The systematic screening studies for antibiotics inhibiting Piricularia oryzae, a cause of rice plant disease, have been made in our laboratory with cooperation of Fukunaga and others, National Institute of Agricultural Science, Tokyo.
A strain isolated from a soil sample collected at Gazaki, Wakayama Prefecture, produced antifungal substances which were named blasticidins A, B and C. This strain was identified to be a new species, Streptomyces griseochromogenes. These results were briefly reported by Fukunaga and others1.
During further studies on blasticidins, an other antibacterial substance was isolated from the culture broth of the same strain. This antibiotic was different from blasticidins A, B and C and exhibited antibacterial effects on miscellaneous bacteria including Pseudomonas, and also a strong inhibition on Piricularia oryzae. It was named blasticidin S by the present authors. The production, isolation, and properties of blasticidin S are presented in this paper.
A research for new antibiotic produced by soil actinomycetes, has been carried in our laboratory for the past several years. Streptomyces No. 63 was found to produce a very unstable substance showing characteristic broad antimicrobial spectrum. Recently the crystal of its sulfate was obtained and it was studied in detail and confirmed to be a new antibiotic on the basis of its physical, chemical and biological properties. This unstable antibiotic was named Latumcidin.Comparing with the known antibiotics, it has been found to resemble in some points with eulicin which was reported by Charney, et al.(1)(2) in 1955. However, latumcidin seems to be somewhat different from eulicin in Sakaguchi reaction and other respects.The physical appearance of this organism and its growth characteristics on various media were not in the standard references, but this strain was considered to belong to a species related to Streptomyces reticuli.Tentatively, this strain was designated as Streptomyces reticuli var. latumcidicus.
As briefly reported in a previous paper1), the authors isolated an antibiotic from a Streptomyces which was assigned to a new species, Streptomyces mitakaensis, and the antibiotic was named mikamycin. It is active against gram-positive and acid-fast bacteria and low toxic. In this paper the authors present taxonomic studies on S. mitakaensis, and process for the isolation of the antibiotic as well as its chemical, physical and biologoical properties.
In the previous paper1), mikamycin was reported to be closely related to streptogramin described by Cheney and others2) and the antibiotic No. 899 described by De Somer and Van Dijck3). Paper chromatographic studies made by the latter authors demonstrated three active substances in streptogramin and four active substances in the antibiotic No. 899. As described in previous papers1,4), mikamycin was a single antibiotic demonstrated by the paper chromatography, and properties of mikamycin suggested a closed relationship with the main active principles in streptogramin and the antibiotic No. 899.
Samples of streptogramin and the antibiotic No. 899 obtained through the courtesy of Dr. Charney and Dr. De Somer were comparatively studied with mikamycin. Results suggesting the identity of mikamycin with the main active substance of these two antibiotics are presented in this paper. Descriptions on streptogramin-producing strain were informed by Dr. Charney, and different points in characteristics of S. mitakaensis from S. graminofaciens are also described.