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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.

ORGANISM(S): Streptococcus mutans UA159

PROVIDER: GSE18355 | GEO | 2010/03/05

SECONDARY ACCESSION(S): PRJNA118107

REPOSITORIES: GEO

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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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Gene expression of Streptococcus mutans pknB mutant versus wild type strain

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