Structure and Function Predictions of the Msa Protein in \u3ci\u3eStaphylococcus aureus\u3c/i\u3e

Background Staphylococcus aureus is a human pathogen that causes a wide variety of life-threatening infections using a large number of virulence factors. One of the major global regulators used by S. aureus is the staphylococcal accessory regulator (sarA). We have identified and characterized a new gene (modulator of sarA: msa) that modulates the expression of sarA. Genetic and functional analysis shows that msa has a global effect on gene expression in S. aureus. However, the mechanism of Msa function is still unknown. Function predictions of Msa are complicated by the fact that it does not have a homologous partner in any other organism. This work aims at predicting the structure and function of the Msa protein. Results Preliminary sequence analysis showed that Msa is a putative membrane protein. It would therefore be very difficult to purify and crystallize Msa in order to acquire structure information about this protein. We have used several computational tools to predict the physico-chemical properties, secondary structural features, topology, 3D tertiary structure, binding sites, motifs/patterns/domains and cellular location. We have built a consensus that is derived from analysis using different algorithms to predict several structural features. We confirm that Msa is a putative membrane protein with three transmembrane regions. We also predict that Msa has phosphorylation sites and binding sites suggesting functions in signal transduction. Conclusion Based on our predictions we hypothesise that Msa is a novel signal transducer that might be involved in the interaction of the S. aureus with its environment

Proceedings of the Fourth Annual Conference of the MidSouth Computational Biology and Bioinformatics Society

<p/> <p/> <p/

Deletion of Putative msa Operon Gene Fragment and Its Phenotypic Characterization in Community Acquired-Methicillin Resistant \u3ci\u3eStaphylococcus aureus\u3c/i\u3e USA300 Strain LAC

Staphylococcus aureus is an important human pathogen that causes a wide variety of diseases. Many S. aureus strains have emerged which are resistant to the penicillin class of antibiotics. Of primary importance is methicillin-resistant S. aureus (MRSA), which has cause frequent hospitalizations due to infections. In the past, MRSA was typically confined to hospital settings, but recently, community-associated MRSA (CA-MRSA) have been reported. CA-MRSA poses a major public health threat because of increased virulence and success in infecting otherwise healthy individuals. Previously we discovered a gene, msa, which plays a critical role in biofilm formation and regulation of the disease process. Recent studies indicate that msa is part of a three open reading frame operon and that the upstream neighboring genes may play a role in the regulation of the msa operon. In this study, we investigated the possibility that genes 1294-1298 regulate virulence factors of S. aureus. We constructed a 1294-1298 mutant in CA-MRSA USA300 strain LAC using the allelic replacement vector pKOR1 and found that it produced a weaker biofilm in addition to increased autolysis, protease production, pigmentation production, hemolysin production and lipase production-all indicators that genes 1294-1298 play a role in the virulence of S. aureus. We hope to explore the possibility of exploring the regulatory network of the msa operon and its neighboring genes and exploit them as a target for therapy for recalcitrant staph infections

The Role of \u3ci\u3emsa\u3c/i\u3e in \u3ci\u3eStaphylococcus aureus\u3c/i\u3e Biofilm Formation

BackgroundStaphylococcus aureus is an important pathogen that forms biofilms. The global regulator sarA is essential for biofilm formation. Since the modulator of sarA (msa) is required for full expression of sarA and regulates several virulence factors, we examined the capacity of the msa mutant to form biofilm. ResultsWe found that mutation of msa results in reduced expression of sarA in biofilm and that the msa mutant formed a weak and unstable biofilm. The msa mutant is able to adhere to surfaces and begins to form biofilm but fails to mature indicating that the defect of the msa mutant biofilm is in the accumulation stage but not in primary adhesion. ConclusionThe msa gene plays an important role in biofilm development which is likely due to its role in modulating the expression of sarA. This finding is significant because it identifies a new gene that plays a role in the development of biofilm

The Role of msa in Staphylococcus aureus Biofilm Formation

<p>Abstract</p> <p>Background</p> <p><it>Staphylococcus aureus </it>is an important pathogen that forms biofilms. The global regulator <it>sarA </it>is essential for biofilm formation. Since the modulator of <it>sarA </it>(<it>msa</it>) is required for full expression of <it>sarA </it>and regulates several virulence factors, we examined the capacity of the <it>msa </it>mutant to form biofilm.</p> <p>Results</p> <p>We found that mutation of <it>msa </it>results in reduced expression of <it>sarA </it>in biofilm and that the <it>msa </it>mutant formed a weak and unstable biofilm. The <it>msa </it>mutant is able to adhere to surfaces and begins to form biofilm but fails to mature indicating that the defect of the <it>msa </it>mutant biofilm is in the accumulation stage but not in primary adhesion.</p> <p>Conclusion</p> <p>The <it>msa </it>gene plays an important role in biofilm development which is likely due to its role in modulating the expression of <it>sarA</it>. This finding is significant because it identifies a new gene that plays a role in the development of biofilm.</p

