Global gene expression in Staphylococcus aureus following exposure to alcohol Moshe Korem, Yael Gov, Mel Rosenberg * Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Ramat Aviv 69978, Israel article info Article history: Received 28 June 2009 Received in revised form 26 October 2009 Accepted 2 November 2009 Available online 10 November 2009 Keywords: Hemolysis MACH (microbial alcohol-conferred hemolysis) Ethanol RNAIII Pathogenicity Stress abstract It was recently shown that, as in yeast, alcohols selectively increase the hemolytic properties of certain staphylococci strains. This phenomenon has been called ‘microbial alcohol-conferred hemolysis’(MACH). Here we present the changes in gene expression by Staphylococcus aureus 8325-4, in response to ethanol. Ethanol upregulated the expression of multiple toxins and increase the pathogen potential of S. aureus strain 8325-4. Ethanol also increased the level of genes considered necessary for production and viability of biofilm, such as: icaAD, sdrDE, pyr, and ure. Increased urease activity appeared to be an important factor in the ethanol response along with macromolecule repair mechanisms. Oxidative-stress responses, such as increased expression of sodA1, sodA2 and upregulation of zinc-containing alcohol dehydrogenase, alcohol-acetaldehyde dehydrogenase (adhE) and two aldehyde dehydrogenases (aldA1 , aldA2), which can generate more reducing power, were also induced. Upregulation of fatty acid metabolism appears to be important in enabling the bacteria to handle excess amounts of ethanol which ultimately may lead to synthesis of lytic lypids. The patterns of regulation were confirmed by quantitive reverse transcriptase PCR (QRT-PCR). These results, taken together, suggest that exposure to ethanol increases pathogenic traits and induce oxidative-stress responses. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Staphylococcus aureus are Gram-positive bacteria that are part of the normal flora of humans and animals but can become patho- genic and cause disease once they produce toxic exomolecules or biofilm [37]. These bacteria may cause a variety of diseases, from benign skin infections to life-threatening meningitis, endocarditis, septicemia and Toxic Shock Syndrome [37]. Among their wide arsenal of virulence factors, cytolytic enzymes are by far the most studied. These include four hemolysins: a, b, g and d. The produc- tion of some of these virulence factors is regulated by quorum- sensing mechanisms through activation of the gene locus agr and production of the regulatory mRNA molecule RNAIII [46,47]. The agr system consists of two divergently transcribed loci (w3 kb) controlled by two promoters, P2 and P3, that regulate the tran- scription of a cell-density-sensing two-component regulator and RNAIII [47]. There are four genes controlled by P2: agrA, agrC, agrD, and agrB. AgrC is the transmebrane histidine kinase component of the agr two-component regulatory system, with AgrA being the response regulator. AgrD is a small peptide that is processed by AgrB into a cyclic thiolactone peptide also known as the autoinducing peptide [41]. When the extracellular concentration of the autoinducing peptide reaches a threshold level, the probability that it will complex with AgrC is increased, leading to the activation of the kinase domain [36]. Upon the transfer of a phosphate from AgrC to AgrA, AgrA is activated and increases transcription from the P2 and P3 promoters [29]. Transcription from P2 is a type of autocrine regulation that increases the biosynthesis of the agr cell- density-sensing system. Transcription from P3 produces the predominantly untranslated riboregulator RNAIII [46]. RNAIII enhances the synthesis of secreted virulence determinants (e.g., alpha-toxin and serine protease) and represses the synthesis of surface-associated proteins (e.g., protein A) [16]. Bacterial hemolysis on blood agar has long been considered to be indicative of pathological traits, especially in streptococci and staphylococci [5,60]. We recently showed that, alcohols selectively increase the hemolytic properties of certain staphylococci strains [30]. This phenomenon has been called ‘microbial alcohol- conferred hemolysis’ (MACH) and may have medical relevance, as alcohol can aggravate staphylococcal skin infections [28]. Results from recent studies contribute to the growing realiza- tion that alcohol extensively affects microbial activity in the human body. Examples include profound effects on the shape of cells, colony morphology and the ability to form biofilms [64]. All of these characteristics may be related to pathogenicity. In S. epidermidis, ethanol supplementation increases biofilm expression, by acti- vating expression of ica genes [12,27]. * Corresponding author. Tel.: þ972 3 6405137; fax: þ972 3 6429311. E-mail address: melros@post.tau.ac.il (M. Rosenberg). Contents lists available at ScienceDirect Microbial Pathogenesis journal homepage: www.elsevier.com/locate/micpath 0882-4010/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.micpath.2009.11.002 Microbial Pathogenesis 48 (2010) 74–84