Unknown,Transcriptomics,Genomics,Proteomics

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The CdaA Regulon in Streptoccus mutans

ABSTRACT: Nucleotide signaling pathways are found in all kingdoms of life and are utilized to coordinate a rapid response to changes in the environment. One more recently discovered signaling nucleotide is the secondary messenger cyclic diadenosine monophosphate (c-di-AMP), which is widely distributed among bacteria and is also found in several archaea. This cyclic nucleotide has been shown to involve in several important cellular processes, including maintenance of DNA integrity, cell wall metabolism, stress tolerance, transcription regulation and virulence. However, the mechanisms by which c-di-AMP modulates these physiological changes have remained largely unknown.In the present study, we identified and characterized a c-di-AMP synthase (CdaA) in S. mutans UA159. Furthermore, we investigated the role of CdaA in S. mutans cell physiology and global gene expression by utilizing cdaA gene in-frame deletion mutant. Our findings suggest that CdaA is an important global modulator of optimal growth and environmental adaption in this pathogen. Streptococcus mutans UA159 whole-genome arrays (8 x 15 K) were obtained from Agilent and included 1998 probes for S. mutans transcripts. For microarray analysis, S. mutans UA159 and S. mutans ?cdaA cells were routinely grown at 37°C anaerobically (90% N2, 5% CO2, 5% H2) in brain heart infusion broth (BHI; Difco, Sparks, MD, USA) to an optical density at 600 nm (OD600) of 0.5. Four RNA samples isolated from four independent cultures of UA159 and cdaA mutant strains were hybridized to the arrays and analyzed.

ORGANISM(S): Streptococcus mutans

SUBMITTER: Yu-Qing Li

PROVIDER: E-GEOD-65511 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Dental caries is closely associated with the virulence of Streptococcus mutans (S. mutans). The stress adaptation of S. mutans in the fluctuating oral environment is critical to the virulence expression of this bacterium. Here we used whole-genome microarrays to profile the dynamic transcriptomic responses of S. mutans during physiological heat stress. We also evaluated the phenotypic changes, including initial biofilm formation, acid production and ATP turnover of S. mutans during heat stress. We found that S. mutans responded to heat stress in a distinct pattern, which featured a differential transcription of 885 genes in total and 114 “core” transcripts throughout the six post-exposure time points investigated (5 min, 10 min, 15 min, 30 min, 45 min and 60 min). Further gene ontology analysis showed that transcriptional changes of genes involved in transcriptional regulation and cellular homeostasis were critical for heat stress responses of S. mutans. In addition to those highly conserved heat-shock proteins, we observed differential expression of multiple transcriptional regulators. The expression of genes involved in sugar transport, soluble glucans biosynthesis (gtfC) and binding (gbpC) were upregulated, whereas genes involved in ABC transporters, insoluble glucans biosynthesis (gtfB) and binding (gbpB), which are critical for biofilm skeleton, were either down-regulated or unchanged. These results together with enhanced glycolytic activity, attenuated sucrose-dependent initial attachment and impaired biofilm architecture indicate metabolic adaptations by this bacterium to compensate the extra energy demand for a better fitness under adverse conditions. We used time series microarrays to detect the dynamic changes of S. mutans under heat stress. Mid-logarithmic phase cell cultures of S. mutans (OD600nm = 0.5) were incubated at 42℃ for 5 min, 10 min, 15 min, 30 min, 45 min and 60 min, which were compared with the S. mutans cultured at 37℃. We applied three biological replicates at each time point.

