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

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Microbiologists have traditionally focused on free-floating bacteria growing in lab cultures; yet they have recently come to realize that in the natural world more than 99% of all bacteria live in biofilm communities. As a result, biofilms research is now one of the hottest topics in microbiology. Biofilms are ubiquitous and can developed on virtually every natural and man-made surface. The cost to society associated with biofilms (e.g. equipment damage, product contamination) 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 bacterial suicide can occur as a feature of the dynamics of some bacterial populations that encounter stresses. Most bacterial chromosomes contain a number of suicide or toxin genes that induce cell growth arrest or death. This research proposal raises the hypothesis that bacteria tightly regulate the expression of their suicide systems to foster survival of their progeny in the biofilm. By regulating their suicide systems under various stresses, a subpopulation of cells in the community dies to permit the survival of the population as a whole (altruism). Streptococcus mutans will be used as model as this bacterium depends on a biofilm lifestyle for its survival in its natural ecosystem. The toxic activity of its toxin will be demonstrated using a protein expression system and the mechanism of action of the toxin characterized. The gene expression profiling of the suicide system after exposure to several environmental stressors will be determined. Finally, reporter systems will be constructed to study the transcriptional activities in in vivo biofilms. These results will provide knowledge of the mechanisms that determine microbial self-destruction for a better understanding of 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.