title: Involvement of gshAB in the interspecies competition within oral biofilm.
abstract: Although Streptococcus sanguinis has been reported to produce H2O2 to gain a competitive edge over Streptococcus mutans, the molecular mechanisms evolved by S. mutans to counter this "peer stress" are still to be identified. The current study was designed to investigate the ecological role of glutathione synthetase (gshAB) in the interspecies interaction between S. mutans and S. sanguinis. A gshAB in-frame deletion strain of S. mutans was constructed, and its phenotypic traits were characterized. The spatio-temporal interaction of the gshAB mutant with S. sanguinis was further investigated in a dual-species biofilm model by fluorescence in situ hybridization. We found that, although less tolerant for H2O2, the gshAB mutant produced more extracellular polysaccharides by up-regulating gtfs expression, so as to cluster as condensed microcolonies. In addition, the mutant was more susceptible to the conditioned medium of S. sanguinis, and its competitiveness was significantly compromised. Taken together, we believe that gshAB is essential for the competitiveness and prevalence of S. mutans through detoxifying the H2O2 produced by S. sanguinis. Given the ecological importance of bacterial equilibrium within the oral biofilm, gshAB may represent a promising target to modulate the S. mutans/S. sanguinis ratio under cariogenic conditions, thus contributing to the management of dental caries.
authors.affiliation: State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China.
authors.forename: X
authors.initials: X
authors.lastname: Zheng
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: X
authors.initials: X
authors.lastname: Zhou
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: R
authors.initials: R
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: W
authors.initials: W
authors.lastname: Shi
authors.forename: X
authors.initials: X
authors.lastname: Xu
mesh_terms: D000898:Antibiosis / Q000502:physiology; D018441:Biofilms; D017077:Culture Media, Conditioned; D003731:Dental Caries / Q000382:microbiology; D003773:Dental Plaque / Q000382:microbiology; D005981:Glutathione Synthase / Q000235:genetics / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D056265:Microbial Interactions / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology; D010641:Phenotype; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D013295:Streptococcus mutans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D013298:Streptococcus sanguis / Q000201:enzymology* / Q000254:growth & development; D015854:Up-Regulation / Q000502:physiology
chemical_list: D017077:Culture Media, Conditioned; D011135:Polysaccharides, Bacterial; D006861:Hydrogen Peroxide; D005981:Glutathione Synthase
keywords: Streptococcus mutans; Streptococcus sanguinis; antibiosis; dental caries; fluorescence in situ hybridization; glutathione synthase