Project description:Amino sugars, particularly glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) are abundant carbon and nitrogen sources that are continually supplied in host secretions and the diet to biofilms colonizing the human mouth. Evidence is emerging that these amino sugars may provide an ecological advantage to beneficial commensals over oral pathobionts. Here we performed transcriptome analysis on Streptococcus mutans and Streptococcus gordonii growing in single-species or dual-species cultures with glucose, GlcN or GlcNAc as the primary carbohydrate source. Compared to glucose, GlcN caused drastic transcriptomic shifts in each bacterium when they were cultured alone. Likewise, co-cultivation in the presence of GlcN yielded transcriptomic profiles that were dramatically different than the single-species results from GlcN-grown cells. In contrast, GlcNAc elicited only minor changes in the transcriptome of either organism, in both single- and dual-species cultures. Interestingly, genes involved in pyruvate metabolism were among the most significantly affected by GlcN in both species, and these changes were consistent with measurements of pyruvate in culture supernates. Differing a previous report, growth of S. mutans alone with GlcN inhibited expression of multiple operons required for mutacin production. Co-cultivation with S. gordonii consistently increased the expression by S. mutans of two manganese transporter operons (slo and mntH) and decreased expression of mutacin genes. Conversely, S. gordonii appeared to be less affected by the presence of S. mutans, but did show increases in genes for biosynthetic processes in the co-cultures. In conclusion, amino sugars profoundly altered the interactions between the pathogen and the commensal, likely by reprogramming their central metabolism.
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.
Project description:We have previously shown that responses of the oral bacterium Streptococcus gordonii to arginine are co-ordinated by three paralogous regulators: ArcR, ArgR and AhrC. This set of experiments was designed to assess the effects of the ArcR gene regulator on global gene expression in Streptococcus gordonii under high arginine or following a shift to no arginine.
Project description:We have previously shown that responses of the oral bacterium Streptococcus gordonii to arginine are co-ordinated by three paralogous regulators: ArcR, ArgR and AhrC. This set of experiments was designed to assess the effects of the AhrC gene regulator on global gene expression in Streptococcus gordonii under high arginine or following a shift to no arginine.
Project description:Periodontal diseases are one of the most common human maladies and appear to be caused by the interaction of proximal pathogens such as Porphyromonas gingivalis but only as part of the polymicrobial community known as dental plaque. Streptococcus gordonii is an early colonizing oral organism that binds to oral surfaces and provides adherence for organisms such as P. gingivalis. Together P. gingivalis and S. gordonii form one of the simplest models of potentially pathogenic dental plaque. We used RNA sequencing to monitor the transcriptome of P. gingivalis over time in a biofilm model both in the presence and absence of S. gordonii. Samples were taken at 5, 30, 120, 240, and 360 minutes after shifing from planktonic to sessile conditions and growth media to PBS. When compared to planktonic cells increased transcripts were found for stress, amino acid catabolism, and comeptence and decreased transcripts for DNA replication. The presence of S. gordonii resulted in fewer changes from planktonic cells implying physiological support to Pl gingivalis making the transition from planktonic to sessile easier.
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.