Release of Lipopolysaccharide in Escherichia coli Resistant to the Permeability Increase Induced by Ethylenediaminetetraacetate

Mutants of Escherichia coti that fail to show the characteristic increase in permeability induced by brief treatment with ethylenediaminetetraacetate have been isolated.They were examined to see whether they release lipopolysaccharide as expected during such a treatment.Mutants derived from two strains released only 20 to 40% less lipopolysaccharide than their parents, but further analysis of one mutant and its parent showed that this represented reduction of a specific lipopolysaccharide fraction.Both organisms released two lipopolysaccharide components differing in sedimentation rate in sucrose density gradients, but while both released similar amounts of the faster moving component, the mutant released only about one-third as much of the slower moving component.These results suggest that release of the slower component may be required for the permeability increase induced by EDTA. Brief treatment of Escherichia coli with ethylenediaminetetraacetate increases cell permeabilityand releases part of the lipopolysaccharide of the cell wall into the medium (1, 2).The relationship of these two phenomena has not been defined.If they are related, then mutants selected for absence of the permeability effect might not be expected to release LPS.1 This paper describes the isolation and characterization of two mutants resistant to the permeability-promoting effect of EDTA.These mutants release LPS, but in reduced amounts.Further study of one mutant revealed that its LPS, like that of its parent, yielded two fractions on sucrose gradient ultracentrifugation, and that one of these was released in normal, and the other in reduced amounts.