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Li M, Huang R, Zhou X, Qiu W, Xu X, Gregory RL. Effect of nicotine on cariogenic virulence of Streptococcus mutans. Folia Microbiol (Praha) 2016; 61:505-512. [PMID: 27381088 DOI: 10.1007/s12223-016-0465-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/30/2016] [Indexed: 02/05/2023]
Abstract
Nicotine has well-documented effects on the growth and colonization of Streptococcus mutans. This study attempts to investigate the effects of nicotine on pathogenic factors of S. mutans, such as the effect on biofilm formation and viability, expression of pathogenic genes, and metabolites of S. mutans. The results demonstrated that addition of nicotine did not significantly influence the viability of S. mutans cells. The biofilms became increasingly compact as the concentrations of nicotine increased. The expression of virulence genes, such as ldh and phosphotransferase system (PTS)-associated genes, was upregulated, and nlmC was upregulated significantly, while ftf was downregulated. The lactate concentration of S. mutans grown in 1 mg/mL of nicotine was increased up to twofold over either biofilm or planktonic cells grown without nicotine. Changes in the metabolites involved in central carbon metabolism from sucrose indicated that most selected metabolites were detectable and influenced by increased concentrations of nicotine. This study demonstrated that nicotine can influence the pathogenicity of S. mutans and may lead to increased dental caries through the production of more lactate and the upregulation of virulence genes.
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Affiliation(s)
- Mingyun Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, No. 14, 3rd Section of Ren Min Nan Rd, Chengdu, Sichuan, 610041, China. .,Department of Biomedical and Applied Sciences, School of Dentistry, Indiana University, 1121 W. Michigan Street, Indianapolis, IN, 46202, USA.
| | - Ruijie Huang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, No. 14, 3rd Section of Ren Min Nan Rd, Chengdu, Sichuan, 610041, China.,Department of Biomedical and Applied Sciences, School of Dentistry, Indiana University, 1121 W. Michigan Street, Indianapolis, IN, 46202, USA.,Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, No. 14, 3rd Section of Ren Min Nan Rd, Chengdu, Sichuan, 610041, China
| | - Wei Qiu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, No. 14, 3rd Section of Ren Min Nan Rd, Chengdu, Sichuan, 610041, China
| | - Xin Xu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, No. 14, 3rd Section of Ren Min Nan Rd, Chengdu, Sichuan, 610041, China
| | - Richard L Gregory
- Department of Biomedical and Applied Sciences, School of Dentistry, Indiana University, 1121 W. Michigan Street, Indianapolis, IN, 46202, USA. .,Department of Pathology and Laboratory Medicine, School of Medicine, Indiana University, Indianapolis, IN, 46202, USA.
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Mao MY, Yang YM, Li KZ, Lei L, Li M, Yang Y, Tao X, Yin JX, Zhang R, Ma XR, Hu T. The rnc Gene Promotes Exopolysaccharide Synthesis and Represses the vicRKX Gene Expressions via MicroRNA-Size Small RNAs in Streptococcus mutans. Front Microbiol 2016; 7:687. [PMID: 27242713 PMCID: PMC4861726 DOI: 10.3389/fmicb.2016.00687] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 04/26/2016] [Indexed: 02/05/2023] Open
Abstract
Dental caries is a biofilm-dependent disease that largely relies on the ability of Streptococcus mutans to synthesize exopolysaccharides. Although the rnc gene is suggested to be involved in virulence mechanisms in many other bacteria, the information regarding it in S. mutans is very limited. Here, using deletion or overexpression mutant assay, we demonstrated that rnc in S. mutans significantly positively regulated exopolysaccharide synthesis and further altered biofilm formation. Meanwhile, the cariogenecity of S. mutans was decreased by deletion of rnc in a specific pathogen-free (SPF) rat model. Interestingly, analyzing the expression at mRNA level, we found the downstream vic locus was repressed by rnc in S. mutans. Using deep sequencing and bioinformatics analysis, for the first time, three putative microRNA-size small RNAs (msRNAs) targeting vicRKX were predicted in S. mutans. The expression levels of these msRNAs were negatively correlated with vicRKX but positively correlated with rnc, indicating rnc probably repressed vicRKX expression through msRNAs at the post-transcriptional level. In all, the results present that rnc has a potential role in the regulation of exopolysaccharide synthesis and can affect vicRKX expressions via post-transcriptional repression in S. mutans. This study provides an alternative avenue for further research aimed at preventing caries.
