Constancy of Characters Differentiating Intermediates in the Escherichia-Aerobacter Group and their Interpretation

Abstract

Strains were grown in milk, in the presence of inhibitory dyes, in coldblooded animals, on stones immersed in water and in soil. Tests were made at intervals to determine departures from original type under these changed environmental conditions as judged by the following criteria: Methyl red and Voges-Proskauer tests, utilization of citrate, indol production and ability to grow at 46[degree]C (Eijkman test). Some changes were noted, particularly in indol production, citrate utilization and the Eijkman test, but the complete persistence of the differential characteristics of the Escherichia shows that reliance should be placed on the identification of this genus (perhaps including Citrobacter) as an index of fecal pollution rather than upon tests to indicate the immediate environment from which the organism was introduced.