At the heart of this bacterium-plant relationship lies the soil bacterium Agrobacterium tumefaciens. Agrobacterium lives in the rhizosphere, the region in the soil close to plant roots. This area is full of secreted molecules from the plant as well as plenty of other soil microorganisms.

Agrobacterium tumefaciens is a versatile bacterium with two distinct lifestyles. In its free-living state, it happily lives and grows in the soil.

However, the bacterium also responds to some plant molecules, like sugars and acids, through its sensors on the surface. These molecules are often a sign of a wound within the plant root.

Once Agrobacterium tumefaciens detects such a molecule, it activates its virulence and makes it move toward the plant. The otherwise harmless bacterium is now a pathogen and can sneak into the plant where it goes on a big mission.

But just like animals, plants have defence mechanisms against bacterial pathogens as they recognise their bacterial surface. Depending on the plant’s immune system, the plant can be resistant or susceptible to the incoming intruder.

Luckily, Agrobacterium tumefaciens has the right weapons to counterattack, which is why it can infect many different plants.

Agrobacterium transfers its DNA into plants

Agrobacterium’s remarkable capability lies in its unique ability to transfer its own DNA into plant cells. For this, the bacterium has a special exporting machine sitting in its outer envelope.

Through this machinery, the bacterium sends some of its DNA. But not just any part. Agrobacterium tumefaciens has a special DNA portion in the form of a circle for this process. And on this so-called T-plasmid are only genes that help the bacterium during the plant-infection process.

When arriving in the plant cell, the T-plasmid is coated with specific bacterial proteins. These help the plasmid find its way to the nucleus of the plant cell.

Once landed in the nucleus, some of the plant’s systems are hijacked to destroy the proteins around the bacterial plasmid. This sets the plasmid free and it can now interact with the DNA of the plant cell.

Since the bacterial DNA-plasmid contains similar sequences as the plant DNA, these overlap so that the bacteria-DNA can integrate into the plant-DNA. Now, the bacteria-DNA is part of the plant-DNA and the plant activates the bacterial genes just as they were its own.

Transformed plants grow tumours as bacterial houses

Some of these activated bacterial genes cause the plant to produce certain plant hormones at very high levels. This hormonal imbalance triggers the cells to divide rapidly without control. The plant grows plant tumours, or so-called galls. You have probably seen them on the stems of plants or trees.

But Agrobacterium tumefaciens doesn’t merely cause tumours. Some of its genes – now present within the plant DNA – become factories to produce opines. Opines are an exclusive food source for the bacterium, allowing it to grow and thrive within its newly established plant-tumour home.

With Agrobacterium tumefaciens from microbiology to biotechnology

Once Agrobacterium tumefaciens’ superpower to transfer DNA into plant cells was discovered and understood, researchers used it extensively in the biotechnology field. They learned to introduce random pieces of DNA into plants, uncovering plant physiology and paving the way for genetically modified organisms.

By engineering specific DNA segments in the bacterium, researchers can transfer desirable traits and functions into plants. This technique, known as plant transformation, has enabled the development of genetically modified plants that resist pests, withstand harsh conditions or produce pharmaceutical proteins and vaccines.

A bacterium helps us unravel plant physiology

As we’ve seen so often in the microbial world, the smallest actors often have the grandest roles. Agrobacterium tumefaciens, a humble soil bacterium, is a true superhero when it comes to plant interactions.

Its ability to infect plants, exchange signals and transform its own genetic material has offered us valuable insights into the fascinating partnership between bacteria and plants. From the soil to the laboratory, Agrobacterium tumefaciens is at the forefront of illuminating the mysteries of nature and guiding us toward a deeper understanding of both the botanical and microbial worlds.

The post Learning with Agrobacterium tumefaciens: Understanding plants better appeared first on Bacterialworld.
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.

The post Bacterial killer weapons as biocontrol to protect plants appeared first on Bacterialworld.
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.

