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Open Access Highly Accessed Research article

Biofilm formation and virulence expression by Streptococcus mutans are altered when grown in dual-species model

Zezhang T Wen1*, David Yates2, Sang-Joon Ahn2 and Robert A Burne2

Author Affiliations

1 Department of Oral and Craniofacial Biology and Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA 70119, USA

2 Department of Oral Biology, College of Dentistry, University of Florida, Box 100424, Gainesville, FL 32610, USA

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BMC Microbiology 2010, 10:111  doi:10.1186/1471-2180-10-111

Published: 14 April 2010

Abstract

Background

Microbial 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.

Results

As 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.

Conclusions

These results suggest that the presence of specific oral bacteria differentially affects biofilm formation and virulence gene expression by S. mutans.