A Novel Regulator Modulates Glucan Production, Cell Aggregation and Biofilm Formation in Streptococcus sanguinis SK36.

ABSTRACT: Streptococcus sanguinis is an early colonizer of tooth surfaces and a key player in plaque biofilm development. However, the mechanism of biofilm formation of S. sanguinis is still unclear. Here, we showed that deletion of a transcription factor, brpL, promotes cell aggregation and biofilm formation in S. sanguinis SK36. Glucan, a polysaccharide synthesized from sucrose, was over-produced and aggregated in the biofilm of ?brpL, which was necessary for better biofilm formation ability of ?brpL. Quantitative RT-PCR demonstrated that gtfP was significantly up-regulated in ?brpL, which increased the productions of water-insoluble and water-soluble glucans. The ?brpL?gtfP double mutant decreased biofilm formation ability of ?brpL to a level similar like that of ?gtfP. Interestingly, the biofilm of ?brpL had an increased tolerance to ampicillin treatment, which might be due to better biofilm formation ability through the mechanisms of cellular and glucan aggregation. RNA sequencing and quantitative RT-PCR revealed the modulation of a group of genes in ?brpL was mediated by activating the expression of ciaR, another gtfP-related biofilm formation regulator. Double deletion of brpL and ciaR decreased biofilm formation ability to the phenotype of a ?ciaR mutant. Additionally, RNA sequencing elucidated a broad range of genes, related to carbohydrate metabolism and uptake, were activated in ?brpL. SSA_0222, a gene involved in the phosphotransferase system, was dramatically up-regulated in ?brpL and essential for S. sanguinis survival under our experimental conditions. In summary, brpL modulates glucan production, cell aggregation and biofilm formation by regulating the expression of ciaR in S. sanguinis SK36.

SUBMITTER: Zhu B 

PROVIDER: S-EPMC5987052 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature