The Latest in Medical-Biology: Oxbridge Prep Article

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The Miracle of Microbiota

By Síle, PhD Graduate Medicine (Oxford)

The Miracle of Microbiota

Applying to Oxbridge or an equivalent high level University, it’s hugely important to read around your subject and especially in the Sciences, be aware of any current developments in the field. u2 mentor, Síle (PhD graduate & Graduate Medicine student at Oxford) discusses the amazing wonders of ‘microbiota’:

Did you know that you have ten times more bacterial cells in your body than human cells? Collectively, these bacterial cells are known as our ‘microbiota’ and they live on pretty much every surface we’ve got along with parasites, fungi and other microbes. We have them on our skin, in our noses, our mouths and very importantly, in our gut. Although we often think of bacteria as being dangerous, these bacteria that live inside and on us are important for everyday functions such as digesting food, providing nutrients for the brain and protecting us from infection by other, more dangerous bacteria. Furthermore, our microbiota is linked to pure responsiveness to certain drugs such as cancer chemotherapies and HIV-prevention drugs. Here, we will discuss only some of the amazing contributions the microbiota has to our overall well-being such as helping digestion, shaping our immune system and contributing to brain activity.

The microbiota and our gut

Our large intestine contains an astronomical 1 x 1012 (one million million) bacteria per gram. Bacterial colonization of the gut begins at birth and continues throughout our lives. Much of the bacteria we have at the beginning come from our mothers when they give birth to us. Subsequent changes are induced by environmental factors such as the water we drink and the food we eat. The bacteria within our guts are very helpful to us: they digest certain foods we eat so we can extract important nutrients that we might otherwise be short of. Furthermore, they protect us from dangerous bacteria such as Clostridium difficile which can cause severe diarrhea. This is apparent when we take a course of antibiotics, which wipe out our gut bacteria, allowing the nefarious Clostridium to take over our and make us sick. This is one of the reasons why it is imperative that we don’t take antibiotics unnecessarily!

The microbiota and our immune system

The bacteria in our gut are also critical for establishing our immune system. It has been shown time and time again that an imbalanced gut microbiota can result in a dysfunctional immune system. This is particularly evident in autoimmune diseases which are prevalent in people whose microbiota was not properly established. This is thought to happen, for example, in children who are born by Caesarian section who are known to have an aberrant microbiota at birth and are also known to have a higher incidence of autoimmune diseases compared to the general population. One study looked at the effect of birth by Caesarian section on the development of asthma in mice. The mice that were born by Caesarian section had a higher incidence of asthma than mice born by natural delivery. Interestingly, mice born by Caesarian section that were reconstituted with a ‘healthy microbiota’ immediately after birth were more similar to the natural delivery group suggesting that a healthy microbiota can help prevent the onset of autoimmune disease. There are numerous reports in the media of late describing a clinical practice called ‘seeding’, whereby a baby born by Caesarian section is swathed with a towel covered in bacteria from the birthing canal in a bid to create a healthy microbiota for the child. However, this process has polarized opinions in the medical field, as the benefits seen in animal experiments have yet to be evaluated in humans. 

The microbiota and our brains

There is an ever-growing body of evidence to demonstrate the importance of a healthy microbiota on good brain function. This relationship is often referred to as the ‘gut-brain axis’. The bacteria in our gut can synthesis molecules which our brains use to function. These neurotransmitters are essential for transmitting information between neurons (hence the name) and the absence of certain types of bacteria which make these molecules can results in psychiatric illnesses such as depression and anxiety disorders. In fact, mice born into special sterile environment without a microbiota exhibit depressed stress reactions and erratic behavior, suggesting of an important role for the microbiota in maintaining our mental health.

What can I do to keep a healthy microbiota?

 So now that we know how important our microbiota is for our health, what can you do to ensure its healthy? There is huge public (and commercial) interest in the use of probiotics in preventing and treating a multitude of disorders. A number of studies in animals have found probiotics to be beneficial in treating depression, anxiety disorders, gut inflammation and even cancer. In one of these studies, one bacterium in particular, Bifidobacterium, was found to be more effective at treating mice with clinical depression than anti-depressive medication. These studies and others are giving us reasons to believe in probiotics as a reasonable measure to protect our microbiota, but we still need evidence from long term studies in humans to be absolutely sure.

One certain intervention we can take to protect our microbiota is to avoid the unnecessary use of antibiotics. Examples include the common cold or flu, which are viral infections and as such, do not respond to antibiotics. There are some studies which suggest long term disruption of the microbiota following antibiotic use which caused long term susceptibility to gut inflammation.

There is also an emerging treatment option known as a ‘fecal transplant’; this is where poo from a person with a ‘healthy’ microbiota is given to someone with an ‘unhealthy’ microbiota in a bid to ‘reset’ the bacterial community in the gut of the latter. It sounds gross, but the results have been very persuasive in animal and pre-clinical studies, meriting further investigation of the power of the microbiota on the overall health of an individual.

 In summary, our microbiota is amazing - it protects us, feeds us and keeps our brains functioning. There are an ever-increasing number of roles for our bacteria that are being discovered, and it is apparent that we must take care of them!