Spontaneous zygogenesis in Escherichia coli, a form of true sexuality in prokaryotes

Abstract

A new type of mating, differing from classic conjugation and previously observed in a certain strain ofEscherichia coliK-12, has also been found in strains derived from ordinary F−cells ofE. coliK-12 exposed to an exogenous factor originating in anE. coliclinical isolate. Immunofluorescence and electron microscopy after single and double labelling of DNA were used to produce evidence in favour of a novel mating mechanism by cell contact at the poles of the bacterial rod. These findings are supported by genetic analyses indicating complete genetic mixing. Unstable complementing diploids were formed, which throw off phenotypically haploid cells, of which some showed a parental phenotype and some were true genetic recombinants. Recombination was observed even when one parent was a UV-inactivated F−RecA−strain. The name ‘spontaneous zygogenesis' (Z-mating, for short) is proposed for this kind of mating.