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

And some of these microbes learned to adapt to these special – or extreme – conditions. They can’t even cope in normal environments.

Extreme conditions or extreme environments can be anything that we consider uninhabitable for us. This can be extremely high or low temperatures, extremely high or low pressure, radiation or toxicity.

Some of these microbes actually love the extremes. And these so-called extremophiles have special superpowers that help them survive in hostile places – like the bottom of the sea.

What are extremophiles

For example, so-called thermophiles live and grow at temperatures above 50 °C and hyperthermophiles even at temperatures above 80 °C. On the other hand, psychrophiles love temperatures below 10 °C. Plus, researchers keep finding interesting new species in the permafrost soils of the Arctic and Antarctic.

Some extremophiles also have superpowers to survive in extremely salty or acidic places like saline lakes or acid mine drainages. And other extremophile microbes grow in places with high metallic or toxic concentrations or high pressure like at the deep sea of the ocean.

These extreme environments put a lot of pressure on microbes, which means they need to adapt to these conditions or they won’t survive. Hence, in these extreme environments, microbes are mutating more often or exchanging more DNA with other species to learn to cope with these challenging conditions.

Here, we will look at microbes and extremophiles that live and grow in the deep sea. In this dark place, microbial communities have developed fascinating mechanisms to adapt. And from here, they can also impact our global climate.

Extremophiles living in the deep sea

Imagine the bottom of the sea about 30 km underwater: It is dark since sunlight cannot shine this far. It is 2 – 3 °C cold while close to hydrothermal vents, it can be up to 400 °C all of a sudden. And the pressure at the sea bottom is extremely high since all that water is extremely heavy pushing everything down.

And yet, the bottom of the sea is full of happily-living, growing microbes that enjoy their times together, feeding each other and stabilising our ecology. These microbes can swim around in the open sea. Most of them attach to dirt or sediment particles on which they form biofilms.

As you can imagine, this environment doesn’t offer much food or energy. So, it is incredibly important that microbes interact with each other here to exchange meals and information. That’s why many microbes in the deep sea feed each other with one microbe producing a special substrate that another microbe likes to eat.

These microbial food webs are very important for our global nutrient cycles as deep-sea microbes sequester atmospheric gasses, like CO2, and degrade contaminants and pollutants. For example, thermophilic bacteria like Desulfovulcanus ferrireducens and Oceanithermus profundus live close to hydrothermal vents which is why they grow best at about 65 °C. These extremophiles get their energy from hydrogen gas and organic acids that swim in the ocean.

Also, during oil spillages in the ocean over recent years, researchers found many bacteria and fungi that can eat and degrade oil or petroleum. Hence, their need for food cleans our oceans of these harmful components.

How extremophiles adapt to the deep sea

The deeper you are in the ocean, the less oxygen is available for microbes to breathe. Hence, microbes had to become creative about where to get their energy from. For example, Desulfovulcanus ferrireducens mainly uses iron components for respiration and growth while Oceanithermus profundus prefers nitrogen gas. All over the oceans, there are SO MANY microbes eating these iron components and nitrogen gas. Hence, all their metabolic activities impact the iron and nitrogen cycles of the whole planet.

But microbes and bacteria in the deep sea did not only have to adapt their meals to these conditions. Deep-sea extremophiles also had to develop mechanisms to withstand the pressure and the cold of this hostile place.

At very low temperatures, proteins often get out of shape so that they lose their functions. This can mess up the whole bacterial cell, which is why psychrophilic bacteria have so-called chaperones that constantly check the bacterium for proteins that are out of shape. These chaperones then help the protein get back into normal shape and thus to its normal functioning state.

Extremophile bacteria have different membranes

Another way to adapt to hot and cold temperatures is for bacteria to change their membranes. As you might know from experience, fat gets solid when it’s cold and fluid when it’s hot. And since bacterial membranes are mainly made out of lipids and fats, thermophilic and psychrophilic bacteria need to make sure their membranes can cope with the extreme temperatures.

To prevent membranes from becoming too fluid and leaky at high temperatures, thermophilic microbes solidify their membranes. On the contrary, psychrophilic bacteria like Psychromonas and Marinomonas need to make sure that their membranes stay flexible at cold temperatures.

Luckily, this special cold-adapted membrane also helps bacteria withstand the high pressure in the deep sea. And to counteract the pressure inside the cell, piezophile bacteria produce a lot of stuff and basically crowd their cells with proteins. This aims to keep the cell pressure inside high against the high pressure from the outside.