The post Floating veils for large bacteria to attach to and fetch nutrients appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

So, they talked of cocci and bacilli based on the spheres and rods that they saw under the microscope.

And they classified microbes and bacteria based on these shapes.

It came only with later, modern technologies that scientists learned that there was more to bacteria than their shapes. Even though bacteria looked similar, they had different superpowers.

Yet, some of these bacterial superpowers are indeed influenced by their cell shapes.

So, what is it about bacterial shapes? Why do bacteria look differently? And how do the different shapes of bacteria help them survive and thrive?

What gives bacteria their shapes?

To protect themselves from the environment, bacteria as well as all other organisms have cell envelopes. These keep the cellular machines and internal parts together so that a bacterium can function within this envelope.

And this envelope also gives bacteria their shape.

Both Gram-positive and Gram-negative bacteria have a layer of so-called peptidoglycan within their envelope. This peptidoglycan layer is made of sugars that are linked together by very strong bonds. This is why the peptidoglycan layer is pretty rigid and stiff and has a specific shape in each bacterium.

Either on the inside or on the outside, the peptidoglycan layer is linked to the cellular membranes. Together, these make up the bacterial envelope with a specific cell shape.

What different shapes do bacteria have?

Microbiologists have different ways to classify known bacterial shapes. Here, I will introduce you to the bacterial shapes according to what makes the most sense to me.

Rod-shaped bacteria

As the name suggests, these bacteria have a rod or cylindrical shape. Examples of rod-shaped bacteria are Escherichia coli and Bacillus subtilis.

Scientists are also convinced that rod-shaped bacteria are the evolutionary ancestors of all other bacterial shapes.

The shape comes from proteins that form long cables within the bacterial cell. These span out the whole bacterium from one end to the other.

Rod-shaped bacteria grow by two modes that we talk about in Why bacteria divide into two and grow with the help of a strong ring: First, they extend their cell size by growing the peptidoglycan, the cable proteins and the membrane.

Second, the cable proteins determine the middle of the cell, where the bacterium produces a special ring. Eventually, this ring narrows so that the bacterium divides and two bacterial cells form.

Spherical bacteria

The spherical bacteria – or so-called cocci – include many pathogenic bacteria like Staphylococcus aureus, Streptococcus pneumoniae and Neisseria gonorrhoeae.

Microbiologists think that spherical bacteria were once rod-shaped as well. However, spherical bacteria do not have these long cable proteins that extend their cell bodies. Thus, they stay spherical and grow by dividing their spherical cells right in the middle.

However, sometimes the two daughter cells do not completely divide and they stay attached to each other. This is why some spherical bacteria live as so-called diplococci.

Curved bacteria

Curved bacteria have the shape of a comma or banana and are sometimes also slightly twisted. Examples of curved or banana-shaped bacteria are Caulobacter crescentus and Vibrio cholerae.

These curved bacteria usually live in watery environments where there are flows. Here, the curved shape helps the bacteria to align with the flow while staying attached to a surface.

In the case of Caulobacter crescentus, one end of the bacterium is glued to a surface with a strong super glue. When this bacterium divides in the middle, one daughter cell remains attached to the surface, while the other one can swim away and find a new location to settle down.

Spiral bacteria

Spiral bacteria are a mix of rods and curves which give them a helical twist. Hence, these bacteria have a corkscrew shape.

Many pathogenic bacteria use their corkscrew shape to swim through gel-like solutions. This includes Helicobacter pylori and Campylobacter jejuni.

Since spiral – or helical – bacteria are also thinner, they can reach locations that are too narrow for other bacteria to reach. They also use their flagella to push themselves forward and “wriggle” through narrow pores.

Star-shaped bacteria

Some bacteria look even fancier than others: They are real stars – yes, bacteria with a star shape.

While we don’t know much yet about star-shaped bacteria, they belong to the so-called Stella species or are Methylomirabilis oxyfera. These usually grow in freshwater, soil and sewage.

