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Updated: Apr 27, 2026
Nanomechanics of Drug-target Interactions and Antibacterial Resistance Detection
Published on: October 25, 2013
Accumulation of phosphatidic acid increases vancomycin resistance in Escherichia coli
Holly A Sutterlin1, Sisi Zhang2, Thomas J Silhavy3
1Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
Abstract:
In Gram-negative bacteria, lipopolysaccharide (LPS) contributes to the robust permeability barrier of the outer membrane, preventing entry of toxic molecules such as antibiotics. Mutations in lptD, the beta-barrel component of the LPS transport and assembly machinery, compromise LPS assembly and result in increased antibiotic sensitivity. Here, we report rare vancomycin-resistant suppressors that improve barrier function of a subset of lptD mutations. We find that all seven suppressors analyzed mapped to the essential gene cdsA, which is responsible for the conversion of phosphatidic acid to CDP-diacylglycerol in phospholipid biosynthesis. These cdsA mutations cause a partial loss of function and, as expected, accumulate phosphatidic acid. We show that this suppression is not confined to mutations that cause defects in outer membrane biogenesis but rather that these cdsA mutations confer a general increase in vancomycin resistance, even in a wild-type cell. We use genetics and quadrupole time of flight (Q-TOF) liquid chromatography-mass spectrometry (LC-MS) to show that accumulation of phosphatidic acid by means other than cdsA mutations also increases resistance to vancomycin. We suggest that increased levels of phosphatidic acid change the physical properties of the outer membrane to impede entry of vancomycin into the periplasm, hindering access to its target, an intermediate required for the synthesis of the peptidoglycan cell wall.
Insights
Rare genetic mutations in cdsA enhance vancomycin resistance in Gram-negative bacteria by increasing phosphatidic acid levels. This modification strengthens the outer membrane barrier, impeding antibiotic entry and improving cell survival.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Gram-negative bacteria possess a robust outer membrane, crucial for resisting toxic molecules like antibiotics.
- Mutations in lptD disrupt lipopolysaccharide (LPS) assembly, increasing antibiotic susceptibility.
- Understanding mechanisms of antibiotic resistance is vital for developing new therapeutic strategies.
Purpose of the Study:
- To identify genetic suppressors that confer vancomycin resistance in bacteria with compromised outer membranes.
- To elucidate the molecular mechanisms by which these suppressors increase resistance.
- To investigate the role of phosphatidic acid in modulating outer membrane permeability and antibiotic resistance.
Main Methods:
- Genetic screening to identify vancomycin-resistant suppressor mutations.
- Whole-genome sequencing and mapping to pinpoint mutated genes (e.g., cdsA).
- Quadrupole time-of-flight liquid chromatography-mass spectrometry (Q-TOF LC-MS) to analyze lipid profiles.
- Genetic manipulation to induce phosphatidic acid accumulation through alternative pathways.
Main Results:
- Seven independent vancomycin-resistant suppressors were identified, all mapping to the essential gene cdsA.
- cdsA mutations resulted in partial loss-of-function, leading to phosphatidic acid accumulation.
- The observed vancomycin resistance was not limited to lptD mutants but also occurred in wild-type cells.
- Pharmacological or genetic induction of phosphatidic acid accumulation conferred vancomycin resistance.
Conclusions:
- Accumulation of phosphatidic acid, a phospholipid precursor, enhances bacterial outer membrane barrier function.
- Increased phosphatidic acid levels impede vancomycin entry into the periplasm, reducing its efficacy.
- This study reveals a novel mechanism of antibiotic resistance involving alterations in membrane lipid composition.
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