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Affiliation(s)
- Meng-Ying Mao
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Ying-Ming Yang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Ke-Zeng Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan UniversityChengdu, China; Department of Dentistry, Yan'an Hospital Affiliated to Kunming Medical UniversityKunming, China
| | - Lei Lei
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Meng Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Yan Yang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Xiang Tao
- Chengdu Institute of Biology, Chinese Academy of Sciences Chengdu, China
| | - Jia-Xin Yin
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
| | - Ru Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan UniversityChengdu, China; Department of Endodontics and Operative Dentistry School of Stomatology, Capital Medical UniversityBeijing, China
| | - Xin-Rong Ma
- Chengdu Institute of Biology, Chinese Academy of Sciences Chengdu, China
| | - Tao Hu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University Chengdu, China
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Peng X, Zhang Y, Bai G, Zhou X, Wu H. Cyclic di-AMP mediates biofilm formation. Mol Microbiol 2016; 99:945-59. [PMID: 26564551 PMCID: PMC5003771 DOI: 10.1111/mmi.13277] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2015] [Indexed: 12/27/2022]
Abstract
Cyclic di-AMP (c-di-AMP) is an emerging second messenger in bacteria. It has been shown to play important roles in bacterial fitness and virulence. However, transduction of c-di-AMP signaling in bacteria and the role of c-di-AMP in biofilm formation are not well understood. The level of c-di-AMP is modulated by activity of di-adenylyl cyclase that produces c-di-AMP and phosphodiesterase (PDE) that degrades c-di-AMP. In this study, we determined that increased c-di-AMP levels by deletion of the pdeA gene coding for a PDE promoted biofilm formation in Streptococcus mutans. Deletion of pdeA upregulated expression of gtfB, the gene coding for a major glucan producing enzyme. Inactivation of gtfB blocked the increased biofilm by the pdeA mutant. Two c-di-AMP binding proteins including CabPA (SMU_1562) and CabPB (SMU_1708) were identified. Interestingly, only CabPA deficiency inhibited both the increased biofilm formation and the upregulated expression of GtfB observed in the pdeA mutant. In addition, CabPA but not CabPB interacted with VicR, a known transcriptional factor that regulates expression of gtfB, suggesting that a signaling link between CabPA and GtfB through VicR. Increased biofilm by the pdeA deficiency also enhanced bacterial colonization of Drosophila in vivo. Taken together, our studies reveal a new role of c-di-AMP in mediating biofilm formation through a CabPA/VicR/GtfB signaling network in S. mutans.
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Affiliation(s)
- Xian Peng
- Department of Pediatric Dentistry, University of Alabama at Birmingham, School of Dentistry, Birmingham, AL, USA
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
| | - Yang Zhang
- Center for Immunology and Microbial Disease, MC-151, Albany Medical College, 47 New Scotland Avenue, Albany, NY, USA
| | - Guangchun Bai
- Center for Immunology and Microbial Disease, MC-151, Albany Medical College, 47 New Scotland Avenue, Albany, NY, USA
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, China
| | - Hui Wu
- Department of Pediatric Dentistry, University of Alabama at Birmingham, School of Dentistry, Birmingham, AL, USA
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Cheng X, Zheng X, Zhou X, Zeng J, Ren Z, Xu X, Cheng L, Li M, Li J, Li Y. Regulation of oxidative response and extracellular polysaccharide synthesis by a diadenylate cyclase in Streptococcus mutans. Environ Microbiol 2015; 18:904-22. [PMID: 26548332 DOI: 10.1111/1462-2920.13123] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/29/2015] [Accepted: 11/01/2015] [Indexed: 02/05/2023]
Abstract
Cyclic diadenosine monophosphate (c-di-AMP) has been implicated in the control of many important bacterial activities. However, the function of this molecule in Streptococcus mutans, the primary aetiological agent of human dental caries, is unknown. In this study, we identified and characterized a diadenylate cyclase, named CdaA, in S. mutans. Furthermore, we showed that in-frame deletion of the cdaA gene in S. mutans causes decreased c-di-AMP levels, increased sensitivity to hydrogen peroxide and increased production of extracellular polysaccharides. Global gene expression profiling revealed that more than 200 genes were significantly upregulated or downregulated (> 2.0-fold) in the cdaA mutant. Interestingly, genes with increased or decreased expression were clustered in cellular polysaccharide biosynthetic processes and oxidoreductase activity respectively. Notably, the expression of several genomic islands, such as GTF-B/C, TnSmu, CRISPR1-Cas and CRISPR2-Cas, was found to be altered in the cdaA mutant, indicating a possible link between these genomic islands and c-di-AMP signalling. Collectively, the results reported here show that CdaA is an important global modulator in S. mutans and is required for optimal growth and environmental adaption. This report also paves the way to unveil further the roles of c-di-AMP signalling networks in the biology and pathogenicity of S. mutans.
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Affiliation(s)
- Xingqun Cheng
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xin Zheng
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jumei Zeng
- Department of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Zhi Ren
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xin Xu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Lei Cheng
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Mingyun Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jiyao Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Yuqing Li
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Mutation of the Thiol-Disulfide Oxidoreductase SdbA Activates the CiaRH Two-Component System, Leading to Bacteriocin Expression Shutdown in Streptococcus gordonii. J Bacteriol 2015; 198:321-31. [PMID: 26527641 DOI: 10.1128/jb.00800-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Streptococcus gordonii is a commensal inhabitant of the human oral cavity. To maintain its presence as a major component of oral biofilms, S. gordonii secretes inhibitory molecules such as hydrogen peroxide and bacteriocins to inhibit competitors. S. gordonii produces two nonmodified bacteriocins (i.e., Sth1 and Sth2) that are regulated by the Com two-component regulatory system, which also regulates genetic competence. Previously we found that the thiol-disulfide oxidoreductase SdbA was required for bacteriocin activity; however, the role of SdbA in Com signaling was not clear. Here we demonstrate that ΔsdbA mutants lacked bacteriocin activity because the bacteriocin gene sthA was strongly repressed and the peptides were not secreted. Addition of synthetic competence-stimulating peptide to the medium reversed the phenotype, indicating that the Com pathway was functional but was not activated in the ΔsdbA mutant. Repression of bacteriocin production was mediated by the CiaRH two-component system, which was strongly upregulated in the ΔsdbA mutant, and inactivation of CiaRH restored bacteriocin production. The CiaRH-induced protease DegP was also upregulated in the ΔsdbA mutant, although it was not required for inhibition of bacteriocin production. This establishes CiaRH as a regulator of Sth bacteriocin activity and links the CiaRH and Com systems in S. gordonii. It also suggests that either SdbA or one of its substrates is an important factor in regulating activation of the CiaRH system. IMPORTANCE Streptococcus gordonii is a noncariogenic colonizer of the human oral cavity. To be competitive in the oral biofilm, S. gordonii secretes antimicrobial peptides called bacteriocins, which inhibit closely related species. Our previous data showed that mutation of the disulfide oxidoreductase SdbA abolished bacteriocin production. In this study, we show that mutation of SdbA generates a signal that upregulates the CiaRH two-component system, which in turn downregulates a second two-component system, Com, which regulates bacteriocin expression. Our data show that these systems are also linked in S. gordonii, and the data reveal that the cell's ability to form disulfide bonds is sensed by the CiaRH system.
