Genetic analysis of a double male strain of Escherichia coli K12

Abstract

The behavior of a double male strain of Escherichia coli K12 was compared to that of its parents and a primary F' strain carrying F14 in order to determine whether the genome of the double male, responsible for the double origin mode of gene transmission, is composed of 1 or 2 linkage groups. F prime plasmids carrying leu and pyrB and argG and metC were detected following mating an F- recA- recipient with the double male. Their existence strongly supports the contention that the double male is composed of a single linkage group with 2 integrated sex factors. Data from acridine orange curing experiments place the frequency of double male cells in the population of growing cells in the two chromosome configuration as less than 1%. Evidence for a unique origin and terminus of DNA replication deduced by the density labelling and transduction of double male DNA supports the contention that the double male is best considered a cell with a single chromosome carrying 2 integrated F plasmids.