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Chapter 21 : Heterotypic Streptococcus gordonii-Porphyromonas gingivalis Communities: Formation, Gene Regulation, and Development
Category: Genomics and Bioinformatics
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Heterotypic Streptococcus gordonii-Porphyromonas gingivalis Communities: Formation, Gene Regulation, and Development, Page 1 of 2< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817107/9781555815035_Chap21-1.gif /docserver/preview/fulltext/10.1128/9781555817107/9781555815035_Chap21-2.gif
The composition of oral biofilm communities, and their pathogenic potential, may depend on interspecies binding and communication interactions. Multivalent coadhesive interactions characterize the binding of Porphyromonas gingivalis to oral streptococci such as Streptococcus gordonii and drive subsequent development of heterotypic S. gordonii-P. gingivalis communities. Gene regulation by two-component systems (TCSs) is a common mechanism used by bacteria to modulate cell behavior in response to environmental changes. Following the initial binding interaction between P. gingivalis and S. gordonii, adherent P. gingivalis cells undergo a programmatic phenotypic shift in order to prepare for community living. P. gingivalis produces autoinducer 2 (AI-2) and responds both to homologous signal and to AI-2 from other organisms such as S. gordonii and Actinobacillus actinomycetemcomitans. The expression of GTF, Rgg, and exo-β;-D-fructosidase (fructanase) is downregulated in the absence of LuxS, whereas expression of tagatose 1,6-diphosphate aldolase is elevated. Contact with S. cristatus propagates a signal in P. gingivalis that causes downregulation of fimA expression. Signaling is mediated by arginine deiminase (ArcA) on the surface of Streptococcus cristatus. Biofilms tend to be polymicrobial in nature, and the subgingival plaque biofilm is an exemplar of this situation, with as many as 200 species present in any one individual.
S. gordonii community- and biofilm-related gene cluster SGO_0275 to SGO_0307 (coordinates 292331 to 328700; 36.4 kb). Genes regulated in S. gordonii-P. gingivalis communities are number coded by putative community-related function. 1, transcriptional regulation and/or signaling; 2, capsule or cell wall biosynthesis; 3, protein folding and associated processing; 4, physiology.
Role of Ltp1 in S. gordonii-P. gingivalis communities. Contact with S. gordonii transduces a signal (dashed arrow) that upregulates Ltp1 expression. Ltp1 downregulates (flat arrow) expression of exopolysaccharide and LuxS and upregulates (arrow) expression of the hmu locus. Ltp1 also dephosphorylates Kgp. Phenotypic outcomes of Ltp1 activity include restricted biofilm development, reduced AI-2 signaling, increased uptake of hemin, and decreased cell-associated Kgp activity.
Blast analysis of streptococcal and related species genome sequences with BAR sequence
S. gordonii genes required for community development with P. gingivalis cells