Chemical and electrophoretic changes induced by polymyxin B on outer membrane components from Serratia marcescens
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Abstract:
The effects of polymyxin B (PB) on outer membrane (OM) components from resistant (strain 08) and sensitive (strain Bizio) cells of Serratia marcescens were characterized by chemical analysis and polyacrylamide gel electrophoresis (PGE) in sodium dodecylsulfate. Chemical analysis revealed no major differences in the OM fractions after PB treatment of both strains, except for the loss of protein in PB treated OM of the sensitive strain. The yield and composition between the lipopolysaccharides (LPS) of the two strains were different both before and after treatment. PGE revealed that there was a complex formation between the LPS of resistant strain and PB but both dissociation and degradation occurred in the LPS components in the sensitive strain. In addition, it was found that the protein components were destabilized by PB with subsequent loss of some of the components from OM of the sensitive strain. The difference in the amount of LPS and their ability to complex with PB may reflect different degrees of antibiotic susceptibility of these two strains of S. marcescens. A sequential multistep mechanism is proposed for the action of PB on outer membranes of this species.
Insights
Polymyxin B affects Serratia marcescens outer membranes differently based on antibiotic resistance. Sensitive strains show LPS degradation and protein loss, while resistant strains form complexes, suggesting varied antibiotic susceptibility mechanisms.
Area of Science:
- Microbiology
- Biochemistry
- Pharmacology
Background:
- Polymyxin B (PB) is a crucial antibiotic for treating infections caused by Gram-negative bacteria.
- Understanding the interaction of PB with bacterial outer membrane (OM) components is vital for combating antibiotic resistance.
- Serratia marcescens exhibits varying susceptibility to PB, necessitating investigation into its OM response.
Purpose of the Study:
- To elucidate the differential effects of Polymyxin B on the outer membrane components of resistant and sensitive Serratia marcescens strains.
- To characterize the chemical and electrophoretic changes in lipopolysaccharides (LPS) and proteins upon PB treatment.
- To propose a mechanism for PB action on Serratia marcescens outer membranes.
Main Methods:
- Chemical analysis of outer membrane fractions.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PGE) for protein and LPS component separation.
- Comparative analysis of PB-treated and untreated resistant (strain 08) and sensitive (strain Bizio) Serratia marcescens.
Main Results:
- PB treatment caused protein loss from the OM of sensitive strains but not resistant strains.
- Differences in lipopolysaccharide (LPS) yield and composition were observed between strains, both before and after PB exposure.
- Resistant strains formed complexes between LPS and PB, while sensitive strains exhibited LPS dissociation and degradation, alongside protein destabilization.
Conclusions:
- The distinct interactions of PB with LPS and proteins in resistant versus sensitive Serratia marcescens strains contribute to differential antibiotic susceptibility.
- A sequential, multi-step mechanism is proposed for PB's action on the outer membranes of Serratia marcescens.
- These findings offer insights into antibiotic resistance mechanisms and potential therapeutic strategies.