TetR Family Regulator brpT Modulates Biofilm Formation in Streptococcus sanguinis.

Jinlin Liu,Xiuchun Ge,Madison Tang,Fadi Elrami,Ping Xu,Victoria N Stone

doi:10.1371/journal.pone.0169301

Jinlin Liu, Xiuchun Ge + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0169301

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Journal: PloS one	Publication Date: Jan 3, 2017
Citations: 15	License type: CC BY 4.0

Affiliation: Virginia Commonwealth University

Abstract

Biofilms are a key component in bacterial communities providing protection and contributing to infectious diseases. However, mechanisms involved in S. sanguinis biofilm formation have not been clearly elucidated. Here, we report the identification of a novel S. sanguinis TetR repressor, brpT (Biofilm Regulatory Protein TetR), involved in biofilm formation. Deletion of brpT resulted in a significant increase in biofilm formation. Interestingly, the mutant accumulated more water soluble and water insoluble glucans in its biofilm compared to the wild-type and the complemented mutant. The brpT mutation led to an altered biofilm morphology and structure exhibiting a rougher appearance, uneven distribution with more filaments bound to the chains. RNA-sequencing revealed that gtfP, the only glucosyltransferase present in S. sanguinis, was significantly up-regulated. In agreement with these findings, we independently observed that deletion of gtfP in S. sanguinis led to reduced biofilm and low levels of water soluble and insoluble glucans. These results suggest that brpT is involved in the regulation of the gtfP-mediated exopolysaccharide synthesis and controls S. sanguinis biofilm formation. The deletion of brpT may have a potential therapeutic application in regulating S. sanguinis colonization in the oral cavity and the prevention of dental caries.

Highlights

We show that brpT influences biofilm formation in S. sanguinis, deletion of brpT alters the spatial structure of the biofilm and increases the ability of S. sanguinis to accumulate glucans
The growth rates of the wild-type, the brpT mutant and the complemented mutant were first examined and we found no significant change in the bacterial overnight growth of brpT mutant (S2 Fig)
Biofilms for the brpT mutant, the wild-type and the complemented mutant were quantified by crystal violet (CV) staining

Summary

Introduction

Through the continued study of our S. sanguinis genome-wide gene mutant library [18], we identified a new biofilm-related gene, brpT, a TetR family transcriptional regulator. The preliminary screening indicated that the brpT deletion mutant displayed an increased biofilm phenotype compared to the wild-type SK36, when grown in either BM or trypticase soy broth (data not shown). To better understand these morphological differences, biofilms for the wild-type, the brpT mutant and the complemented mutant were grown under anaerobic conditions in flat-bottom polystyrene microtiter plates and examined by confocal laser scanning microscopy (CLSM).

Results

Conclusion