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.

The post How bacteria help feed the world by fixing nitrogen appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Yes, also plants have a lot of delicious and nutritious food for bacteria.

And just as bacteria can be good or bad for us and our bodies, bacteria can be good or bad for plants. Some bacteria help plants grow while other bacteria harm plants. These are the so-called plant-pathogenic bacteria.

These plant-pathogenic bacteria can infect plant leaves, roots or fruit. You might have seen weird spots on plant leaves or on crops or opened a spoiled piece of fruit.

You can imagine that some bacteria developed some really smart ways to live in or on our bodies. Similarly, some bacteria found methods to live and thrive in and on plants and protect themselves from their immune attacks.

This means that plant-pathogenic bacteria learned to recognise that they landed on plants, enter them and cause diseases to use the plant’s nutrients. But before any of that happens, let’s have a look at where plant-pathogenic bacteria come from.

How do bacteria land on plants?

Bacteria are everywhere around us. They live on almost any surface – be it alive or not – but also in the air we breathe.

And some bacteria even live in clouds or on sand dust. Hence, through rain or sand storms, these bacteria are transported to new areas and arrive on new soils.

Other bacteria use animals or little bugs to get transported. When the transporting animal comes into contact with plants, it can brush off the hitchhiking bacteria.

When a bacterium comes into contact with a plant leaf, it uses special adhesion proteins to link to the plant surface. These proteins bind specifically to proteins on the plant.

After this happened, some plant-pathogenic bacteria like Xanthomonas form biofilms. These work like slimy houses that surround the bacteria and protect them from weather, sunshine or drought.

So, for now, the bacteria are safe inside their biofilm houses. In there, they can grow and reproduce and get ready for their big attacks.

How do bacteria know when they arrived on plants?

Before launching an attack to infect a plant, the bacterium needs to know that it actually IS on a plant. And for that, some bacteria learned to speak the language of plants.

Yes, also plants send out words to tell themselves and other plants what is going. These words are chemical molecules. And some bacteria developed special antennae or receptors on their surfaces to bind these molecules.

This means bacteria can listen to and understand what plants say. And this tells bacteria that they actually arrived on a plant.

However, one bacterium cannot launch a plant-destroying attack by itself. It needs to know that it has support from its sibling bacteria. And for that, bacteria also talk to each other.

So, bacteria also send out words in the form of chemicals. And they listen to their own words so that they know that they are not alone. Now, they can start their attacks to make their way into the plant.

But plants also know how to protect themselves: Plants can interfere with bacterial chatter. For that, plants produce chemicals that bind these bacterial words. Now, bacteria cannot talk to each other anymore and think they are on their own, so an attack is probably not worth it.

And then there is the plant microbiome that protects the plant from bad things like harmful bacteria. However, plant-pathogenic bacteria learned to fight off the plant protection shields.

How do plant-pathogenic bacteria make their way into plants?

Even though plants have special protection mechanisms to keep bacteria from entering, plant-pathogenic bacteria found clever ways around them. Just as pathogenic bacteria can fight off our immune defences and end up making us sick.

As one way to protect against pathogenic bacteria, plants cover their surfaces with a waxy layer. This is a physical barrier for bacteria while it also prevents the water inside the plant from evaporating.

However, the bacterium Pseudomonas syringae developed its very own bacterial superpower to circumvent this barrier: This plant pathogen produces ice crystals even above freezing temperatures.

These ice crystals harm the waxy layer, cut open the plant envelope and cause the so-called frost injury. With such an injury, the plant loses water and the bacteria can enter the plant through the open wound.

Other plant pathogens move specifically towards the stomata on the surface of plants. These are the gates that let gases like carbon dioxide enter the plant. And interestingly, these bacteria produce certain chemicals that keep these gates open so that the bacteria can enter the plant.

Once the bacteria are inside the plant, they can start their attacks. For this, they use special bacterial weapons that transport toxins into the plant. These toxins then disrupt the plant from functioning properly and make them sick.

So, just as pathogenic bacteria learned to bind to and enter our human bodies, plant-pathogenic bacteria developed mechanisms to specifically enter plant organs. Hence, one goal of researchers is to understand how bacteria achieve this. The idea is to create plants that are resistant to plant-pathogenic bacteria.

The post How plant-pathogenic bacteria understand plant language and make them sick appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

How are they aware of their bacterial neighbours? 

They cannot see them or hear them. 

But do bacteria talk to other bacteria?

Yes, they do!

Like humans, bacteria talk to each other and socialize. But obviously, they cannot send messages or call each other. They have completely different communication channels that are not based on words.

So how do bacteria speak to other bacteria and even interact with them? 

They use special molecules. Researchers call these kinds of molecules extracellular signalling molecules. This means, bacteria produce these molecules and send them outside of the cell (extracellular). There, they can be a signal to other bacteria.

Microbiologists call this phenomenon quorum sensing. This means that a bacterium “senses” its “quorum”. A quorum means the number of other bacteria in the surrounding. Hence, with quorum sensing, a bacterium knows exactly how many other bacteria are nearby. 

The next step is then population-density dependent cell-to-cell communication. This fancy term means that only when enough bacteria are together (a high population), do they talk to each other (cell-to-cell communication).

But why is it important to bacteria to have all this bacterial chatting going on? Do they not like being lonely?

Why do bacteria need to talk to each other?

A community is always stronger than an individual. And the same is true for bacteria.

Many bacteria together can face the harshest environmental challenges. We also discuss the power of microbial communities when talking about multicellular organisms. 

But by using quorum sensing, bacterial cells are still individual cells. Yet, they act and react as a community; a real microbial community.

Bacteria have been using quorum sensing for millions of years. And it did shape evolution because bacteria learned to include others in their decision making. 

When bacteria face harsh conditions, they use quorum sensing to tell other bacteria in the surrounding that they are not alone. And as a community, they coordinate and tackle that challenging condition together. Therefore, bacteria developed mechanisms that respond to quorum sensing. 

For example, only when many bacteria live in the human body do they produce toxic virulence factors to make us sick. 

