Why do coliform bacteria smell so bad? I have done multiple cultures of _E. coli_ bacteria and related species over the course of my education. Almost every time, they had this revolting smell. However, other organisms used for genetics experiments (eg. _Saccharomyces cerevisiae_ ) rarely have a bad scent, if a scent whatsoever. My question is, what is it about the coliform metabolism that produces such a pungent and revolting odor? Any and all answers are appreciated.

_E. coli_ and other bacteria metabolize tryptophan into odoriferous skatole and other indole compounds.

If you're culturing these organisms in medium that contains tryptophan, that may be what you're smelling.