Antagonism by Aerobacter Strains

Abstract

The antagonistic action of an Aerobacter strain was tested against 21 common bacterial spp. by a semi-quantitative method involving the determination of the ratios of viable cells of the test organism to viable Aerobacter cells at intervals in mixed cultures. Definite antagonism of varying degree was exerted against 6 of the 7 Gram-positive species and 8 of the 14 Gram-negative spp. tested. Only minor differences were exhibited in the effects of 8 Aerobacter strains on 3 test spp. Attempts to demonstrate resistant forms of affected spp. were unsuccessful, and no appreciable differences were observed between the antagonistic action of a common stable Aerobacter variant and its parent strain. Berkefeld and Seitz filtrates of Aerobacter cultures were inactive as well as cultures heated to 60[degree]C for 1 hr. A marked bactericidal action was evident, but whether or not complete destruction of the cells of any species occurred was not established. Though the mechanism of the antagonism described is unknown, it may involve some direct action of living cells.