Browsing by Subject "staphylococcus aureus"
Now showing 1 - 5 of 5
- Results Per Page
- Sort Options
Item Analysis of a Tn917 Transposon Mutant and Preliminary Characterization of NonHemolytic, Catalase-Deficient Variants of Staphylococcus aureus(1999-06-01) Crum, Russell M.Crum, Russell M., Analysis of a Tn917 Transposon Mutant and Preliminary Characterization of Nonhemolytic, Catalase-Deficient Variants of Staphylococcus aureus. Masters of Science (Microbiology). June 1999. Pages-101. Tables-15. Figures-10. A Tn917 transposon mutant of Staphylococcus aureus S6C was isolated and analyzed due to its deficiency in hemolysin and lipase activities. The transposon insertion did not occur in any of the known genetic regulators, which suggested the insertion occurred in a novel regulator of at least, hemolysin and lipase activities. One end of the region where the insertion occurred was isolated, sequenced, and compared with known DNA databases. Sequence comparisons revealed the insertion occurred in one of six rRNA DNA operons, which was confirmed by Southern analysis. Transduction of the transposon insertion back into the parental strain did not result in a mutant phenotype thereby indicating that the transposon insertion into a rRNA DNA operon was not responsible for the observed mutant phenotype. Further analysis of the parent strain, S. aureus S6C, revealed a population of four relatively stable variants differing in their hemolysin and catalase activities. These data suggest that the Tn917 mutant was one of these four S6C variants.Item Effects of Serine Protease-Like F (SPLF) on Alpha-Toxin Expression in Staphylococcus aureus(2003-05-01) Pulse, Mark E.; Mart Hart; Jerry Simecka; Ming-Chi WuPulse, Mark E., Effects of Serine protease-like F (Sp1F) on Alpha-Toxin Expression in Staphylococcus aureus. Master’s of Science (Microbiology). May 2003. Pages-67. Table-5. Figures-9. Transposon mutagenesis (Tn551) was used to generate agr-suppressor mutations in the agr-null Staphylococcus aureus strain RN6911 (Δagr;;tmn). Firty-four suppressor mutants displaying changes in hemolysin, protease, and lipase activities were isolated, and only twenty-six mutants contained Tn551 within their chromosomes. Transposon insertion sites for seven mutants were determined by sequencing amplicons generated by arbitrary-PCR. One of the insertion sites was within the serine protease-like F (spʅF) gene. Alpha-toxin message levels for the spʅF mutant were similar to RN6911. However, alpha-toxin activity in spent media isolated from the spʅF mutant were similar to RN6911. However, alpha-toxin activity in spent media isolated from the spʅF mutant was increased ten-fold as compared to RN6911. Transduction of the spʅf:Tn551 mutation back into the parental strain verified the link between the phenotype and the mutation. Whole cell lysates from Escherichia coli cells containing a plasmid copy of spʅF displayed protease activity on casein. These data suggest that SpʅF may be post-translationally modifying alpha-toxin through proteolysis.Item Lethality of Staphylococcus in Murine Pneumonia is Due to Alpha-Toxin and Other Secreted Factors Regulated by AGR and SAR(2003-08-01) Overheim, Katie A.; Dan Dimitrijevich; Glenn Dillon; James CaffreyOverheim, Katie A., Lethality of Staphlococcus aureus in Murine Pneumonia is Due to Alpha-Toxin and Other Secreted Factors Regulated by agr and sar. Doctor of Philosophy (Biomedical Sciences), August, 2003, 91 pp, 6 Tables, 9 illustrations, bibliography, 106. The purpose of these studies was to determine if the S. aureus global regulators agr and sar play a role in staphylococcal pneumonia and if the virulence factors regulated by them contributed to the severity of staphylococcal pneumonia. To determine this, we established a pneumonia model in mice in order to identify if S. aureus global regulators agr and sar play a role in the pathogenesis of staphylococcal pneumonia. As well, we took steps to identify the extracellular factors responsible for the lethality in a murine model of staphylococcal pneumonia and determine if these factors involved in disease process could be used as targets for immune therapy. My work revealed that lethal pneumonia in a mouse model is dependent on the S. aureus global regulators agr and sar. This study also revealed that the lethality associated with our model is due to secreted factors, regulated by S. aureus global regulators agr and sar. Further investigation demonstrated the alpha-toxin is a major virulence factor involved in the lethality in our model. By generating an alpha-toxin deficient