Symbiosis - Wikipedia
Symbiosis is any type of a close and long-term biological interaction between two different . An example of mutualism is the relationship between the ocellaris clownfish that dwell among the tentacles of Ritteri sea anemones. The territorial It is derived from the English word commensal, used of human social interaction. Some have lifelong relationships with other organisms, called symbiotic relationships. There are three different types of symbiotic relationships: mutualism. Commensalism is a type of relationship where one of the organisms benefits Example: Dogs and humans have enjoyed a mutualistic symbiosis for centuries.
But these bacteria sometimes are involved in pathogenesis and so the signalling can be bad. The signalling pathways, for example, the important ones are found deep in the distal gut of your body. It's been found, for example that bacteroides which we'll talk a little bit about later - they provide the capacity to produce short chain fatty acids. These include things like acetic acid, propionic acid and butyric acid. Acetic acid, your listeners should of course know is present in vinegar.
It turns out when you eat vinegar as part of your diet it gets absorbed in the proximal part of your gut and it cannot penetrate deep into your distal gut. But the bacteria that live in the distal gut produce these short chain fatty acids including acetate, and it's been shown that the acetate can have a couple of functions. It can act as a food source for epithelial cells that line your gastrointestinal tract, nourishing them in what is actually a fairly nutrient poor environment because you've extracted all the goodies out early in your digestive tract.
Secondly these molecules act as signalling molecules. So, in particular a paper came out in where they demonstrated that acetate combined to a signalling protein called a G protein-coupled receptor on the surface of a subclass of T cells. These were T helper cells and it stimulates the T helper cell, and T helper cells are an important subclass of T cells that control other T cells.
T cells generally are a group of cells that play a central role in how we combat infection and the status of our immune system. We're talking about the human microbiome and the chemistry of gut microbes here on Up Close. The last 50 years of western diet has meant we're eating more processed foods and consuming an array of pharmaceutical drugs. There is an increase in heart disease, diabetes, even Autism Spectrum Disorder.
Spencer, surely we would see a change in the ecosystem of the gut. So is there any correlation between these particular diseases and changes in the microbiome? So a big question has been is this just a correlation that's coincidental or is there a cause? A change in the composition of your microbiome somehow causing these diseases. Increasingly the answer for some of these diseases appears to be yes.
There was a lovely study done about half a decade ago where they took a rat that was genetically predisposed to becoming obese and they did a transplant of microbiome from its gut into a lean mouse and they were able to show that the lean mouse, simply by changing the nature of the microbiome in its gut, became more obese. So I think that's a really nice clear example where the composition of the microbiome has a big effect on what we consider a very complex problem like obesity.
There's many other examples that are becoming identified and the particular one that I have an interest in is Crohn's disease.
Crohn's disease is an autoimmune disease that's poorly understood but it leads to poor bowel function, usually diarrhoea, regular passage, often many trips to the toilet every hour, let alone many trips to the toilet every day.
So it's a severe debilitating disease that has a profound effect on those suffering from it. Crohn's disease is often caused by a bacterium Clostridium difficile, so the basis of that disease is fairly clear in many cases that it's Clostridium difficile that's causing the problem. People with Crohn's diseases often have more of that bug, people that don't have Crohn's disease either have none of that bug or only a little bit of it.
That is, how does the microbiome respond to foods like artificial sweeteners? The body has never encountered these molecules before, how does it cope? Artificial sweeteners are an interesting thing that's become common in our diets since the s.
An interesting point about artificial sweeteners is that it doesn't seem to have an impact on the amount of sugar that we eat. We seem to have an insatiable appetite for sweetened foods, even if we take artificial sweeteners we still tend to consume significant amounts of normal sweeteners like sucrose. But this recent study looked at the effect on animals that were fed diets containing artificial sweeteners. So things like aspartame and saccharin, which I guess is now banned, and sucralose and related artificial sweeteners.
They showed that rats and mice fed these artificial sweeteners induced metabolic syndromes, a metabolic syndrome encompasses a wide variety of different conditions that include obesity and Type 2 diabetes. It appears from this study that consumption of these artificial molecules that are present in artificial sweeteners was one of the causes for the induction of metabolic syndrome.
So the outcome of this study was that these artificial sweeteners correlated to an increase in obesity and diabetes, this was done in animals so whether or not this transfers into humans is an open question but it's something that definitely needs additional study.
Can we create good environments like the sort of prebiotic approach? Or can we actually replace the bugs as a sort of probiotic approach? One is simply to inoculate somebody with what we think are good bacteria and perhaps hope they will displace the bad bacteria or perhaps give them a course of antibiotics to kill off the bad bacteria and hope to repopulate with good bacteria.
That's what you'd call a probiotic approach and we kind of use these approaches already through consumption of yoghurts and the like but I think there's a good chance that we could expand this sort of approach to include a wider range of bacteria and perhaps even genetically engineered bacteria that have the capacity to produce molecules that we're now learning are good for health.
A second approach is to change our diet. Do certain bugs prefer certain food sources in things that we eat and might other bugs prefer other food sources in the things that we eat, and by changing our diet or having certain additives, might we promote the growth of one bacteria, hopefully a beneficial bacteria, in preference to a bacteria that causes disease.
