Project description:Transcriptional Profiling of Streptococcus mutans UA159 Grown in Continuous Culture using TV Media Supplemented With 10 mM vs 100 mM Glucose. The genetic and phenotypic responses of Streptococcus mutans, an organism known to be strongly associated with the development of dental caries, to changes in carbohydrate availability were investigated. S. mutans UA159 or a derivative of UA159 lacking ManL, which is the EIIAB component (EIIABMan) of a mannose/glucose permease of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) and a dominant effector of catabolite repression, were grown in continuous culture to steady-state in conditions of excess (100 mM) or limiting (10 mM) glucose. Microarrays using RNA from S. mutans UA159 revealed that 174 genes were differentially expressed in response to changes in carbohydrate availability (P < 0.001). Glucose-limited cells possessed higher PTS activity, could acidify the environment more rapidly and to a greater extent, and produced more ManL protein than cultures grown with excess glucose. Loss of ManL adversely affected carbohydrate transport and acid tolerance. Comp arison of the HPr protein in S. mutans UA159 and the manL deletion strain indicated that the differences in behaviors of the strains were not due to major differences in HPr pools or HPr phosphorylation status. Therefore, carbohydrate availability alone can dramatically influence the expression of physiologic and biochemical pathways that contribute directly to the virulence of S. mutans, and ManL has a profound influence on this behavior. Two-condition experiment, growth in 10 mM vs 100 mM glucose. Biological replicates: 3 per condition, independently grown and harvested. One replicate per array
Project description:Bacteria can detect, transmit and react to signals from the outside world by using two-component systems an serine-threonine kinases and phosphatases. Streptococcus mutans contains one serine-threonine kinase, encoded by pknB. A gene encoding a serine-threonine phosphatase, pppL, is located downstream of pknB. In this study, the phenotypes of single mutants in pknB and pppL and a pknBpppL double mutant were characterized. All mutants exhibited a reduction in genetic transformability and biofilm formation, showed abnormal cell shapes, grew slower than the wild type strain in several complex media and had lost acid tolerance. The mutants had reduced cariogenic capacity, but no defects in colonization in a rat caries model. Whole genome transcriptome analysis revealed that pknB mutant showed reduced expression of genes involved in bacteriocin production and genetic competence. Among the genes that were diferentially regulated in the pknB mutant, severeal were likely to be involved in cell wall metabolism. One such gene, SMU.2146c and two genes encoding bacteriocins, were showed to be also down-regulated in vicK, which encodes a sensor kinase involved in response to oxidative stress. Collectively, the results suggest that PknB can modulate the activity of the two-component signal transduction systems vicKR and comDE. Real-time PCR showed that the genes down-regulated in the pknB mutant were up-regulated in the pppL mutant, indicating that PppL served to counteract PknB.
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.