The star shape comes from six little arms that extend out of the bacterial cell. These push and grow to the outside giving these bacteria a shiny star shape.

Why do bacteria have different shapes?

Now that we have seen the different shapes of bacteria, you might ask yourself, why do bacteria have these different shapes? How do they help them?

As always in biology, it comes down to how a property helps a bacterium survive in a certain location. Often, the cell shape gives a bacterium advantages over other bacteria and it is easier for them to settle down and face harsh environments.

For example, spherical cells have the lowest surface-to-volume ratio. This means they have a large envelope surface through which they can take up a lot of nutrients. All this while their cell volume is relatively small. So they don’t actually need that many nutrients. This helps cocci to grow in locations where there are little amounts of nutrients.

On the other hand, rod-shaped bacteria often have flagella. And thanks to their shapes, they are efficient swimmers. This allows them to swim to new places in cases of danger or the lack of nutrients.

Bacterial cell shapes help face harsh environments

Also, straight rod cells can pack into biofilms more efficiently and build organised structures. This helps them colonise different locations and resist dangerous environments.

Many rod-shaped bacteria also form longer filamentous organisms. These stronger and larger structures protect bacteria from being eaten by other organisms. Another advantage of these multicellular organisms is that they allow more cells to attach to surfaces and colonise hosts.

Lastly, both curved and helical bacteria use their shapes to get better around their environments. Curved bacteria grow in watery environments but also in our guts. Here, their shapes help them align with the flow of water or our gut content while they stay attached to a surface or the gut wall. This keeps them at their preferred location and protects them from being flushed away.

Spiral bacteria use a fascinating helical movement to screw through gel-like or viscous fluids. This for example helps pathogens swim through the mucus of our stomach and guts and colonise us and make us sick.

Bacteria and their shapes

Here, we looked at the different shapes that bacteria have and how these help them survive. Bacteria always face harsh and new environments and conditions and only survive if they have the right tools or means.

So, by adapting their shapes, bacteria often have advantages over other bacteria. Plus, they look cool and fabulous!

The post Looking fabulous: Why bacteria need to stay in shape too 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

Bacteria become resistant to antibiotics. 

Cancer spreads like never before. 

And a virus determines how we live our lives. 

Why do we need to transport drugs within our bodies?

These three major problems need researchers to develop new drugs, like new antibiotics, efficient chemotherapeutics, or long-lasting vaccines.

But we also need to transport these drugs into our bodies and to a specific location. This could be the site of a bacterial infection or the tumor that we’re trying to kill. 

For this, researchers have been working on new delivery methods to transport drugs to a specific site. And, interestingly, many of these methods are based on bacterial mechanisms. So, we felt it was more than worth discussing some of these mechanisms here with you. This will show you another way of how bacteria can save this planet by transporting drugs within our bodies.

Let’s dig in.

Outer membrane vesicles

In Bacteria firing toxic bubbles, we learned that Gram-negative bacteria can form bubbles of their outer membranes. These bubbles are called outer membrane vesicles and they can be filled with stuff.

And researchers also tried to use these bubbles to deliver drugs.

Luckily, our immune system can recognise and respond to outer membrane vesicles. This means our bodies can produce antibodies against the surface of these outer membrane vesicles. 

Outer membrane vesicles carrying stuff on their surface

For example, researchers made the bacterium Escherichia coli produce outer membrane vesicles. Only the lipids of the vesicles – nothing else. They then gave these outer membrane vesicles to mice. These outer membrane vesicles were not dangerous and the mice did not produce antibodies against them.

Then the researchers engineered the vesicles. Between the lipids, the vesicles now carried proteins from the pathogenic bacterium Acinetobacter baumanni. Hence, the protein becomes a so-called antigen. This means, that the mice produced antibodies against the antigen. This made them immune against an Acinetobacter baumanni infection. 

This is an option of how to transport antigens into our body to make us immune against different pathogens.

