ABSTRACT
Objective@#To investigate the effects of srtA on the oxidation tolerance of the Streptococcus mutans UA159 strain and to explore the potential mechanism.@*Methods@#The oxidation tolerance in the planktonic state and biofilm state were compared among UA159, the srtA-deleted strain and the complementary strain through oxidative tolerance experiments. The RNA-sequencing data from both the exponential and stationary phases of UA159 and the srtA-deleted strain were obtained by using the Illumina HiSeq 4 000 sequencing platform to determine the impact of srtA knockout on S. mutans genomic transcription. We compared the differences in the transcriptional expression of oxidative tolerance-related genes between the UA159 strain and the srtA gene deletion strain and further explored the intrinsic relationship between the changes in oxidative tolerance and the genetic transcriptome. qPCR was used to verify the changes in the expression level of oxidation tolerance-related genes.@*Results @#The oxidation tolerance of the srtA-deleted strain decreased significantly in both the planktonic state and the biofilm state compared to that of UA159 (P < 0.05). A total of 33 oxidation tolerance-related genes were differentially expressed according to transcriptome sequencing. There was no significant change in the expression of peroxide synthesis- and metabolic-related enzyme genes, but in the stationary phase samples, the two-component signal transcription systems lrgA, lrgB, and lytT were significantly downregulated (2.2- to 2.4-fold) in the srtA-deleted strain. qPCR further confirmed that in both the exponential and stationary phases, lrgB and lytT expression in the planktonic state was reduced 11.01-53.51-fold, while the expression of the other two-component system-encoding gene vicK was reduced by 6.57-10.88-fold (P < 0.001).@*Conclusion@#SrtA gene deletion did not change the expression level of peroxide synthesis-related and metabolic enzyme-encoding genes but downregulated the expression of the associated transcription regulation factors to reduce the oxidation tolerance of S. mutans.
ABSTRACT
<p><b>OBJECTIVE</b>This study intends to explore the mechanism underlying the support of sortase A (SrtA) of the cariogenicity of Streptococcus mutans (S. mutans).</p><p><b>METHODS</b>We performed a metabonomics study based on ¹H nuclear magnetic resonance spectroscopy (NMR), in which we compared the extracellular metabolites of wild-type S. mutans UA159 with those of its SrtA-deficient strain. Metabolite differences among strains were identified using a combination of principal component analysis and orthogonality partial least square discriminant analysis.</p><p><b>RESULTS</b>Several differences corresponding mostly to unknown metabolites were identified. Some amino acids such as leucine and valine (δ 0.92×10⁻⁶-1.20×10⁻⁶), lactic acid ( δ1.28×10⁻⁶), oxoglutaric acid (δ 3.00×10⁻⁶), and glycine (δ 3.60×10⁻⁶) differed among strains.</p><p><b>CONCLUSIONS</b>This work establishes the feasibility of using ¹H NMR-based metabonomics to provide leads for research into molecular factors that promote caries. The database of microbial metabolites should be also improved in further studies.</p>
ABSTRACT
Objective To determine the localization of histidine triad protein(Htp) on Streptococcus suis 2(S.suis 2) and the effect of disruption of sortase A(srtA) gene on the expression level of Htp.Methods Antiserum against Htp was prepared by immunizing rabbit with recombinant Htp.Bioinformatics analysis was adopted to evaluate the amino acid sequence characteristic of Htp.Flow cytometry was applied to localize Htp on S.suis 2 bacteria.Results Bioinformatics analysis demonstrated that Htp had the characteristic of cell surface protein with signal sequence and transmembrane sequence.Flow cytometry showed the localization of Htp was on the surface of S.suis 2 and the expression level of Htp on cell surface decreased by deletion of srtA.Conclusions Htp is located on the cell surface of S.suis 2.The results provide a foundation for further investigation of the role of Htp in the infection of S.suis 2.