eli5 why does E-coli is in our digestive system even though it’s dangerous


Okay so of course everyone know what E-coli is, it’s a bacteria that can cause food poisoning. But a few years ago in biology class I realized it’s also a microbe in our gut system. So how does something that’s dangerous live inside our gut without affecting us?

In: 2

It’s mostly harmless. E Coli is all over the place, you ingest it regularly. Only some strains of it, mostly from cattle, IIRC, are dangerous.

I’ll try to go for a true ELI5 here. The E. coli which lives in our gut is harmless because it’s the domesticated variety. But sometimes these bacteria can become wild and dangerous, and that is the pathogenic variety. They will attempt to make a living from the parts of a human body that they are not supposed to, causing disease.

Strains that cause diseases have evolved to produce toxins or invade through intestinal lining, unlike e coli that, along many other bacteria, lives in our digestive tract without harm. Some of notable ones are enteropathogenic, enterotoxigenic, enterohaemorrhagic etc.

E. coli is usually harmless. Its presence just shows that water has been probably contaminated with sewage water or sth similar, and that is why it makes us concerned

It’s harmless if it stays where it is I.e the gut but can cause problems if it goes elsewhere such as the urethra which causes about 90% of urine infections