The same is true for biofilms. Bacteria only build their biofilm houses when they have other bacterial neighbours. 

On the contrary, a bacterium knows it is completely alone because no quorum sensing is happening. And when the bacterium also has no food, it might decide to sporulate. With this, the lonely bacterium assures to survive on its own until better times come.

Yes, quorum sensing controls a lot in the bacterial life, so how does this important mechanism actually work?

How does quorum sensing work? 

It all starts with one bacterium. 

One bacterium that produces these special quorum-sensing molecules. Researchers call these molecules autoinducers. And the bacterium sends these autoinducers out into the environment. We call this bacterium the sender.

Now, when another bacterium from the same family is nearby, it can recognize the autoinducer. This bacterium is the recipient. Both bacteria have specific receptors on its surface to which the autoinducer binds. 

Next, the recipient takes up the autoinducer. Inside the bacterial cell, the autoinducer can regulate genes. But only, when the amount of autoinducer inside the bacterium is high. 

Hence, when one bacterium sends out autoinducers, the recipient can only take up a few autoinducers. And these few molecules are not doing much on their own.

But now imagine, there are a hundred bacterial cells around. And each of them produces a few autoinducer molecules. Now, all recipient bacteria take up a lot of autoinducers. And a lot of autoinducers inside a bacterial cell start controlling genes. 

All these autoinducers can trigger the bacterium to produce nasty virulence factors or biofilm.

Therefore, with many bacteria around, they produce a lot of autoinducers and more bacteria take them up. Thus, more bacteria listen to each other. And then they produce more autoinducers and send them to the surrounding. Like this, they start chatting and making decisions together.

But what if the chatting bacteria are from different families? Do they still understand each other?

Is quorum sensing a microbial language? 

Researchers found that many bacteria use autoinducers to communicate with each other. And they also found that not all bacteria use the same autoinducer to communicate. 

It is like speaking different languages. 

And interestingly, some bacteria only produce one autoinducer. This is as if they only say one word. All the time.

And other bacteria produce several different autoinducers. So they speak several different words.

Imagine in a mixed microbial community. Different microbes produce hundreds of different autoinducers and send them to the environment. This means hundreds of different words spoken. Therefore, hundreds of different conversations and as such, a lot of chatting going on. 

But all these conversations are not always friendly. In some bacteria, quorum sensing also controls killer weapons. As soon as bacteria “hear” via the quorum sensing channel that other bacteria are around, they turn into fighters to kill the neighbour bacteria. 

As such, quorum sensing as a microbial language can lead to cooperation or competition between bacteria. And bacteria always try to adapt to new conditions. Therefore, by listening and responding to other bacteria, they developed new mechanisms. This is why quorum sensing played such an important role throughout evolution.

Where can we see bacteria talking in real life?

Scientists can see quorum sensing in the lab all the time. Often they grow bacteria in liquid in a glass flask. At the beginning, the bacteria are not many, so nothing happens.

After a while, bacteria grow in the flask and become a lot more cells and they do quorum sensing. And many bacteria start to produce colourful molecules as a response of quorum sensing.

For example, the bacterium Vibrio fischeri starts producing bioluminescence. Hence, the liquid with the bacteria starts to glow.

And these bacteria also use bioluminescence in nature. The Vibrio fischeri bacteria usually live inside the so-called light organ of the bobtail squid.

And at night, the bacteria grow and divide and do quorum sensing inside the squid. After a while, the bacteria start producing bioluminescence and the squid shines light towards the seafloor. Like this, it looks as if the squid is not present as it does not throw a shadow anymore.

With this mechanism, bacteria help the squid to survive at night. And all this through quorum sensing.

Quorum sensing – a fascinating language

Did we just convince you once again how amazing bacteria are?

Do you also think that quorum sensing is a fascinating language?

And is it not remarkable how bacteria can talk to each other and help each other?

So, yes, we think so. With this amazing mechanism, bacteria know they are not alone. And they can launch an appropriate response to an incoming signal. Just as you say “yes?” when someone calls your name. 

However, bacteria have their own language. And we are still learning to understand it.

The post Quorum sensing – or how bacteria talk to each other appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Do bacteria always only live in one form; either they are single cells or multicellular?

How do we distinguish between unicellular and multicellular bacteria?

Which advantage do bacteria gain from sticking together and forming multicellular organisms?

What are some examples of multicellular bacteria?

In this article, we will answer exactly these questions!

Let’s dig in!

What makes multicellular bacteria?

Scientists define multicellularity as a form of “biological organisation in which a permanent cell aggregate exhibits an activity more complex than that of the individual cells“.

This means that multicellular bacteria are only present in their multicellular forms. True multicellular organisms cannot go back being single-celled.

Hence, bacterial biofilms are no true multicellular organisms. Bacteria can decide between these two lifestyles; they actively produce the biofilm when needed and they break it off and become single cells again.

Also, a bacterial colony in a petri dish is not a multicellular organism. In a colony, a bunch of bacterial cells grow on top of each other. But the cells in the colony are not organised and they do not function in an organised manner.

Multicellular bacteria are organised

The difference here lies in the term biological organisation. Multicellular bacteria are organised due to two different concepts:

They work in an organised manner; bacteria within the multicellular organism need to communicate with each other. Thanks to communication, every bacterium within the organism knows what is going on, so it can react in an organised manner.

Just as when your stomach is empty, it tells your brain that you’re hungry and you react accordingly by eating. Your stomach and your brain are communicating with each other.

The second way to organise multicellular bacteria is by using different functions to advance the whole organism. Within a multicellular organism, some bacteria undergo a process called cell differentiation. Cell differentiation is what makes a human stem cell develop into a skin cell or a blood cell. And this skin or blood cell has more specialised functions than the stem cell that it was before.

The same can happen in multicellular bacteria. Some bacteria develop into specialised cells. These specialised bacterial cells have functions that other cells (or the single version of the bacteria) do not have.

Now, some of the bacteria have additional functions or abilities. And thus, the whole multicellular organism gains new bacterial superpowers that can advance the organism.

