Whatever you do throughout your day, you are constantly bringing microbes onto and into your body. Especially when eating, you introduce a mix of microbes into your gastrointestinal tract.

In this dark, airless place, microbes flourish, working tirelessly to keep you in good shape. They improve your body’s health starting from the gut and strengthen your gut’s defences by fighting off unwelcome intruders.

Gut bacteria break down the food you eat from which they produce all sorts of molecules. The most important ones are called short-chain fatty acids. These small molecules impact the health of your gut and your overall body.

Here, we’re looking at gut bacteria that produce short-chain fatty acids and how they maintain the health of your gut. We’ll also explore ways to help bacteria make even more of these beneficial molecules.

Let’s start by understanding how your gut protects your body.

The mucus layer of the gut as a first line of defence

The food you eat passes through your body, yet it is always in contact with your body’s outer layer of cells. Only in the gastrointestinal tract do your gut cells absorb molecules from food and transport them into the body.

This means the outer layer of your gut, the so-called epithelium, faces away from the body and is in constant contact with the outside. One of its main jobs is to prevent harmful components from getting too close or even entering the body.

That is why goblet cells, which are special gut epithelial cells, produce a thick, slimy mucus. As they constantly secrete mucus, the cells actively push everything away from the epithelium, while the ever-growing mucus layer sits like a protective shield on top of the the intestinal epithelium.

When the mucus layer is too thin or broken, harmful microbes and bacteria can come into contact with the gut. This can trigger inflammatory immune responses, resulting in chronic diseases such as inflammatory bowel diseases.

Commensal gut bacteria produce short-chain fatty acids

While this slimy physical barrier is already a strong first line of defence for your gut, you can also rely on your gut microbes. Those that reside in and on your body over a long time are called commensal microbes.

One way to make them stay with you is by feeding them their favourite foods. Gut bacteria eat what you eat, while some commensals like Ruminococcus gnavus and Akkermansia muciniphila also eat the mucus in your gut.

And from your food, the majority of gut commensals prefer the dietary fibre. That is the indigestible part of plant-based foods as it passes through your small intestine unchanged. Once it reaches the large intestine, your gut bacteria get to work.

They break down the fibre, ferment it and produce all sorts of molecules from it. The most important group of molecules are the short-chain fatty acids, including acetate, propionate and butyrate.

The commensals Bacteroides thetaiotaomicron, Bifidobacterium longum, Eubacterium and Blautia coccoides are actually some of the best-known producers of short-chain fatty acids. Just by eating a lot of dietary fibre, you increase both the different microbial strains growing in your gut and the amount of short-chain fatty acids they make.

How short-chain fatty acids improve gut health

From the gut, short-chain fatty acids diffuse through the mucus and reach the epithelial layer. Here, they bind to receptors on the goblet cells and activate certain pathways.

They trigger goblet cells to grow and produce more mucus. This increasing mucus layer, in turn, protects more effectively against harmful bacteria while providing more food for your commensals.

For example, two gut bacteria, Akkermansia muciniphila and Blautia coccoides, produce the short-chain fatty acids acetate and propionate. Both molecules trigger gut cells to make more mucus, improving gut health and feeding commensal bacteria while fighting off intruders. In mice, Bifidobacterium longum induces the growth of mucus, likely by producing acetate.

The diet-microbiome-gut health connection

Now, let’s tie all these pieces together: By eating plant-based fibres, you feed your beneficial gut bacteria. These digest and ferment the fibre and produce short-chain fatty acids, which bind to your gut cells and trigger them to produce more mucus. This increasing mucus layer shields off your gut while feeding your gut bacteria.

Generally, the more fibre we eat, the more beneficial bacteria live in our guts. They become more active at digesting fibre since they lose their appetite for the mucus.

Beneficial bacteria like Blautia can even be found in human stool after 12 weeks of eating high-fibre diets. Hence, it seems that the commensal Blautia decides to settle down in your gut depending on what you eat. So, by eating food full of fibre, you can attract helpful bacteria to you.

On the other hand, when you eat little fibre, your gut bacteria start eating your mucus layer, since their preferred substrate is not available. This can lead to inflammation and other gut health issues.

You are what you and your bacteria eat

When considering the role of your gut bacteria for your health, the saying “you are what you eat” may take on a new meaning.

By eating a lot of different plant fibres, you’re not just feeding yourself — you’re also feeding the bacteria in your gut. Your food gives them the right fuel to produce short-chain fatty acids that strengthen your gut’s protective layer and gut health. This, in turn, impacts the health of your body, mind and cardiovascular system and even your emotional and mental wellbeing.

