Color enhanced TEM of a negatively stained Escherichia coli K12 strain. The colon bacillus E. coli is a short, plump, gram negative, non spore-forming, motile bacilli almost constantly present in the alimentary canal of man where it is normally nonpathogenic. E. coli is responsible for infections in other systems and for enteritis in infants. Certain enteropathogenic strains are a principal cause of traveler's diarrhea. Magnification: x6,250 at 35 mm.