Why do bacteria form multicellular organisms?

Here, evolution plays a massive role since multicellularity has so many advantages.

In multicellular organisms, the labour is divided. Just as it is easier for you and your co-workers to work in a team with everyone doing what they are best at. With bacterial cells taking on new functions through cell differentiation, the whole organism profits.

Another advantage is that when bacteria cluster together, they can protect their core. And some multicellular bacteria keep their spores within the core for protection. Like this, their most vulnerable members are protected.

Also, multicellular bacteria are generally bigger than single bacterial cells. This makes it more difficult for attackers to prey on this organism. And we know how much bacterial warfare is going on in the microbial world.

What are some cool examples of multicellular bacteria?

Researchers have not found that many yet. But those multicellular bacteria, that they started to investigate, are pretty cool.

Well, that’s what I think, but see for yourselves.

Multicellularity in chains: filamentous cyanobacteria

Filamentous cyanobacteria are Earth’s oldest multicellular organisms. And thanks to them, we have all this precious oxygen on our planet.

Some cyanobacteria form long chains, so-called filaments. In such an organisation, the whole chain of cyanobacteria is surrounded by one common outer membrane. This means, that all cyanobacteria cells within the filament share one periplasm. And they use this periplasm to communicate with each other and exchange nutrients.

Also, filamentous cyanobacteria like the Anabaena species can undergo cell differentiation. In the picture above, you can see a chain of Anabaena cells. Some cells are smaller, which are the undifferentiated cells, and some are bigger blobs.

The normal-sized cells have photosystems and they perform photosynthesis to produce oxygen.

But when cyanobacteria do not have enough nitrogen, they start to differentiate into those bigger cells, so-called heterocysts. And these heterocysts are now able to fix nitrogen. This helps the organism with its nitrogen limitation.

The reason why Anabaena needs these two cell types is because the chemical processes of oxygen production and nitrogen fixation interfere with each other. They can not happen within one cell, which is why cyanobacteria need to have a different cell type for each process.

In the end, the cells share the produced oxygen and the fixed nitrogen with the whole filament. So everyone is happy with this arrangement.

Multicellular bacteria as electricity producers: cable bacteria

Cable bacteria form – similarly to cyanobacteria – long filaments that are surrounded by one common outer membrane. And they use this arrangement to transport electrons and conduct electricity.

We talked about multicellular cable bacteria in detail in the article Cable bacteria – unusual microbes conducting electricity. Head there to read about this special kind of multicellular bacteria.

Multicellular organisms in cell aggregates: Myxobacteria

Some bacteria, like the well-characterised Myxobacteria, can form huge cell aggregates of up to 100’000 cells. These cell aggregates are called fruiting bodies and their main function is to feed and transport their spores.

The spores have a special place within the Myxococcus fruiting body: They are kept at the core of the fruiting body. Here, they are safe and protected from the surrounding.

Interestingly, myxobacteria are also known as wolf-pack predators, because of the way they attack their preys. They kill their preys by launching a massive attack and secreting lethal bacterial toxins. This kills the prey instantly and the whole fruiting body can feed on the prey.

Multicellular organisms forming hyphae networks: Streptomyces bacteria

Streptomyces bacteria develop a complex network of hyphae within the soil. With this network, Streptomyces bacteria can branch into different directions and elongate the branch tips.

Within the branches, some hyphae within the soil have secluded compartments with walls to separate them from the rest of the network. Yet, Streptomyces uses the hyphae to transport nutrients and chemicals and to communicate.

But when nutrients are missing, the branches grow out of the soil and into the air. Here, they form spores and produce geosmin and antibiotics. This geosmin attracts insects that distribute the spores in the environment.

Plus, by producing antibiotics, Streptomyces tries to kill those microbes that want to eat the spores.

The superhero of multicellularity: Magnetotactic multicellular prokaryotes

Ever since I heard about these bacteria, they became my favourites. And not only because these multicellular bacteria cannot even survive as single cells.

All cells within the magnetic berry are connected to a common core. On the outside of the berry, bacteria have flagella.

And because many of these bacteria assemble together and each one has several flagella, the whole berry is basically covered in bacterial flagella. When all of these flagella start rotating together, the whole berry becomes incredibly fast.

The second feature is, that these magnetotactic bacteria sense the Earth’s magnetic field lines thanks to their magnetosomes. Hence, this magnetotactic superorganism is even more sensitive to the Earth’s magnetic field, which gives it probably even more superpowers.

Lastly, the multicellular magnetotactic bacteria respond to blue light and swim away from it. This is a completely new bacterial ability and researchers are still not sure why these bacteria do that.

Unfortunately, we do not know much about these fascinating organisms, because they are incredibly difficult to grow in the lab. Until now, researchers could only image these bacteria from environmental samples as they still do not know what these bacteria need to survive in the lab.

Multicellular bacteria – an advanced lifestyle

As we have seen in this article, bacteria can grow either as single cells or as multicellular organisms.

By teaming up with their sibling cells, multicellular bacteria gain new superpowers, they can spread out and protect their weakest team members.

From an evolutionary point of view, forming multicellular organisms was a super important step. Only thanks to this, highly-developed animals with all their different cells and organs could develop.

The post Together we are strong – bacteria form multicellular organisms appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

What is bacterial sporulation?

When a bacterium sporulates, it transforms from a rod-shaped bacterial cell (4-10 μm long) to a round, spherical spore (1-1.5 μm long).

Bacterial spores are surrounded by thick layers of cell wall material or peptidoglycan and many layers of proteins. These make the spore highly resilient and shield it from all kinds of environmental assaults, including UV radiation, desiccation and antibiotics. Within the spore, it protects the genetic material of the parent bacterium.

Now the spore is metabolically dormant. This means that the cell has stopped all activities which require energy, like growth and development.

Spores can remain stable for extremely long periods of time. In fact, researchers found Bacillus spores dating back almost 25 million years in the abdomen of extinct bees preserved in Dominican amber. Other samples date back 250 million years from salt crystals.

Why study sporulation?

