Reduced Content of Lysyl-Phosphatidylglycerol in the Cytoplasmic Membrane Affects Susceptibility to Moenomycin, as Well as Vancomycin, Gentamicin, and Antimicrobial Peptides, in Staphylococcus aureus

Abstract

An association between moenomycin resistance and vancomycin intermediate resistance inStaphylococcus aureus was demonstrated previously. Thus, to elucidate the mechanism of vancomycin intermediate resistance, we searched for factors contributing to moenomycin resistance. Random Tn551 insertional mutagenesis of methicillin-resistant S. aureus strain COL yielded three mutants with decreased susceptibilities to moenomycin. Correspondingly, these mutants also exhibited slightly decreased susceptibilities to vancomycin. Genetic analysis revealed that two of the mutants had Tn551 insertions in the fmtC (mprF) gene, which is associated with the synthesis of lysyl-phosphatidylglycerol. The third Tn551 insertion was located in the lysC gene, which is involved in the biosynthesis of lysine from aspartic acid. Consequently, mutations in both of these loci reduced the lysyl-phosphatidylglycerol content in the cell membrane, giving it a more negative net charge. The positively charged antibiotic gentamicin and cationic antimicrobial peptides such as ␤-defensins and CAP18 were more effective against the mutants. The levels of moenomycin and vancomycin binding to intact cells was also greater in the mutants than in the wild type, while the binding affinity was not altered when cells boiled in sodium dodecyl sulfate were used, indicating that both agents had higher affinities for the negatively charged membranes of the mutants. Therefore, the membrane charge of S. aureus appears to influence the efficacies of moenomycin, vancomycin, and other cationic antimicrobial agents.

Deciphering the tRNA-dependent lipid aminoacylation systems in bacteria: Novel components and structural advances

“…4,58 aa-PGs have been found to modestly enhance bacterial resistance (e.g., a 2-fold increase in the MIC) to other classes of antimicrobials such as β-lactams and glycopeptides. Lys-PG, for example, increases resistance of S. aureus to several β-lactams, 64,65 and vancomycin. 66 Similarly, resistance phenotypes against β-lactams were observed in P. aeruginosa , which produces Ala-PG.…”

Monitoring Lys-tRNALys phosphatidylglycerol transferase activity

“…A staphylococal mprF deletion strain exhibited an attenuated resistance to human neutrophiles killing and a reduced virulence in mice (4). In addition MprF confers resistance to lanthioninecontaining peptides (lantibiotics) secreted by certain bacteria such as nisin produced by Lactococcus lactis (4) and also to several other positively charged antibiotics (aminoglycosides, betalactamines and glycopeptides) (8,9). The MprF pathway plays a role in the virulence of Listeria monocytogenes and may also provide a selective advantage to nonpathogenic organisms during colonization of their natural habitats (10).…”

Antimicrobial Peptide Resistance Mechanisms of Human Bacterial Pathogens

“…Expression of the mprF gene in Escherichia coli was sufficient to confer production of the cationic lysine-substituted phosphatidylglcerol (L-PG), indicating that MprF indeed represents the L-PG synthase enzyme (Staubitz et al, 2004). Reduced lysyl-phosphatidylglycerol content in the cell membrane of S. aureus can also be seen with mutation of the lysC gene, which is involved in the biosynthesis of lysine from aspartic acid, with resulting sensitivity to human β-defensin and cathelicidin killing (Nishi et al, 2004).…”

“…Systemic infection (mice) ) (Nishi et al, 2004) Addition of aminoarabinose to lipid A in LPS pmr genes Defensins, Caths…”