title: Response of methicillin-resistant Staphylococcus aureus to amicoumacin A.
abstract: Amicoumacin A exhibits strong antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA), hence we sought to uncover its mechanism of action. Genome-wide transcriptome analysis of S. aureus COL in response to amicoumacin A showed alteration in transcription of genes specifying several cellular processes including cell envelope turnover, cross-membrane transport, virulence, metabolism, and general stress response. The most highly induced gene was lrgA, encoding an antiholin-like product, which is induced in cells undergoing a collapse of Δψ. Consistent with the notion that LrgA modulates murein hydrolase activity, COL grown in the presence of amicoumacin A showed reduced autolysis, which was primarily caused by lower hydrolase activity. To gain further insight into the mechanism of action of amicoumacin A, a whole genome comparison of wild-type COL and amicoumacin A-resistant mutants isolated by a serial passage method was carried out. Single point mutations generating codon substitutions were uncovered in ksgA (encoding RNA dimethyltransferase), fusA (elongation factor G), dnaG (primase), lacD (tagatose 1,6-bisphosphate aldolase), and SACOL0611 (a putative glycosyl transferase). The codon substitutions in EF-G that cause amicoumacin A resistance and fusidic acid resistance reside in separate domains and do not bring about cross resistance. Taken together, these results suggest that amicoumacin A might cause perturbation of the cell membrane and lead to energy dissipation. Decreased rates of cellular metabolism including protein synthesis and DNA replication in resistant strains might allow cells to compensate for membrane dysfunction and thus increase cell survivability.
authors.affiliation: Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University, Beaverton, Oregon, United States of America.
authors.forename: Amrita
authors.initials: A
authors.lastname: Lama
authors.forename: Jan
authors.initials: J
authors.lastname: Pané-Farré
authors.forename: Tai
authors.initials: T
authors.lastname: Chon
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wiersma
authors.forename: Clarissa S
authors.initials: CS
authors.lastname: Sit
authors.forename: John C
authors.initials: JC
authors.lastname: Vederas
authors.forename: Michael
authors.initials: M
authors.lastname: Hecker
authors.forename: Michiko M
authors.initials: MM
authors.lastname: Nakano
mesh_terms: D000446:Aldehyde-Lyases / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D003062:Codon; D003374:Coumarins / Q000494:pharmacology*; D019915:DNA Primase / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005672:Fusidic Acid / Q000494:pharmacology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D020653:Peptide Elongation Factor G / Q000378:metabolism; D017354:Point Mutation
chemical_list: D000900:Anti-Bacterial Agents; D003062:Codon; D003374:Coumarins; D020653:Peptide Elongation Factor G; C031379:amicoumacin A; D005672:Fusidic Acid; D008780:Methyltransferases; C047346:16S rRNA (adenine(1518)-N(6)-adenine(1519)-N(6))-dimethyltransferase; D019915:DNA Primase; D000446:Aldehyde-Lyases; C023093:tagatose 1,6-diphosphate aldolase