To date, most studies aim to understand sporulation in the model bacterium Bacillus subtilis. Bacillus subtilis is a Gram-positive bacterium with a thick layer of peptidoglycan outside the cellular membrane.

One of the major reasons why is it relatively easy to study sporulation in Bacillus subtilis is its natural ability to take up foreign DNA and integrate it into its genome. This provides scientists with a wide range of tools for gene editing in Bacillus subtilis. And they can study the functions of different molecules in space and time during sporulation.

Some bacterial spore-formers can also be pathogenic in a human or animal host.

Examples include Bacillus anthracis (the causative agent of anthrax), Clostridium difficile (implicated in colon disease) and Clostridiumm botulinum (implicated in food poisoning). Spores of these pathogenic bacteria can secretly survive inside the host due to their ability to withstand harsh environments. But once they get access to nutrients, they germinate again and become viable bacteria. These bacteria can then release lethal toxins to cause diseases in their respective hosts.

There is some good news for the food lovers too though! Spores of a strain of Bacillus subtilis, Bacillus subtilis (natto) are used to ferment soybeans in a traditional Japanese dish called natto. The critical process in natto preparation is the germination of spores which then use nutrients from the soybeans to ferment them. The dish with its powerful smell and flavor is definitely for the bold!

How does sporulation work?

Normally, a bacterial cell divides in the middle to produce two identical daughter cells. Researchers call this process binary fission or vegetative growth.

But when a bacterium sporulates, the cell divides closer to one end of the cell, near a pole. This leads to the formation of two daughter cells of different sizes. The smaller cell is the forespore and the larger cell is the mother cell.

The two cells are separated by a wall made by the invagination of the cell membrane and the peptidoglycan. This wall is the septum.

Cell division leads to separation between spore and mother cell

Surprisingly, the wall separating the two daughter cells is almost four times thinner during sporulation than during vegetative growth (~22 nm vs ~80 nm).

Scientists have always wondered why the cell would need a thinner septum during sporulation. One reason can be that the forespore and the mother cell need to communicate with each other and exchange certain metabolites. A thinner septum can make this a lot easier because channels don’t have to go through a thick wall.

Another reason could be that the thinner septum is likely more flexible and easier to bend and stretch. Hence, the mother cell can move forward to engulf the forespore so that it is completely inside the mother cell.

Transporting DNA into the spore

When a bacterial cell divides vegetatively, it splits the bacterial DNA equally into two daughter cells.  But an interesting phenomenon occurs during sporulation.

The DNA is trapped at the septum such that the forespore has only 1/3^rd of the DNA and the remaining 2/3^rd stays in the mother cell. A transporter then pumps the rest of the DNA from the mother cell to the forespore.

Packing the whole DNA into the small volume of the forespore probably increases the turgor pressure in the forespore. Hence, the forespore inflates like air in a balloon to give it an ovoid shape.

Bringing the spore inside the mother cell

A critical process during endospore formation is when the mother cell engulfs the forespore. This means that instead of lying side by side, the forespore is now within the mother cell.

To engulf the forespore, the mother cell has to overcome two barriers:

(1) the peptidoglycan that surrounds the bacterial cell on the outside (shown by blue circles in the figure below), and

(2) the septum (also peptidoglycan) that separates the two cells (shown by green circles in the figure below).

But the septum and the bacterial cell envelope are also connected. At this so-called leading-edge the two peptidoglycan structures meet. Here, critical activity happens.

First, enzymes within the forespore (denoted by ‘1’ in the figure) make a new bond with the cell wall ahead of the leading edge. With a new bond between the two, the old bond is no longer needed. Thus, enzymes in the mother cell break this old bond (denoted by ‘2’ in the figure).

Like this, the mother cell can slowly move around the spore until it completed warps around it.

Wrapping the spore in a thick coat

Once the mother cell engulfed the forespore completely, the spore needs to mature. For this, the mother cell builds thick and protective layers around the spore to protect it from the environment.

Ultimately, the mother cell lyses and dies and releases the mature spore into the environment. Only when the environmental conditions become favourable again, spores germinate and normal vegetative growth cycle starts again. 

Bacterial sporulation – a tightly regulated process

Although the process of sporulation sounds pretty simple, it can be extremely challenging to comprehend from the point of view of the bacterial cellular machinery. More than 500 genes are active only during sporulation. And these are not active during vegetative growth.

Also, some genes are only active in the mother cell and others only active in the forespore. And each stage of spore formation needs to be tightly regulated!

The studies of spore formation in Bacillus subtilis have undoubtedly increased our appreciation of what else bacteria are capable of.

However, there are still many unanswered questions and unknown genes during sporulation that we need to study.

Also, we need to expand these studies to understand sporulation in pathogenic spore-formers like Clostridium difficile and Bacillus anthracis so that we can develop treatments for these disease-causing organisms!

Recent sequencing analysis of the human gut microbiota also indicate that around 50-60% of bacteria in a healthy host intestine are spore-formers. But we still don’t understand the functional and physiological relevance of the majority of them.

There is definitely lots to explore and understand about this one-of-a-kind process of sporulation in bacteria!

The post Sporulation in Bacillus subtilis: A strategy for bacterial hibernation appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Gladly, we learned to use some of these bacterial superpowers to improve our own lives. This means that bacteria and their superpowers are pretty much everywhere you look. You can find their impact in the food you eat, the medicine you take or the bioplastics you use.

So, yes, you probably use microbes and their superpowers daily without even realising. In this article, we listed 20 of the most fascinating bacterial superpowers and how they help not only bacteria but also us.

Bacteria know exactly where they are going

Bacteria have a so-called flagellum with which they can swim in liquids. This flagellum works together with the super responsive chemotaxis system.

This fascinating mechanism helps bacteria understand where beneficial nutrients or harmful compounds are. The bacterium then decides to swim towards or away from that compound. Chemotaxis is thus essential for the survival of bacteria.

Read Chemotaxis helps bacteria move towards goodies

Bacteria are high-speed swimmers

With the above-mentioned flagella, bacteria can move in liquids. When they rotate their flagella, they can swim in one direction which helps them find nutrients or escape harmful situations.