However, investigating such high pressure is extremely difficult in the lab. That’s why researchers still don’t know much about the pressure adaption of extremophiles in the deep sea.

What we can learn from extremophiles in the deep sea

Even though we still don’t know much about the fascinating microbial life underwater, researchers are optimistic that they will find lots of helpful microbes. Whether adapted to the cold or to the heat, deep-sea microbes have incredible mechanisms to grow at extreme temperatures.

This means they contain proteins that function perfectly on either side of the temperature spectrum. So, researchers hope that we could use that knowledge to design tailor-made proteins for our daily lives. We could for example use them in households or in biotechnology applications, for example, to improve cleaning efficiency or reduce energy input.

Another important aspect is to explore how microbes in the deep sea affect our global climate. With climate change, our oceans are getting warmer and thus they contain less oxygen. This means that also microbes are likely adapting to these changes which in turn influences the global climate.

Hence, understanding how microbes cope with the conditions in the deep sea helps us comprehend the full impact of climate change. This might then give us an idea about how to prevent more damage to our beautiful planet. With the help of microbes.

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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

And more and more people become aware that a plant-based diet is not only better for your health, but also for our planet. Hence, the focus on agriculture right now is to become more sustainable to grow enough plant-based food for everyone.

This means that we need to find better ways to support plant growth and protect plants from diseases. Unfortunately, several plants pathogens make plants sick, so they die or do not grow enough crops.

Currently, we use fertilizers and pesticides to protect plants from pathogens. However, these chemicals are bad for the environment long-term as they contaminate the soil and water.

Hence, we need to find ways to protect plants by either getting rid of dangerous intruders or by strengthening the immune systems of plants.

Enter bacteria and their superpowers.

They do both.

What is biocontrol?

Some bacteria that live in or on plants are called biocontrol agents. These organisms are harmless to the plant and have two main functions: They protect the plant from pests and diseases and support its growth and crops.

Some of these organisms additionally strengthen the plant’s immune system or resistance – again to protect the plant from disease and help it grow.

One such biocontrol agent is the bacterium Pseudomonas putida. It grows near the roots of many plants where it produces helpful molecules for the plant.

And plants are clever too as they make sure that only the right types of bacteria grow near them. For this, several plants release specific molecules through their roots that help Pseudomonas putida grow. The bacterium senses these molecules so that they activate the bacterium’s chemotaxis system.

Now, Pseudomonas putida uses its flagellum to swim towards these molecules. This movement ultimately leads the bacterium to the plant that released the molecules.

Pseudomonas putida as a biocontrol agent

Once the bacterium “found” the plant, it settles down near it and starts building biofilms. Within these biofilms, the bacteria are connected with each other and with the plant. Like this, they can easily exchange molecules and information with each other and with the plant and build close relationships.

Pseudomonas putida now produces molecules to help the plant grow. For example, some molecules extend the tips of the roots so that the plant can better take up nutrients from the soil.

Pseudomonas putida also breaks down complex nutrients in the soil that the plant use. This basically feeds the plant the needed nutrients. Other molecules from the bacterium activate the overall immune system of plants so that plant pathogens have a harder time infecting the plant.

Altogether, Pseudomonas putida has similar features as biofertilizers that help plants grow.

How does bacterial biocontrol protect plants against intruders?

Pseudomonas putida can also directly fight off plant pathogens to protect their plant hosts. For this, it uses two strategies: It either holds back essential nutrients from plant pathogens or kills the intruder.

Not sure which strategy is more evil though…

Pseudomonas putida keeps essential nutrients to inhibit plant pathogens

All living organisms need iron to live and grow. And one efficient strategy to prevent other microbes from growing is by stealing iron from them.

Our immune system does it as well: All iron in our body is bound to specific transporters. Like this, no free iron swims in our blood for microbes to use. This defence mechanism is one of the first strategies of our immune systems to keep harmful bacteria from growing inside our bodies.

Similarly, Pseudomonas putida produces many different iron transporters that bind iron very efficiently. Like this, no free iron is present in the soil that other microbes could use.

Yet, this is not all. Pseudomonas putida is quite a naughty one since it can also steal iron-loaded transporters from other bacteria. This not only prevents the other bacteria from using the iron, but it also helps Pseudomonas putida grow.