Hence, by eating more veggies, fruits and seeds with lots of fibre, you influence which types of bacteria live close to and inside of you. So, what you eat affects how you feel, quite literally from the inside out.

Your gut bacteria will thank you for that extra serving of vegetables. To show their gratitude, they’ll provide you with all the good stuff to keep you healthy.

The post Short-chain fatty acids: what gut bacteria make from fibre appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

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

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

Your gut bacteria defend pathogens with toxic molecules

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

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

Gut bacteria produce bacteriocins

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

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

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

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

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

Gut bacteria produce short chain fatty acids from fibres

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

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

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

Gut bacteria convert bile acids into toxic compounds

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

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

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

Killing pathogens with bow and arrow

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

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

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

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

Keeping nutrients from pathogenic gut bacteria

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

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

Strengthening the mucus layer to block pathogenic gut bacteria

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

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

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

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

How to help your gut bacteria defend pathogens

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

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

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

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

No, but this is pretty much what happens there.

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

Not sure, how that might work? 

Read on to find out!

What’s in your plant food?

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

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

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

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

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

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

Arabinogalactan – a complex glycan from plants

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

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

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

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

Okay, so far for the main chain.

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

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

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

Enter our microbial friends in our guts.

Bacteria degrade complex plant polymers

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

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

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

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

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

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

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

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

Bacteria get their share of food

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

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

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

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

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

Bacteria share food with each other and keep us healthy

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

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

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

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

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

Help your bacteria share food and you keep yourself healthy

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

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

The post You are what you eat: Gut bacteria share plant leftovers appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world

Yes, the bacteria in your gut have certain superpowers that we benefit from. They help us digest food, keep us mentally and physically healthy, activate our immune system and keep out harmful pathogens.

Here, we will explore some of these fascinating aspects of a healthy gut microbiome, what it is, what it does and how you can keep its superpowers. Learn more about what a healthy gut microbiome actually means and does for you.

What is the gut microbiome?

The gut microbiome consists of all microbial communities that live in your gastrointestinal tract. In there, you can find many diverse players, like bacteria, viruses, fungi and archaebacteria. Here, we will focus on the bacterial members of our gut microbiome, but don’t forget that they all work together to achieve their goals.

Every person has their own unique gut microbiome. So, everyone – depending on their socio-economic state, diet, age, geography, drugs, sleep and other environmental substances – has their own special microbial friends. And studies showed that each person’s gut microbiome is stable over time, even after antibiotic treatment, acute intestinal infections and modified diets.

When you think about it, your gut is a very welcoming environment for most bacteria. It is always about 37 C, a lot of food from your meals and many other microbial friends to party with.

Surprisingly, many bacteria are unable to grow in the lab, so researchers still don’t know much about them. That’s because we don’t know what these gut bacteria need to grow outside of the gut. Yet, researchers found their bacterial DNA in human guts, so they must be living there, somewhere…

Our gut microbiome plays many roles in our wellbeing

In comparison to other microbial niches within our bodies, the gut microbiome is probably best characterized. However, many studies also try to characterise the microbiomes of other parts of our body, as different skin areas. Imagine different organisms living on your feet than on your hand or under your armpits, ears or even eyes.

The reason why researchers mainly study the gut microbiome is due to the accessibility of samples. The sample comes out of your body, so you can directly use it without swapping a person.

Second, the gut microbiome plays important roles in many diseases. So, a lot of research focuses on understanding the interplays between these diseases and the gut microbiome. The aim here would be to find cures or intervention therapies.

How do gut bacteria support our health?

While researchers are still trying to unravel the full impact of our gut microbiome on our health, we are understanding it better and better now. By now we know that a few important players in our gut microbiome are a sign of good health. These are Faecalibacterium, Roseburia, Lachnospiraceae, Eubacterium and Akkermansia muciniphila.

For example, our friendly gut bacteria help us in food digestion. Some of the foods that we eat, we can’t fully digest ourselves, like many complex sugars. In this case, the bacteria in our gut break down these indigestible molecules and produce compounds that we otherwise would not have.

For example, they produce gasses and certain molecules called short-chained fatty acids. While the gasses eventually make their way out of our gut, the short-chain fatty acids play important roles in our overall well being.

These molecules have a positive impact on our mental health, while they also strengthen the gut wall to keep our gut intact. Short-chain fatty acids also strengthen our immune system and help our friendly gut bacteria to grow better. On the other hand, pathogenic bacteria do not like short-chain fatty acids and have thus a harder time settling down in our guts.

