Project description:Streptococcus gordonii, an important primary colonizer of dental plaque biofilm, specifically binds to salivary amylase via the surface-associated amylase-binding protein A (AbpA). We hypothesized that amylase binding to S. gordonii modulates expression of chromosomal genes, which could influence bacterial survival and persistence in the oral cavity. Gene expression profiling by microarray analysis was performed to detect differentially expressed genes in S. gordonii strain CH1 in response to the binding of purified human salivary amylase as compared to exposure to heat-denatured amylase. Selected genes found to be differentially expressed were validated by qRT-PCR. Five genes from the fatty acid synthesis (FAS) cluster were highly (10-35 fold) up-regulated in amylase treated S. gordonii CH1 cells compared to the denatured-amylase treated cells. An abpA-deficient strain of S. gordonii exposed to amylase did not show a similar response in FAS gene expression as observed in the parental strain. Predicted phenotypic effects of amylase binding to S. gordonii strain CH1 associated with increased expression of FAS genes leading to changes in fatty acid synthesis were noted, as evidenced by increased bacterial growth, survival at low pH, and resistance to triclosan. These changes were not observed in the amylase exposed abpA-deficient strain, suggesting for the role of AbpA in amylase-induced phenotype. These results provide evidence that the binding of salivary amylase elicits a differential gene response in S. gordonii, resulting in a phenotype adjustment that is potentially advantageous for bacterial survival in the oral environment.
Project description:Streptococcus gordonii, an important primary colonizer of dental plaque biofilm, specifically binds to salivary amylase via the surface-associated amylase-binding protein A (AbpA). We hypothesized that amylase binding to S. gordonii modulates expression of chromosomal genes, which could influence bacterial survival and persistence in the oral cavity. Gene expression profiling by microarray analysis was performed to detect differentially expressed genes in S. gordonii strain CH1 in response to the binding of purified human salivary amylase as compared to exposure to heat-denatured amylase. Selected genes found to be differentially expressed were validated by qRT-PCR. Five genes from the fatty acid synthesis (FAS) cluster were highly (10-35 fold) up-regulated in amylase treated S. gordonii CH1 cells compared to the denatured-amylase treated cells. An abpA-deficient strain of S. gordonii exposed to amylase did not show a similar response in FAS gene expression as observed in the parental strain. Predicted phenotypic effects of amylase binding to S. gordonii strain CH1 associated with increased expression of FAS genes leading to changes in fatty acid synthesis were noted, as evidenced by increased bacterial growth, survival at low pH, and resistance to triclosan. These changes were not observed in the amylase exposed abpA-deficient strain, suggesting for the role of AbpA in amylase-induced phenotype. These results provide evidence that the binding of salivary amylase elicits a differential gene response in S. gordonii, resulting in a phenotype adjustment that is potentially advantageous for bacterial survival in the oral environment. In order to identify amylase-regulated genes, S. gordonii CH1 was grown statically in 40 ml CDM at 37°C in a candle jar to mid-log phase corresponding to an optical density at 600 nm of 0.5 to 0.6.The mid-log phase bacterial culture was divided into two aliquots of equal volume. Bacterial cells from all aliquots were pelleted by centrifugation at 6,000 x g in a Sorvall RC6 centrifuge at 20°C, and washed once with simulated salivary buffer preconditioned to 37°C. Simulated salivary buffer containing 0.4 mg/ml purified, non-glycosylated salivary amylase (native amylase) and preconditioned to 37°C was added to the cells of the fist aliquot; to the cells of the second aliquot simulated salivary buffer containing 0.4 mg/ml of the same salivary amylase denatured by heating to 100°C {Heinen, 1976} and cooled to 37°C was added, as a negative control. Each aliquot, amylase treated and control, was incubated statically for 15 min at 37°C in a candle jar. Total RNA was immediately isolated by the hot acid phenol method as described previously {Vickerman, 2007}, followed by treatment with TurboDNase (Applied Biosystems/Ambion, Austin, TX) according to manufacturer’s protocol. Remaining contaminants were removed using the RNeasy minikit column (Qiagen, Valencia, CA) with the cleanup protocol. Total RNA was quantified using the Nanodrop 2000 spectrophotometer and RNA integrity determined by agarose gel electrophoresis. Total RNA was used immediately for cDNA synthesis. The Cy dye-labeled cDNA from the amylase-treated aliquot of the culture was mixed with Cy dye-labeled cDNA from the denatured amylase-treated control aliquot, and used to probe the S. gordonii microarray slides. Each amylase-exposure experiment was repeated from four biological replicates. To confirm microarray results the cDNA from each strain was labeled with the opposite Cy dye and hybridized to similar arrays for the flip-dye comparison. Overall design 4 samples were analyzed. The quality controls were 4 biological replicates and dye-swap technical replicates for each biological replicate.