Pseudomonas putida kills intruding plant pathogens

Lastly, Pseudomonas putida is a real fighter when it comes to protecting its host plant. This bacterium uses a special nanoweapon to kill plant pathogens.

Our bacterial fighter carries a bow and arrow and is not afraid of using them to keep intruders off the plant. Pseudomonas putida actively shoots arrows together with lethal toxins into other bacteria to kill them. Many bacteria use this killer machine, called the type 6 secretion system. But interestingly, Pseudomonas putida seems to have a more efficient killing device than others.

Scientists proved that with a simple experiment. When different plant pathogens were growing inside plant leaves, the leaves got sick. However, when Pseudomonas putida was additionally living in the leaves, the plant leaves did not get sick.

Finally, the scientists let the plant pathogens grow together with a Pseudomonas putida bacterium that could not shoot its bow and arrow. Now, the plant leaves got sick again and the plants suffered from the plant pathogens.

These results show that Pseudomonas putida uses its bow and arrow to actively kill other harmful bacteria to protect plants. Even though the experiment was done in plant leaves, scientists are convinced that something similar happens in the root area of plants.

Bacteria as biocontrol agent to save our planet?

As soon as we better understand how exactly this plant warden protects its host from harmful bacteria, we could use Pseudomonas putida on a large scale. This would improve the health of plants so that they can grow more and better crops.

Hence, such a biocontrol agent would eventually help us have more food available for everyone.

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

But what do bacteria and fungi use antibiotics for? Why do they produce them? And what are the advantages of microbes having antibiotics as molecular weapons?

What are antibiotics?

The father of antibiotics, Selman Waksman, first used the word antibiotics for any small molecule made by a microbe that can inhibit the growth of other microbes.

So, microbes – especially bacteria and fungi – use antibiotics to kill other microbes. These other microbes can be bacteria, fungi or bigger organisms. Not viruses though!!!

Why not viruses?

Because antibiotics bind and inhibit cellular machines in living organisms. These molecules often bind to so-called targets. Antibiotic targets can be proteins or enzymes that make for example the cell wall, other proteins or components of the respiration complex.

These proteins are generally essential. So, when antibiotics inhibit the proteins, the cells are missing these essential functions. And without them, they cannot survive and die.

Hence, like other bacterial toxins, antibiotics are lethal.

Interestingly though, bacteria and fungi make antibiotics from simple building blocks. These are present in every cell and can be amino acids, lipids or even sugars.

But instead of using these building blocks for their normal functions, microbes link them together in different ways. With this, they create new – and fancier – molecules that barely resemble the original blocks.

Then, they transport these antibiotics to the outside or send them off in outer membrane vesicles. When the antibiotic hits another microbe, there are two possibilities: either the microbe is resistant to the activity of the antibiotic or it dies from it.

But what about the microbe that produces the antibiotic? Is it resistant to the antibiotic itself?

Why are microbes that produce antibiotics not get killed?

Since antibiotics are meant to KILL other microbes, then why do producing microbes not get killed by their own antibiotics? The answer is self-protection!

Whenever bacteria or fungi produce antibiotics, they always also produce some sort of self-protective means. Just as when bacteria produce other toxins, they always need to make sure they are not killed by their own weapons.

These self-protectors usually keep the antibiotic in an inactive state. For example, they completely surround the antibiotic molecule so that it cannot bind to its usual target within the cell. Another strategy is to add a small molecule to the antibiotic – again to keep it from binding to its target.

Then, when the microbe is ready to transport the antibiotic outside of the cell, it takes the self-protection off the antibiotic. This releases only the toxic part – the antibiotic itself – into the surrounding.

Note, however, that these self-protection mechanisms are not antibiotic resistance mechanisms. Self-protection mechanisms are meant to inactive antibiotics only temporarily. Hence, these mechanisms are reversible. The antibiotic can still become active and thus toxic.

Resistance mechanisms, on the other hand, are meant to inactive antibiotics permanently. Hence, these mechanisms are irreversible. Since this usually completely destroys the antibiotic, it cannot become active anymore.

But what triggers microbes and especially bacteria to produce antibiotics? How do antibiotics help the producing cell in their daily circumstances?

Why do bacteria produce antibiotics?

To answer this question, we need to look at where the bacteria live that make antibiotics. And two-thirds of the known antibiotics are made by bacteria from the Actinobacteria family. Within this family, Streptomyces is the best-known member that produces half of all known antibiotics.