Yet, our friendly gut bacteria protect us actively from harmful pathogens that can cause diseases. For example, they fight pathogenic bacteria with harmful killer weapons or produce compounds that are toxic to them.

Also, don’t forget that after a single pathogenic bacterial cell somehow made its way to our gut, it encounters billions and trillions of bacteria that already live there. So, altogether, our microbiota developed many strategies to ensure that any invading pathogenic bacterium feels unwelcome in this environment.

What does an unhealthy gut microbiome look like?

However, once in a while, our gut microbiome seems to be “out of balance”. This can often lead to disease or irritation.

While researchers still don’t know exactly, what the “normal” gut microbiome actually looks like, they are analysing the microbiomes of people with specific diseases. For this, they compare the gut bacteria from people with a disease with the gut bacteria from people that do not have that disease.

And very often, they find that healthy people have a broader variety of bacteria living in their guts. So, somehow all these different bacteria grow together and work as a team to keep us healthy.

This means, one or two bacterial species are often more present in the microbiomes of people with diseases. For example, the bacterium Faecalibacterium prausnatzi likely has beneficial effects on our gut health. However, unhealthy people often have less of this bacterium.

This shift in our microbial gut flora is what researchers call gut dysbiosis. However, whether this shift is the cause or the result of the disease is still not always clear.

Generally, people with gut dysbiosis have fewer bacteria that produce short-chain fatty acids. At the same time, they have more bacteria that degrade the mucus layer of the gut. And the mucus layer is what keeps our gut healthy and intact, so its degradation is usually not a good sign.

Many chronic diseases seem to be associated with gut dysbiosis. For example, type 2 diabetes, obesity, inflammatory diseases or Crohn’s disease, but also mental disorders like depression. However, the exact links are not clear yet.

How can I keep a healthy gut microbiome?

Researchers agree here: You are what you eat!

Diversity is key when it comes to our gut microbiome. This means that you want to make sure ALL of your bacteria stay happy within your gut. So, to keep your diverse bacteria with you, it is vital to eat everything.

Your aim should be to grow those bacteria within you that produce short-chain fatty acids from your food. And for that to happen, you should feed them foods that are high in complex sugars, like fibres.

Also, some studies suggest that certain food additives impact your gut bacteria negatively. These include for example emulsifiers, which work like soaps and kill certain bacteria. Also, stabilisers were shown to induce colitis in animals and artificial sweeteners led to changes in the microbial composition and glucose intolerance in mice.

Most importantly, antibiotics have drastic effects on our gut microbiota. Researchers actually think this is one of the main causes of our modern chronic diseases.

What are probiotics and prebiotics?

The FAO/WHO considers “live microorganisms which when administered in adequate amounts confer a health benefit on the host” as probiotics. These are mainly bacteria that usually live in our guts and that have been well characterised by researchers before.

Interestingly, probiotics do not stay in your gut for a long time. This means to have a long-lasting effect, you should keep eating them regularly.

For example, a probiotic strain of Escherichia coli can slow down the growth of a pathogenic Salmonella strain. Escherichia coli has transporters that specifically bind iron and uptake iron into the cell. With this mechanism, the Escherichia strain uses the iron of the environment, so that there is none left for Salmonella. Because Salmonella and all other bacteria need iron for growth, Salmonella has trouble growing and colonising the gut environment.

Foods with probiotics are for example fermented foods, like yoghurt, kefir, kimchi, kombucha or fermented vegetables. But beware here, as not all of this food actually contains approved probiotic strains.

And to feed your gut bacteria the right food, make sure to eat enough prebiotics as well. They are basically the food for your gut microbiome party.

These include foods that your body cannot digest, which is why your gut bacteria take care of them. Like this, prebiotics promote the growth of probiotic bacteria in your gut. You can mostly find prebiotics in fibres as complex sugars in many vegetables, especially in asparagus, onions or garlic.

Lastly, synbiotics are combinations of probiotic bacterial strains and prebiotics. This basically means that the right bacteria come and bring their own food to your gut party.

Help your gut microbiome help you

So, by eating the right food, you can make sure the right, helpful bacteria grow and live in your gastrointestinal tract. And as a thank you for feeding them, they make sure to protect you and keep you healthy. Great bacteria and their superpowers.

The post How a healthy gut microbiome protects you and how to keep its superpower appeared first on Bacterialworld.
Bacterialworld - A blog about bacteria: from scientific studies to vivid stories about the fascinating bacterial world