Project description:Staphylococcus aureus (S. aureus) is a known pathogen able to infect humans and animals. Human S. aureus isolates are often associated with carriage of Sa3int prophages combined with loss of beta-hemolysin production due to gene disruption, whereas animal isolates are positive for beta-hemolysin associated with absence of Sa3int prophages. Sa3int prophages are known to contribute to staphylococcal fitness and virulence in human host by providing human-specific virulence factors encoded on the prophage genome. Strain-specific differences in regard to phage transfer, lysogenization and induction are attributable to yet unknown staphylococcal factors specifically influencing prophage gene expression. In this work we used tagRNA-sequencing approach to specifically search for these unknown host factors and differences in prophage gene expression. For this purpose, we established a workflow revealing the first direct comparison for differential gene expression analysis on two distinct single-lysogenic S. aureus isolates. Further, global gene expression patterns were investigated in two S. aureus isolates upon mitomycin C treatment and compared to uninduced conditions. This provides new insights into the tightly linked host-phage interaction network.
Project description:The present work comprises the study of wound pathogenic bacteria as part of a community. It considers the interactions of two different S. aureus isolates with B. thuringiensis and K. oxytoca; all of them isolated from the same chronic wound of a patient with epidermolysis bullosa. Particular focus has been given on the interactions of S. aureus with other microbes due to its high prevalence among chronic wounds. During cultivation, no species performed as dominant or inhibited the growth of one another. Mass spectrometry was used to explore the inherent relationships between the staphylococcal strains and the coexisting bacteria exproteomes. The analysis showed an important reduction in the amount of staphylococcal cytoplasmic proteins when co-cultured with K. oxytoca and B. thuringiensis, this decrement did not occur with klebsiella and bacillus proteins. Interestingly, K. oxytoca and B. thuringiensis seemed to have a more evident response towards the presence of S. aureus in the culture, while the opposite was not observed with the staphylococcal isolates. Genomic analysis revealed isolate t13595 hypermutable characteristics, placing the interactions between staphylococcal isolates in the context of a chronic wound. Overall, the nature of the exoproteome variations among cultures suggests that adaptive mechanisms differ in all strains.
Project description:Staphylococcus aureus (S. aureus) has already to be one of the most commonly identified bacteria that cause food poisoning. S. aureus colonization in humans can cause serious infections, toxinoses and life threatening diseases. The bacteriocin nisin has been extensively used as potential natural preservative in the food industry, but the overall transcriptional response mechanisms of S. aureus to nisin are still poorly understood. To detect the possible molecular mechanism of nisin against S. aureus, Affymetrix GeneChips were used to determine the global comparative transcription of S. aureus cells triggered by treatment with sub-inhibitory concentrations of nisin.
Project description:Staphylococcus aureus is a Gram-positive human pathogen causing a variety of human diseases in both hospital and community settings. This bacterium is so closely associated with prophages that it is rare to find S. aureus isolates without prophages. Two phages are known to be important for staphylococcal virulence: the beta-hemolysin (hlb) converting phage and the Panton-Valentine Leukocidin (PVL) converting phage. The hlb-converting phage is found in more than 90% of clinical isolates of S. aureus. This phage produces exotoxins and immune modulatory molecules, which inhibit human innate immune responses. The PVL-converting phage produces the two-component exotoxin PVL, which can kill human leucocytes. This phage is wide-spread among community-associated methicillin resistant S. aureus (CA-MRSA). It also shows strong association with soft tissue infections and necrotizing pneumonia. Several lines of evidence suggest that staphylococcal prophages increase bacterial virulence not only by providing virulence factors but also by altering bacterial gene expression: 1) Transposon insertion into prophage regulatory genes, but not into the genes of virulence factors, reduced S. aureus killing of Caenorhabditis elegans.; 2) Although the toxins and immune modulatory molecules encoded by the hlb- converting phages do not function in the murine system, deletion of ϕNM3, the hlb-converting phage in S. aureus Newman, reduced staphylococcal virulence in the murine abscess formation model. 3) In a preliminary microarray experiment, prophages in S. aureus Newman altered the expression of more than 300 genes. In this research proposal, using microarray and high-throughput quantitative RT-PCR (qRT-PCR) technologies, we will identify the effects of the two important staphylococcal phages on the gene expression of S. aureus in both in vitro and in vivo conditions. This project is intended to be completed within one year. All the data – microarray, qRT-PCR and all the primer sequences- will be made available to public 6 month after completion. Data from this project will help us to understand the role of prophages in the S. aureus pathogenesis and can lead to development of a strategy to interfere with the pathogenesis process.