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56
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Son M, Shields RC, Ahn SJ, Burne RA, Hagen SJ. Bidirectional signaling in the competence regulatory pathway of Streptococcus mutans. FEMS Microbiol Lett 2015; 362:fnv159. [PMID: 26363019 DOI: 10.1093/femsle/fnv159] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2015] [Indexed: 11/14/2022] Open
Abstract
Streptococcus mutans expresses comX (also known as sigX), which encodes a sigma factor that is required for development of genetic competence, in response to the peptide signals XIP and CSP and environmental factors. XIP (sigX inducing peptide) is derived from ComS and activates comX unimodally in chemically defined media via the ComRS system. CSP (competence stimulating peptide) activates comX bimodally in peptide-rich media through the ComDE two-component system. However, CSP-ComDE activation of comX is indirect and involves ComRS. Therefore, the bimodality of CSP-dependent activation of comX may arise from either ComRS or ComDE. Here we study, at the single-cell level, how genes in the CSP signaling pathway respond to CSP, XIP and media. Our data indicate that activation of comX stimulates expression of comE. In addition, activation of comE requires intact comR and comS genes. Therefore, not only does CSP-ComDE stimulate the ComRS pathway to activate comX expression, but ComRS activation of comX also stimulates expression of the CSP-ComDE pathway and its regulon. The results demonstrate the mutual interconnection of the signaling pathways that control bacteriocin expression (ComDE) and genetic competence (ComRS), both of which are linked to lytic and virulence behaviors.
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Affiliation(s)
- Minjun Son
- Department of Physics, University of Florida, Gainesville FL 32611, USA
| | - Robert C Shields
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA
| | - Sang-Joon Ahn
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA
| | - Robert A Burne
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA
| | - Stephen J Hagen
- Department of Physics, University of Florida, Gainesville FL 32611, USA
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Loss of NADH Oxidase Activity in Streptococcus mutans Leads to Rex-Mediated Overcompensation in NAD+ Regeneration by Lactate Dehydrogenase. J Bacteriol 2015; 197:3645-57. [PMID: 26350138 DOI: 10.1128/jb.00383-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/02/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Previous studies of the oral pathogen Streptococcus mutans have determined that this Gram-positive facultative anaerobe mounts robust responses to both acid and oxidative stresses. The water-forming NADH oxidase (Nox; encoded by nox) is thought to be critical for the regeneration of NAD(+), for use in glycolysis, and for the reduction of oxygen, thereby preventing the formation of damaging reactive oxygen species. In this study, the free NAD(+)/NADH ratio in a nox deletion strain (Δnox) was discovered to be remarkably higher than that in the parent strain, UA159, when the strains were grown in continuous culture. This unanticipated result was explained by significantly elevated lactate dehydrogenase (Ldh; encoded by ldh) activity and ldh transcription in the Δnox strain, which was mediated in part by the redox-sensing regulator Rex. cDNA microarray analysis of S. mutans cultures exposed to simultaneous acid stress (growth at a low pH) and oxidative stress (generated through the deletion of nox or the addition of exogenous oxygen) revealed a stress response synergistically heightened over that with either stress alone. In the Δnox strain, this elevated stress response included increased glucose phosphoenolpyruvate phosphotransferase system (PTS) activity, which appeared to be due to elevated manL transcription, mediated in part, like elevated ldh transcription, by Rex. While the Δnox strain does possess a membrane composition different from that of the parent strain, it did not appear to have defects in either membrane permeability or ATPase activity. However, the altered transcriptome and metabolome of the Δnox strain were sufficient to impair its ability to compete with commensal peroxigenic oral streptococci during growth under aerobic conditions. IMPORTANCE Streptococcus mutans is an oral pathogen whose ability to outcompete commensal oral streptococci is strongly linked to the formation of dental caries. Previous work has demonstrated that the S. mutans water-forming NADH oxidase is critical for both carbon metabolism and the prevention of oxidative stress. The results of this study show that upregulation of lactate dehydrogenase, mediated through the redox sensor Rex, overcompensates for the loss of nox. Additionally, nox deletion led to the upregulation of mannose and glucose transport, also mediated through Rex. Importantly, the loss of nox rendered S. mutans defective in its ability to compete directly with two species of commensal streptococci, suggesting a role for nox in the pathogenic potential of this organism.
