Bacteria as vitamin suppliers

[pegasus10]

Hello, I read that bacteria that live in our gut are able to synthetize some vitamins. My question is: if we are in poor nutritional status, are they still able to do it? For example, I was thinking about niacin (vitamin B3): in order to produce it, we have to start from tryptophan, so if we don't eat enough tryptophan-containing foods, we are not able to synthetize this vitamin. But are our gut bacteria still capable of doing it?

Thanks in advance.

[PhilGeis]

Yes - e.g. E. coli can synthesize its own tryptophan.