Daptomycin inhibits cell envelope synthesis by interfering with fluid membrane microdomains

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Daptomycin is a critical last-resort antibiotic targeting bacterial cell membranes.
• Its precise mechanism of action remains incompletely understood, with competing models proposed.
• Previous hypotheses included cell wall synthesis blockage, pore formation, or altered membrane curvature.

Purpose of the Study:

• To comprehensively elucidate the mode of action of daptomycin.
• To differentiate between proposed mechanisms of daptomycin's bactericidal activity.
• To investigate daptomycin's effects on the bacterial membrane using Bacillus subtilis.

Main Methods:

• Proteomics, ionomics, and fluorescence light microscopy were employed.
• Fluorescent lipid probes were used to analyze membrane fluidity and domain organization.
• Protein localization and membrane potential changes were monitored.

Main Results:

• Daptomycin induced gradual membrane depolarization without forming discrete pores.
• Cell wall synthesis inhibition was confirmed, but altered membrane curvature was not observed.
• Daptomycin binding caused significant rearrangement of fluid lipid domains, decreasing membrane fluidity.
• This rearrangement led to the detachment of key enzymes MurG and PlsX from the membrane.
• Clustering of fluid lipids by daptomycin likely causes hydrophobic mismatches, facilitating proton leakage.

Conclusions:

• Daptomycin's primary mechanism involves targeting and disrupting fluid lipid domains within the bacterial membrane.
• Delocalization of essential enzymes like MurG and PlsX due to lipid domain alteration is a key factor in cell wall synthesis inhibition.
• Proton leakage resulting from hydrophobic mismatches explains the observed membrane depolarization.
• Targeting fluid lipid domains represents a novel antibiotic strategy with implications for developing new membrane-active agents.