Helminthosporium類縁菌類の生産する抗生物質オフィオボリン,チザニン,ピレノホリン,シッカニンのTrichophyton mentagrophytesに対する抗生作用の機作を検討して次の結果が得られた.
(1) Trichophyton mentagrophytesの生育初期の菌糸を飢餓培養せず洗滌菌体として使用し, 4種の抗生物質とも静菌作用の濃度で自家呼吸阻害を示した.
(2) オフィオボリンはpyruvateおよびlactate,チザニンはpyruvate,ピレノホリンはlactate,シッカニンはlactateを基質とした呼吸増加を静菌作用濃度で阻害した.
(3) オフィオボリン,チザニン,シッカニンはそれぞれの静菌作用の濃度で,培地中から菌体内への燐酸の取り込みを阻害し,冷TCA可溶区分および核酸区分の燐酸の取込みを阻害することを放射性同位光素³²Pを使用して明らかにした.

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以上我々の実験を要約すると
(i) 菌株改良の手段としてナイトロージェン・マスタード処理及びCo⁶⁰をsourceとするγ-線照射処理を採択検討した.
(ii) ナイトロージェン・マスタード処理株約350株のうち2株,γ-線照射処理株約350株のうちから2株の高単位生産株を振盪培養による第1次,第2次及び最終スクリーニングからCandida albicansを被検菌として選択した.
γ-線照射処理の場合形態上或は生産能の面から見て変質度の著しい菌株が得られ,この様なことはナイトロージェン・マスタード処理では認められなかった.
(iii) 高単位を示す菌株について二,三形態的,生理的性状を検討し,併せてその安定度,生活物等の検討を行い工場菌株としての利用可能であるという結果を得た.

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Helminthosporium類縁菌類の生産する抗生物質オフィオボリン,チザニン,ピレノホリンおよびシッカニンのTrichophyton mentagrophytesに対する抗生作用の機作を検討して次の結果が得られた.
(1) Trichophyton mentagrophytesの胞子の発芽に対して,オフィオボリン,チザニン,ピレノホリンは3～6μg/ml濃度,シッカニンは0.1～0.3μg/ml濃度で阻害し,これら4種の新抗生物質とも添加後の時間の経過とともに阻害が弱くなる傾向を示した.
(2) Trichophyton mentagrophytesの生育初期の菌糸の生育に対しては,オフィオボリン,チザニン,ピレノホリンは1～6μg/ml濃度で静菌的な阻害作用を示し, 25μg/ml濃度で強い静菌的な阻害作用を示した.シッカニンはこの3種の抗生物質より阻害力が強く0.1～0.5μg/ml濃度で静菌的な阻害を示し, 25μ/mlでほとんど殺菌的な阻害を示した.

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Blasticidin Sはいもち病菌胞子および菌糸の glucose, pyruvate, succinate, glutamate を基質とした際の基質による呼吸増加率をそれぞれ静菌的濃度 (胞子では1μg/ml, 菌糸では0.1μg/ml) で阻害した。阻害率は胞子の場合前者を基質とした時, 約45%で, glutamate が基質の時, 約60%であり, 菌糸の場合も前3者では約60%, glutamate では80%以上になり, glutamate を基質とした際の呼吸増加の阻害が特に著しかつた。また胞子呼吸よりも菌糸呼吸をより低濃度で阻害したことは本剤のいもち病菌の胞子発芽および菌糸生育に対する阻害効果の傾向と一致した。
Blasticidin Sはいもち病菌の胞子および菌糸の基質添加による呼吸増加は阻害するが自家呼吸は阻害せず, また薬剤濃度を増加しても阻害率は増加せず, ほぼ一定していたことと, 菌糸ミトコンドリアの電子伝達系に対して阻害がみられなかつたことから, 呼吸阻害は本剤の1次的作用ではなく他の酵素系に対する阻害の2次的作用によるものであると推察される。

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1) Effect of Blasticidin S on glycolysis in Piricularia oryzae was-examined by measuring lactic acid according to the method of Backer Sammerson, using the suspension of washed mycelium prepared by the method described previously. The glycolysis was almost not inhibited by Blasticidin S, but was remarkably inhibited by phenyl mercuric acetate and monoiodoacetate.
2) Eflect of Blasticidin S on succinic dehydrogenase in cell free extract of the mycelium of Piricularia oryzae was examined by the method in which TTC reduction was measured by the Thunberg technique. Blasticidin S had no significant influence on the succinic dehydrogease.
3) Effect of Blasticidin S on the oxidative phosphorylation by mitochondrial fraction from rat liver was examined. Oxygen consumption was measured manometrically and phosphorylation was estimated by the determination of inorganic phosphate. The oxygen uptake and the oxidative phosphorylation by the rat liver mitochondria were not affected by Blasticidin S, but both reactions were inhibited by phenyl mercuric acetate and Blastmycin.
4) Effect of Blasticidin S on the turnover of inorganic phosphate by respiring mycelium of Piricularia oryzae was studied with the aid of exogenous inorganic phosphate labelled with ³²P. ³²P from labelled phosphate in the medium was taken up more into the nucleic acid fraction than into the phospholipid or the protein fraction of the mycelium. Each fraction was isolated by the method of Schneider. It was found that the incorporation of ³²P into each of the fractions was not influenced by Blasticidin S.
5) Addition of ¹⁴C-glutamic acid to the suspension of the mycelium above mentioned resulted in the incorporation of ¹⁴C into the mycelium. Since ¹⁴C-glutamic acid was incorporated more into the protein fraction than into the nucleic acid or the phospholipid fraction, the incorporation was taken as a measure of examinig protein synthesis. The incorporation into the protein fraction of the mycelium was strongly inhibited by Blasticidin S at a concentration of 1μg/ml. Because this inhibitory concentration was almost equal to the minimum growth inhibitory concentration (0.1-1.0μg/ml), it seemed that the inhibition of protein synthesis was a primary effect of Blasticidin S on the metabolism of Piricularia oryzae.

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In order to apply antibiotics as agricultural chemicals, the establishment of the testing methods for their antifungal activities in the laboratory seems to be most important. In this paper, three methods of the agar streak dilution method, the paper disk diffusion methods and the spore germination test on the slide glass were compared. As the test organisms, Piricularia Oryzae, Ophiobolus Miyabeanus, Macrosporium bataticola, Alternaria Kikuchiana, Sclerotinia Mali, Penicillium Q 176 and Aspergillus niger were used. As the test antibiotics, Antipiriculin A (Antimycin A), Aureothricin, Eurocidin and Trichomycin were used, and phenyl mercuric acetate was employed as the control. A definite quantitative relation between the antifungal activities obtained by the three testing methods could not be found. The results obtained by three testing methods gave the different antifungal activities by each organism, and the relation between three methods was different by each antibiotic. But, generally, the concentration required to decide the antifungal activity of each antibiotic was lowest in the agar streak dilution method, and the next in the spore germination test, and highest in the paper disk diffusion method. Among these antibiotics there was no one which showed higher activity than phenyl mercuric acetate, but Aureothricin and Trichomycin were better than the others.

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