Another example is bacteria from the Myxococcus family. So, where do Streptomyces and Myxococcus bacteria live? Interestingly, these bacteria call the soil their home.

And in the soil, they often confront lots of friends and foes. And they need to constantly fight for their own survival.

Myxococcus is known as a wolf-pack predator because it kills its prey in massive attacks. Colonies of Myxococcous roll over their prey, secrete antibiotics and thus kill them and feed on them.

Streptomyces, on the other hand, uses its antibiotics a bit more civil.

To move in the environment, Streptomyces bacteria grow as long filaments throughout the soil. They build long chains and branch out into the soil as multicellular organisms. These branches are filled with Streptomyces cells but also spores so that the bacteria can extend to new places.

When the bacteria hit a period of bad weather or don’t find much food, they release their spores as a survival strategy. Plus, they start releasing nutrients for the spores. But these nutrients also attract other organisms like bacteria.

Hence, at the same time, Streptomyces produces a huge amount of antibiotics to fend off these putative food-stealers. Like this, Streptomyces makes sure their spores are safe and can survive in their new homes for a while.

How do antibiotics produced by bacteria help others?

Like Streptomyces, lots of bacteria use antibiotics to fight off predators. This assures their own survival and that of their species.

Yet, more and more research finds that bacteria not only kill other species with antibiotics so they can survive. The killing also benefits their hosts.

For example, the bacterium Janthinobacterium lividum lives on frogs where it produces the antibiotic violacein. This antibiotic kills fungi so that the bacterium protects the frog from deadly fungal infections.

Also, a bacterium that lives in our noses is the harmless Staphylococcus lugdunensis. This bacterium produces the antibiotic lugdunin. That inhibits the harmful Staphylococcus aureus from settling down in our noses. Now, scientists look into how we could use the harmless Staphylococcus lugdunensis to protect us from infections.

Another example of microbes that produce antibiotics to help others is the three-member association of ants, Streptomyces and a fungus. Several species of ants grow fungi for food. They feed their fungi with fresh plants and let them grow in special underground gardens.

To not contaminate these fungal gardens, ants carry symbiotic Streptomyces that produce antibiotics. Like this, the antibiotics kill other microbes and keep the fungal gardens free of harmful intruders. As a thank you, the ants feed the Streptomyces and give them a place to live.

About antibiotic-producing microbes

So, just as we use antibiotics to kill harmful bacteria and fungi, antibiotic-producing microbes do the same. They want to fight off predators and assure their own survival.

When you think about it: we use their own killer weapons against them. Poor microbes!

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

And when it comes to the size of an organism, one thing is quite clear: The bigger, the more food they need.

This is also true for bacteria. Depending on the shape of a bacterium, bacterial cells are differently big or small. And the bigger a bacterium is, the more energy they need.

So, in a location where there is not much food, this might be a problem.

Not for superhero bacterium Thiovulum majus. This one is a huge bacterium with an incredibly amazing mechanism to find and get food for itself and its brothers and sisters.

Read on to find out what this bacterium does to not run out of food.

Large bacteria run out of food easily

Thiovulum majus is one of the bigger bacteria with about 10 – 15 μm cell length. Average-sized bacteria are usually around 1 μm in length and the smallest nanobacteria even only 0.2 μm.

This makes Thiovulum majus a giant under the bacteria. It is about 10 – 15 times bigger than other bacteria. And this means it also needs a lot more energy and nutrients.

Thiovulum majus also has an interesting lifestyle. It lives at the bottom of salt marshes, close to water sediments. Here, the water contains a lot of sulfur, which Thiovulum majus uses to gain energy.

However, Thiovulum majus also needs oxygen to live. Hence, within water, it needs to be in the perfect spot with the right oxygen and sulfur concentrations. Sounds easy, but is pretty complicated if you’re a bacterium drifting in water.

First, to find the optimal spot in water, Thiovulum majus uses chemotaxis to follow the right oxygen concentration. As soon as they are satisfied with a location, they need to make sure to stay in this position. And Thiovulum majus found an amazing mechanism to achieve that.

A floating veil keeps bacteria in place

Interestingly, Thiovulum majus produces a so-called tether or stalk. This is a strong but flexible string made of mucus. It is pretty sticky and works like the superglue of Caulobacter crescentus.

