[Effect of colicinogenic plasmids on mutagenesis and the induction of colicin E1 synthesis]

The frequency of UV-induced arg+ and his+ reversions is found to be enhanced by the presence of colicinogenic plasmids Ib-P9 and Ia-CA53 and reduced by the presence of plasmid V-K30. The effect of Ib-P9 on the UV-induced mutagenesis depended on recA and lexA genes and was independent on uvrA and recB genes. Plasmids Ib-P9 and V-K30 proved to exert no influence on the frequency of 2-aminopurine-induced mutations. The presence of Ib-P9 reduced the ability of cells carrying the colicinogenic factor E1 to induce colicin E1 synthesis under the action of DNA-damaged agents (UV, nitrosoguanidine, mitomycin C), while plasmid V-K30 enhanced the induction of colicin E1 synthesis. However this effect of plasmids on the induction of colicin E1 synthesis was not observed when the induction occurred under the action of chloramphenicol. Possible mechanisms governing the participation of plasmid gene products in processes related to the repair of DNA are discussed.