The Microbiome: Exploring the Trillions of Bacteria, Viruses and Fungi that Tirelessly Keep You Alive

“New Premium All-in-One Exclusive Gold Mega Super-Sanitiser Kills 99.9% Of Bacteria!”

...

“But what happens to the other 0.1%?”

Having grown up in a world where adverts manage to find their way into just about every online or real life space physically possible (bar certain internet firewalls), I'm sure you've all seen ones like this, and the more inquisitive of you will have probably noticed that 99.9% does not equal 100%. But given bacteria's reputation of causing widespread disease and collapsing entire empires, this begs the obvious question of why nobody has tried to increase their product's sanitising efficiency by what seems like a meagre 0.1%.

Firstly, it is highly likely that a few bacteria would have randomly developed resistances due to mutation. This barrier is difficult to overcome, so achieving 100% efficiency is pretty much impossible anyway. Boring, isn't it? However, another reason is that there is simply little reason to do so - many of those 0.1% of bacteria are, in fact, beneficial for us.

Microbiomes - An Overview

Let’s say you decided to abduct someone and wantonly breach biological procedure by failing to sterilise the subject before examining their body under a microscope lens. One thing would immediately be striking: there are a lot of microbes. According to New Scientist, these microbes outpopulate even our own body cells; an average human body consists of 30 trillion human cells, a figure dwarfed by the 38 trillion microbial cells - mainly bacteria, viruses and fungi - that share the living space.

Their population density is highest in the guts, although many inhabit other regions: the skin, lungs, nose, mouth, even the brain, to name a few. In fact, it is difficult to find a place devoid of them; even within the lymphatic system - the graveyard of microbes, patrolled tirelessly by white blood cells - some slip under the radar.

However, what differentiates the bacteria in the former and the latter is the way the body responds to them. In lymph fluid, the presence of microbes is usually a sign of infection and can cause inflammation or even grow into systemic disease, thus an immune response is stimulated to eliminate them - a familiar procedure for microbes inside organisms.

On the other hand, the much more obscure outcome is ironically the one that occurs far more often for bodily microbes - they form symbiotic relationships with their host organs, allowing them to both thrive and provide services for their host, such as digesting food molecules in the gut that the body’s own biomolecules cannot handle on their own. These bacterial populations within our bodies grow rapidly, to the point where in most healthy humans, they actually outnumber cells. These sanctuaries, known as microbiomes, are where many of the bacteria from the remaining 0.1% tend to end up (thankfully, the few harmful ones usually succumb to a fate more similar to the lymph fluid one).

Now, back to our friend under the microscope lens. To spare him from dissection (and us from bureaucratic legal paperwork), let’s focus on his skin microbiome. With one glance down the lens, you would immediately find it swarming with bacteria, viruses, mites and even fungi - not exactly what many people would imagine wanting on their skin. But don’t put our friend in quarantine just yet - because, in fact, these microbes are actually essential for the functioning of the skin, rather than just a product of failure to shower (well...unfortunately that possibility isn't entirely out of the question either).

The Skin Microbiome

The Importance of the Skin Microbiome

Our skin microbiomes have existed since birth, originating from maternal vaginal and gut bacteria, and have grown over time as increased contact with the outside world caused microbes to accumulate on our skin, fed and nurtured by sebum naturally produced by our skin cells. Throughout childhood, these microbes trained our immune system to identify stimuli from harmless sources and ignore them, instead focusing on detecting and attacking those from genuinely harmful pathogens. In fact, studies show that people with greater skin bacteria diversity are less likely to have allergies than their counterparts.

The existence of these microbes on the skin also prevents new pathogens from being able to attach, as there is little space available for them. The microbiome can even directly get involved in defending the skin from pathogens, by secreting chemicals inhibit their growth or kill them directly. For example, Staphylococcus epidermidis is a species which produces antimicrobial peptides to combat more harmful bacteria, such as Staphylococcus aureus, a strain notable for causing skin blisters and painful swelling.

Furthermore, the microbiome is essential for beauty - the layers of cells that form our skin are held together and protected by lipids that make our skin appear smooth and wrinkle-free. Certain bacteria in the microbiome help produce and replenish these lipids, such as Cutibacterium, a species which stimulates the production of sebum, a mixture of lipids that maintains skin moisture and acts as a protective barrier against foreign pathogens, and Streptococcus thermophilus, a species which produces ceremides, lipids with the same function as sebum. Therefore, they are vital for maintaining the structure of the skin.

This can be proved by the effects of ageing. As we get older, the skin microbiome can be disrupted and gradually degenerate, as the helpful bacteria get replaced by harmful ones. This change has been linked to acne and eczema among other skin diseases, and problems with wound repair.

How to Nurture your Microbiome

There is currently research into multiple forms of treatment, some...more orthodox than others. They range from the usual prebiotics (taking supplements of nutrients that keep the healthy bacteria alive), probiotics (the more direct method of smothering helpful bacteria directly onto the skin), and postbiotics (applying the products of beneficial bacteria to the skin as a supplement); to activities such as mud therapy (yes, it's exactly what it says on the tin) and gardening, which increases diversity of bacteria in the skin through outside exposure, albeit temporarily (most new bacteria fall off and disappear after 12 hours).

However, the easiest way to look after your skin microbiome naturally is to simply have a balanced diet, involving plenty of vitamins, minerals, and fibres, to enable the unobstructed growth of our beneficial bacteria. This is due to a phenomena known as the ‘gut-skin axis’, which shows how the gut microbiome influences skin health. Evidence suggests there is a trend between fast-food heavy diets and acne, supporting this claim.

Now that our friend has shown us an example of a diverse microbiome, it is reasonable to say he has played his role, and it is unfortunately time to end our Schadenfreude and let him go, accompanied with a bag of sweets, a shower operating manual, and a sticker to brag to the world that he was once a test subject.

If there is anything for you to take away from this, it is that looking after your skin microbiome is important. This doesn’t mean don’t shower - in fact, not showering is likely to reduce microbiome diversity, as pathogens can take over the microbiome. Furthermore, most evidence suggests that washing skin has little to no adverse effect on the skin microbiome, providing strong products are not used excessively (though admittedly, accurate data is difficult to obtain due to the abundance of control variables). Therefore, it’s time for some of the people we know to accept that even for their skin microbiome diversity, all indicators show that the benefits of showering obviously outweigh the costs.