When Thiovulum majus swims in water, it carries this stalk at its end. Here, it can grow up to ten times as long as the bacterial cell itself. And the stalk can stick to stalks from other bacteria or particles in the water.

When many stalks stick to each other and to particles, they form a net-like layer in the water. This layer, or a white veil, floats above the sediment in the water and can become several centimetres in size.

Now, the bacteria are attached to this veil since their stalks are stuck within this mesh of stalks. Scientists found that on a veil with the surface area of your fingernail, around 100’000 Thiovulum majus bacteria are attached.

Every once in a while one such stalk breaks and thus releases the bacterium. However, Thiovulum majus uses its chemotaxis to swim in a U-shaped pattern which brings it back to the veil. Growing a new stalk, the bacterium attaches to the veil again to make sure it stays in the right location.

Hence, using chemotaxis and attaching to the veil keeps Thiovulum majus in a more or less fixed position in the water. And this location has the optimal concentration of both oxygen and sulfur.

High-speed rotating bacteria bring nutrients to the population

Now imagine, lots of Thiovulum majus bacteria live at this location of optimal oxygen concentration. At some point, the bacteria have used the available oxygen in that surrounding.

How to bring in new oxygen?

Looking at the Thiovulum majus bacteria, you can see that they have many flagella on their cell surfaces. And by rotating these flagella, the bacteria start to rotate as well. And by rotating the whole bacterial cells, the bacteria induce a water flow. This flow draws water from above towards the bacterial cells and the veil. And this freshwater brings a lot of oxygen to the bacterial population.

This rotation is incredibly fast and researchers studied this movement in the lab. They attached the bacteria to a glass surface and let them rotate. Through the rotation, it looked as if the bacteria formed little cells around them and they also pulled neighbouring cells close. This started to look like crystals of rotating bacterial cells.

This rotation of flagella lets Thiovulum majus swim with a speed of up to 600 μm/s. Don’t forget that Thiovulum majus is about 10 μm long. This means it can swim 60 times its own cell length in one second!

It’s as if you could swim about 100 m in one second. Yet, the World Record for swimming 100 m freestyle is currently at just below 45 seconds.

This high swimming speed makes Thiovulum majus the second-fastest bacterium that we know of. And this superpower explains why this bacterium is so powerful in inducing a water flow. With this constant mixing of water, the bacteria make sure they always have enough oxygen and nutrients to live.

Bacteria found ways to survive in different environments

I’m always impressed by the superpowers that bacteria have and their resilience. They learned to make the best out of each situation, found ways to use whatever they come across and adapted to live anywhere.

The question that remains now is: Why did Thiovulum majus become such a big bacterium? When they started using their rotating mechanism they brought in more nutrients. Did this help them become bigger because they had all the nutrients at hand?

Or did the bacterium grow big and then needed to find a mechanism to find and bring in more food? These are the kinds of questions scientists are probably looking into right now. And I can’t wait to learn the answer.

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

Even though about 70% of the Earth’s surface is covered by water, a majority of that water we cannot drink.

The water that is available to drink can also be contaminated with toxic chemicals or certain microorganisms that would sicken us.

But not all microbes are bad. In fact, many microbes are helping us save our planet. One way of doing this is by cleaning up our drinking water.

We don’t have enough clean freshwater

Everyone needs water to drink.

Humans can only drink freshwater, which makes up less than 3% of the world’s water supply. Freshwater is found in lakes, rivers, and streams. It is also locked away in the icecaps as glaciers, up in the atmosphere as water vapor, and deep in the soil as groundwater.

Of the small amount of freshwater easily accessible to us, we have used or contaminated much of that freshwater. Agricultural practices have diverted many sources of freshwater for animals and crops. Climate change and warmer temperatures cause farmers to use more freshwater resources as well. And global industrial practices can lead to toxic chemicals entering the environment and water.

This means that now we have less freshwater available to drink than ever.

We have learned ways to clean our drinking water, but this requires a lot of chemicals, energy, and money. Good thing microbes can help us decontaminate our drinking water in faster, easier, and cheaper ways.

Microbes clean water by filtering out bad bacteria

Drinking certain types of bacteria can make us sick. You have probably heard of outbreaks of E. coli or Salmonella leading to people being ill.

These microbes normally live in animals’ digestive tracks and are excreted in their wastes. They can enter the water system from runoff from farms, and ingesting them can make us really unwell. Luckily, microbes can help remove pathogenic bacteria from our water.

