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

生物膜是附着在不同的惰性或活性表面上的各种微生物群落。它们无处不在，几乎可以在任何自然和人造表面上发展。据估计，与生物膜相关的社会成本每年在数十亿美元之间。生物膜代表了一种受保护的生长模式，使细胞能够在各种环境挑战中生存。许多因素被认为是造成这种著名的生物膜坚韧性的原因。最近，有人提出，基因决定的细胞自杀过程可能作为一些细菌种群在遇到环境压力时的动态特征而发生。大多数细菌染色体含有许多自杀或毒素基因，这些基因会导致细胞生长停滞或细胞死亡。该研究项目提出了一个假设，即细菌严格调节其自杀系统的表达，以促进其后代在生物膜群落中的生存。通过在各种压力条件下调节它们的自杀系统，社区中的一个细胞亚群死亡，以允许整个群体的生存。口腔细菌变形链球菌将被用作模式生物，因为这种细菌依靠生物膜生活方式在其自然生态系统中生存和持久。利用蛋白质表达系统和毒素的作用机制，对链球菌毒素在同源和异源菌株中的毒性活性进行了论证。利用实时荧光定量PCR，我们将确定暴露于几种环境应激源后自杀系统的差异基因表达。最后，我们将构建报告系统来研究生物膜中自杀系统的转录活性。这些结果将提供决定调控杀伤的机制的知识，以便更好地理解在易受微生物污染的任何表面的生物污染中发生的细胞分化和死亡事件。从应用的角度来看，本研究结果可能会导致工业和环境技术中控制和利用生物膜现象的新策略的发展。

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.