Expression of genes involved in the pathogenesis of is controlled by global regulatory loci including two-component regulatory systems and transcriptional regulators. was observed in expression of the gene only in strain RN6390. Expression of and was observed in all strains but the level of expression varied from strain to strain. INTRODUCTION is an opportunistic commensal pathogen and among the most common causes of bacterial infections in the community and the hospital. It can cause acute food poisoning pneumonia meningitis skin conditions (e.g. acne boils and cellulitis) arthritis osteomyelitis endocarditis and toxic shock syndrome (Gordon & Lowy 2008 Klevens strains Benidipine hydrochloride are resistant to a wide spectrum of antibiotics including meticillin and vancomycin which often makes treatment of infections extremely difficult. Therefore there is considerable interest in identifying novel drug targets based on an analysis and a better understanding of staphylococcal molecular genetics. Most infections begin as minor colonization of skin or soft tissue from which the organism can spread to the bloodstream and subsequently disseminate into various tissues (Gordon & Lowy 2008 Klevens produces a large number of factors that include adhesins enzymes toxins capsular polysaccharides and other gene products that facilitate tissue colonization tissue destruction and immune evasion. The expression of these factors is coordinately controlled by regulatory systems such as two-component regulatory systems (e.g. family isolates including UAMS-1 MRSA252 and RF122 and in other species (Cassat family of Benidipine hydrochloride genes mostly in laboratory strains derived from 8325-4 suggests that many of these genes have distinct phenotypes which arise due to regulation of the expression of virulence factors regulatory genes and genes involved in biofilm formation oxidative stress and metabolic processes. Several members of the family are Benidipine hydrochloride involved in regulation of the locus a pivotal regulator for virulence factors expression and a potential drug target in family such as and or undetectable transcription is associated with repression mediated by MgrA and SarA while undetectable transcription is enhanced in a mutant (Manna & Cheung 2003 Manna and genes leads to altered expression of large numbers of genes in and family of genes is important and contributes to reductions in both Benidipine hydrochloride virulence and bacterial counts in different organs. Our knowledge of global regulatory systems is predominantly based on studies with strains derived from the easily manipulated laboratory strain 8325-4 which has a mutation in the gene that results in reduced production of the stress-responsive alternative SigB factor (Giachino strains were routinely grown in tryptic soy broth (TSB) without antibiotic selection. The cells were grown overnight in TSB medium and then inoculated at 0.5?% (v/v) (OD600 ～0.05) into 10?ml fresh TSB and grown with vigorous aeration at 230?r.p.m. in a 45 degree angle attached stand in a New Brunswick air shaker at 37?°C in 18?mm diameter borosilicate glass tubes. Extraction of RNA and Northern blot hybridization. Total RNA from various strains was prepared using a Trizol isolation kit (Invitrogen) and a reciprocating shaker as described previously (Manna & Cheung 2001 2003 Manna and coding regions respectively were amplified by PCR using chromosomal DNA from RN6390 as the template and primers containing flanking restriction sites BL21 (DE3) pLysS. The His6-SarV Rot and SarU protein expression GLB1 and purification were done in a manner similar to that described for other Sar-family proteins (Ballal gene originates from two different promoters (P1 and P2) but the translational product is MgrA (17?kDa). Expression of the transcripts was similar in all tested strains of decreased at the stationary (or overnight) phase in all strains. Western blot analysis of cell extracts from three different phases of growth with anti-MgrA monoclonal antibody clearly showed that MgrA was produced in all strains but the level of expression varied between strains and at different phases of growth (Fig.?1). A substantial reduction (approximately twofold) in expression of MgrA was observed in the post-exponential phase of growth (OD ～1.7) as compared with the exponential phase of growth (OD ～1.1) where maximal expression of MgrA was observed. The.