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Effect of plasmid RP1 on phase changes in inner and outer membranes and lipopolysaccharide from Acinetobacter
M J Loeffelholz1, F Rana, M C Modrzakowski
1Department of Chemistry, Ohio University, Athens 45701.
Abstract:
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.
Insights
Transferring the resistance plasmid RP1 to Acinetobacter calcoaceticus increased antibiotic resistance. This involved changes in outer membrane fluidity and lipopolysaccharide composition, impacting bacterial defense mechanisms.
Area of Science:
- Microbiology
- Bacterial genetics
- Membrane biophysics
Background:
- Gram-negative bacteria possess an outer membrane crucial for antibiotic resistance.
- Lipopolysaccharide (LPS) is a key component of the Gram-negative outer membrane.
- Plasmid-mediated resistance is a significant challenge in clinical settings.
Purpose of the Study:
- To investigate the effects of the resistance plasmid RP1 transfer on Acinetobacter calcoaceticus.
- To determine alterations in outer membrane properties and lipopolysaccharide composition.
- To explore the relationship between plasmid acquisition and antibiotic resistance mechanisms.
Main Methods:
- Conjugation of resistance plasmid RP1 into Acinetobacter calcoaceticus.
- Analysis of fatty acid composition in lipopolysaccharide fractions.
- Measurement of outer membrane permeability.
- Fourier transform infrared spectroscopy (FTIR) to detect lipid phase transitions.
Main Results:
- RP1 plasmid transfer conferred resistance to kanamycin and tetracycline.
- Plasmid-harboring cells exhibited altered LPS fatty acid composition and increased outer membrane permeability.
- FTIR revealed higher phase transition temperatures in outer membranes and LPS of plasmid-containing cells.
- Inner membranes showed minimal changes in phase transition temperatures.
Conclusions:
- The RP1 plasmid significantly alters the outer membrane properties of Acinetobacter calcoaceticus.
- Increased outer membrane rigidity and altered LPS composition may contribute to antibiotic resistance.
- Plasmid-induced changes in membrane fluidity could influence susceptibility to host immune responses.