Outer membrane vesicle bubbles filled with stuff

Another way of using bubbles from bacteria to transport drugs is by filling them with stuff. 

For this, the outer membrane vesicle carries a specific protein. This protein fits like a key to a lock of a certain cell type. Like this, the outer membrane vesicle can dock onto a specific human cell and interact with it. 

Just as you can see in the picture above how outer membrane vesicles are formed, this mechanism can also work the other way around. An outer membrane vesicle can “melt” into a human cell. Then, the content of the outer membrane vesicle flows into the human cell. 

For example, researchers engineered outer membrane vesicles and filled them with a chemotherapeutic. This outer membrane vesicle then specifically melted with cancer cells and shed their content into these. This did not completely kill the tumour but inhibited its growth.

Researchers also developed new vaccines that have DNA or RNA inside these lipid membranes. Read more about vaccines made by bacteria.

As exciting as this mechanism sounds at the moment, it still requires more research to fully understand how we could use outer membrane vesicles as drug-delivering vehicles.

Magnetosomes – bubbles following a magnetic force

Magnetosomes are similar to outer membrane vesicles, as they are bubbles made of a lipid membrane. But in How bacteria read and follow the Earth’s magnetic field, we learned that magnetosomes also have iron-clusters that make them magnetic.

Researchers have the idea to guide magnetosomes with a magnet to a specific location in our bodies. Like this, magnetosomes can go deep into tumour tissue and work their magic there.

Now, similarly to outer membrane vesicles, magnetosomes can be filled with drugs like antibiotics or chemotherapeutics. These drugs are then shed into tumour cells or into the surrounding of tumour cells. 

So far, researchers showed this method in mice. They filled magnetosomes with a vaccine against a tumour, gave them to the mice and held a magnet right next to the tumour. This treatment protected the mice from the tumour and could be used at some point in the clinic. 

Bacterial ghosts – a shell of a dead bacterium

Ghosts of bacteria in your body? That is certainly a science fiction idea.

For this, researchers grow bacteria in the lab and engineer them to produce a protein of interest. This could be for example an antigen that will trigger an immune response in the human body. 

When the bacteria are fully grown, researchers trigger them to produce massive tunnels in their outer membrane. All the content of the bacterial cell will flow out into the surrounding. This means, the bacterium itself is dead and cannot grow anymore. But the bacterial envelope with the antigen is still stable. 

Studies showed that bacterial ghosts with antigens triggered antibody production in rabbits.

In another study, researchers filled the bacterial ghosts with anti-cancer drugs. Fortunately, the bacterial ghosts release the drugs very slowly. Like this, the drug is administered over a long time and is thus more efficient. However, researchers did these basic experiments only on cell lines so far. Hence, a lot more research is required to better understand this mechanism of drug delivery.

Living bacteria to transport drugs

Transporting drugs in the body using living bacteria sounds pretty challenging. But researchers know how to engineer strains that have no damaging effects on our bodies and our immune system. 

Using living bacteria to transport drugs in the body even has many advantages.

Bacteria are attracted by certain chemicals

Bacteria do chemotaxis which means they are attracted by certain chemicals or molecules. 

For example, some bacteria are attracted by areas with low or no oxygen at all. Cancer tissue generally lacks oxygen and the surrounding tissue has very low oxygen concentrations.

Hence, some bacteria are already directly attracted by tumours or cancer tissue.

Also, researchers are trying to engineer bacteria that are attracted to other chemicals. For example, they improve chemotaxis in some bacterial strains. And now these bacteria are more efficient in recognising certain molecules within tumour tissue.

Bacteria move with their flagella

After being attracted by a certain molecule, bacteria actively swim towards this molecule. For this, they use their flagella and pili. 

Hence, this swimming behaviour brings them efficiently to the site of infection.

Bacteria produce drugs on the spot

Bacteria are drug production machines. 

