Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression of Streptococcus mutans pknB mutant versus wild type strain

ABSTRACT: 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. Wild-type strain UA159 and a pknB mutant derivative were grown planktonically until OD600nm was 0.3. RNA was extracted, converted to cDNA, labelled and hybridized on S. mutans microarrays. The experiment was done in triplicate including one dye swap.

ORGANISM(S): Streptococcus mutans UA159

SUBMITTER: Danusia Banu

PROVIDER: E-GEOD-18355 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Oral streptococci metabolize carbohydrate to produce organic acids, not only decrease the environmental pH, but also increase osmolality of dental plaque fluid due to tooth demineralization and consequent calcium and phosphate accumulation. Thus, to persevere in the dental plaque, acidogenic bacteria should evolve sophisticated molecular machineries to counter the detrimental effect of elevated osmolality. This study was aimed to obtain a global view on strategies taken by streptococcus mutans to deal with physiologically relevant elevated osmolality, and preserves within a cariogenic dental plaque. We investigated phenotypic change of S. mutans biofilm upon sub-lethal level of hyperosmotic challenge. We found that hyperosmotic condition was able to initiate S. mutans biofilm dispersal by reducing both microbial content and extracellular polysaccharides matrix. We then used DNA microarray with qPCR validation to systemically investigate the underlying molecular machinery of this bacteria in response to hyperosmotic stimuli. Among those identified 50 differentially regulated genes, down-regulation of gtfB and comC were believed to be responsible for the observed biofilm dispersal. Further analysis of microarray data showed significant up-regulation of genes and pathways involved in carbohydrates metabolism. Specific genes involved in heat shock response and acid tolerance were also upregulated, indicating potential cross-talk between hyperosmotic and other environmental stress. Based on the data obtained in this study, we believe that although hyperosmotic condition may induce significant stress response on S. mutans, this cariogenic bacterium has evolved sophisticated molecular machineries to counter those elicited detrimental effects. In the meantime, it will take full advantage of these environmental stimuli to better fit the fluctuating environments within oral cavity, and thus emerge as numeric-predominant bacteria under cariogenic conditions. A six-chip study using total RNA recovered from mid-logarithmic phase of S. mutans UA159 from three separate cultures of strains submitted for 15 minutes to hyperosmotic stimuli (0.4M NaCl) and three separate cultures of strains kept under no stress condition.

Project description:In the oral biofilm, the mitis streptococci are among the first group of organisms to colonize the tooth surface. Their proliferation is thought to be an important factor required for antagonizing the growth of cariogenic species such as Streptococcus mutans. In this study, we used a 3-species mixed culture to demonstrate that another ubiquitous early colonizing species, Veillonella parvula, could greatly impact the competitive outcome of a mixed culture of S. mutans and S. gordonii. Transcriptome analysis further revealed that S. mutans responds differentially to its friend (V. parvula) and foe (S. gordonii). In the mixed culture with S. gordonii, all but one S. mutans sugar uptake and metabolic genes were down-regulated, while genes for alternative energy source utilization and H2O2 tolerance were up-regulated, resulting in a slower but persistent growth. In contrast, when cultured with V. parvula, S. mutans grew equally well or better than in monoculture and exhibited relatively few changes within its transcriptome. When V. parvula was introduced into the mixed culture of S. mutans and S. gordonii, it rescued the growth inhibition of S. mutans. In this 3-species environment, S. mutans increased the expression of genes required for the uptake and metabolism of minor sugars, while genes required for oxidative stress tolerance were down-regulated. We conclude that the major factors affecting the competition between S. mutans and S. gordonii are carbohydrate utilization and H2O2 resistance. The presence of V. parvula in the tri-species culture mitigates these two major factors and allows S. mutans to proliferate, despite the presence of S. gordonii. In this study, we used microarrays to investigate how S. mutans responds to different species. S. mutans was grown as either monospecies, dual-species cultures with S. gordonii or Veillonella, or tri-species cultures with S. gordonii and Veillonella. The transcriptional profile of the whole genome was examined with microarray.

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Gene expression of Streptococcus mutans pknB mutant versus wild type strain

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