Abstract
Species composition and growth-temperature characteristics of coliforms isolated from several types of environmental samples were investigated. It was possible to divide these isolates into eight distinct groups, six species groups and two unidentified, on the basis of their biochemical properties. The isolates included in the unidentified groups, giving IMViC reactions of --++ and -+-+, were tentatively termed "typical psychrotrophic coliform (TPC)" bacteria because of their ability to grow at 1°. The TPC bacteria and Citrobacter freundii constituted the normal coliform flora of mountain soil and stream water samples. In contrast, Escherichia coli and Klebsiella pneumoniae were major predominant coliforms in polluted river water and sewage samples, the former being most common in human feces samples. In testing the growth response at different temperatures, the isolates of E. coli and the TPC bacteria showed relatively constant temperature preferences regardless of origin, whereas those of other coliform members gave varied results dependent upon their sources. The results provided circumstantial evidence that population densities of coliforms able to grow in EC broth at 43° and above but not in ordinary nutrient broth at 5° within 7 days of incubation in the environment are directly proportional to the degree of potential fecal contamination.
