I have studied actinomycetes and their antibiotics over thirty-eight years except eight years for which I had been engaged in the research on the quality control for sterilization of microorganisms. My colleagues and I were successful to discover twelve new species of actinomycetes and fourteen new group antibiotics. In this review, I would like to describe rufomycins, enduracidins, validamycins, maridomycins, T-2636 antibiotics and ansamitocins in terms of their discovery, producers and/or industrial development.
Rufomycins (cyclic peptides) with a specific activity to mycobacteria was discovered from
Streptomyces atratus, a new species, in our screening program targeting anti-tuberculosis antibiotics. Enduracidins (Enramycins; cyclic peptides with a fatty acid side chain) were screened as antibiotics with low toxicity and strong bactericidal spectrum including multiple drug -resistant streptococci. As to aminocyclitol antibiotics, validamycins, new assay methods (reversed layer method and dendroid-test method) were established in order to develop an industrial fermentation for their agricultural use. As to T-2636 antibiotics with macrolacton ring, the esterase catalyzing the transformation of T-2636 C to T-2636 A was identified in the producing organism,
S. rochei subsp.
volubillis and then the industrial enzymatic transformation was established. Maridomycins, new macrolide antibiotics, were discovered as a complex of about twenty components from
S. hygroscopicus No. B-5050. Selective and improved production of maridomycin III was established by strain improvement by mutation on the basis of the regulation of amino acid metabolism involved in maridomycin biosynthesis. Ansamitocins, new antitumor antibiotics, were discovered form a new species of
Actinosynnema and turned out to be similar in structure to maytansine with a strong mitosis-arrest activity from tropical plants.
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