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  • Alex Cloherty

Bacterial philosophy: What does it mean to be good or bad?

Merry Christmas, everybody! This one is coming to you from a Canadian time zone, so it's a bit shifted from usual. And since it's Christmas, this post is inspired by peace. More specifically, the bacteria we live in peace with.

It all stems from a question that my Mum asked: what is the difference between "good" and "bad" bacteria? I like to look at this from an evolutionary perspective. In my view, the "bad" bacteria are simply the ones we haven't learned to live in peace with yet.

Think of the relationship we have with the bacteria in our guts. You probably don't think about it too regularly, but we have whole civilizations of bacteria in our intestines. And we get along with these just perfectly! These "good" bacteria help us with our digestion, and even with fighting off "bad" bacteria that could make us sick. In return, we give the bacteria a warm, safe home with lots of food. These mutually beneficial relationships between our human bodies and the "good" bacteria have developed over millennia. The "good" bacteria are the ones that we need now to stay healthy.

I divide the "bad" bacteria into two subtypes. The first type I think of as bad due to placement, and the second as bad due to timing. You can think of the poorly placed bacteria as just being lost. For instance, Staphylococcus aureus is a bacteria that is normally found on the skin, and is totally harmless while it's there. However, if it gets into your bloodstream, it can be bad news. It's just"bad" if it's in the wrong place.

What about the poorly timed bacteria? I like to think of them this way: if we humans are the parents in the house, these bacteria are like the teenagers. We'll get along with them again when we're all a little older. On an evolutionary (read: huge) timescale, that is. These bacteria would include ones like Clostridium difficile, which can cause terrible intestinal infections. But, maybe if we humans have another few million years of living with these bacteria, we'll both evolve to the point where we can get along. Do note that this is just a hypothesis (an educated guess), though - it's hard to measure things on evolutionary timescales!

That's all for this week's post; it is short and sweet. With it I hope to leave you with a Christmas-y message: we can live in peace, with time!

Til next week,


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