カナマイシンを作用させた結核菌の電子顕微鏡的研究

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The earlier biochemical studies on the acting mechanism of kanamycin, one of aminoglycoside antibiotics, have revealed that kanamycin acts on the ribosomes and inhibits the protein synthesis, and also causes a damage of the cell membrane and a decrease of the activities of respiratory enzymes in the bacterial cells. In this study, the fine structures and sites of activities of respiratory enzymes in the tubercle bacilli treated with kanamycin were investigated with electron microscope. Mycobacterium tuberculosis var. hominis H37Ra cultivated in Dubos medium for 7 days was incubated in the medium containing kanamycin (10 mcg/rni) at 37CC for 24 and 48 hours. Succinic dehydrogenase activity was demonstrated by the method of Sedar and Burde using tetranitroblue tetrazolium (TNBT) and succinate. Cytochrome oxidase activity was demonstrated by the amine method of Burstone. The specimens were fixed in 1% 0s04 buffered with acetateveronal buffer of Michaelis (pH 6.1). The fixed cells were treated in 0.5% uranyl acetate, dehydrated in a graded series of ethanol and embedded in Epon 812 according to Luft. In the tubercle bacilli treated with kanamycin, the cytoplasm appeared to be c o arse. The fine granular structures of ribosomes were not obvious. The homogeneous, slightly dense, large granules and the vacuoles were occasionally observed in the cytoplasm. These morphological changes of the cytoplasm may be explained by the degeneration of ribosomes affected by kanamycin and the inhibition of the formation of ribosomes caused by the inhibition of the protein synthesis. The mesosomes appeared to be poorly organized or to be broken into fragments. Enzyme activities of succinic dehydrogenase and cytochrome oxidase, as evidenced by the deposition of dense reaction products, were located on the mesosomes, but a remarkable decrease of enzyme activities was demonstrated in the kanamycin-treated cells. These cytochemical findings were also found to be consistent with the results of biochemical determinations. Accordingly, in the case of tubercle bacilli, it is reasonable to suppose that the degeneration or the abortive formation of mesosomes occurres under the influence of kanamycin, and that the mesosomes are essential to the activities of respiratory enzymes and the growth of the cells. The elongated membrane structures, occasionally to the proximity of the large dense granules and the vacuoles, were also observed in the cytoplasm. These membrane structures may corelate with the appearance of the large granules and the vacuoles.
日本結核病学会の論文

カナマイシンを作用させた結核菌の電子顕微鏡的研究

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