To grow and produce crops under almost any condition, plants need to make good use of all nutrients available to them. While they are masters at absorbing some nutrients from the air and soil, they are struggling with others.

One such problematic element is nitrogen. Even though nitrogen makes up about 80% of the atmosphere, it is mainly present as dinitrogen gas N₂.

This means two nitrogen atoms are tightly bound to one another via three strong and energy-rich bonds. In this form, plants can neither take up the nitrogen nor use any of the nitrogen atoms to make other molecules from them.

Yet, they need nitrogen since it is part of every DNA molecule, protein, the energy provider ATP and many vitamins. Hence, plants need a way to acquire that element in a simple way that does not cost them too much energy.

Enter bacteria.

Diazotrophic bacteria fix nitrogen

The so-called diazotrophs have developed a highly efficient enzyme complex to capture, or fix, dinitrogen from the atmosphere and break up its energy-rich bonds. This complex is the nitrogenase, and all diazotrophs use one of three types of nitrogenase.

The most efficient nitrogenase contains a molybdenum ion at its core, while other nitrogenases use vanadium or iron. These metals are extremely rare in the environment. Hence, depending on which one is available, bacteria regulate which of the three nitrogenases to produce.

After capturing a dinitrogen molecule, the nitrogenase enzyme transfers energy in the form of protons and electrons to it. This eventually breaks up the bond between the two nitrogen atoms and produces two ammonium ions NH₃⁺.

Bacteria then use the ammonium ions for their own growth and share the surplus with their friends and partners. In Nature, several symbiotic relationships exist between bacteria and other organisms which are based around the nitrogen-fixating superpower of bacteria.

Soil bacteria share fixed nitrogen with plants

The best known nitrogen-fixing organisms are soil bacteria from the families Bradyrhizobium, Frankia, Bacillus, Clostridium, Burkholderia and Pseudomonas. These either live freely in the soil or form symbiotic relationships with plants.

Especially important are symbiotic rhizobia like Bradyrhizobium and Frankia. Plants attract these soil bacteria to their roots by sending out special molecules, which the bacteria respond to via their quorum sensing receptors. Within the root network of legume plants, the bacteria then build little nodules in which they live protected from the surrounding.

Within the nodules, bacteria fix and convert nitrogen with their enzyme complexes, which requires a lot of energy. Gladly, the host plant provides this energy in the form of sugars and organic acids that it produces with photosynthesis. The plant then transports these molecules into the root nodules, where the bacteria break them up, extract their electrons and thus gain the necessary energy.

After breaking up the nitrogen using these very electrons, the bacteria transport the produced ammonium from the nodules into the plant. With the ammonium, the plant makes DNA, proteins and vitamins; everything that it needs to grow and produce crops and fruiting bodies. Hence, rhizobia bacteria are highly important for the health of plants as well as crop production and yield.

Marine bacteria can fix nitrogen

Soil bacteria are not the only nitrogen-fixing organisms; marine bacteria are also important for global nutrient cycles. For example, cyanobacteria form long filamentous multicellular organisms, with some cells specialised in nitrogen fixation.

Often, cyanobacteria are closely associated with other marine bacteria with which they share nitrogen. So far, scientists do not fully understand these types of interactions but are sure that nitrogen-fixing organisms are crucial for the marine food web and the survival of many species under water.

When temperatures are high enough and nitrogen concentrations are optimal, you can pretty much see the nitrogen-fixation process. A green blanket on the water surface is a sign for cyanobacteria that power both photosynthesis and nitrogen fixation with the carbon dioxide and nitrogen from the air. This so-called algae bloom is mainly due to cyanobacteria like Aphanizomenon, Dolichospermum, Anabaena and Synechococcus bacteria.

Soil bacteria as biofertilisers for sustainable food production

Since some soil bacteria are so efficient in fixing nitrogen and providing it to the plant, they have also become valuable in agriculture. Some so-called biofertilisers consist of bacteria that are added to soil or plants to build symbiotic relationships with them, helping them grow better and produce bigger crops.

Hence, biofertilisers containing bacteria are an efficient and sustainable way to produce more food and in higher quality. With this, farmers will rely less on synthetic fertilisers while maintaining high crop yields. Additionally, using nitrogen-fixing bacteria as biofertilisers helps protect the health of the soil and the environment.

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

Those bacteria that call your gut their home are the so-called commensal bacteria. Luckily, they have a special superpower: They can protect us from bacteria that cause infections and make us sick. For this, our commensal gut bacteria developed some extraordinary strategies to defend these pathogens.

So, by nurturing our friendly gut bacteria, you are also strengthening your protection against diseases. Here, we will look at what kind of bacterial wars are going on in your gut and how your gut bacteria defend pathogens and keep you healthy.

Your gut bacteria defend pathogens with toxic molecules

Bacteria have many different means to kill other microbes, competitors or even their own siblings. Often, these bacteria produce molecules that are toxic to their prey, which means they inhibit cellular proteins or machineries. Without these machineries, the prey is then lacking an essential cell function to grow or survive, so that it eventually dies.

Interestingly, gut bacteria produce and deliver many different toxic molecules of various shapes and sizes, functions and even origins.

Gut bacteria produce bacteriocins

Many bacteria produce molecules that are like antibiotics specifically to kill bacteria. These are called bacteriocins.

Some bacteriocins are simple and small molecules, while others can be big and fancy. However, they all have a similar goal: they bind to a specific target in the prey bacterium and prevent that target from working properly.