Generally, researchers engineer bacteria in a way that they start producing drugs only when they reach a specific location.

Like this, bacteria produce the right drug at the right time and the right location. 

And they can even produce multiple different drugs. How efficient!

Bacterial hybrid delivery systems – Microbots as the future?

Using a hybrid system between an engineered bacterium and a non-living unit sounds a lot like science fiction. These systems are even called microbots or bactobots. But also here, they have only been tested in the lab, and no studies on humans were done yet (at least to my knowledge!).

A microbot consists of a bacterium that does chemotaxis. So, they could be attracted to tumours or cancer tissue.

And this bacterium carries a nanoparticle that is filled with a drug. Like this, the bacterium steers the particle, and thus the drug, to the place of infection. Here, it can release the nanoparticle, which can now work its magic.

So far, researchers showed in a preliminary study in mice, that bacteria can successfully deliver nanoparticles covered with DNA into specific organs.

However, there are still so many obstacles to consider. But it certainly sounds like a promising and very efficient science-fiction idea.

Bacteria and their organelles can transport drugs within our bodies

Here, I showed you some ideas of how researchers are trying to use bacteria or their organelles to transport drugs within our bodies.

We looked at “bacterial organs” like outer membrane vesicles or magnetosomes. These could carry drugs and deliver them to certain body tissue.

We then discussed how researchers are trying to better understand bacterial ghosts to use them as drug vehicles.

And we explored living bacteria and why researchers think they can use them to transport drugs within our bodies.

Microbots, however, sound like science fiction so far. But, who knows, maybe at some point, we will eat a bacterium that carries a nanoparticle filled with drugs.

I hope we could yet again show you a fantastic way of how bacteria can save our medical problems and thus our planet. So, now is the time to lose the fear of bacteria and believe in them. 

Together with bacteria, we can save this planet.

The post Of microbots and bacterial ghosts – How bacteria could transport drugs within our bodies appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Read on to learn what this fascinating superpower is and why magnetotactic bacteria work like a compass.

What are magnetotactic bacteria?

So-called magnetotactic bacteria are those bacteria that sense magnetic field lines and align with them. They then decide whether they swim toward the North or the South.

To actively swim through water, magnetotactic bacteria, like many other bacteria, have flagella. And they can have one flagellum on one side or one on each side or a bundle of flagella.

So far, researchers found magnetotactic bacteria on the whole planet and they mostly live in water sediments and oceans. Some magnetotactic bacteria even live in extreme spots like the hot springs in northern Nevada. Here, they grow happily at about 55 °C. 

Researchers gave these fascinating bacteria names that already let you guess their superpowers: Magnetospirillum magnetotacticum, Magnetospirillum magneticum, Magnetospirillum gryphiswaldense, Magnetococcus marinus or Desulfovibrio magneticus. And obviously, scientists keep discovering new species that can sense magnetic field lines.

Okay, now we know what magnetotactic bacteria are. Let’s look at what gives magnetotactic bacteria their superpowers to read magnetic field lines.

What are magnetosomes?

Magnetotactic bacteria can sense magnetic field lines because they have so-called magnetosomes.

Magnetosomes are tiny crystals of iron oxide or iron sulfide. And these crystals are surrounded by a lipid membrane within a so-called organelle. Magnetosome organelles lie within the bacterium and import and export iron from the bacterial cytosol.

These magnetosomes can have different shapes and sizes. Some crystals are cuboctahedral, prismal-shaped or even bullet-shaped. Like the super cool magnetosomes in the pictures below.

As you can see in the pictures, bacteria do not only have one magnetosome but several. And these magnetosomes can align in a perfectly straight line or cluster together on one side of the bacterium.

For a magnetosome chain or cluster to work, bacteria need to keep their shapes perfectly. For this, magnetotactic bacteria use so-called scaffold proteins. These scaffold proteins position the magnetosome within the bacterium and hold this chain in its place.

How do magnetotactic bacteria grow magnetosomes?

