A new antimicrobial agent, proceomycin, has been isolated from fermentation broths of a strain of Streptomyces named Streptomyces albolongus nov. sp. The antibiotic is a weakly acidic substance of yellowish-orange color and inhibits the growth of a variety of Gram-positive bacteria.

This paper summarizes the characteristics of the new Streptomyces strain and some of the chemical, physical and biological properties of proceomycin.

A new crystalline antibiotic named cranomycin has been isolated from culture broth of Streptomyces SE-801, new species.¹⁾

Cranomycin is a basic antibiotic and active principally against Gram-positive bacteria and some phytopathogenic microorganisms, such as Xanthomonas oryzae, and toxic to mice. Cranomycin is effective in the curative test against the bacterial blight leaf of rice-plants.

In the present publication, production process and characterization of cranomycin are described.

Showdomycin have been reported by Nishimura et al. ¹⁾, as a new antibiotic produced by Streptomyces showdoensis, n. sp. In their preliminary experiments, showdomycin was shown to exhibit an antitumor effect against Ehrlich ascites carcinoma both in vitro (using the so-called contact test technic) and in vivo.

In the present study, the antitumor activities of this new antibiotic were examined in detail.

Kanamycin and streptomycin belong to a group of basic glycoside antibiotics and the biological activities are similar. A number of investigations, concerning the mechanism of action of these antibiotics have been performed. They include effects on or by aerobic respiration^1～5), a damage of cytoplasmic membrane^6～17), a reaction with nucleic acids^{18, 19)} or an inhibition of protein synthesis^20～25).

Erdös and Ullman^{20, 21)} revealed that streptomycin inhibits the incorporation of ¹⁴Camino acids into protein in a cell-free system from a strain of Mycobacterium. Flaks et al.^24,25) observed an inhibition of polyphenylalanine synthesis by streptomycin, using a cell-free amino acid incorporating system from E.coli. The ¹⁴C-phenylalanine incorporation, stimulated by polyuridylate, was inhibited by the presence of streptomycin. They concluded that the inhibition of polypeptide synthesis is due to binding of streptomycin to the ribosome, and an origin of streptomycin resistance is located in the ribosome. Later it was revealed that streptomycin does not interfere with the attachment of polyuridylate to the ribosome.^{32 ,33)} Rosenkranz²⁶⁾ reported that a strain of E. coli, carrying an episome for multiple drug resistance (the resistance transfer factor), has decreased permeability for streptomycin.

An inhibition of protein synthesis by kanamycin was observed in the previous study²³⁾. Tanaka et al.²⁷⁾ studied with a kanamycin-resistant mutant of E. coli, and found that resistant changes are located in the ribosome. It was concluded that the primary site of action may be the ribosome. They observed one-way cross resistance in leucine incorporation into protein with the ribosomes and native messengers from streptomycin-resistant and kanamycin-resistant mutants as in the case of growth-inhibitory activity. However, no cross resistance was demonstrated with polyphenylalanine synthesis, which is dependent on a synthetic messenger, polyuridylate. It suggested that the binding site of kanamycin is different from that of streptomycin on the ribosome.

For the purpose of elucidating the detailed site of action of kanamycin on protein synthesis, studies were performed with a cell-free system from E. coli and rat liver, with particular reference to the selective toxicity. The results are presented in this publication.

Chromomycin A₃ (Toyomycin) is an anti-tumor antibiotic discovered by investigators^{1, 2, 3)} of the Takeda Chemical Industries. Only a little is known on the mode of action of this antibiotic. Ueda and Kawamata⁴⁾ stated at a meeting that this antibiotic may inhibit protein and nucleic acid syntheses in Bacillus subtilis, but the data are still not published. Sato et al.⁶⁾ reported that the antibiotic inhibited incorporation of ³²P into the DNA and RNA of sarcoma 180 ascitic tumor cells. Katsumata et al. ⁶⁾ reported that the antibiotic inhibited metabolism of alpha-ketoglutaric acid in B. aneurinolyticus.

The purpose of the present study is to observe the mode of action of this antibiotic by use of a Mycobacterium.

The bioassay of blasticidin S had been reported by Takeuchi et al.²⁾ using Bacillus subtilis PCI 219 as the test organism. The procedure reported covered the concentration range of about 50—1,000 u/ml by a cup-plate method. Afterwards, Iizuka⁸⁾ and Koyama⁸⁾ revealed that Bacillus cereus is more excellent in the formation of the clear-cut zone with blasticidin S than Bacillus subtilis PCI 219. Thus, at present time, Bacillus cereus is used widely for the purpose of the bioassay of blasticidin S. However, to keep accuracy of the determination, the relative insensitivity of Bacillus cereus to blasticidin S is quite unsatisfactory for the assay procedure in which the further precision of the assay is required. Aiming the selection of the more sensitive test organism than Bacillus cereus for the assay procedure of blasticidin S, the authors have found Bacillus circulans IAM-1112 as the most favorable test organism for the assay procedure of blasticidin S. It is the purpose of this paper to describe the merits of Bacillus circulans in the cup-plate assay procedure for blasticidin S.