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Fontaine L, Wahl A, Fléchard M, Mignolet J, Hols P. Regulation of competence for natural transformation in streptococci. INFECTION GENETICS AND EVOLUTION 2015; 33:343-60. [DOI: 10.1016/j.meegid.2014.09.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 08/28/2014] [Accepted: 09/07/2014] [Indexed: 02/02/2023]
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Kaspar J, Ahn SJ, Palmer SR, Choi SC, Stanhope MJ, Burne RA. A unique open reading frame within the comX gene of Streptococcus mutans regulates genetic competence and oxidative stress tolerance. Mol Microbiol 2015; 96:463-82. [PMID: 25620525 DOI: 10.1111/mmi.12948] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2015] [Indexed: 01/19/2023]
Abstract
Streptococcus mutans displays complex regulation of genetic competence, with ComX controlling late competence gene transcription. The rcrRPQ operon has been shown to link oxidative stress tolerance, (p)ppGpp metabolism and competence in S. mutans. Importantly, an rcrR polar (ΔrcrR-P) mutant is hyper-transformable, but an rcrR non-polar (ΔrcrR-NP) mutant cannot be transformed. Transcriptome comparisons of the rcrR mutants using RNA-Seq and quantitative real-time polymerase chain reaction revealed little expression in the 5' region of comX in ΔrcrR-NP, but high level expression in the 3' region. Northern blotting with comX probes revealed two distinct transcripts in the ΔrcrR-P and ΔrcrR-NP strains, and 5' Rapid Amplification of cDNA Ends mapped the 5' terminus of the shorter transcript to nt +140 of the comX structural gene, where a unique 69-aa open reading frame, termed XrpA, was encoded in a different reading frame than ComX. Two single-nucleotide substitution mutants (comX::T162C; comX::T210A) were introduced to disrupt XrpA without affecting the sequence of ComX. When the mutations were in the ΔrcrR-NP genetic background, ComX production and transformation were restored. Overexpression of xrpA led to impaired growth in aerobic conditions and decreased transformability. These results reveal an unprecedented mechanism for competence regulation and stress tolerance by a gene product encoded within the comX gene that appears unique to S. mutans.
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Affiliation(s)
- Justin Kaspar
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, 32610, USA
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60
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The formation of Streptococcus mutans persisters induced by the quorum-sensing peptide pheromone is affected by the LexA regulator. J Bacteriol 2015; 197:1083-94. [PMID: 25583974 DOI: 10.1128/jb.02496-14] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The presence of multidrug-tolerant persister cells within microbial populations has been implicated in the resiliency of bacterial survival against antibiotic treatments and is a major contributing factor in chronic infections. The mechanisms by which these phenotypic variants are formed have been linked to stress response pathways in various bacterial species, but many of these mechanisms remain unclear. We have previously shown that in the cariogenic organism Streptococcus mutans, the quorum-sensing peptide CSP (competence-stimulating peptide) pheromone was a stress-inducible alarmone that triggered an increased formation of multidrug-tolerant persisters. In this study, we characterized SMU.2027, a CSP-inducible gene encoding a LexA ortholog. We showed that in addition to exogenous CSP exposure, stressors, including heat shock, oxidative stress, and ofloxacin antibiotic, were capable of triggering expression of lexA in an autoregulatory manner akin to that of LexA-like transcriptional regulators. We demonstrated the role of LexA and its importance in regulating tolerance toward DNA damage in a noncanonical SOS mechanism. We showed its involvement and regulatory role in the formation of persisters induced by the CSP-ComDE quorum-sensing regulatory system. We further identified key genes involved in sugar and amino acid metabolism, the clustered regularly interspaced short palindromic repeat (CRISPR) system, and autolysin from transcriptomic analyses that contribute to the formation of quorum-sensing-induced persister cells.
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61
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In vitro manganese-dependent cross-talk between Streptococcus mutans VicK and GcrR: implications for overlapping stress response pathways. PLoS One 2014; 9:e115975. [PMID: 25536343 PMCID: PMC4275253 DOI: 10.1371/journal.pone.0115975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 12/03/2014] [Indexed: 11/19/2022] Open
Abstract
Streptococcus mutans, a major acidogenic component of the dental plaque biofilm, has a key role in caries etiology. Previously, we demonstrated that the VicRK two-component signal transduction system modulates biofilm formation, oxidative stress and acid tolerance responses in S. mutans. Using in vitro phosphorylation assays, here we demonstrate for the first time, that in addition to activating its cognate response regulator protein, the sensor kinase, VicK can transphosphorylate a non-cognate stress regulatory response regulator, GcrR, in the presence of manganese. Manganese is an important micronutrient that has been previously correlated with caries incidence, and which serves as an effector of SloR-mediated metalloregulation in S. mutans. Our findings supporting regulatory effects of manganese on the VicRK, GcrR and SloR, and the cross-regulatory networks formed by these components are more complex than previously appreciated. Using DNaseI footprinting we observed overlapping DNA binding specificities for VicR and GcrR in native promoters, consistent with these proteins being part of the same transcriptional regulon. Our results also support a role for SloR as a positive regulator of the vicRK two component signaling system, since its transcription was drastically reduced in a SloR-deficient mutant. These findings demonstrate the regulatory complexities observed with the S. mutans manganese-dependent response, which involves cross-talk between non-cognate signal transduction systems (VicRK and GcrR) to modulate stress response pathways.