Interestingly, the Olympic recordist for 50 metres freestyle swims 1.17 body lengths per second. However, the bacterium Escherichia coli swims 15 body lengths per second and the tiny Bdellovibrio bacteriovorus swims even 10x faster, moving 160 body lengths in one second.

Read Bacteria wrap themselves in their swimming flagella

Floating veils for large bacteria to attach to and fetch nutrients

Bacteria produce oxygen and give superpowers to everyone

This may sound a little trivial because we take oxygen for granted. But bacteria known as cyanobacteria first produced oxygen on this planet. A large part of the atmosphere’s oxygen today is produced in oceans by these bacteria and other single-celled organisms.

You can also find more on cyanobacteria in this article.

Bacteria can produce electricity

Some bacteria can align into long filaments – so-called cable bacteria. This alignment allows bacteria to produce electrons on one side by oxidizing metals. They can then transport the electrons along the filament. Bacteria on the other side of the filament use these electrons for oxygen reduction.

Thus, bacteria produce an electric current within certain water sediments, which researchers measured. Maybe one day they can use these filaments in some kind of seawater-based batteries.

Read Cable bacteria – unusual bacteria conduct electricity

Bacteria use superpowers to align to the magnetic fields

Some bacteria, like the Magnetospirillum, that live in water, have so-called magnetosomes. These are storage units for iron crystal-like structures. The iron inside can align with a magnetic field and even along the magnetic Earth field.

These aligned magnetosomes then give magnetic momentum to the bacterium. Based on that, the bacterium aligns itself with the magnetic field and can find an optimal location in its environment.

Read How bacteria read and follow the Earth’s magnetic field

Bacteria can reduce and produce gold – highly valuable bacterial superpowers

In gold mines in Australia, researchers found bacteria that form biofilms on gold particles. For example, the bacteria Delftia acidovorans and Cupriavidus metallidurans can reduce toxic gold-ions to elementary gold.

This means that these bacteria are directly involved in the biogeochemical cycling of this precious metal.

Bacteria kill their competitors

To survive and grow, bacteria have learned to outcompete other bacteria and microbes. For this, they developed fascinating nanoweapons that kill their competitors and leave them as the sole survivor.

Interestingly, there are several different of these bacterial nanoweapons, all working slightly differently. Read more about this bacterial superpower:

Bacterial killer weapons as biocontrol to protect plants

Nanoweapons make the killer differences in bacterial siblings

Understanding the type 6 secretion system spike of a bacterial killer machine

Bacteria and contact-dependent growth inhibition: Death on a stick

Bacteria have various superpowers to protect their hosts

Microbes and bacteria live in and around bigger organisms like the human body, plants or animals. They developed fascinating mechanisms to protect their hosts and support them in different ways.

Bacteria might help them digest food, help them grow or fight off harmful intruders. For example, our bodies would not work without the microbiome – all those microbes and bacteria in and on us. Read more about the human microbiome:

How bacteria in your gut microbiome defend pathogens

Bacteria on your hands strengthen your unique skin microbiome

“Follow your gut instinct” – how your gut microbiome influences your mental health

How a healthy gut microbiome protects you and how to keep its superpower

Bacteria and their superpowers light the way

Some bacteria have the superpower to produce light in a process called bioluminescence.

Interestingly, bioluminescent bacteria often live with other organisms in symbiosis. For example, some bioluminescent bacteria occupy the lure of the female anglerfish. This fish also uses them as a fishing rod for hunting.

Bacteria withstand heat and cold

Whether too cold or too hot. Some bacteria really don’t care.

Certain bacteria can survive at temperatures as low as -20°C, which is why they are called hypothermophiles. On the contrary, other bacteria live in hot water steams up to 122°C. Similarly, these bacteria are hyperthermophiles.

These extremophiles have special repair enzymes to keep their DNA and cell envelope intact even at such extreme temperatures. Consequently, some of these enzymes are being used in research and are daily tools in each research lab. Learn more about extremophiles:

Even at the dark and cold bottom of the sea, microbes flourish

Bacteria tolerate harmful radiation

Another extreme-loving bacterium: the radiotolerant Deinococcus radiodurans. This bacterium has very efficient proteins to protect its DNA. Plus, it produces special DNA repair machines. They super quickly recognize and repair any damage in the DNA after exposure to radiation.

With these mechanisms, these extremophiles can survive exposure to ionizing radiation. Some bacteria even survive in the cooling systems of nuclear reactors.

Bacteria go to sleep by forming spores

Some bacteria can form so-called spores which are bacteria “on hold”.

Bacteria go into this state in times of greatest starvation or drought. Their aim is to keep its genetic material safe while turning down all non-essential functions. In this state, bacteria do not have an active metabolism nor do they interact with the environment. They solely wait for better times to come until nutrients become available again.

Bacteria produce some of our favourite foods

Did you know that bacteria produce many of the foods you are consuming? By fermenting sugars to alcohols or acids, lactic bacteria and some yeasts give a delicious taste to common foods like cheese, yoghurt and kefir, kombucha, kimchi and sauerkraut, beer and wine, as well as chocolate.

Reason enough to be grateful for bacterial superpowers to produce amazing foods.

Bacteria can endure high pressure in the deep sea

Researchers found bacteria that can live up to 10 km deep inside the ocean. Yes!

This means these bacteria can endure pressures of up to 100 MPa. But, researchers don’t know yet how these bacterial cells function at such high pressure. However, they think that the proteins inside these bacteria form some kind of super glue-like complexes. This would then make the bacterial content more viscous to endure the pressure.

Read Even at the dark and cold bottom of the sea, microbes flourish

Bacteria produce oil

Many microorganisms, amongst them bacteria, produce natural oils which is why they are called oleaginous microorganisms. Mainly algae, bacteria and yeasts can produce biodiesel, while fungi, and some algae can produce healthy omega-3 fatty acids.

Now, researchers focus on engineering these organisms to enhance the accumulation of produced lipids, biodiesel and omega-3 fatty acids.

