Mutants of Escherichia coli K12 Sensitive to Acidic pH

Institute of Microbiology, Warsaw University, Nowy Swiat 67, 00 064 Warsaw, Poland ABSTRACT SUMMARY: Four mutants of Escherichia coli K12 were isolated on the basis of their sensitivity to pH 5.4. Under non-permissive conditions their growth was reversibly inhibited. At pH 7.0 these mutants showed a highly pleiotropic phenotype, which included altered phage and detergent sensitivities and leakage of periplasmic proteins. The findings suggest a defect in the outer membrane, perhaps in lipopolysaccharide. Two mutants mapped in or near the rfa locus, while the other two were remote from this region.