A simple method of water filtration includes having water flow over a bed of microbes and sand to remove any contaminates, called ‘slow sand filtration.’ At the top of the sand is a gelatinous layer of microbes, known as a biofilm. In such a biofilm live various bacteria, fungi, protozoa, archaea, and other aquatic microorganisms.

This layer is the so-called Schmutzdecke, which is German for “dirty layer.” As water flows over this biofilm, microbes in the Schmutzdecke trap and consume particles and pathogenic microbes. Every Schmutzdecke layer has a unique community of microbes based on the contaminants in the water. In this way, beneficial microbes remove harmful ones and decontaminate our drinking water.

Slow sand filters can purify away 90-99% of contaminating bacteria! The Schmutzdecke removes most of the fecal contaminating bacteria like E. coli. This system does not involve the use of chemical disinfectants, which can select possibly pathogenic bacteria that become resistant to decontamination efforts.

Also, the Schmutzdecke feeds on the microbes and organic matter found in the contaminated water. Hence, slow sand filters are a cheap and low-maintenance way to filter water in resource-limited areas throughout the world.

Microbes clean our drinking water by preventing bacterial build-up

The Schmutzdecke is an example of a community of microbes filtering water to remove pathogenic microbes and make the water safe to drink. But decontaminating water does not always need a whole community of microbes. Sometimes just one part of a microbe is enough to clean the water. In fact, researchers have found a protein from bacteria that can help stop bacterial contamination.

Pathogenic bacteria like Pseudomonas aeruginosa can contaminate water lines that carry water to homes and businesses. To let other P. aeruginosa know they have found a place to stay, bacterial cells send messages to each other in the form of chemical molecules. This communication system, called quorum sensing, allows bacteria to ‘sense’ the number of other bacteria, (a ‘quorum’) around them.

If enough P. aeruginosa cells grow in the same area and send the same message, they will start to form a biofilm. Just like the Schmutzdecke, biofilms act as a gelatinous layer and are difficult to break up. That’s where that special bacterial protein comes in to help stop biofilm formation.

This protein is called AiiA_DH82 and comes from the deep-sea bacterium Bacillus velezensis (DH82 strain). AiiADH82 binds and degrades the chemical messages that bacteria use to communicate with each other.

Without those chemical signals, bacteria do not know they should start forming a biofilm. Adding AiiA_DH82 to P. aeruginosa cultures decreased bacterial growth and significantly inhibited biofilm formation in P. aeruginosa-contaminated water. Scientists hope one day to apply the AiiA_DH82 protein to water lines and drinking fountains. In these, bacteria could group to reduce bacterial contamination and keep our drinking water safe.

Microbes clean our drinking water

People everywhere need clean water for cooking, cleaning, and drinking. However, clean drinking water is a limited resource. Toxic chemicals or pathogenic microbes can pollute our water. Current methods to purify water cost a lot of energy and money.

We are fortunate that microbes are here to help us clean up our water and our environment. As the global population increases, using microbes to clean drinking water is a cheaper, sustainable and more environmentally friendly way to produce the needed levels of clean water. A great example of how microbes are making our world better.

Along with microbes, we can save the planet!

Take away messages from this week’s article:

• Clean drinking water is a limited and necessary resource for everyone on the planet
• Microbes can clean polluted drinking water by reducing the growth of pathogenic bacteria
• Microbial decontamination of drinking water is a sustainable and inexpensive way to provide clean drinking water to our increasing global population

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

So, yes, also bacteria are always trying to find their siblings and communicate with them. And once they know they are not alone, they start reacting as a group.

Some bacteria start building biofilms – houses to keep the bacteria inside safe. Others like to talk to each other and produce goodies that everyone can enjoy. And other bacteria even form multicellular organisms with new superpowers.

Yet, some bacterial species like to move only in groups. Researchers call this bacterial movement twitching.

Bacteria can only twitch and move in groups when they have so-called twitching pili. Not all bacteria have these types of pili and – unfortunately for us – many bacterial pathogens produce them. And these bacteria use their pili to infect us and make us sick.

So, let’s have a look at what these bacterial pili are.

What are bacterial pili?

Bacterial pili look like little hair that grow out of bacterial cells.

This hair is anchored to the bacterial cell envelope and can be attached to any site of the bacterial surface. Some bacteria only have on pilus, others have two pili at opposite ends and some bacteria even produce bundles of pili that work together.