Bacteria repair their DNA super efficiently

Bacteria have to endure all sorts of environmental stresses, for example, temperature changes, antibiotics or challenges by competitors. To ensure that under all circumstances, their DNA remains undamaged after an attack, bacteria developed incredibly efficient DNA repair and fixing machines. These machines recognise any small damage in the DNA.

Read

How does Salmonella deal with stress – a journey through the human body

Bacteria destroy proteins to understand the environment

Bacteria nucleate ice and let it rain

Some bacteria can trigger water to form ice crystals at temperatures close to the melting point. One of these bacteria is Pseudomonas syringae.

This bacterium has special proteins on its outer surface that interact with water and triggers ice formation. These bacteria are even used to produce artificial snow in winter sports areas around the world.

Bacteria keep our environment clean

Some bacteria surely love their heavy metals! Many bacteria have special enzymes to reduce toxic metal ions. These bacteria are even used to clean waste in industrial waters or mines and are the basis for green chemistry.

Read Microbial bioremediation: microbes cleaning-up our toxic messes

Bacteria can change our blood types for a short amount of time

Some bacteria live in our blood and when they get hungry, they start cleaving off sugar molecules from our red blood cells. While this is not harmful to us at all, in clinical tests, this may look like a different blood type than our original one.

However, as soon as the body produces new blood cells, they will have our original sugars and therefore our normal blood type.

Read Bacteria changing blood types

Some bacteria are super small

Super small but super powerful!

While bacteria have all these superpowers, I am most amazed by the fact that they are so tiny and yet SO powerful. All these superpowers in such a small box!

To actually see bacteria, we need microscopes. And to have really good photographs of them, we then need EXTREMELY good microscopes. Look at the bacterial cells in the pictures here! They are just about 2 micrometres long…

Thank bacteria and their superpowers

After having read this list of bacterial superpowers, are you even more amazed by our bacterial friends now? Which of these bacterial superpowers is your favourite? Which of them would you like to learn more about? Let us know in the comment section below or send us an email with your question. We’re looking forward to hearing from you!

The post The incredible superpowers of bacteria: unveiling nature’s tiny heroes appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

And this process is very interesting to researchers. It tells them how bacteria move in the environment, advance their populations and evolve in general. So, here we explain one mechanism of how bacteria break biofilms.

The bacterium Desulfovibrius vulgaris likes water pipes

As you might know, bacteria are basically everywhere. And they like to build their biofilm houses on pretty much any surface they can find. Be it in or on our bodies or somewhere in nature and the environment.

For example, the bacterium Desulfovibrio vulgaris likes to live on metallic surfaces in the soil. These could be water systems or pipelines that are wet and warm.

Here, the bacterium builds its biofilm house to be protected from the surrounding. Now, Desulfovibrio vulgaris can use the metal from the pipe to gain energy, so it “breathes” the metal. But this metabolic activity leads to the metal pipes corroding or rusting.

And when these metal pipes start corroding, they stop functioning properly which can lead to some serious health issues. So, researchers decided to look into how these bacteria build and break their biofilms.

Bacteria build and break biofilms

The researchers looked at the genes of Desulfovibrio vulgaris with bioinformatic tools. And they found some genes that the bacterium uses to produce less biofilm. Researchers already know some of these genes from other bacteria. Here, these genes also prevented the bacteria from producing a lot of biofilm.

So, the researchers decided on one of these genes and looked at them in more detail. They found that the gene produced a specific enzyme, which is a protein with a special activity.

And in this case, the enzyme’s activity was that it works like a scissor and breaks the biofilms of Desulfovibrio vulgaris. But the researchers also found that this scissor can break the biofilms of other bacteria.

Scientists have always tried to find some kinds of scissors in bacteria that can break biofilms. However, they usually focused on biofilms formed by bacteria in hospital settings. Now, they finally found a new pair of such scissors made by bacteria that live in the environment.

Why do bacteria produce scissors?

Do they not like living in their biofilm houses?

To answer this question, we need to understand that the bacterial biofilm lifestyle works as a cycle. Bacteria build biofilms and use them as houses. As soon as nutrients are scarce or there are too many bacteria within a biofilm, some bacteria break the biofilms to cut themselves loose.

For this, bacteria need to break down parts of their biofilm houses for which they use their special scissors. After cutting themselves free from the biofilm, they start swimming and looking for a new place to live. Once they found it, they will settle down and build a new biofilm house.

By discovering these new kinds of scissors, scientists now have novel tools to combat bacterial biofilms. These tools could inhibit bacterial biofilms in many different settings like the environment or in hospitals.

The post Bacteria breaking free from home appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Yes, you read correctly.

So-called cable bacteria transport electrons from cell to cell over centimetre-long distances and thus conduct electricity.

Mind-blowing.

It all started when in 2001, researchers measured electric currents in aquatic sediments. Soon afterwards, they found that this current is due to specific bacteria that exchange electrons with the surrounding.

And they called these bacteria cable bacteria.

So, let’s look at these fascinating species in more detail.

What are cable bacteria?

Cable bacteria are multicellular bacterial organisms meaning many bacteria from the same family are living very closely together. They usually share the same food and nutrients and help each other out. This tightness makes the whole bacterial community stronger and often gives them new superpowers – like in this case, the multicellular cable bacteria can conduct electricity.

Until now, researchers do not know much about cable bacteria, as they usually live in marine, freshwater and salt-marsh sediments. Here, they often use unusual components like sulfur or sulfur complexes to gain energy and grow. Such conditions are pretty difficult to imitate. So currently, researchers are struggling to grow them in a lab.

However, recent studies managed to find out what cable bacteria look like and how cable bacteria conduct electricity.

What do cable bacteria look like? 

For this, researchers took water samples from different locations. They then visualised the cable bacteria with different spectroscopic techniques. With these machines, researchers can magnify the tiniest things and get high-resolution pictures of bacterial cells.

Within these pictures, they actually saw that one “cable bacterium” is a multi-cellular microorganism. In the pictures below, you can see long chains or cables. Interestingly, these are completely surrounded by isolating walls. And within these cables, you can see single compartments, which are the bacterial cells.

