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Staphylococcus aureus expresses diverse proteins at different stages of growth. The immunodominant staphylococcal antigen A (IsaA) is one of the proteins that is constitutively produced by S. aureus during colonisation and infection. SACOL2584 (or isaA) is the gene that encodes this protein. It has been suggested that IsaA can hydrolyse cell walls, and there is still need to study isaA gene disruption to analyse its impact on staphylococcal phenotypes and on alteration to its transcription and protein profiles. In the present study, the growth curve in RPMI medium (which mimics human plasma), autolytic activity, cell wall morphology, fibronectin and fibrinogen adhesion and biofilm formation of S. aureus SH1000 (wildtype) was compared to that of S. aureus MS001 (isaA mutant). RNA sequencing and liquid chromatography–tandem mass spectrometry were carried out on samples of both S. aureus strains taken during the exponential growth phase, followed by bioinformatics analysis. Disruption of isaA had no obvious effect on the growth curve and autolysis ability or thickness of cell walls, but this study revealed significant strength of fibronectin adherence in S. aureus MS001. In particular, the isaA mutant formed less biofilm than S. aureus SH1000. In addition, proteomics and transcriptomics showed that the adhesin/biofilm-related genes and hemolysin genes, such as sasF, sarX and hlgC, were consistently downregulated with isaA gene disruption. The majority of the upregulated genes or proteins in S. aureus MS001 were pur genes. Taken together, this study provides insight into how isaA disruption changes the expression of other genes and has implications regarding biofilm formation and biological processes.

Staphylococcus aureus is well known for its biofilm formation with rapid emergence of new clones circulating worldwide. The main objectives of the study were (1) to identify possible differences in protein expression among various and closely related clonal types of S. aureus, (2) to establish the differences in protein expression in terms of size of protein spots and its intensities between bacteria which are grown statically (biofilm formation) with that of under aeration and agitation, and (3) to compare the differences in protein expression as a function of time (in hours). In this study, we selected six clinical isolates comprising two similar (MRSA-527 and MRSA-524) and four different (MRSA-139, MSSA-12E, MSSA-22d, and MSSA-10E) types identified by spa typing, MLST and SCCmec typing. We performed 2D gel migration comparison. Also, two MRSA isolates (527 and 139) were selected to determine quantitative changes in the level of extracellular proteins at different biofilm growth time points of 12, 24, and 48 h. The study was done using a strategy that combines 2-DGE and LC-MS/MS analysis for absolute quantification and identification of the extracellular proteins. The 2DGE revealed that the proteomic profiles for the isolates belonging to the similar spa, MLST, and SCCmec types were still quite different. Among the extracellular proteins secreted at different time points of biofilm formation, significant changes in protein expression were observed at 48 h incubation as compared to the exponential growth at 12 h incubation. The main conclusion of the work is that the authors do observe differences among isolates, and growth conditions do influence the protein content at different time points of biofilm formation.

Staphylococcus aureus (S. aureus) is a highly versatile pathogen that can survive under diverse in vitro and in vivo environmental conditions. The success of S. aureus is mainly driven by the extracellular proteins (exoproteins). Understanding the exoproteome of S. aureus isolates from different host and clinical manifestations as well as the host humoral and inflammatory responses is important in identifying potential virulence and diagnostic markers, and vaccine candidates. Firstly, silver staining technique was optimized prior to proteomic study to obtain a clear resolution of proteome. The modified silver staining helped to visualize the lower molecular mass and low abundant protein spots. Besides that, enhancedresolution images of co-migrating spots with variable abundance intensities were also achieved. The modified silver staining allowed the detection of proteins loaded at extremely low concentrations, ranging from 0.0048 to 0.0480 μg/μL. Therefore, all further investigations were carried out with modified silver staining method. Analysis of the exoproteome of pig-associated S. aureus strain (sequence type 9 (ST9)) isolated from human and pig showed similar protein patterns, however variation in the protein spot intensity was observed. The protein spots intensities were on average higher in S. aureus ST9 strain isolated from pigs than pig handlers. Variation in the spot positional correlation between the isolates from two different hosts was found to be less. From the comparative exoproteome, IsaA was found to be dominantly expressed in S. aureus, irrespective of their source. A comprehensive analysis of the exoproteome (pI 4-7) of S. aureus of similar or distinct genetic backgrounds (based on sequence type) isolated from healthy carriers (n = 6) and different clinical manifestations such as SSTIs (n = 6) and bacteremia (n =6) was performed. These included ST8, ST30, ST1963 and ST1964 from carriers,ST30, ST239, and ST1 from SSTIs and ST1, ST80, ST1179 and ST

Presence of secreted proteins is the key for sustenance of Staphylococcus aureus strains in the host system. General secretory (Sec) system is a well known and major secretion system that is responsible for the transportation of exoproteins across the bacterial cytoplasmic membrane and cell wall. In order to define the secretome of S. aureus, the availability of combination of two-dimensional gel electrophoresis (2-DE) with the latest advanced techniques (MALDI-TOF and ESI-MS/MS) has provided a powerful tool for the investigation of a large number of protein spots with the aim of identifying new drug candidates and discovering new diagnostics tools. In this paper, we present a short review regarding S. aureus general secretory system and role of secreted protein in host cells, and discuss the proteomic, together with genomics of S. aureus.