Because magnetosomes are made of iron, magnetotactic bacteria have very special iron uptake systems. These iron importers help the bacteria get as much iron into the cell as possible.

Then the bacterium needs to transport the iron toward the magnetosome. The problem is that free iron is actually toxic to the cell.

Hence, the bacterium needs to assure the iron does not come into contact with the cell content. Therefore, magnetotactic bacteria produce iron transporters that shield the iron from the surrounding. 

Now, the bacterium needs to carefully crystallise the iron to grow the magnetosome. This process is actually not well understood yet and researchers are on it to shed light on it.

Okay, now we know what magnetosomes are and how they are formed. Let’s look at how magnetosomes help bacteria sense the Earth’s magnetic field.

How do magnetotactic bacteria sense magnetic field lines?

Because magnetosomes are highly-concentrated iron crystals, they have a magnetic dipole. And since a bacterium has many magnetosomes aligned in a straight line, the magnetic dipole is increased.

So, the magnetosome chain works similarly to a compass needle and aligns along magnetic field lines. Just as a compass needle aligns with magnetic field lines and you align your position according to the compass needle.

And we have the scaffolding proteins that keep the magnetosome chains in place within the bacterium. Because of them, the whole bacterium aligns with the magnetosomes. So, when you think about it; the bacterium aligns with the magnetic field lines in a passive way.

Imagine you put a worm on a compass needle that it can’t move away from. The compass needle will always point North and thus the worm will always point North as well. So, no matter where the compass goes or how fast you turn yourself with that compass, the needle and the worm will always face north. But the worm is only aligning North passively. Same as the bacterium.

As we said at the beginning, magnetotactic bacteria always have a flagellum that helps them swim around. Similar to other motile bacteria, a bacterium swims because it rotates its flagellum. This moves the bacterium forward or backward.

But since the magnetotactic bacterium is aligned to the North or South, it will only swim toward the North or South.

And researchers found that magnetotactic bacteria can be either North-bound or South-seeking. Hence, depending on whether the bacterium lives in the northern or southern hemisphere, it will swim towards the North- or the South pole.

So, next time you want to hitchhike on a magnetotactic bacterium, ask it first where it is going!

Why do magnetotactic bacteria sense magnetic field lines?

Researchers do not have a clear answer to this one yet.

One hypothesis is that within the depth of the water, a bacterium has three dimensions to align to, swim to and explore. By aligning the bacterium to the Earth’s magnetic field, the bacterium only moves in one dimension. This makes the search for the perfect location easier. Otherwise, bacteria might swim aimlessly in all three dimensions and get lost.

Also, most magnetotactic bacteria are chemotactic and even aerotactic. This means they move towards oxygen – again to find the perfect spot to live and to find nutrients.

And some magnetotactic bacteria are even phototactic and swim away from blue light. Researchers think that because blue wavelengths are a sign of deep water, bacteria are trying to avoid going too deep. But this still needs some more research.

Do magnetotactic bacteria help other organisms?

Researchers found an amazing example of a symbiotic relationship in the microbial world.

They discovered magnetotactic bacteria that live on a eukaryotic protist. The two species exchange metabolic molecules, so they feed each other.

What I find really fascinating is that these two species together become a swimming magnetic superorganism. The researchers saw that the magnetotactic bacteria completely cover the surface of the protist. And because the magnetotactic bacteria have magnetosomes, they align with the magnetic field. Thus, the entirety of bacteria on the protist aligns the whole protist with the magnetic field. 

Interestingly, this species of magnetotactic bacteria lost their flagella during evolution. So they are unable to swim. But the protist still has a swimming rotor. Thus, because of the symbiosis, this multi-organism is able to sense and swim along the magnetic field lines. 

Magnetotaxis – a bacterial superpower

Okay, I hope I could convince you yet again how amazing bacteria are and that they do have superpowers.