These cables or chains, researchers call filaments and they can get up to 7 cm long.

What are cable bacteria made of?

Researchers are still trying to classify the family of cable bacteria. However, they know so far that cable bacteria are rod-shaped Gram-negative bacteria. This means these bacteria have an inner and an outer membrane as a surrounding and protecting wall.

Generally, between the inner and outer membrane is a liquid space that is the periplasm. This space kind of works as a flexible and soft buffer zone between the two membranes.

However, in cable bacteria, one bacterial cell is surrounded by an inner membrane to protect its cellular content. Then these cells arrange into a chain and share one common liquid periplasm. Next, one common outer membrane surrounds and stabilizes this bacterial-cell-periplasm chain. So, one outer membrane isolates the whole bacterial chain from the outside.

The whole chain is further held together by so-called fibres. You can see these fibres as those long dark grey lines in the pictures above. These fibres go along the cells through the whole periplasm of the cable filament. Researchers think, that these fibres give the cable its structure, stabilise the cable and protect it from breaking. 

As you can see, this whole structure indeed looks like a cable and insulate the bacteria on the inside from the outside. That’s pretty much where these bacteria got their name from. 

How do cable bacteria transport electrons and conduct electricity?

And why would they even create an electric current?

The short answer is to survive. As always, all organisms just want and need to survive.

So, let’s look at this in more detail.

Cable bacteria live in water sediments. These waters are full of oxygen in the top layers close to the surface. And they are full of sulfur in the deeper layers.

And cable bacteria use this oxygen-sulfur gradient to conduct electricity.

Cable bacteria now actually sense the oxygen in the water and align perpendicular to the waterfront. This means one end of the cable is in the oxygen-rich area at the top and the other end in the sulfur-rich area towards the bottom. Similar to the model below.

Bacteria breathe sulfur and conduct electricity

Now the filament works as a half-cell.

The bacteria in the deeper layers “breathe” the sulfur. This produces electrons (e^–) and protons (H⁺) as an anodic half-reaction. These electrons then travel along the cable within the liquid periplasm to the upper part of the cable. Here, the bacteria consume these electrons to reduce oxygen in a cathodic half-reaction.

These oxidation and reduction processes are part of each cell’s metabolism. So, this is what keeps every cell alive.

However, usually, both reactions happen within the same cell so that one cell gains energy from both reactions at the same time. Interestingly, cable bacteria found a way to uncouple the oxidation and reduction reactions.

Hence, oxidation and reduction mechanisms happen in different cells – one reaction in cells at the bottom of the cable, the other reaction in cells at the top of the cable. Yet, they somehow learned to do both reactions within one system – the cable. And this is the mind-blowing part.

What does it mean for the environment?

This unusual metabolism of cable bacteria has some interesting effects on their surroundings. These reactions produce protons in the deeper water layer and reduce them in the surface layer. This leads to a drop in pH in the deeper layer and an increase in the pH near the surface. This can mineralise and demineralise metal complexes. 

Researchers suggest that these (de-)mineralisation processes also have an impact on the geochemistry within the local environment in the water. However, how exactly the metabolism of cable bacteria influences the environment and maybe other species is still not well understood.

Since researchers only recently discovered cable bacteria, it is understandable that there are still many questions unanswered. But I am convinced that we will hear many more interesting facts about them and who knows, maybe one day bacteria will fuel some kind of seawater-based batteries…

Takeaway from this week’s articles:

• cable bacteria are filaments of a multitude of bacterial cells
• they can produce and consume electrons and transport them from one end to the other
• this electric current shapes the local environment in water sediments

The post Cable bacteria – unusual bacteria conduct electricity appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

How does this bacterium make sure it won’t be disturbed in its new quiet environment? Easy – it builds a house to protect itself and its siblings.

But a bacterial house is a special one – we call it a bacterial biofilm. And bacteria form a biofilm when they want to protect themselves from their surrounding, form communities and grow and reproduce.

Let’s read on to find out what these bacterial houses are and how they build them.

Why do bacteria form a biofilm?

Just like you need a roof over your head to protect yourself from the outside weather, bacteria form a biofilm that works like a house. And they build these houses from scratch.

A bacterial biofilm has protecting walls and a roof around it. These barriers defend them from all sorts of stresses of chemical or mechanical nature.

And there are so many advantages for bacteria to live in such a house:

• Most antibiotics cannot penetrate biofilm so that bacteria are safe inside.
• Bacteria keep their own nutrients and water and oxygen within the biofilm.
• In the case of desiccation or starvation, they can survive inside.
• Immune cells cannot break through a biofilm, hence bacteria inside are protected from the host immune system. 

So, basically, a biofilm is the master accommodation for bacteria. 

Where do bacteria form a biofilm?

Biofilm is the stuff that you can feel on your teeth in the morning after you woke up. But don’t worry, you easily brush it off your teeth. 

Biofilm is the gloomy stuff that grows on your kitchen sponge and it is the crust in your kitchen sink if you haven’t cleaned it for a while.

Some bacteria can form a biofilm on contact lenses, which can lead to eye infections.

Unfortunately, bacterial biofilms are also one of the major burdens in hospital settings. Here, bacteria form biofilms on medical devices like catheters, joint replacements, implants or pacemakers.

Researchers even found microbial biofilms in 3.2 million-year-old fossils from volcanoes.  

So, generally, bacteria can form a biofilm on any surface.

What does a microbial biofilm consist of?

Many microbes and especially bacteria can form a biofilm. And dependent on the microbial and bacterial species, the biofilm can have a different colour, thickness and texture. 

Generally, biofilms consist of bacterial cells (either only one species or many different ones), as well as other microbes as for example viruses or phages. All these microbes inside the biofilm talk to each other and communicate.

Inside the biofilm, bacteria glue themselves together with so-called extra-polymeric substances. These are big molecules that bacteria produce and excrete.

These extra-polymeric substances are proteins, lipids, sugar molecules or polysaccharides and DNA. And these substances give the biofilm its gloomy or slimy texture.