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62
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Cortes PR, Piñas GE, Cian MB, Yandar N, Echenique J. Stress-triggered signaling affecting survival or suicide of Streptococcus pneumoniae. Int J Med Microbiol 2014; 305:157-69. [PMID: 25543170 DOI: 10.1016/j.ijmm.2014.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 12/01/2014] [Accepted: 12/01/2014] [Indexed: 01/27/2023] Open
Abstract
Streptococcus pneumoniae is a major human pathogen that can survive to stress conditions, such as the acidic environment of inflammatory foci, and tolerates lethal pH through a mechanism known as the acid tolerance response. We previously described that S. pneumoniae activates acidic-stress induced lysis in response to acidified environments, favoring the release of cell wall compounds, DNA and virulence factors. Here, we demonstrate that F(0)F(1)-ATPase is involved in the response to acidic stress. Chemical inhibitors (DCCD, optochin) of this proton pump repressed the ATR induction, but caused an increased ASIL. Confirming these findings, mutants of the subunit c of this enzyme showed the same phenotypes as inhibitors. Importantly, we demonstrated that F(0)F(1)-ATPase and ATR are necessary for the intracellular survival of the pneumococcus in macrophages. Alternatively, a screening of two-component system (TCS) mutants showed that ATR and survival in pneumocytes were controlled in contrasting ways by ComDE and CiaRH, which had been involved in the ASIL mechanism. Briefly, CiaRH was essential for ATR (ComE represses activation) whereas ComE was necessary for ASIL (CiaRH protects against induction). They did not regulate F0F1-ATPase expression, but control LytA expression on the pneumococcal surface. These results suggest that both TCSs and F(0)F(1)-ATPase control a stress response and decide between a survival or a suicide mechanism by independent pathways, either in vitro or in pneumocyte cultures. This biological model contributes to the current knowledge about bacterial response under stress conditions in host tissues, where pathogens need to survive in order to establish infections.
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Affiliation(s)
- Paulo R Cortes
- Departamento de Bioquímica Clínica-CIBICI (CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Cordoba, Medina Allende esq. Haya de la Torre, Ciudad Universitaria, CP, X5000HUA Cordoba, Argentina
| | - Germán E Piñas
- Departamento de Bioquímica Clínica-CIBICI (CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Cordoba, Medina Allende esq. Haya de la Torre, Ciudad Universitaria, CP, X5000HUA Cordoba, Argentina
| | - Melina B Cian
- Departamento de Bioquímica Clínica-CIBICI (CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Cordoba, Medina Allende esq. Haya de la Torre, Ciudad Universitaria, CP, X5000HUA Cordoba, Argentina
| | - Nubia Yandar
- Departamento de Bioquímica Clínica-CIBICI (CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Cordoba, Medina Allende esq. Haya de la Torre, Ciudad Universitaria, CP, X5000HUA Cordoba, Argentina
| | - Jose Echenique
- Departamento de Bioquímica Clínica-CIBICI (CONICET), Facultad de Ciencias Químicas, Universidad Nacional de Cordoba, Medina Allende esq. Haya de la Torre, Ciudad Universitaria, CP, X5000HUA Cordoba, Argentina.
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63
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Role of the Streptococcus mutans CRISPR-Cas systems in immunity and cell physiology. J Bacteriol 2014; 197:749-61. [PMID: 25488301 DOI: 10.1128/jb.02333-14] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems provide adaptive microbial immunity against invading viruses and plasmids. The cariogenic bacterium Streptococcus mutans UA159 has two CRISPR-Cas systems: CRISPR1 (type II-A) and CRISPR2 (type I-C) with several spacers from both CRISPR cassettes matching sequences of phage M102 or genomic sequences of other S. mutans. The deletion of the cas genes of CRISPR1 (ΔC1S), CRISPR2 (ΔC2E), or both CRISPR1+2 (ΔC1SC2E) or the removal of spacers 2 and 3 (ΔCR1SP13E) in S. mutans UA159 did not affect phage sensitivity when challenged with virulent phage M102. Using plasmid transformation experiments, we demonstrated that the CRISPR1-Cas system inhibits transformation of S. mutans by the plasmids matching the spacers 2 and 3. Functional analysis of the cas deletion mutants revealed that in addition to a role in plasmid targeting, both CRISPR systems also contribute to the regulation of bacterial physiology in S. mutans. Compared to wild-type cells, the ΔC1S strain displayed diminished growth under cell membrane and oxidative stress, enhanced growth under low pH, and had reduced survival under heat shock and DNA-damaging conditions, whereas the ΔC2E strain exhibited increased sensitivity to heat shock. Transcriptional analysis revealed that the two-component signal transduction system VicR/K differentially modulates expression of cas genes within CRISPR-Cas systems, suggesting that VicR/K might coordinate the expression of two CRISPR-Cas systems. Collectively, we provide in vivo evidence that the type II-A CRISPR-Cas system of S. mutans may be targeted to manipulate its stress response and to influence the host to control the uptake and dissemination of antibiotic resistance genes.
