[Localization of Rsf- mutation in Escherichia coli HfrC7].

The contransduction frequency of MAAs, UVs phenotype of Escherichia coli HfrC7 and its 7-51F- derivative with purE markers is found to be 1-2% which indicates that the mutation N 7 is located close to the F integration site in HfrC strain. E. coli strains K-12 7-51F+ and 7-51ColV2+ transfer chromosome markers in the same direction as does HfrC strain. The results suggest the presence of an integrated F fragment (sfa locus) into K-12 7-51F- chromosome.