Interestingly, each microbe and bacterium produces a slightly different kind of polysaccharide. And each of these polysaccharides has slightly different chemical properties. This makes the texture of biofilms from different bacteria also slightly different.

Within the biofilm, bacteria can store everything, for example, metal ions bound to DNA, nutrients like sugar, bacteriophages, oxygen… And bacteriophages even protect the bacteria inside the biofilm.

How do bacteria decide to form a biofilm?

This is an important question scientists are currently trying to understand. As soon as we understand how bacteria regulate biofilm formation, we might be able to develop drugs that prevent bacteria from biofilm formation. 

There is a general model of how bacteria form biofilm.

The general idea is that a few bacteria attach to a surface. For this, they use special adhesion proteins that help stick to the surface.

Now, bacteria want to settle down so that they do not need to move anymore. This is why they stop all movement mechanisms like swimming.

As mentioned already, inside the biofilm, bacteria talk to each other. Like this, they know when they are many together and they can start producing these extra-polymeric substances. By excreting them, bacteria get glued to each other. This helps them completely encapsulate themselves with this hydrogel. 

Interestingly, once in a while, a bacterium spontaneously explodes. Then, the other bacteria use the cellular content (so all the DNA and proteins and lipids) of the dead bacterium to form more biofilm.

Inside such a so-called mature biofilm, bacteria happily grow and divide inside.

However, as soon as nutrients become scarce inside the biofilm, the bacteria need to find a new place to live. Then they will start producing scissors to break the biofilm. And when they activate their swimming and motility motors they can detach from the biofilm towards a new place where they start all over again.

How do we research bacterial biofilms?

This is actually pretty easy, as there are many different stains that specifically bind to bacterial biofilm and make them visible. In the picture below you can see two examples.

These are two different stains that visualise bacterial biofilms. With the stain crystal violet, we can see a purple ring of biofilm on plastic and with congo red, we can visualise the structure of a biofilm.

In the above picture, in the left column (PAK) is a biofilm of the bacterium Pseudomonas aeruginosa. This one does not make much biofilm because you can barely see any violet or red stain. The other two columns are different mutants that produce more biofilm. These biofilms you can recognise by the strong violet or red colours.

With these experiments, researchers can understand under which conditions bacteria form more or less biofilm or whether their texture changes. This will eventually help us get a clearer picture of the fascinating life of bacteria and how to counteract them.

We still don’t understand biofilms very well. And so far we know that some enzymes exist that break a biofilm apart. However, the big goal would be to prevent bacteria from forming biofilms in the first place.

The post Bacteria building houses appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

However, to get into a human body, a bacterium needs to have certain mechanisms to stick to it and then to enter it.

Plus, the intruding bacteria need to overcome the defence mechanisms of the host itself. These defences can be our friendly bacteria that fight pathogenic bacteria or the immune system that sends off fighters. Also, our own microbiome works like a block against incoming new microbes.

And yet, some pathogenic bacteria developed some clever ways to stick to a host and infect it. Here, we will look at the different steps of how bacteria attach to a host and infect it.

Bacteria stick to a host

For a bacterium to infect a host cell, it first need to understand that it is actually close to one. For this, bacteria have so-called pili, which look like thin hairs sticking out of them.

These pili have special little patches at their ends. And when such a patch finds the right cell type, it can stick to it. Like this, certain bacteria can only stick to a specific host cells.

For example, the uropathogenic bacterium Escherichia coli can infect our bladders. This means that this bacterium has special patches at its pilus that specifically stick to cells in our urogenital tract.

Now, that the bacterium knows that it is close to a host cell, it shortens the pilus. This movement pulls the bacterium close to the cell itself.

The next step for the bacterium is to connect tightly to the host cell.

Bacteria connect to a host

To attach tightly to a host, pathogenic bacteria have little hooks called adhesins. These proteins can bind to specific components on the surface of the host cell.

So, after a bacterium pulled itself close to a cell, the adhesin binds to the cell more tightly. Also, not every bacterium has the right adhesin to binds to every host cell. Again, for this binding mechanism to work, they need specific adhesins for specific cells.

From this tight binding, the bacterium can easily enter the host cell. Once inside, it fires off its weapons like the T3SS or the T6SS. In the end, these weapons are what make the cell sick.

How a host fights off invading bacteria

Obviously, our body doesn’t want to get sick. Hence, it will not allow bacteria to easily invade us. This is why we have many different strategies to protect us from foreign microbes, toxic molecules or anything that could be harmful for us.

Here, we will look at a few mechanisms that our body uses to get rid of pathogenic bacteria.

Washing bacteria off

To avoid that bacteria come and attach to our cells, our body uses shear stress. This means that there is a constant flow of either air or blood to wash off all bacteria from the cells, so they don’t get (too) attached.

For example, in our nose we have little hairs which move with every inhale and exhale. These moving hairs are trying to wipe off incoming bacteria.

And don’t forget our very own microbiota. The good bacteria on our body also help us fight off incoming bad bacteria.

Fighting off bacteria

Our body developed a whole army that is trained to recognise and fight foreign microbes and bacteria. This is the immune system that consists of many different players that work together in incredibly complex mechanisms with the goal to protect us.

And some of these players are specifically trained to fight off incoming pathogenic bacteria.

For example, macrophages swim around our body always on the lookout for invading bacteria. There is this amazing video in which a macrophage chases a single bacterium and guess who wins?

However, many pathogenic bacteria found ways to escape these host immune cells. They have so-called flagella which they use to swim away from the immune cell.

How bacteria get too attached to a host

Here, we had a quick glimpse into the life of a pathogenic bacteria and how they infect a host. By better understanding how bacteria connect to hosts, we can develop more practical treatments to inhibit this mechanism. This would eventually keep bacteria from sticking to host cells and infecting them. In general, that would keep us free of disease and infections.

If you want to learn more about any of these steps here, please leave a comment in the boxes below. We will explore those topics in upcoming blog stories. We are looking forward to your ideas!

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