The human LL-37 peptide exerts antimicrobial activity against Legionella micdadei interacting with membrane
Marta Palusińska-Szysz1, Małgorzata Jurak2, Nicolas Gisch3
1Department of Genetics and Microbiology, Institute of Biological Sciences, Faculty of Biology and Biotechnology, Maria Curie-Sklodowska University, Akademicka 19 St., 20-033, Lublin, Poland.
Abstract:
Legionella micdadei is responsible for community- or nosocomial-acquired pneumonia as well as the influenza-like illness Pontiac fever. The aim of this study was to investigate the ability of L. micdadei to utilize extracellular choline for phosphatidylcholine (PC) synthesis and its consequences for the phospholipid composition of its membrane system and the interaction with the human LL-37 peptide. Comparative analysis of the PC content using isotopic labeling revealed that in presence of exogenous choline 98% of the total PC was synthesized via the Pcs pathway while the remaining 2% were generated via the PE-methylation (PmtA) pathway. PC species were to a greater extent defined by the Pcs pathway in the outer membrane than in the inner membrane. While no major changes in the bacterial lipid content were observed using 31P NMR, indication for utilization of longer acyl chains and slight increase of PG in response to choline addition was observed by a top-down lipidomics screen. The LL-37 peptide inhibited L. micdadei growth in a dose-dependent manner. Bacteria cultured with exogenous choline were more sensitive to the LL-37 peptide when compared to the standard culture condition. Our biophysical investigations show that the peptide perturbs bacterial-derived phospholipid monolayers and this interaction is dependent on the molar portion of PC. This interaction is responsible for the observed changes in the anti-L. micdadei activity of the LL-37 peptide.
Insights
Legionella micdadei uses external choline to synthesize phosphatidylcholine (PC), altering membrane composition. This change increases bacterial susceptibility to the antimicrobial peptide LL-37.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Legionella micdadei causes pneumonia and Pontiac fever.
- Understanding bacterial phospholipid synthesis is crucial for developing new treatments.
Purpose of the Study:
- Investigate L. micdadei's use of extracellular choline for phosphatidylcholine (PC) synthesis.
- Determine the impact of choline on bacterial membrane composition.
- Assess the consequences for L. micdadei's interaction with the LL-37 peptide.
Main Methods:
- Isotopic labeling to quantify PC synthesis pathways (Pcs and PmtA).
- 31P NMR and lipidomics to analyze phospholipid composition.
- Growth inhibition assays and biophysical studies to evaluate LL-37 peptide interaction.
Main Results:
- Exogenous choline primarily drives PC synthesis via the Pcs pathway (98%).
- Choline influences PC species distribution in bacterial membranes and suggests longer acyl chains and increased PG.
- L. micdadei grown with choline exhibits increased sensitivity to LL-37.
- LL-37 peptide perturbs bacterial phospholipid monolayers in a PC-dependent manner.
Conclusions:
- L. micdadei efficiently utilizes extracellular choline for PC synthesis, modulating its membrane's phospholipid profile.
- Altered membrane composition enhances susceptibility to the antimicrobial peptide LL-37, offering potential therapeutic insights.
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