THE BIOLOGICAL CHARACTERISTICS OF STREPTOMYCIN-DEPENDENT MYCOBACTERIUM RANAE

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Abstract
Quantitative data are presented on the origin and occurrence of mutants from streptomycin-dependent strains of M. ranae. A 2d streptomycin-dependent variant, B1, was isolated from a streptomycin-resistant population of M. ranae which was sensitive to sulfonamides. All attempts to demonstrate streptomycin-dependent variants in the parent streptomycin-susceptible population were unsuccessful. B1 variants grew in concns. of streptomycin as low as 0.05 [mu]g./ml. Repeated subculturing in very low concns. of streptomycin gave rise to a strain that neither grew in the absence of streptomycin nor in the presence of high conens. of streptomycin. Streptomycin-susceptible strains were recovered from streptomycin-dependent strains, the no. varying with the size and character of the population and with the concn. of streptomycin in which the dependent cells were growing.