Bacteriocins and survival in the biofilm environment

生物膜代表了细菌生命的主要形式。当出现有利于生长的表面或界面和条件时，细菌几乎总是会聚集成一组细胞，这些细胞被包裹在自我产生的保护性细胞外基质中。生物膜允许细菌在恶劣环境中生存，如紫外线照射、脱水、盐度和几种消毒剂和杀菌剂。当细菌在生物膜内生长时，它们会分泌信号分子，这些信号分子的浓度随着细胞密度的增加而增加。在一个被称为群体感应的过程中，细菌通过使用信号分子来调节它们的基因表达，以响应细胞种群密度的波动，从而相互交流。广泛的表型是由群体感应控制的，包括生物膜的形成、细菌素的产生和获得外源DNA的遗传能力。因此，群体感应使细菌在适应环境、定植和防御竞争对手的过程中表现出统一的反应。细菌素是核糖体合成的蛋白质抗菌肽。它们选择性地干扰其他细菌的生长，并且调节细菌素的产生在细菌生物膜的竞争性相互作用中起着重要作用。我的团队所做的大量工作表明，群体感应也可以作为一种应激诱导系统，通过触发向细菌群体发出的信号来启动适应性反应，从而产生不同的结果。生物膜非常复杂，细菌的一个基本特性是它们在面对波动环境时调节细胞生长的能力。细菌素的产生和分泌是对环境压力的反应，在与同一生态位中存在的其他细菌竞争时，可能赋予生产者独特的生态优势，或者在遗传能力状态下作为从其他物种获取DNA的可能机制。选择变形链球菌作为模型是因为它与生物膜生活方式的相关性，我的总体目标是回答以下问题：微生物生长调节剂，如细菌素，是否在生物膜的竞争、生物多样性和生态适应性中发挥作用？我实验室的研究（过去的和正在进行的）表明，群体感应（信号）、细菌素激活（反应）和生物膜持久性（表型）之间存在复杂的相互作用，作为对环境扰动的反应。利用最先进的技术来阐明生物膜的生理和基因活动，我的研究有可能有助于开发具有成本效益的生物杀灭策略，以控制和/或根除微生物生物膜。

Biofilms represent the predominant form of bacterial life. When presented with a surface or an interface and conditions advantageous for growth, bacteria almost always will assemble as a group of cells encapsulated within a self-produced protective extracellular matrix. Biofilms allow survival of bacteria in hostile environments, such as UV exposure, dehydration, salinity, and several disinfectants and biocidal agents. When bacteria are growing within biofilms, they secrete signaling molecules that increase in concentration as a function of cell density. In a process called quorum sensing, bacteria communicate with one another by using signaling molecules to regulate their gene expression in response to fluctuations in the cell population density. A wide array of phenotypes is controlled by quorum sensing including biofilm formation, bacteriocin production, and genetic competence for acquisition of exogenous DNA. Thus, quorum sensing allows bacteria to display a unified response that benefits the bacteria during adaptation to environment, colonization, and defense against competitors. Bacteriocins are ribosomally synthesized proteinaceous antibacterial peptides. They selectively interfere with the growth of other bacteria, and regulation of bacteriocin production plays an important role in the competitive interactions in bacterial biofilms. Extensive work done by my group showed that quorum sensing can also function as a stress-inducible system by triggering the signaling to the bacterial population to initiate an adaptive response that results in different outcomes. Biofilms are very complex and a fundamental property of bacteria is their ability to regulate cell growth when faced with a fluctuating environment. The production and secretion of bacteriocins in response to environmental stressors could confer a distinct ecological advantage to the producer in competing against other bacteria that are present in the same ecological niche or as a possible mechanism for the acquisition of DNA from other species during the genetic competence state. Using Streptococcus mutans as a model chosen because of its relevance of a biofilm lifestyle, my overall goal is to answer the following question: Do microbial growth modulators such as bacteriocins play a role in competition, biodiversity and ecological fitness of the biofilm? Research (past and ongoing) from my lab suggests a complex interplay between quorum sensing (signal), bacteriocin activation (response), and biofilm persistence (phenotype) as a reaction to the environmental perturbations. Using state-of-the-art technology to elucidate the physiology and gene activities of biofilms, my research has the potential to contribute to the development of cost-effective biocidal strategies for the control and/or eradication of microbial biofilms.