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Sztajer H, Szafranski SP, Tomasch J, Reck M, Nimtz M, Rohde M, Wagner-Döbler I. Cross-feeding and interkingdom communication in dual-species biofilms of Streptococcus mutans and Candida albicans. THE ISME JOURNAL 2014; 8:2256-71. [PMID: 24824668 PMCID: PMC4992082 DOI: 10.1038/ismej.2014.73] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 01/30/2023]
Abstract
Polymicrobial biofilms are of large medical importance, but relatively little is known about the role of interspecies interactions for their physiology and virulence. Here, we studied two human pathogens co-occuring in the oral cavity, the opportunistic fungus Candida albicans and the caries-promoting bacterium Streptococcus mutans. Dual-species biofilms reached higher biomass and cell numbers than mono-species biofilms, and the production of extracellular polymeric substances (EPSs) by S. mutans was strongly suppressed, which was confirmed by scanning electron microscopy, gas chromatography-mass spectrometry and transcriptome analysis. To detect interkingdom communication, C. albicans was co-cultivated with a strain of S. mutans carrying a transcriptional fusion between a green fluorescent protein-encoding gene and the promoter for sigX, the alternative sigma factor of S. mutans, which is induced by quorum sensing signals. Strong induction of sigX was observed in dual-species biofilms, but not in single-species biofilms. Conditioned media from mixed biofilms but not from C. albicans or S. mutans cultivated alone activated sigX in the reporter strain. Deletion of comS encoding the synthesis of the sigX-inducing peptide precursor abolished this activity, whereas deletion of comC encoding the competence-stimulating peptide precursor had no effect. Transcriptome analysis of S. mutans confirmed induction of comS, sigX, bacteriocins and the downstream late competence genes, including fratricins, in dual-species biofilms. We show here for the first time the stimulation of the complete quorum sensing system of S. mutans by a species from another kingdom, namely the fungus C. albicans, resulting in fundamentally changed virulence properties of the caries pathogen.
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Affiliation(s)
- Helena Sztajer
- Research Group Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Szymon P Szafranski
- Research Group Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Jürgen Tomasch
- Research Group Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Michael Reck
- Research Group Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Manfred Nimtz
- Research Group Proteomics, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Manfred Rohde
- Central Facility for Microscopy, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Irene Wagner-Döbler
- Research Group Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
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Ayala E, Downey JS, Mashburn-Warren L, Senadheera DB, Cvitkovitch DG, Goodman SD. A biochemical characterization of the DNA binding activity of the response regulator VicR from Streptococcus mutans. PLoS One 2014; 9:e108027. [PMID: 25229632 PMCID: PMC4168254 DOI: 10.1371/journal.pone.0108027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 08/18/2014] [Indexed: 02/03/2023] Open
Abstract
Two-component systems (TCSs) are ubiquitous among bacteria and are among the most elegant and effective sensing systems in nature. They allow for efficient adaptive responses to rapidly changing environmental conditions. In this study, we investigated the biochemical characteristics of the Streptococcus mutans protein VicR, an essential response regulator that is part of the VicRK TCS. We dissected the DNA binding requirements of the recognition sequences for VicR in its phosphorylated and unphosphorylated forms. In doing so, we were able to make predictions for the expansion of the VicR regulon within S. mutans. With the ever increasing number of bacteria that are rapidly becoming resistant to even the antibiotics of last resort, TCSs such as the VicRK provide promising targets for a new class of antimicrobials.
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Affiliation(s)
- Eduardo Ayala
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
| | - Jennifer S. Downey
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
| | - Lauren Mashburn-Warren
- Center for Microbial Pathogenesis, The Research Institute, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
| | - Dilani B. Senadheera
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Canada
| | - Dennis G. Cvitkovitch
- Dental Research Institute, Faculty of Dentistry, University of Toronto, Toronto, Canada
| | - Steven D. Goodman
- Department of Molecular and Computational Biology, Division of Biomedical Science, Herman Ostrow School of Dentistry, The University of Southern California, Los Angeles, California, United States of America
- Center for Microbial Pathogenesis, The Research Institute, Nationwide Children’s Hospital, Columbus, Ohio, United States of America
- * E-mail:
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Cheng X, Xu X, Chen J, Zhou X, Cheng L, Li M, Li J, Wang R, Jia W, Li YQ. Effects of simulated microgravity on Streptococcus mutans physiology and biofilm structure. FEMS Microbiol Lett 2014; 359:94-101. [PMID: 25109245 DOI: 10.1111/1574-6968.12573] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/05/2014] [Accepted: 08/05/2014] [Indexed: 02/05/2023] Open
Abstract
Long-term spaceflights will eventually become an inevitable occurrence. Previous studies have indicated that oral infectious diseases, including dental caries, were more prevalent in astronauts due to the effect of microgravity. However, the impact of the space environment, especially the microgravity environment, on the virulence factors of Streptococcus mutans, a major caries-associated bacterium, is yet to be explored. In the present study, we investigated the impact of simulated microgravity on the physiology and biofilm structure of S. mutans. We also explored the dual-species interaction between S. mutans and Streptococcus sanguinis under a simulated microgravity condition. Results indicated that the simulated microgravity condition can enhance the acid tolerance ability, modify the biofilm architecture and extracellular polysaccharide distribution of S. mutans, and increase the proportion of S. mutans within a dual-species biofilm, probably through the regulation of various gene expressions. We hypothesize that the enhanced competitiveness of S. mutans under simulated microgravity may cause a multispecies micro-ecological imbalance, which would result in the initiation of dental caries. Our current findings are consistent with previous studies, which revealed a higher astronaut-associated incidence of caries. Further research is required to explore the detailed mechanisms.