Again, it is not a hundred percent clear yet, how sensing magnetic field lines help bacteria to survive. But as usual with evolution, if some species kept such an impressive superpower, it must have a big advantage. 

We just don’t understand it yet.

The post How bacteria read and follow the Earth’s magnetic field 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

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

Think about how you get food.

First, you realise that you are hungry. Then, you need to know where your closest food source is. This might be your fridge or the nearest takeaway. Once you figured that out, you move toward the food.

Also, bacteria need to find food and move toward it. And to do that, they have a special system that is called chemotaxis. Chemotaxis tells bacteria where their nearest food source is and makes bacteria move to that food source.

Let’s look at how the chemotaxis system works.

When bacteria get hungry, they move too

Scientifically speaking, chemotaxis is the bacterial movement toward or away from a chemical. This means, that a chemical can activate the chemotaxis system. Such a chemical can be a nutrient like sugar, an amino acid, nitrogen or oxygen. Also, metals, hormones or even neurotransmitters can activate the bacterial chemotaxis system.

And because these chemicals have systemic effects, they are also called chemoeffectors. Since these chemoeffectors can be good or bad for the bacterium, the movement can be toward or away from this chemical.

So, in case the bacterium is hungry and found some sugar nearby, the chemotaxis system makes the bacterium swim to the food. Yet, moving the whole bacterium costs a lot of energy. That’s why the chemotaxis system is very well regulated so that the bacterium does not waste any energy.

Just as you have to be very hungry to drag yourself up the sofa to move towards the fridge ?

How does chemotaxis work?

First of all, a bacterial cell needs to understand that it is hungry. You know that you’re hungry when you feel that empty stomach. A bacterium senses its energy levels similarly, to know that it is low on nutrients.

For example, in our figure, the bacterium misses a nutrient that is sugar (in blue). To understand whether there is any sugar in its surrounding, our bacterium has different chemoreceptors on its surface. These are the purple antennae on the outside of the bacterium.

These chemoreceptors contain two parts: one half sits on the outside of the cell while the other half is stuck on the inside. Both parts are connected through the bacterial cell membrane.

On the outside, the chemoreceptor can bind the specific chemoeffector. This binding activates the chemoreceptor as you can see with the star in the figure.

On the inside of the cell, the chemoreceptor is bound to a specific response system, the so-called two-component system. This sytem gets activated when the chemoreceptor binds the fitting effector on the outside.

Chemotaxis helps bacteria sense and react

In this case, one partner – the sensor protein – actives a second partner – the response regulator. This protein is the purple pacman that is responsible to respond to the incoming signal. 

It responds by binding to the flagellum of the bacterium. This flagellum is a fascinating little machine that works like a little rotor with a propeller.

Thus, the binding of the response regulator activates the flagellum and it starts spinning. This spinning now moves the bacterium.

If the chemoeffector is good for the bacterium, it will move towards the chemical. We call this behaviour positive chemotaxis since it has an advantage for the bacterium.

However, if the chemoeffector is dangerous or toxic, the bacterium will move away from it. This negative chemotaxis protects the bacterium from dangerous chemicals. Hence, chemotaxis helps bacteria stay safe, too!

Chemotaxis helps bacteria in different situations

Interestingly, bacteria do not only use chemotaxis to find nutrients. When they arrive within the human body or a plant they can also sense certain hormones or even neurotransmitters. In this case, the bacterium realises that it arrived inside a human body or plant.

Then it can respond by swimming towards it. And it starts producing virulence factors to infect the cell and thus the body. 

In any case, chemotaxis helps bacteria to survive either by finding nutrients or by helping them infect cells and grow within them. 

Take away from this week’s article:

• chemotaxis helps bacteria know that they found a specific chemical
• presence of the chemical activates their flagellum which allows them to swim
• chemotaxis helps bacteria decide the direction of their movement: it swims toward the chemical if it supports bacterial growth or away if it is damaging

The post Chemotaxis helps bacteria move towards goodies appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world