Misrepair mutagenesis in Myxococcus xanthus: Induction of rifampicin-resistant mutants by N-methyl-N′-nitro-N-nitrosoguanidine and ultraviolet-irradiation

Abstract

In the ultraviolet (UV)-mutable bacterium, Myxococcus xanthus, dose response curves for the induction of rifampicin-resistant (Rifr) mutants were compared with dose response curves for Weigle(W)-reactivation of the UV-irradiated phage Mx4 at a phage survival of 5 X 10(-6). In most strains examined, including a uvr mutant, these curves are largely similar. Unexpectedly the UV-sensitive strain M. xanthus Bt, which is unable to perform W-reactivation, is nevertheless UV-mutable. This result may indicate that the repair pathway involved in phage reactivation is only partly responsible for UV-mutagenesis or alternatively is not able to act on phage DNA in M. xanthus Bt cells. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment of M. xanthus cells also results in marked W-reactivation of the UV-irradiated phage Mx4 at the same survival of 5 X 10(-6). The MNNG-stimulated phage reactivation is of the same order of magnitude as the UV-stimulated phage reactivation. Also the dose response curves for the induction of Rifr mutants by MNNG and the MNNG-stimulated phage reactivation are quite similar. This coincidence may indicate that misrepair mutagenesis is involved in both UV and MNNG-mutagenesis. It is suggested that M. xanthus is a useful organism with which to study misrepair mutagenesis in bacteria.

LexA‐independent DNA damage‐mediated induction of gene expression in Myxococcus xanthus

“…It has been shown to contain two copies of the recA gene, only one of which ( recA2 ) is DNA damage‐inducible (Norioka et al ., 1995). Likewise, the existence of cell reactivation of UV‐irradiated phages as well as of UV‐mediated mutagenesis have been also reported in M. xanthus (Herdrich and Grimm, 1981; McCann and Clarke, 1981). But nothing is known about the regulatory mechanisms of these responses against the DNA‐damaging agents.…”