Effect of plasmid RP1 on phase changes in inner and outer membranes and lipopolysaccharide from Acinetobacter calcoaceticus: A Fourier transform infrared study

Michael J. Loeffelholz, Fazale Rana, Malcolm C. Modrzakowski, Jack Blazyk

Research output: Contribution to journalArticle

16 Scopus citations


The successful transfer of the resistance plasmid RP1 into the Gram-negative bacterium Acinetobacter calcoaceticus resulted in increased resistance of this microorganism to the antibiotics kanamycin and tetracycline. Microorganisms harboring the RP1 plasmid showed altered fatty acid composition in the lipopolysaccharide fraction and increased outer membrane permeability compared to organisms without the plasmid. Thermotropic gel to liquid crystal lipid phase changes were detected in both inner and outer membranes and purified lipopolysaccharide by Fourier transform infrared spectroscopy. The phase transition temperatures observed in the outer membranes and isolated lipopolysaccharide of the plasmid-containing cells were significantly higher than those of the plasmid-free organisms, while little difference was observed for the inner membranes. The plasmid-induced decrease in outer membrane fluidity may play a mediating role in the mechanisms of antibiotic resistance and susceptibility to host immune cells in Gram-negative microorganisms.

Original languageEnglish (US)
Pages (from-to)6644-6648
Number of pages5
Issue number21
StatePublished - 1987
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry

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