Guess it's time for a shower!
Many of them are good.
There are bacteria in the gut that make a chemical. A chemical that if you didn’t have it, your clotting ability would go crazy.
It was never at least early on identified as a vitamin, because just about everyone has enough of it from the bacteria, so deficiencies were unknown - but now they know.
Vitamin K.
Alot of the good bacteria pretty much are happy to just hang out, they crowd out any bad stuff from getting in.
Your immune system is constantly being refined and tuned - something like 70 percent of a humans immune system lives in their gut - where there is a possibility of being infected by something you eat.
I think I read something somewhere about bacteria having a positive affect on Vitamin E metabolism also.
So they’re not all bad!