Bacterial function can contribute to replication of Salmonella phage P22.

Abstract

The UV sensitive bacterial mutants (abbreviated ms mutant) were isolated after N-methyl-N′-nitro-N-nitrosoguanidine (NG) mutagenesis. The ms mutants were found to be Hcr+, Rec+ and sensitive to UV and NG. The significance of the ms mutants was inability to support the multiplication of several mutant phages of P22 which were also isolated by NG mutagenesis. These characters of ms mutants were caused by a single point mutation. Some of the mutant phages unable to grow in ms host were also unable to grow in recA hosts and determined to be erf mutants. The remaining phages were classified in two groups. One group of mutants formed minute plaques on wild type host and fell in the same complementation group (x mutation) and the other formed larger plaques than wild type plaques and belonged to an another complementation group (y mutation). These newly found two genes were essentially involved in the replication of viable P22 DNA. Of the three mutants, x and erf were moderately sensitive to UV irradiation in comparison with y and wild type. Study of lysis patterns showed that the y or erf infected ms culture lysed despite their inability of forming viable progenies, whereas, the x infected ms culture did not lysed. The new x and y genes were both mapped in the early gene segment of P22 chromosome, on the left side of erf gene and between c3 and c2 genes, respectively. Based on these findings the contribution or substitution of the bacterial functions to the replication of bacteriophage was discussed.