I'll give one example of, again another recent study that came out right at the start of this year in In this study, dealing with Clostridium difficile which as I mentioned is one of the causes of Crohn's disease, they ask the question why does Crohn's disease populate the gut and is it displacing some other bacterium, and if you could identify which other bacterium it's displacing maybe you could super colonise an infected person with this other bacterium that should have been there in the first place.
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What this lovely study published in Nature demonstrated was there was another variety of Clostridium that is not pathogenic but has the ability to super colonise and displace Clostridium difficile. So it's actually a bacteriotherapy that you would use to manipulate the microbiome and alleviate the symptoms of Crohn's disease.
In this episode we're talking about our microbiome with chemist Spencer Williams. Now humans have been eating fermented food and drink, including beer and bread, for the last years. This has led to the evolution of bacteria eating yeast from the fermented foods.
The bacteria, known at Bt may possibly hold the key to strengthening the immune system in humans and treat various bowel disorders like Crohn's disease. Spencer, lower us in. How does yeast eating bacteria operate in our digestive system? So humans domesticate other organisms to act in our service, obviously cattle and sheep are one example but we've also domesticated microorganisms and it's estimated around years ago that we domesticated yeast and it's become a common part of our diet.
You mentioned of course in fermented food, so things that we eat like bread and particularly bottle fermented ales, also soy sauce. We regularly eat small amount of fungus as part of our diet. So I guess it's not unexpected that our gut may have adapted to this change in our diet.
This recent study that we published in Nature in demonstrated that there are special bacteria that exist in our guts that provide the capacity to break down cell wall components of yeast in our diet.
Human and Bacteria Mutualism by Kelly Lee on Prezi
As I mentioned, humans have done a lot of domestication of different organisms and in fact this flows through in to other animal species. So we went looking for where this bacteria can be found and can it be found in other organisms. In fact the only other place we were able to locate this bacteria were in pigs and they were located in a piggery adjacent to a brewery.
Of course a brewery, one of the by-products of a brewery is spent brewer's grain. So this is grain that's been fermented with yeast and it's an industrial by-product that you then feed to pigs and of course now these pigs have a history of consuming domesticated yeast and those pigs as well also had bacteria in the guts - that had the same capacity that we thought was uniquely in humans, well in fact it has spilled over to one animal species that we were able to identify.
When we consume foods, early in our digestive system we break down certain polysaccharides, so things like starch and sucrose, they get broken down and we use them as food. Other polysaccharides which include things like dietary fibre and in this case includes the cell wall of the yeast, pass through our gastrointestinal tract and reach our distal gut. It's there where the bacteria lives and it uses the cell wall components of the yeast as a type of food. Now what our work has shown is that the bacterium has a really complex machinery of enzymes that are found on the surface of the bacteria that can trim these very complex structures in the yeast cell wall, then import them into what's called the periplasmic space, so a space between the outer wall and the inner wall, where they are then degraded down to individual monosaccharides, so just single sugars that are directly useable for energy.
What Is a Symbiotic Relationship? | Sciencing
You mentioned in your opening that these bacteria are involved in a symbiosis and in fact this bacteria produces those short chain fatty acids that I mentioned before. So upon digesting the yeast cell wall and in fact other polysaccharides, they produce a wide range of short chain fatty acids which are then released and that nourishes our cell wall.
One of the interesting components of our study was sometimes Bacteroides thetaiotaomicron, acts as a keystone species and other bacteria can live around it. But in particular with this component of the yeast cell wall it has a selfish mechanism, it takes it up exclusively and does not release anything out.
So this idea of a particular food source that can only be utilised by a particular bacterial strain may have uses in biotechnology and possibly in treating human health.
So how does this relate to Crohn's disease? It's a fairly complex story but let's slowly work through the issues. So the direct correlation is perhaps not there but there's lots of interesting connections. Patients with Crohn's disease often have a marker antibody that they produce called the ASCA antibody. So people with severe Crohn's disease often have an anti-body that's against yeast.
Mimicry Mimicry is a form of symbiosis in which a species adopts distinct characteristics of another species to alter its relationship dynamic with the species being mimicked, to its own advantage. Batesian mimicry is an exploitative three-party interaction where one species, the mimic, has evolved to mimic another, the model, to deceive a third, the dupe.
In terms of signalling theorythe mimic and model have evolved to send a signal; the dupe has evolved to receive it from the model. This is to the advantage of the mimic but to the detriment of both the model, whose protective signals are effectively weakened, and of the dupe, which is deprived of an edible prey.
For example, a wasp is a strongly-defended model, which signals with its conspicuous black and yellow coloration that it is an unprofitable prey to predators such as birds which hunt by sight; many hoverflies are Batesian mimics of wasps, and any bird that avoids these hoverflies is a dupe. Amensalism is an asymmetric interaction where one species is harmed or killed by the other, and one is unaffected by the other.
Competition is where a larger or stronger organism deprives a smaller or weaker one from a resource. Antagonism occurs when one organism is damaged or killed by another through a chemical secretion. An example of competition is a sapling growing under the shadow of a mature tree. The mature tree can rob the sapling of necessary sunlight and, if the mature tree is very large, it can take up rainwater and deplete soil nutrients. Throughout the process, the mature tree is unaffected by the sapling.
Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling.