Aggregation deficient Escherichia coli K-12 female mutants with altered lipopolysaccharide.

Two F- mutants deficient in conjugation with F-donors have been characterized. They map at about 83 minut position, show resistance to T3 and T7 bacteriophages, and form mating aggregates in the liquid medium with lowered efficiency. Mutants have no detectable alterations in their outer membrane protein composition.