Abstract
To observe in detail the influence of Streptomycin on the growth of SM dependent type, the author chose B. subtilis (ATCC 558) and made experiments on its responses to Streptomycin, with special reference to the relation of the SM concentration with spore formation of its SM dependent type together with germination and outgrowth of the spores formed. The results are as follows.
1. Among 18×109 cells of wild type of B. subtilis (ATCC 558) about 3, 200 cells of SM resistant and one cell of SM dependent are found as its mutant.
2. B. substilis (ATCC 558) shows normal growth at SM concentration below 10γ/ml, but the growth declines rapidly between SM 10γ/ml-20γ/ml, and the growth stops entirely at SM concentration 20γ/ml.
3. SM resistant type grows well between SM 0.1γ/ml-SM 2, 000γ/ml, the growth declines rapidly at about SM 10, 000γ/ml.
4. SM dependent type shows normal growth between SM 10, 000γ/ml-20γ/ml, the growth get worth below SM 10γ/ml, and the cell shape elongates several times, at SM below 1γ/ml each cell becomes filamentous form and has several ten times length of normal cell, as if the cells have stopped to divide at low SM concentration.
5. The spore formation of SM dependent type begins at SM 40 γ/ml, and the spore formation rate goes up with increase of SM concentration, and reaches 70 %-80 % when SM concentration is over 6, 000γ/ml.
6. The germination and outgrowth of spores of the SM dependent type slow down with decline of SM concentration, but the germinated spores grow in normal forms until SM concentration reaches 7.8γ/ml, then the germination becomes much slower, and the cells grow in filamentous forms or irregular forms. At extremely low SM concentration both germination and outgrowth nearly stop.