The Role of MSA in the Global Regulation of Virulence in \u3ci\u3eStaphylococcus aureus\u3c/i\u3e

Staphylococcus aureus is an important pathogen causing life threatening diseases in humans. Previously we showed that msa modulates the activity of sarA (Staphylococcal accessory regulator), which is one of a major global regulator of virulence in S. aureus. The objective of this study is to characterize the role of msa (Modulator of SarA) in the global regulation of virulence in S. aureus. Structure and function predictions were done using several computational tools and approaches to understand the nature of msa. A novel S. aureus microarray meta-database (SAMMD) was designed and developed to compare and contrast other transcriptomes with msa transcriptome. msa and sarA transcriptomes were generated using the microarray technology. Phenotypic and molecular assays were performed to support microarray results. The results show that msa is a putative transmembrane protein, with three transmembrane segments, a distinct N-terminal cleavable signal peptide, four phophorylation sites (two outside and two inside the membrane) and a binding site in the cytoplasmic region. Microarray results and comparative transcriptome analysis using SAMMD showed that several genes regulated by msa are also regulated by sarA. Based on these results I hypothesize that msa is a novel signal transducer, which modulates the activity of genes involved in virulence in a sar/\-dependent manner, while modulating the activity of genes involved in metabolism in a sar-4-independent manner

Role of \u3ci\u3eMSA\u3c/i\u3e in Immune Evasion, Persistence, and Protease Regulation in the Human Pathogenic Strains of \u3ci\u3eStaphylococcus aureus\u3c/i\u3e

Opportunistic pathogens like Staphylococcus aureus on entering the host can stay colonized at the foci of infection or evade the immune system to disseminate to other sites. In this study we investigated the regulatory influence of the modulator of sarA (msa) on immune evasion and host persistence, employing the hospital-acquired strain S. aureus UAMS-1 and community-acquired strain S. aureus USA300 LAC. In the murine sepsis model, mutation of the msa gene in LAC showed no change in dissemination of infection; however, in UAMS-1 a decrease in microbial load was observed in the lungs. Differential regulation by the msa gene was also observed in the blood survival and neutrophil assays. Several evasion factors were found to be regulated by msa, namely the scn, clfA, spa, aur, and sak genes. Interestingly, the combination of factors and the regulation of these factors differed in the two strains. S. aureus form biofilms on post-surgical wounds, prosthetic devices, and various host tissues that are resilient to immunological clearance and antimicrobial treatments. Biofilm detachment is a stage of biofilm development that aids in metastasis of infection. Proteases are one of the factors that trigger biofilm detachment. In our study, we observed msa to regulate proteases of S. aureus strain LAC when they are not in the form of a biofilm community; however, when they form biofilms the regulatory effect on proteases by the msa gene is absent. Thus, we show the environment-dependent behavior of the msa gene

Regulation of Biofilm and Antibiotic-Resistance by the Modulator of SarA (MSA) in \u3ci\u3eStaphylococcus aureus\u3c/i\u3e

Staphylococcus aureus is an important human pathogen that is the causative agent of life-threatening diseases such as endocarditis and osteomyelitis. The ability of S. aureus to thrive as a successful pathogen can be partially attributed to its ability to form biofilm. Biofilm is an extracellular polysaccharide, protein, and DNA-based slime layer that protects the bacterial community. The global regulator sarA is essential for biofilm formation. Since the modulator of sarA (msa) gene regulates several virulence factors and is required for the full expression of sarA, the capacity of the msa mutant to form a biofilm was examined. The mutation of msa results in reduced expression of sarA, and the msa mutant formed a weak and unstable biofilm. The msa mutant is able to adhere to surfaces and begins to form biofilm, but fails to mature indicating that the defect of the msa mutant biofilm is in the accumulation stage but not in primary adhesion. This finding is significant because it identifies a new gene that plays a role in the development of biofilm. Antibiotic resistance in Staphylococcus aureus has become an issue of paramount importance as the rate of MRSA (Methicillin-Resistant Staphylococcus aureus)-related deaths have surpassed HIV-related deaths in the United States over the last decade. In this study, mutation of the msa gene leads to increased susceptibility (MIC 3 �g/ml) to oxacillin in comparison to wild type MRSA strain COL (MIC 1600 �g/ml). RT-qPCR analysis was utilized to identify the genes that were differentially expressed. Apart from the fem genes, genes such as aux14, sigB, mecA, murAB and mraY were all differentially expressed in the msa mutant in comparison to the wild type strain COL. Additional functional assays and TEM studies show that the bacterial cell wall is compromised upon mutation of msa. The results from this study collectively indicated that msa plays an important role in antibiotic resistance by regulating cell wall and cell wall-precursor synthesis. Given these results and the possibility that Msa is a membrane protein, it is possible that Msa could serve as a target for therapeutic agents designed against Staphylococcus aureus