Outer membrane permeability of Actinobacter calcoaceticus mediates susceptibility to rat polymorphonuclear leukocyte granule contents

Growth of Acinetobacter calcoaceticus on specific alkanes altered the outer membrane permeability of the organism, as indicated by a change in sensitivity to the antibiotic actinomycin D. As the carbon length of the alkane energy source decreased, outer membrane permeability and susceptibility to actinomycin D increased. Concomitant with the increase in outer membrane permeability, A. calcoaceticus became more susceptible to the oxygen-independent antimicrobial activity of extracted contents from rat polymorphonuclear leukocyte granules. Individual fractions of granule extract possessed no antimicrobial activity against A. calcoaceticus. The alkane-induced change in outer membrane permeability was not associated with alterations of lipopolysaccharide O antigen. An outer membrane permeability mechanism, independent of changes in lipopolysaccharide content, mediating susceptibility to the oxygen-independent antimicrobial activity of rat polymorphonuclear leukocyte granule contents is suggested.