الفهرس Only 14 pages are availabe for public view
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Abstract
So far little is kown about how staphylococcus epidermidis responds to stress therefore we conducted a comparative study between the well studied S. aureus and epidermidis looking into the response to stress was conducted. The study focused some of the major stress regulator such as SaeR, SigB and CymR and known stress regulated proteins such as osmoprotectant transporter (OpucC) and superoxide dismutase (SodA) in addition to some virulence factor (lipase and urease). Bioinformatic analyses revealed high identity between S. epidermidis ATCC 12228 and those from S. aureus in all the proteins investigated. Two different pHs were studied, pH 5 (skin pH) and pH 7.4 (blood pH) while for the oxidative stress, 18 mM H2O2 is used. Studying the transcriptional analysis of these different genes in S. epidermidis was performed by quantitative real time RT - PCR and showed up regulation of the two regulators saeR and sigB at pH 7.4 relative to pH 5. In the case the oxidative stress, saeR and cymR showed up regulation in the presence of H₂O₂ while sigB shows down regulation. The two stress-regulated genes, osmoprotectant transporter (opucC) showed down regulation at pH 7.4 compared to pH5 and superoxide dismutase, sodA showed down regulation in the presence of H₂O₂. Quantitative determination of some phenotypic activities showed an increase in lipase activity using tributyrin agar plate technique for both S. aureus and S. epidermidis at pH7.4 to pH5. Using the weatherburn assay, the urease activity of S. aureus was found to decreas while it increased in case of S. epidermidis during the stationary phase that was reversed in exponential phase under pH 7.4 relative to pH5