The pilus hair is a helix of an endless number of the same protein: the so-called pilin protein. This pilin works like a perfect puzzle piece: Each end of the pilin fits the next pilin piece. Like this, endless pilin puzzle pieces attach to each other in a circular manner and form a stable hair-like helix structure.

But not to lose their precious hair, bacteria need to attach the pilus to their cell envelope. For this, bacteria have a huge anchoring complex on the inside of their cell envelope. And this anchor holds the pilus at the correct location.

To make this pilus dynamic, bacteria link the anchor to a tiny motor. This motor has a ring shape that surrounds the anchor and thus the hair. And bacteria need this motor for the actual moving process.

How do bacteria move with pili?

This circular motor on the inside of the cell envelope has two main functions: to extend and retract the pilus. Endless circles of extending the pilus, attaching to a surface and retracting the pilus allow bacteria to move.

To extend or lengthen the pilus hair, the motor (orange) binds the pilin proteins inside the bacterium (grey circles) and transports them outside of the cell. This costs energy, which is why bacteria need this little motor. Hence, by adding more pilin protein to the pilus from the inside, the pilus hair (grey) extends towards the outside.

On the outside at the end of the pilus hair sits a protein (green) that can stick to surfaces. When this protein attaches to a surface, the motor on the inside of the bacterium changes its direction. Instead of adding pilins to the pilus and lengthening the hair, the motor takes pilins off the pilus and thus shortens the hair.

Now, the bacterium is attached to a surface while the pilus shortens. Like this, the bacterium pulls itself towards that surface.

This means that the attachment to the surface has to be so strong, that it can pull the bacterial cell towards this new location. This works like the bacterial superglue that some bacteria use to grow and survive.

What is the function of bacterial pili?

Bacterial pili can attach to all sorts of surfaces. Mainly, bacteria use this movement in environments of low water or on wet surfaces like human tissue.

For example, a bacterium can connect with its pilus to another bacterial cell. Now, when the bacterium retracts the pilus, it pulls the other bacterium closer. Like this, bacteria can form aggregates which helps them in the first steps of settling down and building biofilm houses.

Also, when several bacteria stick together and form bigger groups, they can move along a surface in a coordinated manner. This helps bacteria conquer new environments quicker and find new resources. For example, the bacterium Pseudomonas aeruginosa can reach out in swarms trying to find more space and new places to live in.

Interestingly, multicellular Myxobacteria move as huge cell aggregates to attack their prey. These bacteria use their twitching pili to glide along a surface, attach to a prey and pull the whole aggregate towards the prey. Like this, the Myxobacteria quickly run over their prey so it does not stand a chance.

However, bacterial pathogens also use pili to infect us. The bacterium Neisseria gonorrhoeae can attach its pilus to human epithelial and endothelial cells. When the bacterium then retracts the pilus, it pulls itself closer to the cell and attaches to it more tightly. Now, it can infect the cell and eventually the host.

But not all is lost with bacteria and their pili. Currently, researchers are trying to better understand how bacteria use their pili and how this machine works mechanistically. They will then try to find drugs that inhibit the pili. This could be an alternative way to inhibit bacterial pathogens and maybe even drug-resistant bacteria.

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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

And with an increasing global population, it will be important to find ways to increase the world’s food supply in sustainable ways.

Adding microbial communities, called biofertilizers, to soil can increase crop yield and plant health all without adding any toxic chemicals.

Lucky for us that microbes once again can help save our planet by addressing our global food crisis.

A global challenge

While the global population grows to almost 8 billion people, the land for agriculture remains limited. One way to meet this growing challenge is to increase the quantity of food produced on the same amount of land.

In the past, farmers added expensive chemical fertilizers to their crops. These meant to increase important soil nutrients – specifically nitrogen and phosphorus – and help the plants produce more food.

Unfortunately, these chemicals enter and pollute nearby water systems, harming our health as well as the health of our planet. Plus, producing these chemical fertilizers releases greenhouse gases that add to climate change.

One sustainable method to increase crop production is to add microbial communities to agricultural plants; so-called microbial biofertilizers.

Microbes as biofertilizers

These biofertilizers are soil microorganisms that provide nutrients, stimulate growth, and improve plant health. Also, biofertilizers are more sustainable, less toxic, and cheaper than traditional fertilizers.

