The staphylococcal type VII secretion system impacts daptomycin sensitivity through controlling bacterial cell surface integrity

ABSTRACT: The human pathogen Staphylococcus aureus encodes a specialised type VII secretion system (T7SS), which plays an important role in bacterial virulence during infection. However, the functions the T7SS during infection and in bacterial physiology remain unclear. Here we demonstrate that S. aureus strains lacking the transporter EssC as well as the T7SS effectors, EsxC and EsxA were highly sensitive to the important last resort drug, daptomycin as well as other membrane-targeting antibiotics, including gramicidin and bithionol. To understand how T7SS mediates increased antibiotic sensitivity, we investigated the impact of T7SS on the staphylococcal cell envelope. Interestingly, T7SS mutants displayed decreased membrane fluidity with altered localisation of cell membrane proteins such as flotillin under normal growth conditions. LC/MS analysis showed different protein profiles in the mutant membrane preparations compared to the WT, suggesting that T7SS impacts membrane homeostasis. Scanning electron microscopy analysis demonstrated distinct cell surface morphologies for the T7SS mutants, with altered cell wall synthesis as well cell surface charge. In line with the increased negative surface charge, daptomycin binding was enhanced in the mutants, which demonstrated increased membrane permeability when treated with the drug. T7SS mutants were more sensitive to daptomycin during intracellular infection, and furthermore, in a murine skin infection model, esxC mutants survived less than the WT when treated with daptomycin. Thus, our data show that the T7SS impacts sensitivity of S. aureus to membrane-acting drugs such as daptomycin through modulation of cell membrane integrity, indicating its potential as a drug target

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Staphylococcus Aureus

SUBMITTER: Andrew Bottrill  

LAB HEAD: Meera Unnikrishnan

PROVIDER: PXD047096 | Pride | 2024-04-19

REPOSITORIES: Pride