title: Community signalling between Streptococcus gordonii and Porphyromonas gingivalis is controlled by the transcriptional regulator CdhR.
abstract: Interspecies signalling between Porphyromonas gingivalis and Streptococcus gordonii serves to constrain development of dual species communities. Contact with S. gordonii propagates a tyrosine phosphorylation-dependent signal within P. gingivalis that culminates in reduced transcription of adhesin and signalling genes. Here we demonstrate the involvement of the P. gingivalis orphan LuxR family transcription factor PGN_1373, which we designate CdhR, in this control pathway. Expression of cdhR is elevated following contact with S. gordonii; however, regulation of cdhR did not occur in a mutant lacking the tyrosine phosphatase Ltp1, indicating that CdhR and Ltp1 are components of the same regulon. Contact between S. gordonii and a CdhR mutant resulted in increased transcription of mfa, encoding the subunit of the short fimbriae, along with higher levels of Mfa protein. Expression of luxS, encoding AI-2 synthase, was also increased in the cdhR mutant after contact with S. gordonii. The Mfa adhesive function and AI-2-dependent signalling participate in the formation and development of dual species communities, and consistent with this the cdhR mutant displayed elevated accumulation on a substratum of S. gordonii. Recombinant CdhR protein bound to upstream regulatory regions of both mfa and luxS, indicating that CdhR has a direct effect on gene expression. LuxS was also found to participate in a positive feedback loop that suppresses CdhR expression. Interaction of Mfa fimbriae with S. gordonii is necessary to initiate signalling through CdhR. These results reveal CdhR to be an effector molecule in a negative regulatory network that controls P. gingivalis-S. gordonii heterotypic communities.
authors.affiliation: Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
authors.forename: Aarti
authors.initials: A
authors.lastname: Chawla
authors.forename: Takanori
authors.initials: T
authors.lastname: Hirano
authors.forename: Brian W
authors.initials: BW
authors.lastname: Bainbridge
authors.forename: Donald R
authors.initials: DR
authors.lastname: Demuth
authors.forename: Hua
authors.initials: H
authors.lastname: Xie
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lamont
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction; D054773:Streptococcus gordonii / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors