HYBRIDIZATION BETWEENESCHERICHIA COLIAND SHIGELLA

Abstract

A11 of 16 strains of Shlgella tested could mate with E. coli strains K-12 and C. The shigellae behave like F- strains in the fertility system of E. coll and can be changed to the F+ state. The hybrids exhibit combinations of shigella and coli characters. The frequency of mating, as measured by zygotlc induction of phage lambda, is the same in crosses coli X coli and coli X shigella. The frequency of recombination is much lower in the latter crosses. This, and the failure of certain coli characters to appear in hybrids, indicate an incomplete genetic homology between E. coll and Shigella. Some hybrids between E. coli and S. flexneri possess somatic antigens related to those of S. flexneri Y. The results indicate a role of hybridization in the sero-logical variation of the shigellae and in the evolution of the Enterobacteri-aceae.