The influence of several prophages on the genetic behavior of Flexner dysentery bacteria.

In conjugation experiments of Escherichia coli K-12 Hfr strains and converted clones of Shigella flexneri var. y(-:3,4) that had acquired the capacity to synthesize type of antigens IV or V it is confirmed that the locus linked to lac-pro region in Sh. flexneri chromosome called Tp locus is a site of an attachment of prophages responsible for certain type specific antigens. Lac+ hybrids of the clone converted by phage IV lost the type specific antigen IV with the frequency comparable with the loss of the aforementioned antigen by wild strains of Sh. flexneri ser 4 in similar experiments carried out previously (90,8% and 97% respectively). Lac+ hybrids of the clones converted by phage V did not lose the type antigen that corresponded to the behaviour of wild strains of serotype 5b (V: 7,8) with double lysogenicity. It was shown that the clones converted by the aforementioned phage V had acquired an immunity not only to phage V, but to phage 7,8 as well. An independent segregation of immunity to phages V and 7,8 in lac+ hybrids of the converted clone was observed. It indicates that donor strain NTCC 595/52 carries two prophages, V and "defect" 7,8 (not expressing factor 7,8). A maintenance of antigen V observed in lac+ hybrids of the converted clone in this case confirms previous suggestions that an attachment of prophage 7,8 creates a state of some inhomology in this region disturbing the recombination process. The converting phage V isolated from the strain NTCC 595/52 is probably recombinant. An analysis of the hybrid classes allows to suggest the following approximate order of markers of the prophage on the chromosome of the converted clone: aV--imm V--imm 7,8--lac.