Mutagenic effect of ultraviolet radiation on the non-acid-fast strain of Mycobacterium phlei.

Abstract

The mutability of the PN strain ofMycobacterium phlei was examined after induction of auxotrophic mutants and of STM and VM-resistant mutants, by UV irradiation. A total of 30 auxotrophic mutants were isolated, most of them amino acid-dependent five purine-dependent, and one uracil-dependent. To induce the mutants higher UV doses had to be used so that the survival of cells in the original suspension would not exceed a few per cent. For further genetic work use can be made of 8 auxotrophic mutants (PN try−ura−, PN arg−ura−, PN ileu−val−, PN ileu−, PN leu−, PN lys−, PN lys−-VMr, PN val−), these showing a low frequency of spontaneous reversions. No spontaneous auxotrophic mutants have been found. The frequency of STM and VM-resistant mutants is increased upon UV irradiation, a post-irradiation incubation in a liquid medium without the drug being essential for their phenotypic expression. The highest increase of the number of these mutants is attained after 48 h of post-irradiation incubation and it has been found that, within a certain experimental scatter, the same frequency increase is found on using a complete or a minimal liquid medium. The frequency of spontaneous STM-resistant mutants lies within 5.8×10−6–8.8×10−6, of those VM-resistant between 3.1×10−5 and 4.1×10−5. The highest frequency of induced STM-resistant mutants lies between 3.0×10−5 and 9.3×10−5 and of VM-resistant mutants between 1.1×10−4 and 2.2×10−4