mice or humans). A cat can become infected by eating an infected mouse, then pass the infection to humans via litter.

Toxoplasmosis infections can occur from eating contaminated food or from infected cat droppings. In most cases, the infection is asymptomatic. However, immunocompromised and pregnant people are at risk for complications.

Which one is your favorite among the interesting microbes?

We hope we could give you a broad overview of interesting microbes and bacteria common in the environment and on the human body. This list of common microbes is meant to raise awareness of how multifaceted the microbial world is.

Yes, some of these microbes cause diseases. But thanks to research, we now have ways to boost our immune systems to clear diseases caused by pathogens or to prevent microbial diseases in the first place with vaccines.

And don’t forget that so many microbes are actually super helpful and fun to look at! Just look at this cute water bear dancing around!

If you have questions about any of these microbes or want to learn more about any player in the microbial world, comment below or send us an email.

And if you want to know more about Rachel and interesting bacteria, follow her on Twitter, or connect with her on LinkedIn.

The post 20 interesting microbes everyone should have heard about appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

If you are like me, you would make sure to always have your stock filled with this delicacy.

Especially in tough times, you need it more than ever. And you are trying to hide the chocolate from yourself. Yet, you would always find it again and indulge in its sweet-bitter taste that feels like home to you.

But did you know that chocolate, as well as other foods like beer and wine and bread, would not taste as we know it if it wasn’t for our little microbial friends?

That bacteria and microbes actually make the chocolate taste because they produce certain molecules that give it its flavour?

So, next time you enjoy your piece of chocolate, be grateful to bacteria and their superpowers for providing you with such a delicious fermentation product.

Where does chocolate come from?

It all starts with cocoa beans.

Cocoa beans are the seeds of the fruit pod of the tree Theobroma cacao that grows in tropical regions. These beans usually grow within the slimy white-creamy pulp inside the pod.

When the pods are ripe, people harvest and open them. They take out the beans and the pulp from the pod and leave them in the sun to ferment. This takes up to a week, during which the beans are regularly moved to avoid the growth of toxic fungi.

When the beans are dry, they are roasted to kill the remaining bacteria. This process is also important for the flavour of the beans. Then the beans are crushed into cocoa nibs and separated into cocoa powder and cocoa butter and processed into delicious chocolate.

Which bacteria are involved in cocoa fermentation?

When growing on the tree, the inner of the fruit pod is free of microbes. Only the surface of the pod is covered by different bacteria, yeasts and fungi. This consortium of microorganisms is the co-called COCOBIOTA.

When opening the pods, the microbes from the outside come in contact with the inner pulp where they start doing their magic. Without the microbial activity, the pulp is full of sucrose and citric acid and tastes very “sugary acidic and really good. Really unexpected.” as our graphical wizard, Noémie knows from her own experience.

Interestingly, cocoa fermentation is a naturally occurring process, so no artificial bacterial starter culture is added. Only those microbes that are present on the pod ferment the beans.

And scientists found that the superheroes of chocolate fermentation are lactic acid bacteria like Lactobacillus fermentum and Acetobacter pasteurianus and the yeasts Saccharomyces cerevisiae, Hanseniaspora thailandica, Hanseniaspora opuntiae and Pichia kudriavzevii. Also, many other microbes, that are still not well characterised, are involved in the process.

What happens during cocoa fermentation?

Since the inner pulp of the bean is so acidic, not many bacteria grow on it. However, yeasts and lactic acid bacteria love this kind of sour environment. So, they grow and metabolise the pulp.

First, yeast enzymes break down the sucrose of the pulp into the sugars glucose and fructose.

Next, different yeast strains metabolise the glucose and fructose and produce ethanol from the sugars. This is the actual fermentation process. In the next step, lactic acid bacteria make acetic acid and lactic acid from the ethanol.

Due to the metabolic activity of the microbes, the temperature of the pulp rises. Yeasts generally do not like this warmth and die.

Instead, other microbes break down the citric acid which makes the pulp less acidic. Now it is an environment that is very friendly for other bacteria so that bacteria like Bacillus, and fungi, as for example Penicillium citrinum and Aspergillus fumigatus start growing.

This consortium of microorganisms produces several compounds that diffuse into the cocoa beans. Without the bacterial activity, the raw beans “are definitely far from chocolate taste” as Noémie put it.

What chocolate-tasting molecules do bacteria produce during cocoa fermentation?

Scientists are just starting to understand the microbial network and metabolism that create the chocolate taste. You can understand the bacterial metabolism as the following phenomenon.

When bacteria live in an environment with an overload of nutrients (like within the pulp full of sugar), they switch their metabolism to high activity. In this mode, bacteria use their normal metabolism to grow and divide and be happy. On top of that, they have all that excess sugar with which they fill up the cell storage for bad times. And from these stored sugars, they produce additional fancy molecules, so-called secondary metabolites.

Imagine the sugars as your monthly salary. In normal times, you pay all your basic monthly bills, like rent, electricity etc, and probably put the rest in your savings. When you get a massive paycheck and swim in cash, you do all that as well, plus you buy some additional fancy stuff that you don’t really need to survive. This additional stuff represents those secondary metabolites.

Secondary metabolites are often super complex molecules and certain bacteria even produce unique compounds that no one else produces. For example, antibiotics are secondary metabolites as well and so are certain probiotics.

Bacteria produce the right mix for the chocolate taste

In the case of chocolate, the right composition of the secondary metabolites is important to give chocolate its unique taste.

For example, the bitter taste of chocolate comes from caffeine and theobromine. These compounds are especially important if you prefer chocolate with higher cocoa content as it contains more caffeine and less sugar.

Another group of secondary metabolites that microbes produce during cocoa fermentation is polyphenols. Polyphenols are also prebiotics so they are actually beneficial for our health. You can find other polyphenols also in some fruits, nuts, red wine and, obviously, chocolate.

In all, by producing the right mix of these secondary metabolites, bacteria and fungi change the taste of the cocoa bean into the delicious chocolate flavour that you are familiar with.

Thank bacteria for the delicious chocolate taste

And to make you feel better when enjoying your chocolate: Researchers found in animal and human studies that cocoa itself has health benefits. After eating cocoa, people showed lower rates of cardiovascular disease, diabetes and vasodilation which might even have positive impacts on learning and memory regions.

However, as always when it comes to diet, quantity is key ?

So, the next time you enjoy your chocolate, be grateful to bacteria and their chocolatey superpowers!

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