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Affiliation(s)
- Xingqun Cheng
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Sudhakar P, Reck M, Wang W, He FQ, Wagner-Döbler I, Dobler IW, Zeng AP. Construction and verification of the transcriptional regulatory response network of Streptococcus mutans upon treatment with the biofilm inhibitor carolacton. BMC Genomics 2014; 15:362. [PMID: 24884510 PMCID: PMC4048456 DOI: 10.1186/1471-2164-15-362] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 04/17/2014] [Indexed: 11/26/2022] Open
Abstract
Background Carolacton is a newly identified secondary metabolite causing altered cell morphology and death of Streptococcus mutans biofilm cells. To unravel key regulators mediating these effects, the transcriptional regulatory response network of S. mutans biofilms upon carolacton treatment was constructed and analyzed. A systems biological approach integrating time-resolved transcriptomic data, reverse engineering, transcription factor binding sites, and experimental validation was carried out. Results The co-expression response network constructed from transcriptomic data using the reverse engineering algorithm called the Trend Correlation method consisted of 8284 gene pairs. The regulatory response network inferred by superimposing transcription factor binding site information into the co-expression network comprised 329 putative transcriptional regulatory interactions and could be classified into 27 sub-networks each co-regulated by a transcription factor. These sub-networks were significantly enriched with genes sharing common functions. The regulatory response network displayed global hierarchy and network motifs as observed in model organisms. The sub-networks modulated by the pyrimidine biosynthesis regulator PyrR, the glutamine synthetase repressor GlnR, the cysteine metabolism regulator CysR, global regulators CcpA and CodY and the two component system response regulators VicR and MbrC among others could putatively be related to the physiological effect of carolacton. The predicted interactions from the regulatory network between MbrC, known to be involved in cell envelope stress response, and the murMN-SMU_718c genes encoding peptidoglycan biosynthetic enzymes were experimentally confirmed using Electro Mobility Shift Assays. Furthermore, gene deletion mutants of five predicted key regulators from the response networks were constructed and their sensitivities towards carolacton were investigated. Deletion of cysR, the node having the highest connectivity among the regulators chosen from the regulatory network, resulted in a mutant which was insensitive to carolacton thus demonstrating not only the essentiality of cysR for the response of S. mutans biofilms to carolacton but also the relevance of the predicted network. Conclusion The network approach used in this study revealed important regulators and interactions as part of the response mechanisms of S. mutans biofilm cells to carolacton. It also opens a door for further studies into novel drug targets against streptococci. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-362) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | - Irene W Dobler
- Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, 21073 Hamburg, Germany.
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Jakubovics NS, Yassin SA, Rickard AH. Community interactions of oral streptococci. ADVANCES IN APPLIED MICROBIOLOGY 2014; 87:43-110. [PMID: 24581389 DOI: 10.1016/b978-0-12-800261-2.00002-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
It is now clear that the most common oral diseases, dental caries and periodontitis, are caused by mixed-species communities rather than by individual pathogens working in isolation. Oral streptococci are central to these disease processes since they are frequently the first microorganisms to colonize oral surfaces and they are numerically the dominant microorganisms in the human mouth. Numerous interactions between oral streptococci and other bacteria have been documented. These are thought to be critical for the development of mixed-species oral microbial communities and for the transition from oral health to disease. Recent metagenomic studies are beginning to shed light on the co-occurrence patterns of streptococci with other oral bacteria. Refinements in microscopy techniques and biofilm models are providing detailed insights into the spatial distribution of streptococci in oral biofilms. Targeted genetic manipulation is increasingly being applied for the analysis of specific genes and networks that modulate interspecies interactions. From this work, it is clear that streptococci produce a range of extracellular factors that promote their integration into mixed-species communities and enable them to form social networks with neighboring taxa. These "community integration factors" include coaggregation-mediating adhesins and receptors, small signaling molecules such as peptides or autoinducer-2, bacteriocins, by-products of metabolism including hydrogen peroxide and lactic acid, and a range of extracellular enzymes. Here, we provide an overview of various types of community interactions between oral streptococci and other microorganisms, and we consider the possibilities for the development of new technologies to interfere with these interactions to help control oral biofilms.
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Affiliation(s)
- Nicholas S Jakubovics
- Oral Biology, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
| | - Sufian A Yassin
- Oral Biology, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Alexander H Rickard
- Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan, USA
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CovR and VicRK regulate cell surface biogenesis genes required for biofilm formation in Streptococcus mutans. PLoS One 2013; 8:e58271. [PMID: 23554881 PMCID: PMC3595261 DOI: 10.1371/journal.pone.0058271] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 02/04/2013] [Indexed: 01/31/2023] Open
Abstract
The two-component system VicRK and the orphan regulator CovR of Streptococcus mutans co-regulate a group of virulence genes associated with the synthesis of and interaction with extracellular polysaccharides of the biofilm matrix. Knockout mutants of vicK and covR display abnormal cell division and morphology phenotypes, although the gene function defects involved are as yet unknown. Using transcriptomic comparisons between parent strain UA159 with vicK (UAvic) or covR (UAcov) deletion mutants together with electrophoretic motility shift assays (EMSA), we identified genes directly regulated by both VicR and CovR with putative functions in cell wall/surface biogenesis, including gbpB, wapE, smaA, SMU.2146c, and lysM. Deletion mutants of genes regulated by VicR and CovR (wapE, lysM, smaA), or regulated only by VicR (SMU.2146c) or CovR (epsC) promoted significant alterations in biofilm initiation, including increased fragility, defects in microcolony formation, and atypical cell morphology and/or chaining. Significant reductions in mureinolytic activity and/or increases in DNA release during growth were observed in knockout mutants of smaA, wapE, lysM, SMU.2146c and epsC, implying roles in cell wall biogenesis. WapE and lysM mutations also affected cell hydrophobicity and sensitivity to osmotic or oxidative stress. Finally, vicR, covR and VicRK/CovR-targets (gbpB, wapE, smaA, SMU.2146c, lysM, epsC) are up-regulated in UA159 during biofilm initiation, in a sucrose-dependent manner. These data support a model in which VicRK and CovR coordinate cell division and surface biogenesis with the extracellular synthesis of polysaccharides, a process apparently required for formation of structurally stable biofilms in the presence of sucrose.
