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.