FACTS ON DRINKING WATER. Coliform Bacteria â Total Coliforms & E.Coli. Total coliforms are a group of bacteria commonly found in the environment, for example in soil or vegetation, as. well as the intestines of mammals, including humans. Total coliform bacteria are not likely to cause illness, but their. presence indicates that your water supply may be vulnerable to contamination by more harmful microorganisms. Escherichia coli (E.coli) is the only member of the total coliform group of bacteria that is found only in the intestines of. mammals, including humans. The presence of E.coli in water indicates recent fecal contamination and may indicate.