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

微生物学家传统上专注于实验室培养中生长的自由漂浮细菌；然而，他们最近意识到，在自然界中，超过99%的细菌生活在生物膜群落中。因此，生物膜的研究是目前微生物学研究的热点之一。生物膜无处不在，几乎可以在任何自然和人造表面上形成。据估计，与生物膜相关的社会成本（如设备损坏、产品污染）每年可达数十亿美元。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，细菌自杀的遗传决定过程可能作为某些细菌种群遇到压力时的动态特征而发生。大多数细菌染色体含有一些自杀或毒素基因，这些基因会导致细胞生长停滞或死亡。本研究提出了一种假设，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中的生存。通过在各种压力下调节它们的自杀系统，社区中的细胞亚群死亡以允许整个群体的生存（利他主义）。变形链球菌将被用作模型，因为这种细菌依靠生物膜的生活方式在其自然生态系统中生存。利用蛋白表达系统论证其毒素的毒性活性，并对毒素的作用机制进行表征。暴露于几种环境压力后，自杀系统的基因表达谱将被确定。最后，我们将构建报告系统来研究在体内生物膜中的转录活性。这些结果将提供决定微生物自我毁灭机制的知识，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。

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.