Abstract
Mode of action of myomycin was examined by using Pseudomonas lachrymans, a causal pathogen of angular leaf spot of cucumber plants. The growth of Ps. lachrymans in liquid medium was strongly suppressed by adding the antibiotic at a concentration of 10μg/ml in the middle logarithmic stage of the bacterium. Exogenous respirations of the bacterial cells were inhibited about 60% at 200μg/ml of myomycin with pyruvate or acetate as substrates, but not with glucose, succinate or citrate. Incorporation of 14C-glucosamine into cell wall, 14C-acetate into lipid fraction, 14C-uridine into RNA and 14C-thymidine into DNA were not inhibited at a high concentration of 200μg/ml of the antibiotic. However, incorporation of 14C-phenylalanine into protein fraction was remarkably inhibited at 200μg/ml. Though exogenous respiration in the resistant strain of Ps. lachrymans was inhibited by the antibiotic as well as in the sensitive one, incorporation of 14C-phenylalanine into the protein fraction of resistant cells was not inhibited. These results indicated that the possible site of myomycin action against Ps. lachrymans might be in the process of protein biosynthesis.
