Bacteria: The Good, the Bad and the Ugly

Bacterial Biota of the Body

In our bodies we have a staggering 32 trillion cells, but that stills falls a couple trillion short of our 39 trillion resident bacteria. You might have heard the 10:1 ratio, 100 trillion bacteria to 10 trillion human cells, but scientists are fairly conclusive that that’s an unsupported view and in actual fact, the numbers are close enough for bacteria to fall behind the human cells every time you make a toilet trip!

But regardless of numbers, if you’re up-to-date with science, you’d be well aware of the prominence of our own microbiota in obesity, disease, psychological and even research into our intelligence (these links are all to open-access research articles if you’re interested in further reading).

Anyway, on with our story. What do bacteria in your body actually do? And also, which people have less good bacteria and how do we get more?


Bacterial Benefits

They’re pretty important. Living largely in your large intestine, bacteria play a major role in digestion. They can break down some of the stuff in our food that our body can’t (particularly a lot of high-fibre foods) and produce vitamin B and K and smaller, absorbable that we can then use! It’s a great example of a mutualistic relationship … a type of symbiosis where both parties benefit. In this case, the bacteria are fed and housed without hurting us and we gain from their byproducts of eating our ‘wasted’ food. (However, they do also produce that nasty-smelling hydrogen sulphide in your … ahem, flatulence)

One thing that’s really fascinating is that among our thousands of species we have a strain of Escherichia coli (E. coli), a species with other strains that can also cause severe diarrhoea or other nasty infections. The strains are similar enough to still be considered one species, but one helps us and the other tries to sicken us!

Anyway, back on topic, as a whole, our bacteria do a lot more than just digestion, with some of the stuff the secrete having an effect on our emotions and happiness and how we gain/lose weight, with people predisposed to being thinner or larger based on their personal bacteria.


Building Bacterial Biota

Having a healthy microbiome is then key to living a healthy lifestyle, but how do we achieve it?

Firstly, much of your personal microbiota was inherited from your mum’s birth canal. Yup. That’s where babies pick up their first bacteria and it does also mean that children born via C-section have considerably less diversity and amount of bacteria, which can cause some ongoing issues throughout their life. Similarly, people who have been exposed to high amounts of antibiotics have generally had a considerable amount of their bacteria killed (another reason not to overuse these!!!). Also others who have had their appendix removed face additional bacterial challenges, because the appendix acts as a ‘safe house’ for bacteria if they’re threatened by severe diarrhoea or other nasty gastrointestinal (GI) tract infections. Once the infection’s gone, the bacteria ‘come out of hiding’ and repopulated the large intestine; however, without an appendix this repopulation takes far longer.

Anyway, backing to building up our bacteria.

  1. You can eat high-fibre or fermented foods that feed the bacteria. Veggies and fruit with skins are great for fibre and fermented foods including yoghurt. However, try to avoid too much sugar, as we digest it fine before it gets to our microbes and the poor things get hungry and decide to eat our gut lining. So yeah, avoid excessive sugar.
  2. Try to be less stressed and get more sleep. These go hand-in-hand because if you’re sleeping more, you tend to be less stressed and the state of being stressed releases chemical messengers to your body that harm your bacteria. Plus, being less stressed and sleeping more will help your overall health!
  3. Go exercise! Your bacteria love your good workouts, and when you pay a trip to the gym, they tend to increase in number and diversity benefiting you!
  4. I’m not going to rant about antibiotic overuse.

But actually … antibiotics kill bad bacteria and good alike. That’s a necessary evil if you have a bad bacterial infection, but it will take your gut a while to recover, so only take antibiotics if they’re needed and avoid over-santizing yourself in general. Continually hand-washing and sterilising are not appealing to your bacteria who will pack up and leave. Figuratively, of course, but you don’t need to cover your house in antibacterial cleaning products. Please. For our future. Because they can contribute to antimicrobial resistance, aka, ‘superbugs‘. Trust me, we need to avoid that!


Bad Bacteria

By now, some of you are wondering about the bad bacteria. The nasty ones that make you sick. The terrible superbugs. The ones that have earned bacteria a bad name.

Well they do exist and some of them definitely are living inside you right now; however, the bacteria in our GI tract can’t actually do a lot to you. That’s because technically they’re not inside our bodies. If you think about it, food goes in your mouth, through this tract and back out the other end, almost like there’s a hollow tube running through the middle of your body. Stuff gets absorbed through the thin-walled cells lining the tract but bacteria are big enough that they can’t get in and your cells don’t want to let them in. So that means any bad bacteria are under forced separation from the real interior of your body.

Secondly, there are more good bacteria than bad, so the bad bacteria are outcompeted. Pretty much, the good bacteria are a lot better at living off the food that you’ve eaten than the bad bacteria, so most bad bacteria die and good ones flourish. Yay!


Well, I think we’ve come to the end of a short overview of your personal microbug colony. Living with us since birth, these devoted organisms help us every day and impact us in more complex and subtle ways than we ever imagined as we’re discovering more about them every day.

*Just joking about their devotedness, as mentioned at the beginning, we get rid of several trillion every toilet trip and the rest only ‘live’ for an average of 12 hours before dividing. As bacteria don’t die from age, their lifespan is frequently defined as the amount of time before they divide into two bacteria!

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