Abstract
BackgroundMicrobial cell-cell interactions in the oral flora are believed to play an integral role in the development of dental plaque and ultimately, its pathogenicity. The effects of other species of oral bacteria on biofilm formation and virulence gene expression by Streptococcus mutans, the primary etiologic agent of dental caries, were evaluated using a dual-species biofilm model and RealTime-PCR analysis.ResultsAs compared to mono-species biofilms, biofilm formation by S. mutans was significantly decreased when grown with Streptococcus sanguinis, but was modestly increased when co-cultivated with Lactobacillus casei. Co-cultivation with S. mutans significantly enhanced biofilm formation by Streptococcus oralis and L. casei, as compared to the respective mono-species biofilms. RealTime-PCR analysis showed that expression of spaP (for multi-functional adhesin SpaP, a surface-associated protein that S. mutans uses to bind to the tooth surface in the absence of sucrose), gtfB (for glucosyltransferase B that synthesizes α1,6-linked glucan polymers from sucrose and starch carbohydrates) and gbpB (for surface-associated protein GbpB, which binds to the glucan polymers) was decreased significantly when S. mutans were co-cultivated with L. casei. Similar results were also found with expression of spaP and gbpB, but not gtfB, when S. mutans was grown in biofilms with S. oralis. Compared to mono-species biofilms, the expression of luxS in S. mutans co-cultivated with S. oralis or L. casei was also significantly decreased. No significant differences were observed in expression of the selected genes when S. mutans was co-cultivated with S. sanguinis.ConclusionsThese results suggest that the presence of specific oral bacteria differentially affects biofilm formation and virulence gene expression by S. mutans.
Highlights
Microbial cell-cell interactions in the oral flora are believed to play an integral role in the development of dental plaque and its pathogenicity
We developed a dual-species in vitro model to examine the impact of co-cultivation of S. mutans with S. oralis or S. sanguinis, two primary colonizers and members of the normal flora, or with Lactobacillus casei, a bacterium frequently isolated from carious sites, on biofilm formation by these bacteria and expression of known virulence factors of S. mutans
Bacterial strains and growth conditions S. mutans UA159, S. oralis SK92 and S. sanguinis SK150 were maintained in Brain Heart Infusion (BHI, Becton, Dickinson and Company, MD), and L. casei 4646 was maintained in Lactobacillus MRS (Difco Laboratories, MI)
Summary
Microbial cell-cell interactions in the oral flora are believed to play an integral role in the development of dental plaque and its pathogenicity. The effects of other species of oral bacteria on biofilm formation and virulence gene expression by Streptococcus mutans, the primary etiologic agent of dental caries, were evaluated using a dual-species biofilm model and RealTime-PCR analysis. Oral biofilms are compositionally and structurally complex bacterial communities. More than 750 different species or phylotypes of bacteria have been identified in mature dental plaque [1]. Microbial cell-cell interactions in the oral flora and their impact on bacterial adherence and biofilm formation are beginning to be appreciated [1,2,3,4]. Cross-feeding or metabolic cooperation is well-documented among certain bacterial species in the oral flora. BioMed Central tribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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