So, no wonder that many bacteria in our gut microbiome produce bacteriocins that are toxic to pathogenic intruders. Also, we carry a lot of different bacteria in our guts and they all produce different bacteriocins. Hence, incoming pathogens face this huge load of toxic molecules making it really difficult to establish themselves in our intestines.

For example, one bacterium that loves the warmth and lack of oxygen in our gut is the bacterium Ruminococcus gnavus. And this one produces at least two bacteriocins, Ruminococcin A and C, that are toxic against human gut pathogens like Clostridium perfringens.

Other friendly gut bacteria, like Escherichia coli or Blautia producta, also produce bacteriocins that are toxic to pathogens, like Enterococcus faecalis. And some of their bacteriocins can even impact our gut cells by activating and strengthening our immune response.

Gut bacteria produce short chain fatty acids from fibres

Another way to protect against pathogenic gut bacteria is directly related to your diet. When we eat a lot of fibres, which are non-digestible carbohydrates, our friendly gut bacteria break these up. From these fibres, they produce small molecules that are called short-chain fatty acids, which have many positive health benefits for our overall wellbeing.

Interestingly, when we have a lot of these short-chain fatty acids in our intestine, the pH drops. This is already pretty difficult for most pathogenic bacteria, as not many can handle this acidic environment.

Plus, short-chain fatty acids diffuse into pathogenic gut bacteria where the pH drops as well. This can disturb many cellular machineries from functioning properly and not many bacteria have the right tools to defend against this attack, so they’ll die.

Gut bacteria convert bile acids into toxic compounds

To better digest the fats in food, our liver produces bile acids. These molecules bind fatty acids and lipids so that we can take them up better into our bodies.

But some of our friendly gut bacteria can convert these primary bile acids from our liver. For example, one of these bacteria, Clostridium scindens, transforms them into secondary bile acids that can bind the lipids of bacterial membranes.

Like this, secondary bile acids open the membranes of some pathogenic gut bacteria, like Staphylococcus aureus, Bacteroides thetaiotaomicron or Clostridoides difficile. This eventually kills the intruders and keeps our guts pathogen-free.

Killing pathogens with bow and arrow

Yes, also direct bacterial wars are happening in our guts! And they are nasty!

Some bacteria use tiny little bows to shoot deadly arrows into other bacteria. And these arrows can be incredibly toxic so the shot bacterium has barely any chance to survive the attack.

Luckily, our gut bacteria use their bows and arrows to defend against gut pathogens. For example, commensal bacterium Bacteroides fragilis has three different bows and can shoot various arrows. And research showed that this bacterial friend can protect us from bacteria that otherwise cause intestinal diseases.

Interestingly, Bacteroides fragilis is not opposed to hit’n’kill its own toxic bacterial siblings since some members of his family can indeed make us sick. But our friendly Bacteroides fragilis collected many different immunity proteins against its evil siblings so that their toxic arrows cannot harm it. Instead, Bacteroides fragilis keeps shooting and killing until we are safe from the pathogenic sibling.

Keeping nutrients from pathogenic gut bacteria

Another important way how gut bacteria defend pathogens is by keeping nutrients away from them. In all mixed microbial communities, bacteria fight for nutrients, especially for metals like iron, zinc but also sulphur sources.

Luckily, our gut bacteria developed some sneaky ways to steal these metals from gut pathogenic bacteria. By sending out special proteins that bind these metals very tightly, the commensals make sure to keep these metals from the pathogens. And if the pathogenic bacteria don’t have enough of these essential metals, they won’t survive and will eventually die.

Strengthening the mucus layer to block pathogenic gut bacteria

When you think about it, your gut is not part of your body – even though it is inside of you. All the food that we eat, stays within this digestion tube (mouth, oesophagus, stomach, intestines) until it comes out on the other side.

And to protect us from harmful microbes and molecules, we need to have a clear physical barrier from the content of the tube. This barrier is the so-called epithelial layer, which is covered by a slimy mucus on the outside. And this sticky slime helps keep off intruding microbes so that they cannot breach through the epithelial wall and get into our bodies.

Luckily, our helpful gut bacteria help us maintain this slimy defence wall. As bacteria produce SCFAs close to the mucus layer, the epithelial wall produces more slime. And if the slime gets thicker, gut pathogenic bacteria have more difficulties getting into our bodies.

To help the slime grow, some bacteria adapted very well to the conditions within the gut. For example, the friendly gut bacteria Akkermansia muciniphila and Ruminococcus gnavus cut off the very end of the mucus layer and feed themselves with them. This does not harm the mucus itself, but it keeps these bacteria close by. And this in turn triggers the epithelial wall to produce more mucus. So, everyone wins.

How to help your gut bacteria defend pathogens

Now, that you better understand how your gut microbiome defends pathogenic gut bacteria, make sure you support them keeping you healthy. By feeding your gut bacteria the right foods, you will help them be comfortable and happy in your gut. And when the right bacteria grow within you, they will gratefully protect you from nasty intruders!

Another idea for researchers is to use what they have learned to keep you healthy. The idea is to develop probiotics or prebiotics that help us defend against nasty pathogens. For example, you might take pills containing toxins against pathogenic gut bacteria or probiotics with bacteria that can fight off pathogens.

Whatever it may be, you can always help your gut bacteria be happy in your intestines by eating the right things. That means lots of fibre and veggies! ?

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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?

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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.

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