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Son M, Ahn SJ, Guo Q, Burne RA, Hagen SJ. Microfluidic study of competence regulation in Streptococcus mutans: environmental inputs modulate bimodal and unimodal expression of comX. Mol Microbiol 2012; 86:258-72. [PMID: 22845615 PMCID: PMC3468698 DOI: 10.1111/j.1365-2958.2012.08187.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Streptococcus mutans regulates genetic competence through a complex network that receives inputs from a number of environmental stimuli, including two signalling peptides designated as CSP and XIP. The response of the downstream competence genes to these inputs shows evidence of stochasticity and bistability and has been difficult to interpret. We have used microfluidic, single-cell methods to study how combinations of extracellular signals shape the response of comX, an alternative sigma factor governing expression of the late competence genes. We find that the composition of the medium determines which extracellular signal (XIP or CSP) can elicit a response from comX and whether that response is unimodal or bimodal across a population of cells. In a chemically defined medium, exogenous CSP does not induce comX, whereas exogenous XIP elicits a comX response from all cells. In complex medium, exogenous XIP does not induce comX, whereas CSP elicits a bimodal comX response from the population. Interestingly, bimodal behaviour required an intact copy of comS, which encodes the precursor of XIP. The comS-dependent capability for both unimodal and bimodal response suggests that a constituent - most likely peptides - of complex medium interacts with a positive feedback loop in the competence regulatory network.
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Affiliation(s)
- Minjun Son
- Department of Physics, University of Florida, Gainesville FL 32611-8440
| | - Sang-Joon Ahn
- Department of Oral Biology, University of Florida, Gainesville FL 32611-8440
| | - Qiang Guo
- Department of Oral Biology, University of Florida, Gainesville FL 32611-8440
| | - Robert A. Burne
- Department of Oral Biology, University of Florida, Gainesville FL 32611-8440
| | - Stephen J. Hagen
- Department of Physics, University of Florida, Gainesville FL 32611-8440
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Wayne KJ, Li S, Kazmierczak KM, Tsui HCT, Winkler ME. Involvement of WalK (VicK) phosphatase activity in setting WalR (VicR) response regulator phosphorylation level and limiting cross-talk in Streptococcus pneumoniae D39 cells. Mol Microbiol 2012; 86:645-60. [PMID: 23013245 DOI: 10.1111/mmi.12006] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2012] [Indexed: 11/30/2022]
Abstract
WalRK (YycFG) two-component systems (TCSs) of low-GC Gram-positive bacteria play critical roles in regulating peptidogylcan hydrolase genes involved in cell division and wall stress responses. The WalRK (VicRK) TCSs of Streptococcus pneumoniae (pneumococcus) and other Streptococcus species show numerous differences with those of other low-GC species. Notably, the pneumococcal WalK sensor kinase is not essential for normal growth in culture, unlike its homologues in Bacillus and Staphylococcus species. The WalK sensor kinase possesses histidine autokinase activity and mediates dephosphorylation of phosphorylated WalR∼P response regulator. To understand the contributions of these two WalK activities to pneumococcal growth, we constructed and characterized a set of walK kinase and phosphatase mutants in biochemical reactions and in cells. We identified an amino acid substitution in WalK that significantly reduces phosphatase activity, but not other activities. Comparisons were made between WalRK regulon expression levels and WalR∼P amounts in cells determined by Phos-tag SDS-PAGE. Reduction of WalK phosphatase activity resulted in nearly 90% phosphorylation to WalR∼P, consistent with the conclusion that WalK phosphatase is strongly active in exponentially growing cells. WalK phosphatase activity was also shown to depend on the WalK PAS domain and to limit cross-talk and the recovery of WalR∼P from walK(+) cells.
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Affiliation(s)
- Kyle J Wayne
- Department of Biology, Indiana University Bloomington, 1001 East Third Street, Bloomington, IN, 47405, USA
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Lynch JB, Sonnenburg JL. Prioritization of a plant polysaccharide over a mucus carbohydrate is enforced by a Bacteroides hybrid two-component system. Mol Microbiol 2012; 85:478-91. [PMID: 22686399 PMCID: PMC3404733 DOI: 10.1111/j.1365-2958.2012.08123.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bacteroides is a dominant genus within the intestinal microbiota of healthy humans. Key adaptations of the Bacteroides to the dynamic intestinal ecosystem include a diverse repertoire of genes involved in sensing and processing numerous diet- and host-derived polysaccharides. One such adaptation is the carbohydrate-sensing hybrid two-component system (HTCS) family of signalling sensors, which has been widely expanded within the Bacteroides. Using Bacteroides thetaiotaomicron as a model, we have created a chimeric HTCS consisting of the well-characterized sensing domain of one HTCS, BT1754, and the regulatory domain of another HTCS, BT0366, to explore the regulatory capabilities of these molecules. We found that the BT0366 regulatory region directly binds to and mediates induction of the adjacent polysaccharide utilization locus (PUL) using whole-genome transcriptional profiling after inducing signalling through our chimeric protein. We also found that BT0366 activation simultaneously leads to repression of distal PULs involved in mucus carbohydrate consumption. These results suggest a novel mechanism by which an HTCS enforces a nutrient hierarchy within the Bacteroides via induction and repression of multiple PULs. Thus, hybrid two-component systems provide a mechanism for prioritizing consumption of carbohydrates through simultaneous binding and regulation of multiple polysaccharide utilization loci.
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Affiliation(s)
- Jonathan B Lynch
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
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