Streptomycin II, An Antibiotic Substance Produced by a New Species of Streptomyces*

The production of streptomycin by actinomycetes is limited to certain strains of a single species of the genus Streptomyces, known as S. griseus. In addition to the first 2 streptomycin-producing strains isolated in 1943, only 3 other streptomycin-producing strains have thus far been reported. Although over a hundred cultures of S. griseus, isolated from different substrates, have now been tested in our laboratory for their antibiotic properties, only one culture was found capable of producing streptomycin; several others were capable of producing antibiotic substances such as grisein, which differed, however, from streptomycin. Similar results were obtained by Carvajal, who isolated 2 streptomycin-producing strains of S. griseus. No other organisms culturally different from S. griseus have been found capable of producing streptomycin.In connection with a study of the bacterial population of the waters around Bikini and Rongelap Atolls during the recent atomic bomb experiments in the Marshall Islands, a culture of an actinomycete was isolated from one of the Bikini soils. This culture showed strong inhibition of various Gram-positive and Gram-negative bacteria, as well as of acid-fast bacteria. This culture belonged to the genus Streptomyces, but was distinct from streptomycin-producing S. griseus.This culture was very similar, both morphologically and culturally, to S. griseolus (Actinomyces 96) described by one of us in 1919. It differed, however, in some of its cultural properties and in its ability to produce an active antibiotic substance. Because of these differences and also because of the peculiar natural substrate from which this culture was isolated, it is proposed to designate it as Streptomyces bikiniensis. It produces on synthetic and on organic media containing glucose, a dark gray aerial mycelium, which consists of dichotomous branches with straight chains of conidia. A thick complete pellicle is formed on the surface of stationary cultures, with protein-containing media being pigmented brown to black.