Here, we will look at what biofertilizers actually do and how these microbes work for the plants.

Helping plants get nutrients

All living organisms need nitrogen, but not all nitrogen found in the soil is in a useable form. In fact, nitrogen is a major limiting nutrient for plants because most nitrogen in the soil is in a form that plants cannot use.

Hence, microorganisms first need to “fix” the nitrogen and then convert it into a usable form. For this, bacteria make an enzyme called nitrogenase that converts nitrogen from atmospheric nitrogen (N₂) to ammonia (NH₃). Now, plants can absorb this nitrogen form and use it for energy and growth.

Some plants have evolved to work with bacteria to make it easier for them to absorb the fixed nitrogen. For example, the roots of certain legume plants include special root nodules. In these live nitrogen-fixing bacteria called Rhizobia. When chickpea seeds were grown together with these bacteria, their yield increased 250%. Also, adding Bradyrhizobium species to mung bean plants promoted plant growth and yield and plants had a higher tolerance to insecticides.

Cyanobacteria also help plants fix nitrogen. When wheat plants grew together with cyanobacteria species Calothrix ghosei, Hapalosiphon intricatus, and Nostoc species, they grew higher and had more grain. Additionally, co-cultivation with Nostoc or Anabaena species resulted in increased root length and wheat plant nitrogen levels. Cyanobacteria are important nitrogen-fixing bacteria in aquatic environments too, especially for rice production.

Helping plants grow

Besides nitrogen, soil bacteria can provide plants with many nutrients, vitamins, and plant hormones. These are called phytohormones. Phytohormones promote plant growth by acting as signaling molecules to regulate plant metabolism and stress response.

When Rhizobia bacteria grew together with the mustard plant Brassica juncea and produced phytohormones, the plants grew better. Also, in corn (maize), inoculation with Azospirillum brasilense resulted in increased plant growth correlated with elevated phytohormone levels.

Over 80% of Rhizobia bacteria produce the major phytohormone indole-3-acetic acid (IAA). This phytohormone regulates plant growth, cell differentiation, and stress response. Thus, when bacteria secrete indole-3-acetic acid, it promotes root growth. This helps plants take up nutrients better.

In addition to a single bacterial species, communities of microbes help plants stay healthy and grow. Archaea, bacteria and fungi all associate with the roots of plants and synergistically provide nutrients to the plant. Researchers are studying these communities to understand important microbial interactions. The aim is to design microbial communities specific to each crop that promote higher crop production in the future. Just think, one day you could order a biofertilizer optimized for your unique climate, soil, and plant!

Fighting plant enemies

Not only do microbes provide their hosts with nutrients to promote growth, they also protect their hosts from deadly pathogens. Especially fungal pathogens are known enemies that threaten plants.

For example, Pseudomonas and Bacillus strains release toxic chemicals such as hydrogen cyanide to inhibit fungi that infect coffee plants. Other Bacillus strains produce antifungal molecules and simultaneously increase corn (maize) seedling growth. The bacterium Ochrobactrum anthropi TRS‐2 can fight fungi, and application of this bacterium on tea plants decreased brown root rot caused by the fungi Phellinus noxius.

Some bacteria even produce biofilms on the roots of plants as a barrier against invading fungal pathogens!

Agricultural crops are also prone to infection by nematodes, commonly called roundworms. Nematophagous bacteria can deter nematode growth by sending out toxins, and competing for nutrients. For example, Pasteuria penetransbacteria infects nematodes, while Pseudomonas strains can produce antibiotics against nematodes that infect potato plants. No matter the pathogen, soil bacteria have evolved ways to promote and protect their host plant.

Microbial biofertilizers assist our global challenge

As the world’s population increases, we will need sustainable and inexpensive ways to increase agricultural production. Just as microbes add nutrients and flavors to our meals, bacteria can nourish our crops as well. Plus, biofertilizers are a greener, healthier, and less expensive alternative to traditional chemical fertilizers.

So, next time you go out into your garden, think about adding some biofertilizers like compost or manure instead of chemicals to help your fruits and vegetables grow.

Along with bacteria, we can help save the planet!

Take away messages from this week’s article:

• The increasing human population is creating a global food crisis 
• Microbes can act as biofertilizers by providing important nutrients and helping promote plant growth
• Microbial biofertilizers are a sustainable and inexpensive way to increase global food production

The post Microbes as biofertilizers appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world