Three different Streptomyces producing a new antibiotic albocycline were examined in reference to their taxonomic characteristics. It was concluded that two of the strains, S. MCRL-0129 and S. MCRL-0356, are new species of Streptomyces and they were named S. brunneogriseus nov. sp. and S. roseocinereus nov. sp., respectively. The third strain, S. MCRL-0355, was recognized to be a variety of S. roseochrontogenes and named S. roseochromogenes var. albocyclini var. nov.

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A new antibiotic pigment named aquayamycin, which inhibits growth of Gram positive bacteria, Ehrlich carcinoma in mice, and Yoshida rat sarcoma cells in tissue culture, was isolated from Streptomyces misawanensis nov. sp. Hamada et Okami. It was obtained as orange yellow crystals having the molecular formula C_30-31H_34-40O₁₂. From the physical and chemical properties, aquayamycin was concluded to be a new antibiotic pigment of hydroxyquinone structure.

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An antibiotic was isolated from the culture filtrates of Streptomyces lavendulae and named yazumycin. It was isolated from the broth using cation exchange resin and purified by cellulose chromatography. Yazumycin exhibited inhibitory activities against bacteria, especially Gram-negative bacteria such as Xanthomonas oryzae, Xanthomonas citri and Escherichia coli. No toxicity to mice was shown by intravenous injection of 200 mg/kg.

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Phenomycin, a new polypeptide antibiotic, was observed to exhibit significant inhibitory activity against Ehrlich carcinoma and sarcoma 180 in ddD mice, both ascitic and subcutaneous solid forms. It also showed a marked activity against the growth of adenocarcinoma 755 in C57BL/6 mice. The LD₅₀ for mice was 8 mg/kg both by intraperitoneal and subcutaneous injections.

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The mechanism of action of phenomycin, an antitumor antibiotic, was studied, using mammalian systems. Phenomycin was observed to inhibit protein synthesis, but not RNA or DNA synthesis in growing HeLa cells. Approximately 50 % inhibition of leucine incorporation into protein was demonstrated at a concentration of 100 mcg/ml of phenomycin when the cells were treated with the antibiotic for 24 hours. Phenomycin significantly inhibited protein synthesis in the lysate of Ehrlich carcinoma cells, although only a slight inhibition was observed with intact cells. Protein synthesis in ribosomal systems of rat liver and rabbit reticulocytes with native mRNA was markedly suppressed by the presence of phenomycin. In reticulocyte ribosomes, polyphenylalanine synthesis with poly U was rather resistant to the action of the antibiotic. The site of action of phenomycin in a proteinsynthesizing system was studied, using rabbit reticulocyte system. It was demonstrated that phenomycin did not affect aminoacyl-SRNA formation but inhibited the amino acid transfer from aminoacyl-SRNA to polypeptide. The non-enzymatic binding of lysyl-SRNA to the ribosomes with poly A or with native mRNA was significantly inhibited by phenomycin. Contrary to the mammalian systems, protein synthesis was not significantly affected by the presence of phenomycin, in an E. coli system. The site of action and selective toxicity of phenomycin are discussed.

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A study was undertaken on the in vitro and in vivo antibacterial activities of enduracidin, a basic, peptide antibiotic substance extracted from Streptomyces fungicidicus No. B 5477, and the following was observed.
1. Enduracidin was found to have a high antibacterial activity against Gram-positive cocci and bacilli, but no activity was observed against Gramnegative bacilli. No cross-resistance with other antibiotics was observed.
2. The antibacterial activity of enduracidin was not affected by the pH in a range of 6-8 and nor was influenced by the addition of serum; the activity, however, was considerably affected by the size of inoculum.
3. Enduracidin was found to be therapeutically more effective against experimental Staphylococcus aureus or Staphylococcus hemolyticus infection in mice than penicillin G, and most effective by the intraperitoneal route of administration. Further, the therapeutic activity of enduracidin varied with the route of inoculation in the case of staphylococcal infection.

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The mycological properties and antibiotic activity of strain No. B5477, isolated from a soil sample collected in Nishinomiya, Hyogo Prefecture, were investigated. This strain forms spiral sporophores, spiny spores, and gray aerial mycelium. The culture is non-chromogenic. Strain No. B5477 was compared with known species and identified as a strain of Streptomyces fungicidicus Okami et al. 1954¹⁾. During the course of selecting a strain with high potency, a yellow mutant with yellowish aerial mycelium was obtained and its properties were investigated.
Streptomyces fungicidicus No. B 5477 produces a new antibiotic, enduracidin, with a strong antibiotic activity against Gram-positive bacteria. Acid-fast bacteria and phytopathogenic bacteria are also inhibited. Enduracidin shows no cross resistance with the known antibiotics examined. It is more active in a basic medium and therefore is a basic antibiotic. The antibiotic activity of enduracidin was not affected by horse serum in the assay medium. Its diffusibility was less than that of the other antibiotics examined. The antibiotic activity of enduracidin was assayed by the paper disc method using Sarcina variabilis IFO 3067 as the test organism. Enduracidin was produced mainly in the mycelium. The fermentation conditions for production of the antibiotic were investigated.

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Enduracidin is a basic compound with ultraviolet absorption maxima at 230 and 263mμ in 90% methanol and is a colorless crystalline powder de composing at 225-240°C. It is positive to DRAGENDORFF, ninhydrin, BIURET and BARTON'S¹⁾ reagents but negative to Molisch reagent. Hydrolysis of en duracidin with 6n HC1 yields, aspartic acid, threonine (and/or allo-threonine), serine, glycine, alanine, ornithine, citrulline, α-amino-4-hydroxyphenylacetic acid, α-amino-3, 5-dichloro-4-hydroxyphenylacetic acid and two unidentified basic amino acids.

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Enduracidin showed antibacterial activity in vitro against Gram-positive bacteria and N. GONORRHOEAE, but not against Gram-negative bacteria. The antibacterial activity of enduracidin was not greatly influenced by the pH of the test medium. Enduracidin was more stable at pH 4 and 7 than at pH 9. This antibiotic demonstrated bactericidal as well as bacteriostatic activity in vitro at a similar concentration against Staph. aureus. The development of resistance to enduracidin was slow and no cross resistance was observed between enduracidin and other known antibiotics. Enduracidin was effective against experimental infections produced in mice by strains of Staph. aureus, Sterept. Pyogenes and D. pneumoniae type I. Enduracidin was most effective against streptococcal infection. This antibiotic was effective by the subcutaneous, intraperitoneal and intravenous routes, but not orally. A single intramuscular dose of 2 mg/kg of enduracidin in the rabbit produced significant plasma levels extending even to 24 hours.

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