Decreased conjugation efficiency by Fla-mutants of Escherichia coli K-12 bearing F-like plasmids.

Fla-, Pil-mutants of Escherichia coli K-12 were found to have decreased transfer efficiency of F-like resistance plasmids as compared to the parent strains. This was accompanied by decreased production of conjugation pili and decreased resistance level to some, but not all, of the antibiotics to which resistance was conferred. There was no reduction in pilus production or transfer efficiency in any of the mutants when the plasmid was F'gal. This host-mediated influence on conjugation pilus production is discussed with reference to a possible loss of cell envelope integrity which causes the simultaneous loss of all cellular appendage structures.