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Abstract
The pathogenesis of Staphylococcus aureus is mainly attributed to its capability to adjust to changes in environmental conditions, including those present on human skin or within a wound site. This study investigated the changes in the cytoplasmic and secreted proteins in S. aureus that occurred in response to alterations in the environmental parameters that could be found in the human wound site. In total, sixty differentially regulated cytoplasmic proteins were detected using a label-free quantification approach, and these proteins were classified into ten molecular functions: protein biosynthesis, glycolysis, signal transduction, metabolism, cell cycle, transport, energy generation, cell anchorage, nucleotide biosynthesis and unknown. These changes represented characteristic protein profiles when evaluated by principal component analysis. The bacterium responded to elevated NaCl at pH 6 by decreasing the abundance of the majority of cytoplasmic proteins, while at pH 8 there was an increase in the levels of cytoplasmic proteins in comparison to the untreated cells. The analysis of the secreted proteins showed that there was a high degree of difference in both the intensity and the distribution of many individual protein bands in response to environmental challenges. From these results, it was deduced that specific metabolic homeostasis occurred under each combination of defined environmental conditions.
Highlights
Staphylococcus aureus is a causative agent for many diseases worldwide, ranging from mild skin and tissue infections to highly severe infections, including toxic shock syndrome, endocarditis, and osteomyelitis [1]
S. aureus was grown to the stationary phase of growth under control conditions, centroid or with the addition of 5% NaCl at 39 ◦C and pH 6 representing the environmental parameters existing on the human skin or within a wound site where the temperatures can range from 37 ◦C–39 ◦C, pH 6–7, and NaCl can be elevated above the plasma levels
The findings of this study confirm that the autolysin precursor (Atl) protein, which is the major autolysin produced by S. aureus, is mostly processed into smaller fragments when this bacterium is grown in tryptic soy broth medium (TSB) with no added NaCl
Summary
Staphylococcus aureus is a causative agent for many diseases worldwide, ranging from mild skin and tissue infections to highly severe infections, including toxic shock syndrome, endocarditis, and osteomyelitis [1]. The exact mechanism that enables the switch from a commensal to a pathogenic lifestyle is unclear [2] The threat of this bacterium lies in its remarkable and rapid capacity to sense environmental signals and modulate the cellular responses; this is the major challenge for clinicians and scientists [3,4,5]. Small colony variants (SCVs) represent a good model of an altered bacterial phenotype where the colonies formed are ten-fold smaller in diameter compared with normal colonies [10,11,12]. These variants are highly associated with persistent and recurrent infections, they display attenuated virulence factors [11,13]. The formation of SCVs is possibly a mechanism used by staphylococcal species to combat adverse conditions, but the exact mechanism that enables the switch from a normal colony to a more resilient phenotype, such as a SCV, is unknown
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