Hancock, R. (Harvard Medical School, Boston, Mass.). Early effects of streptomycin on Bacillus megaterium. J. Bacteriol. 88:633–639. 1964.—The sequence of some early effects of streptomycin on Bacillus megaterium was investigated. An increase in the rate of efflux of cellular K ions preceded loss of viability, but efflux of Mg ions remained normal. Loss of viability was closely coincident with reduction in rate of protein synthesis. Nucleic acid synthesis continued after protein synthesis ceased in low-phosphate medium, but ceased simultaneously with protein synthesis in normal minimal medium. Later, after viability had begun to decrease, the respiration rate began to fall and the cellular adenosine triphosphate (ATP) content decreased slowly. No leakage of ultraviolet-absorbing materials into the medium occurred, although uracil was slowly released from nucleic acid after killing had begun. It is concluded that in this organism, as previously observed with Escherichia coli, the actions of streptomycin which led to an increased rate of efflux of K and specific inhibition of protein synthesis are the only ones early enough to be of significance in its bactericidal action, the other effects being later secondary changes
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