title: Psr is involved in regulation of glucan production, and double deficiency of BrpA and Psr is lethal in Streptococcus mutans.
abstract: 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 Strep. 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 compared with 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. Real-time-PCR and Western blot analyses revealed that deficiency of Psr significantly decreased the expression of glucosyltransferase C, a protein known to play a major role in biofilm formation by Strep. mutans. Transmission electron microscopy 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 Strep. mutans.
authors.affiliation: Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Bitoun
authors.affiliation: Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Sumei
authors.initials: S
authors.lastname: Liao
authors.affiliation: Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Briggs A
authors.initials: BA
authors.lastname: McKey
authors.affiliation: Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Yao
authors.affiliation: Department of Comprehensive Dentistry and Biomaterials, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Fan
authors.affiliation: Center for Oral Biology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Abranches
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, St Louis, MO, USA.
authors.forename: Wandy L
authors.initials: WL
authors.lastname: Beatty
authors.affiliation: Department of Microbiology, Immunology, and Parasitology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA.|Department of Oral and Craniofacial Biology, School of Dentistry, Louisiana State University Health Sciences Center, New Orleans, LA, USA.
authors.forename: Zezhang T
authors.initials: ZT
authors.lastname: Wen
mesh_terms: D000143:Acids / Q000633:toxicity; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development; D015153:Blotting, Western; D002473:Cell Wall / Q000648:ultrastructure; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005936:Glucans / Q000378:metabolism*; D050296:Microbial Viability / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013295:Streptococcus mutans / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology
chemical_list: D000143:Acids; D001426:Bacterial Proteins; C454866:BrpA protein, Streptococcus mutans; D005936:Glucans; D012097:Repressor Proteins