Project description:Global transcriptional analysis of acid-inducible genes in Streptococcus mutans: multiple two-component systems involved in acid adaptation pH is a major environmental factor that regulates gene expression in many bacteria. Streptococcus mutans in dental biofilms is regularly exposed to cycles of acidic pH during the ingestion of fermentable dietary carbohydrates. The ability of S. mutans to tolerate low pH is crucial for its virulence and the pathogenesis in dental caries. To better understand its acid tolerance mechanisms, we used DNA microarray to perform genome-wide transcriptional analysis of S. mutans in response to acidic pH. The results showed that adaptation of S. mutans to pH 5.5 for 2 hrs induced differential expression of nearly 14% of genes in the genome, including 169 up-regulated genes and 108 down-regulated genes, largely categorized into six groups. Especially, we found that the genes encoding multiple two-component systems, including CiaHR, LevSR, LiaSR, ScnKR, HK/RR07 and ComDE, were up-regulated during acid adaptation. These findings were further confirmed by real time qRT-PCR and phenotypic assays of the gene deletion mutants. The results support that the multiple two-component systems are required for S. mutans to orchestrate its signal transduction networks for optimal adaptation to acidic pH. Total RNAs were isolated from S. mutans UA159 cells (0.6 at OD600) grown in a TYG broth (3% tryptone, 0.3% yeast extract and 20 mM glucose) at either pH 5.5 or pH 7.5. The RNAs were treated with RNase-free DNase 1 and purified by Qiagen RNeasy mini columns. The purified RNAs were used to generate cDNA probes by an indirect labeling method based on the protocol from TIGR. The cDNAs were coupled with AlexaFluor 555 or AlexaFluor 647 (Invitrogen). The labeled cDNA probes from three different cultures of UA159 were hybridized to the S. mutans microarray slides obtained from PFGRC (http://pfgrc.tigr.org). Array hybridization was conducted using a protocol from the PFGRC with minor modification. After hybridization, washes and dried, the array slides were scanned by ScanArray 5000XL Reader (Perkin Elmer, Boston, MA). After the array slides were scanned, the resulting images were loaded into TIGR Spotfinder software (http://www.tigr.org/software/) and overlaid. A spot grid was created according to TIGR specifications and manually adjusted to fit all spots within the grid, and the intensity values of each spot were determined. Signal intensities of individual channels from an array slide were averaged and normalized using an array data analysis software (MIDAS) by using LOWESS and iterative log mean centering with default settings, followed by in-slide replicate analysis. A t-test was used to determine the consistency of ratios across replicate hybridizations. Only genes whose ratios were â¥ 2-fold changes (either increase or decrease) with 99% confidence interval (P â¤ 0.01) were considered statistically significant.

Project description:The two-component system (TCS) is a specific regulatory system in bacteria and plays an important role in sensing and adapting to the environment. In this study, we evaluated the roles of TCSs in the major cariogenic pathogen Streptococcus mutans in resistance to several types of bacteriocin. In a comprehensive analysis using individual TCS mutants, we found that two novel TCSs were associated with resistance against distinct lantibiotics nisin A (class I type A[I]) and nukacin ISK-1(class I type A[II]). One TCS, SMU.659-660 (designated as NsrRS), was related to resistance against nisin A produced by Lactococcus lactis ATCC 11454. The other TCS, SMU.1146-1145 (designated as LcrRS), was related to resistance against nukacin ISK-1 produced by Staphylococcus warneri ISK-1. NsrRS induced the expression of SMU.658 (designated as NsrX), which constitutes an operon with nsrRS, in response to nisin A. Inactivation of nsrX increased susceptibility to nisin A. Additionally, NsrX expression in S. mutans increased the binding affinity to nisin A compared to a no-expression strain. LcrRS induced the expression of SMU.1148-50 (lctFEG), which encodes an ABC transporter and is located upstream of lcrRS, in response to nukacin ISK-1. Inactivation of lctFEG significantly increased susceptibility to nukacin ISK-1. Electrophoretic mobility shift assay analysis revealed that NsrR and LcrR bound directly to regions upstream of nsrX and lctFEG, respectively. This is the first report that two distinct TCSs, NsrRS and LcrRS, are independently involved in resistance to nisin A and nukacin ISK-1 in S. mutans. Total of 14 samples were analyzed. Total RNA from each test strain and control described below were labeled with Alexa FluorÂ® 555 and Alexa FluorÂ® 647, respectively, and were cohybridized on a single array. Labeling and hybridization were performed once or twice independently. UA159 wild type as control vs. UA159 with nisinA or nukacin ISK-1, UA159 wild type with nisinA or nukacin ISK-1 vs. nsrRS or lcrRS deletion mutant in UA159 with nisinA or nukacin ISK-1.

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The CdaA Regulon in Streptoccus mutans

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