According to BBCiWonder, your body has more micro-organism cells – such as bacteria, archaea, fungi and viruses – than human cells! Some estimates suggest it may be as much as 10 to one, others are more conservative. These organisms make up what’s called your microbiome, and the vast majority of these microbes are bacteria – and we carry around 100 trillion of them. That’s 100,000,000,000,000.
But don’t worry – they aren’t all bad. You actually need most of these bugs to lead a healthy and happy life. Consider some instances
Staphylococcus aureus is an example. It is usually harmless but some strains, like MRSA, are associated with disease, and if a full-blown infection sets in, the result can include life-threatening symptoms.
Luckily most types, S. aureus will not harm us and these bacteria must share your nostrils with their relative and rival Staphylococcus epidermidis, which helps keeps S. aureus in check.
Your mouth provides a warm and hospitable environment for bacteria, colonising sites such as the tongue, the roof of the mouth and around the gums. Approximately 700 bacterial species have been discovered in the human mouth!
Gas-producing bacteria on your tongue cause chronic bad breath, but the most dominant ones are the streptococcal species like Streptococcus mutans, which loves sugar and is responsible for tooth decay.
Also, next time you exchange a passionate kiss, just remember your saliva (and your partner’s) contain around 10 million organisms a millilitre.
Your gut contains the largest, densest and most diverse microbial community in your body. The bacterial load increases as you travel down the gut, with the top of the small intestine having the lowest number of bacteria and the colon being the most heavily colonised. In fact, up to half the mass of faeces consists of microbes (one trillion microbes per gram of poo).
Some bugs, such as Bifidobacterium, can bring out the health benefits of specific foods they help to digest, like chocolate, by producing compounds that are anti-inflammatory. Others, like Escherichia coli, may cause food poisoning.
The microbial community of the vagina is often dominated by Lactobacillus bacteria, which turn sugars to lactic acid, yielding a low pH environment that makes it toxic to pathogens. Conversely, when levels of Lactobacillus drop, the pH becomes more neutral, increasing the risk of infections such as bacterial vaginosis.
As for men, the male sexual organ is inhabited by microbes, both on the outside and inside of the urogenital tract. One of the strongest determinants of the genital microbiome is somewhat surprising. Circumcision drastically alters the microbiome of the penis and uncircumcised men have significantly more bacteria on their penis.
Your largest organ – your skin – is home to around 1,000 different strains of bacteria, and their population vary across the body depending on whether the site is oily (like the side of your nose), dry (like your forearm) or moist (like your armpit). The oily areas have the least diverse communities of bacteria, and dry areas have the most diverse.
A common skin resident and one that prefers moist areas like your armpits, is Corynebacterium. It and other bacteria in your armpit process your sweat, and cause bad body odour.
How Bacteria Help the Body
- The microbiome is critical for immune system development. One idea is that there is a greater tendency to have allergies due to altered microbiomes in infancy.
- When gut bacteria from obese people were transplanted into mice, they gained weight. Transplanting the same bacteria from lean people kept the mice slim, showing the role they play in helping to maintain a healthy weight.
- Gut bacteria help us extract more energy and nutrients from food by breaking down compounds that we cannot digest alone.
- Probiotics are edible cocktails containing live ‘good’ bacteria – such as lactobacilli and bifidobacteria – that may confer health benefits by competing with harmful bugs. An example of probiotics is yoghurt.
How Can You Improve Your Good Bacteria?
- Eating a diverse array of fruit and vegetables is also good for your bugs. They contain prebiotics that we cannot digest, but help the probiotic bacteria in our gut.
- Use antibiotics in moderation – Antibiotics not only kill disease-causing bacteria but also the beneficial bacteria you host. That’s why diarrhoea is a common side-effect of many antibiotics, even short-term antibiotic use can lead to resistant bacterial populations in your gut that lasts for years. One study found that the use of antibiotics in early life may increase the risk of developing eczema by 40%.
Faecal transplantation is a procedure that restores healthy gut bacteria by introducing stool (yes, poo) from a healthy donor into a patient’s gut. It is used to cure deadly C. difficile infections. A trial found that 94% of C. difficile patients were cured with donor faeces, while only 31% were cured with antibiotics.
Now, let it never be said by you that an introduction was never made!