Project description:Streptococcus gordonii is a primary colonizer of the multispecies biofilm on tooth surfaces forming dental plaque, and a potential agent of endocarditis. The recent completion of the genome sequence of the naturally competent strain Challis allowed the design of a spotted oligonucleotide microarray to examine a genome-wide response of this organism to environmental signals. Based on temporal responses to synthetic competence signaling peptide (CSP) as indicated by transformation frequencies, the S. gordonii transcriptome was monitored at increments after CSP exposure. Microarray analysis identified 35 candidate early genes and 127 candidate late genes that were up-regulated at 5 and 15 minutes, respectively; these genes were often grouped in clusters. Findings supported published literature on the S. gordonii competence response, with up-regulation of most, but not all, genes that have been reported to affect this species' transformation frequencies. The CSP-induced transcriptomes of S. gordonii were compared to those of published S. pneumoniae strains. Both conserved and species-specific genes were identified. Putative intergenic regulatory sites such as the conserved combox sequence thought to be a binding site for competence sigma factor, were found preceding S. gordonii late responsive genes. In contrast, S. gordonii early CSP-responsive genes were not preceded by S. pneumoniae conserved direct repeats. These studies provide the first insights into a genome-wide transcriptional response of an oral commensal organism. They offer an extensive analysis of transcriptional changes that accompany competence in S. gordonii and form a basis for future intra- and inter-species comparative analyses of this ecologically important phenotype. Keywords: gene expression design
Project description:Transcriptome profiling of mid-log S. gordonii cells treated for 30 minutes with 1 µM of AFYWWFY heptamer dissolved in dimethyl sulfoxide (DMSO).
Project description:Recent studies have shown that the transcriptional landscape of the pleiomorphic fungus Candida albicans is highly dependent upon growth conditions. Here using a dual RNA-seq approach we identified 299 C. albicans and 72 Streptococcus gordonii genes that were either up- or down-regulated specifically as a result of co-culturing these human oral cavity microorganisms. Seventy five C. albicans genes involved in responses to chemical stimuli, regulation, homeostasis, protein modification and cell cycle were statistically (P ≤0.05) upregulated, while 36 genes mainly involved in transport and translation were down-regulated. Upregulation of filamentation-associated TEC1 and FGR42 genes, and of ALS1 adhesin gene, concurred with previous evidence that the C. albicans yeast to hypha transition is promoted by S. gordonii. Increased expression of genes required for arginine biosynthesis in C. albicans was potentially indicative of a novel oxidative stress response. The transcriptional response of S. gordonii to C. albicans was less dramatic, with only eight S. gordonii genes significantly (P ≤0.05) up-regulated ≥ twofold (glpK, rplO, celB, rplN, rplB, rpsE, ciaR, and gat). The expression patterns suggest that signals from S. gordonii cause a positive filamentation response in C. albicans, while S. gordonii appears to be transcriptionally less influenced by C. albicans. Five Samples; Sample 1 - Candida albicans cells grown in hypha inducing conditions for two hours; Sample 2 - Candida albicans cells grown in hypha-inducing conditions for two hours before co-culture with Streptococcus gordonii cells for one hour in a 2:1 rato; Sample 3 - Candida albicans cells grown in hypha-inducing conditions for two hours before culture in Streptococcus gordonii media for one hour; Sample 4 - Candida albicans cells grown in hypha inducing conditions for two hours, filtered to remove Candida albicans cells and media added to Streptococcus gordonii cells for one hour; Sample 5 - Streptococcus gordonii cells alone for one hour. All samples extracted and sequenced in biological triplicate using Illumina HiSeq2500. Samples 1, 2 and 3 aligned to the reference genome for Candida albicans and Samples 2, 4 and 5 aligned to the reference genome for Streptococcus gordonii.
Project description:We have previously shown that responses of the oral bacterium Streptococcus gordonii to arginine are co-ordinated by three paralogous regulators: ArgR, ArgR and AhrC. This set of experiments was designed to assess the effects of the ArgR gene regulator on global gene expression in Streptococcus gordonii under high arginine or following a shift to no arginine.