Abstract
1) Although with or in Sauton agar medium it was not successful, using egg medium a streptomycin-dependent strain was isolated from a Mycobacterium “Jucho”.
This SM-dependent strain grew in Sauton medium which after isolation contained more than 8μg/ml of streptomycin.
2) SM-dependent mutants gave rise to nondependent cells at the rate of about 3×10-7. About 98 to 99% of the nondependent cells was phenotypically sensitive and only 1-2 & of them were found to be phenotypically resistant. The phenotypical reverse mutation was suggested to be due to the suppressor mutation.
3) SM-dependent mutants showed R-type colony morphology, slow growth rate on Sauton agar medium and kanamycin resistance. Among these changes accompanied by SM-dependent mutation, the R-type colony morphology and the slow growth rate were lost by the reverse mutation to sentivenss.
However, increased kanamycin resistance remained unchanged even after reverse mutation. It seems that these four phenotypes; the SM-dependence, the R-type colony, the slow growth rate and the kanamycin resistance are controlled by a single gene. On the contrary, kanamycin resistance does not accompany SM-dependence.
4) SM-dependent mutants do not show cord formation in the absence of streptomycin. This finding suggests that the mutants undergo a change of cell surface in the absence of streptomycin.
