Environmentally stress-induced suicide module in the biofilm-forming organism streptococcus mutans

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Biofilms are diverse microbial communities attached to distinct inert or living surfaces. They are ubiquitous and can developed on virtually every natural and man-made surface. The cost to society associated with biofilms is estimated to range in the billions of dollars annually. Biofilms represent a protected mode of growth that allow cells to survive a wide range of environmental challenges. A number of factors have been considered to be responsible for this renowned tenacity of biofilms. Recently, it has been proposed that a genetically determined process of cellular suicide can occur as a feature of the dynamics of some bacterial populations that encounter environmental stresses. Most bacterial chromosomes contain a number of suicide or toxin genes that induce cell growth arrest or cell death. This research program raises the hypothesis that bacteria tightly regulate the expression of their suicide systems to foster bacterial survival of their progeny in the biofilm community. By regulating their suicide systems under various stressful conditions, a subpopulation of cells in the community dies to permit the survival of the population as a whole. The oral bacterium Streptococcus mutans will be used as model organism as this bacterium depends on a biofilm lifestyle for its survival and persistence in its natural ecosystem. The toxic activity of the streptococcal toxin in homologous and heterologous strains will be demonstrated using a protein expression system and the mechanism of action of the toxin characterized. Using quantitative real-time PCR, we will determined the differential gene expression of the suicide system after exposure to several environmental stressors. Finally, reporter systems will be constructed to study the transcriptional activities of the suicidal system in biofilms. These results will provide knowledge of the mechanisms that determine regulated-killing for a better understanding of cell differentiation and death events occurring in biofouling of any surfaces susceptible to microbial contamination. From an applied perspective, the results of this study may lead to the development of novel strategies to control and exploit the biofilm phenomenon in industry and environment technology.