strain in S. aureus RN6390, we show a reduced virulence in our disease model. As well, antiserum to alpha-toxin, when administered with a lethal dose of S. aureus RN6390, we show a reduced virulence in our disease model. As well, antiserum to alpha-toxin, when administered a lethal dose of S. aureus RN6390, we show a reduced virulence in our disease model. As well, antiserum to alpha-toxin, when administered with a lethal dose of S. aureus RN6390 protected animals from death. By evaluating the role of alpha-toxin’s ability to contribute to lethality, we assessed numerous strains of S. aureus in our pneumonia model. We discovered that there was a correlation to alpha-toxin production levels and lethality in our pneumonia model. However, our study also demonstrated that alpha-toxin is not the only factor involved in the disease process.Item Molecular Characterization of a Second Superoxide Dismutase Gene (sodM) of Staphylococcus Aureus and Effects of SodM and SodA on Oxidative Stress Resistance and Virulence(2001-11-01) Valderas, Michele Wright; Porunelloor A. Mathew; Richard Easom; Jerry SimeckaValderas, Michelle Wright., Molecular Characterization of a Second Superoxide Dismutase Gene(sodM) of Staphylococcus aureus and Effects of SodM and SodA on Oxidative Stress Resistance and Virulence. Doctor of Philosophy (Biomedical Sciences), November, 2001, 191 pp., 4 tables, 20 illustrations, bibliography, 389 titles. A second gene for superoxide dismutase (SOD) in S. aureus (sodM) was cloned and characterized. This gene was found to be unique to S. aureus among the staphylococci. S. aureus is the first gram-positive bacterium reported to contain two or more SOD activities. The three native SOD enzymes observed for S. aureus can be accounted for by two distinct genes, sodM and sodA. The SodM and SodA proteins form homodimers, but their subunits also interact to form an active heterodimeric SOD. The deduced amino acid sequence from each gene and the relative insensitivity to hydrogen peroxide and potassium cyanide indicated that the S. aureus SODs utilize manganese as a metal ion cofactor. Additionally, viabilities of the soda and sod double mutants, but not the sodM mutant were drastically reduced under conditions of oxidative stress in early exponential growth. However, only the double mutant was affected when oxidative stress was applied in the late-exponential and stationary phases of growth. It was determined, therefore, that while SodA may be the major SOD activity in S. aureus throughout all stages of growth, SodM, under conditions of oxidative stress, becomes a major source of SOD activity during the late-exponential and stationary phases of growth such that the viability of the S. aureus sodA mutant is maintained. Experiments examining the roles of sodM and sodA in virulence determined the ability of S. aureus to cause disease in the mouse lung and subcutaneous abscess formation in mice was unaffected by sod mutation. Lack of SOD activity, however, results in enhanced clearance of S. aureus within the lung and also promotes killing of the organism by mouse macrophage cell lines and human polymorphonuclear leukocytes.Item The Effects of Two Staphylococcal Global Regulators (agr and sar) on Acid Phosphatase production in Staphylococcus aureus(2003-05-01) Agouna-Deciat, Bahrka Olivier; Jerry Simecka; Michael SmithAgouna-Deciat, B. Olivier, The Effect of Two Staphylococcal Global Regulators (agr and sar) on Acid Phosphatase Production in Staphylococcus aureus. Master of Science (Molecular Biology and Immunology), May 2003, 75 pp., 3 tables, 14 illustrations, 16 titles. Staphylococcus aureus produces an extensive number of cell-surface associated proteins, extracellular proteins and enzymes that contribute to its virulence. The key to better preventative or curative approaches resides in identifying and targeting the very genes and their products that play major roles in the survival of the bacteria within the host and the establishment of diseases. Two well known regulatory loci, the accessory gene regulatory (agr) and the staphylococcal accessory regulator (sar), control the expression of most S. aureus genes that encode for its virulence factors. Other virulence gene regulators have recently been isolated. Over 40 proteins and enzymes produced by S. aureus have been identified and several of them have been linked to staphylococcal pathogenesis. In this study, we attempt to determine the role of agr and sar in the regulation of the production of a secreted staphylococcal acid phosphatase (Sap) suspected to contribute to virulence.