title: Copper stress induces a global stress response in Staphylococcus aureus and represses sae and agr expression and biofilm formation.
abstract: Copper is an important cofactor for many enzymes; however, high levels of copper are toxic. Therefore, bacteria must ensure there is sufficient copper for use as a cofactor but, more importantly, must limit free intracellular levels to prevent toxicity. In this study, we have used DNA microarray to identify Staphylococcus aureus copper-responsive genes. Transcriptional profiling of S. aureus SH1000 grown in excess copper identified a number of genes which fall into four groups, suggesting that S. aureus has four main mechanisms for adapting to high levels of environmental copper, as follows: (i) induction of direct copper homeostasis mechanisms; (ii) increased oxidative stress resistance; (iii) expression of the misfolded protein response; and (iv) repression of a number of transporters and global regulators such as Agr and Sae. Our experimental data confirm that resistance to oxidative stress and particularly to H2O2 scavenging is an important S. aureus copper resistance mechanism. Our previous studies have demonstrated that Eap and Emp proteins, which are positively regulated by Agr and Sae, are required for biofilm formation under low-iron growth conditions. Our transcriptional analysis has confirmed that sae, agr, and eap are repressed under high-copper conditions and that biofilm formation is indeed repressed under high-copper conditions. Therefore, our results may provide an explanation for how copper films can prevent biofilm formation on catheters.
authors.affiliation: Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Baker
authors.forename: Sutthirat
authors.initials: S
authors.lastname: Sitthisak
authors.forename: Mrittika
authors.initials: M
authors.lastname: Sengupta
authors.forename: Miranda
authors.initials: M
authors.lastname: Johnson
authors.forename: R K
authors.initials: RK
authors.lastname: Jayaswal
authors.forename: Julie A
authors.initials: JA
authors.lastname: Morrissey
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D018441:Biofilms / Q000254:growth & development*; D003300:Copper / Q000633:toxicity*; D015536:Down-Regulation; D020869:Gene Expression Profiling; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D013211:Staphylococcus aureus / Q000187:drug effects*; D013312:Stress, Physiological; D015534:Trans-Activators / Q000096:biosynthesis*; D014157:Transcription Factors / Q000096:biosynthesis*
chemical_list: C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D003300:Copper; D006861:Hydrogen Peroxide