Plasmid pSK1002-mediated mutator effect and SOS response and SOS mutagenesis of 2,5-dichloronitrobenzol in Salmonella typhimurium.

The plasmid pSK1002 (umuC'-'lacZ) could increase the number of revertants induced by methyl methanesulfonate (MMS) and 4-nitroquinoline-N-oxide (4NQO) in Salmonella typhimurium TA 1535 (his-). The values induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were not different irrespective of the presence or absence of plasmid. However, the plasmid pKM101-mediated mutagenesis-enhancing effect was much greater than that mediated by pSK1002 as induced by the 3 mutagens mentioned above. Moreover, the plasmid pSK1002 could induced umu-mediated SOS response in the presence of any of these 3 mutagens or of mitomycin C, and a dose-response relationship was evident. It shows that pSK1002 (umuC'-'lacZ) has a dual biological effect, namely a mutator effect and the effect of inducing the SOS response. Besides, this study has proved SOS mutagenesis of 2,5-dichloronitrobenzol (2,5-DCNB) because of the dual indicator nature of pSK1002. Therefore, it is probable that pSK1002 could be further developed and applied in studying the relation between the SOS response and mutagenesis and in identifying environmental SOS mutagens.