Psr Is Involved in Regulation of Glucan Production and Double Deficiency of BrpA and Psr Is Lethal in Streptococcus mutans.
LSU Health Sciences Center, New Orleans, LAMicrobiology (Impact Factor: 2.56). 01/2013; 159(Pt_3). DOI: 10.1099/mic.0.063032-0
Streptococcus mutans, the primary causative agent of dental caries, contains two paralogues of the LytR-CpsA-Psr family proteins encoded by brpA and psr, respectively. Previous studies have shown that BrpA plays an important role in cell envelope biogenesis/ homeostasis and affects stress responses and biofilm formation by S. mutans, traits critical to cariogenicity of this bacterium. In this study, a Psr-deficient mutant, TW251, was constructed. Characterization of TW251 showed that deficiency of Psr did not have any major impact on growth rate. However, when subjected to acid killing at pH 2.8, the survival rate of TW251 was decreased dramatically as compared to the parent strain UA159. In addition, TW251 also displayed major defects in biofilm formation, especially during growth with sucrose. When compared to UA159, the biofilms of TW251 were mainly planar and devoid of extracellular glucans. RealTime-PCR and Western blot analysis revealed that deficiency of Psr significantly decreased the expression of glucosyltransferase C, a protein known to play a major role in biofilm formation by S. mutans. TEM analysis showed that deficiency of BrpA caused alterations in cell envelope and cell division, and the most significant defects were observed in TW314, a Psr-deficient and BrpA-down mutant. No such effects were observed with Psr mutant, TW251 under similar conditions. These results suggest that while there are similarities in functions between BrpA and Psr, distinctive differences also exist between these two paralogues. Like Bacillus subtilis but different from Staphylococcus aureus, a functional BrpA or Psr is required for viability in S. mutans.
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ABSTRACT: Streptococcus mutans, the primary etiological agent of dental caries, possesses an YjeE-like protein that is encoded in locus SMU.409, herein designated brpB. In this study, a BrpB-deficient mutant, JB409, and a double mutant deficient of BrpB and BrpA (a paralogue of the LytR-CpsA-Psr family of cell wall-associated proteins), JB819, were constructed and characterized using function assays and microscopic analysis. Both JB409 and JB819 displayed extended lag phases and drastically slowed growth rates during growth in BHI as compared to the wild-type, UA159. Relative to UA159, JB409 and JB819 were more than 60- and 10-fold more susceptible to acid killing at pH 2.8, and more than 1- and 2-log more susceptible to hydrogen peroxide, respectively. Complementation of the deficient mutants with a wild-type copy of the respective gene(s) partly restored the acid and oxidative stress responses to a level similar to the wild-type. As compared to UA159, biofilm formation by JB409 and JB819 was drastically reduced (P<0.001), especially during growth in medium containing sucrose. Under SEM, JB409 had significantly more giant cells with an elongated, rod-like morphology, and JB819 formed marble-like super cells with apparent defects in cell division. As revealed by TEM analysis, BrpB-deficiency in both JB409 and JB819 resulted in the development of low electron density patches and formation of loose nucleoid structure. Taken together, these results suggest that BrpB likely functions in concerto with BrpA in regulating cell envelope biogenesis /homeostasis in S. mutans. Further study is underway to elucidate the mechanism that underlies the BrpA and BrpB-mediated regulation.Microbiology 11/2013; 160(Pt_1). DOI:10.1099/mic.0.072884-0 · 2.56 Impact Factor
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ABSTRACT: Streptococcus mutans, a key etiological agent of the human dental caries, lives primarily on the tooth surface in tenacious biofilms. The SMU864 locus, designated pdxR, is predicted to encode a member of the novel MocR/GabR family proteins, which are featured with a winged helix DNA-binding N-terminal domain and a C-terminal domain highly homologous to the pyridoxal phosphate-dependent aspartate aminotransferases. A pdxR-deficient mutant, TW296, was constructed using allelic exchange. PdxR-deficiency in S. mutans had little effect on cell morphology and growth when grown in brain heart infusion. However, when compared to its parent strain, UA159, the PdxR-deficient mutant displayed major defects in acid tolerance response and formed significantly less biofilms (P<0.01). When analyzed by RealTime-PCR, PdxR-deficiency was found to drastically reduce expression of an apparent operon encoding a pyridoxal kinase (SMU865) and a pyridoxal permease (SMU866) of the salvage pathway of vitamin B6 biosynthesis. In addition, PdxR-deficiency also altered the expression of genes for ClpL protease, glucosyltransferase B and adhesin SpaP, which are known to play important roles in stress tolerance and biofilm formation. Consistently, PdxR-deficiency affected growth of the deficient mutant when grown in defined medium with and without vitamin B6. Further studies revealed that while S. mutans is known to require vitamin B6 to grow in defined medium, B6 vitamers, especially pyridoxal, were strongly inhibitory at millimolar concentrations, against S. mutans growth and biofilm formation. Our results suggest that PdxR in S. mutans plays an important role in regulation of vitamin B6 metabolism, acid tolerance response and biofilm formation.This article is protected by copyright. All rights reserved.11/2014; 30(4). DOI:10.1111/omi.12090
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ABSTRACT: Staphylococcus aureus is an important human pathogen that causes nosocomial and community-acquired infections. One of the most important aspects of staphylococcal infections is biofilm development within the host, which renders the bacterium resistant to the host's immune response and antimicrobial agents. Biofilm development is very complex and involves several regulators that ensure cell survival on surfaces within the extracellular polymeric matrix. Previously, we identified the msaABCR operon as an additional positive regulator of biofilm formation. In this study, we define the regulatory pathway by which msaABCR controls biofilm formation. We demonstrate that the msaABCR operon is a negative regulator of proteases. The control of protease production mediates the processing of the major autolysin, Atl, and thus regulates the rate of autolysis. In the absence of the msaABCR operon, Atl is processed by proteases at a high rate, leading to increased cell death and a defect in biofilm maturation. We conclude that the msaABCR operon plays a key role in maintaining the balance between autolysis and growth within the staphylococcal biofilm. © FEMS 2015. All rights reserved. For permissions, please e-mail: email@example.com.FEMS Microbiology Letters 01/2015; 362(4). DOI:10.1093/femsle/fnv006 · 2.12 Impact Factor
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