Project description:We developed spotted oligonucleotide arrays of the S. pyogenes SF370 (an M1 serotype) genome and compared the transcriptomes of streptococci that adhere to Detroit 562 human pharyngeal cells to non-adherent (“associated”) streptococci within the same experiment. We replicated experiments independently and used dye-swaps to incorporate biological and technical variation, biological replicate experiments. Following filtering and normalization, we analyzed data from four biological replicates with robust summary statistics, Bayesian statistics and permutation algorithms to identify genes differentially expressed with significance during pharyngeal cell adherence. This analysis identified 79 genes (4% of the genome) exhibiting statistically significant fold changes in expression (PF value < 0.05) during adherence from 1769 open reading frames represented on the array. The genes encoding several known virulence factors (e.g. cysteine protease SpeB and streptolysin O) were differentially expressed with significance; however, many were either never before associated with adherence (e.g. phage-encoded genes including speH), or of undefined function. Genes demonstrating up-regulation (n= 45) and down-regulation (n= 34) included virulence factors, prophage-encoded transcripts, metabolic genes and transcriptional regulators (Table 2). Undefined or hypothetical genes comprised 27% of differentially expressed genes (n= 21; 11 chromosomally-encoded, 10 phage-encoded). We conducted TaqMan (qRT-PCR) analysis of 11 differentially expressed genes to validate selected microarray hybridization results. We further analyzed the data with neighbor clustering, using a set of novel computational algorithms (termed “GenomeCrawler”) for evaluating bacterial microarray data, which couples the expression profiles of genes with their physical location on the chromosome. When applied to the microarray data from this study, neighbor clustering identified a greater number of differentially expressed genes, which facilitated the reconstruction of known multimeric proteins, complete metabolic pathways and intact virulence loci that would not have been possible without its application. These data sets and algorithms are freely available for download at www.rockefeller.edu/vaf. Keywords: Pharyngeal cell adherent vs. associated

Project description:A total of 432 genes were found to be differentially expressed in M1SF370 bacterial population internalized in Detroit 562 human pharyngeal cells when compared with the same strain incubated in the absence of Detroit 562 cells. While most of them (349/432 i.e. 80.8%) were up regulated, 83 genes were down regulated contributing to 19.2% of the total differentiated genes. The major contributor of the latter category was phage-related genes (35 genes). Almost ¼ of these genes (106) belonged to a category of Unknown or possible predicted function. Most notably, up-regulated genes belonged to amino acid transport , cell division, cell envelope biogenesis, DNA replication correlated well with up-regulated 67 genes belonged to translation and ribosomal structure. Further, up-regulation of 12/15 virulence-related genes indicated that human host cell internalized bacteria are highly virulent as compared to laboratory grown culture in test-tubes. S. pyogenes strain type M1 SF370 (wild-type) was procured from ATCC (ATCC 700294). Detroit 562 pharyngeal cells were obtained from ATCC and maintained in MEM with 10% FBS in humidified CO2-incubator. Purified cDNA preparations from the Detroit cells-internalized bacteria and that were cultured without Detroit cells, were labeled with either Alexafluor-555 or Alexafluor-647 depending on the experimental design ( i.e. dye swap experiment). Differentially labeled probes were then combined and purified. Using four independently isolated RNA preparations (biological replicates), a total of 8 experiments (incorporating 4 dye swaps) were performed. Accordingly eight hybridization measurements for this mutant were obtained. Exp-1 and -2 (GSM687276, GSM687310-dye swap) are the technical replicates of the biological sample-1, Exp-3 and -4 (GSM687311, GSM687312-dye swap) are technical replicates of biological sample-2, Exp-5 and -6, (GSM687313,GSM687319-dye swap,) are technical replicates of the biological sample-3, and finally Exp-7 and -8, (GSM687320,GSM687321-dye swap) are technical replicates of the biological sample-4. .

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Streptococcus pyogenes

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