Project description:Streptococcus pneumoniae (S. pneumoniae) is a major human pathogen causing morbidity and mortality worldwide. Efficiently acquiring iron from the environment is critical for S. pneumoniae to sustain growth and cause infection. There are only three known iron-uptake systems in Streptococcal species responsible for iron acquisition from the host, including ABC transporters PiaABC, PiuABC and PitABC. Besides, no other iron-transporting system has been suggested. In this work, we employed our newly established translating mRNA analysis integrated with proteomics to evaluate the possible existence of novel iron transporters in the bacterium. We simultaneously deleted the iron-binding protein genes of the three iron-uptake systems to construct a piaA/piuA/pitA triple mutant (Tri-Mut) of S. pneumoniae D39, in which genes and proteins related to iron transport should be regulated in response to the deletion. With ribosome associated mRNA sequencing-based translatomics focusing on translating mRNA and iTRAQ quantitative proteomics based on the covalent labeling of peptides with tags of varying mass, we indeed observed a large number of genes and proteins representing various coordinated biological pathways with significantly altered expression levels in the Tri-Mut mutant. Highlighted in this observation is the identification of several new potential iron-uptake ABC transporters for Streptococcal iron metabolism. In particular, putative protein SPD_1609 in operon 804 was verified to be a novel iron-binding protein with similar function to PitA in S. pneumoniae. These data derived from the integrative translatomics and proteomics analyses provided rich information and insightful clues for further investigations on iron-transporting mechanism in bacteria and the interplay between Streptococcal iron availability and the biological metabolic pathways.
Project description:Multiple levels of interkingdom signaling have been implicated in maintaining the ecological balance between Candida albicans and commensal streptococci to assure a state of oral health. To better understand the molecular mechanisms involved in the initial streptococcal response to the presence of C. albicans that can initiate oral surface colonization and biofilm formation, hypha-forming cells were incubated with Streptococcus gordonii cells for 30 minutes to assess the streptococcal transcriptome response. A genome wide microarray analysis and quantitative PCR validation of S. gordonii transcripts identified a number of genes, the majority of which were involved in metabolic functions, that were differentially expressed in the presence of hyphae. The fruR, fruB and fruA genes encoding the transcriptional regulator, fructose-1-phosphate kinase, and fructose-specific permease, respectively, of the phosphoenolpyruvate-dependent fructose phosphotransferase system, were consistently up-regulated. An S. gordonii mutant in which these genes were deleted by allelic replacement, formed an architecturally-distinct, less robust biofilm with C. albicans than did parental strain cells. Complementing the mutant with plasmid borne fruR, fruB and fruA genes caused phenotype reversion, indicating that the genes in this operon played a role in dual species biofilm formation. This genome wide analysis of the S. gordonii transcriptional response to C. albicans has identified several genes that have potential roles in interkingdom signaling and responses.
Project description:Interspecies coaggregation promotes transcriptional changes of oral bacteria, contributing to the development of structurally balanced biofilms as well as oral diseases such as periodontitis. Streptococcus gordonii (S. gordonii) is an early colonizer of the oral cavity, and Fusobacterium nucleatum (F. nucleatum) may act as a bridge adhering to both early and late oral colonizers. These two species were commonly detected in healthy and periodontitis-diseased oral sites and could interact with immune cells such as macrophages. However, little research explored how intergeneric coaggregation affected transcriptional changes in S. gordonii and F. nucleatum subsp. polymorphum and how these gene changes might affect both species’ pathogenicity. The present study investigated transcriptional changes of both species in response to dual-species physical association using dual RNA-seq. Results indicated that after 30-min dual-species coaggregation, 148 genes were significantly up-regulated, and 124 genes were significantly down-regulated in S. gordonii. A total of 154 genes were significantly down-regulated, and 10 genes were significantly up-regulated in F. nucleatum subsp. polymorphum. A majority of up-regulated S. gordonii genes were involved in the biosynthesis and export of cell-wall proteins and the pathway of carbohydrate metabolism, and a group of down-regulated S. gordonii genes were associated with fatty acid biosynthesis and peptidoglycan biosynthesis. The transcriptome profiles indicated that the interspecies coaggregation led to a reduced level of DNA repair and lipopolysaccharides virulence in F. nucleatum subsp. polymorphum. The present study revealed that dual-species coaggregation induced a wide array of gene changes in S. gordonii and F. nucleatum subsp. polymorphum, enhancing S. gordonii’s adherence ability and attenuating F. nucleatum subsp. polymorphum's ability to produce LPS.
Project description:We report the evolutionary behaviour of Polycomb group proteins, their recruitment factors and their underlying sequences by performing ChIP-seq analysis in 4-5 different Drosophila species. We demonstrate an extremely high conservation of Polycomb repressive domains across Drosophila species We validate few cases of PRE divergence that shows that cis-driven PRE evolution is a rare event. We further show that PHO recruitment to Polycomb domains is evolutionarily robust to motif changes and that PRC1 stabilizes binding of its key recruiter ChIP-seq analysis of histone marks and chromatin associated factors across 4-5 Drosophila species