Bacteriocins and survival in the biofilm environment

生物膜是细菌生命的主要形式。当有一个表面或界面，以及有利于生长的条件时，细菌几乎总是会聚集成一组细胞，包裹在自己产生的保护性细胞外基质中。生物膜允许细菌在恶劣的环境中生存，如紫外线照射、脱水、盐度以及几种消毒剂和杀生剂。当细菌在生物膜内生长时，它们会分泌信号分子，随着细胞密度的增加，信号分子的浓度会增加。在一种称为群体感应的过程中，细菌通过使用信号分子来调节自己的基因表达，以应对细胞种群密度的波动，从而相互交流。广泛的表型由群体感应控制，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，群体感应允许细菌在适应环境、定居和防御竞争对手的过程中表现出统一的反应，这对细菌有利。细菌素是由核糖体合成的蛋白质类抗菌肽。它们选择性地干扰其他细菌的生长，而细菌素的产生调控在细菌生物膜的竞争相互作用中起着重要作用。我的团队所做的广泛工作表明，群体感应也可以作为压力诱导系统，通过触发对细菌群体的信号来启动适应性反应，从而导致不同的结果。生物膜是非常复杂的，细菌的一个基本属性是它们在面对波动的环境时调节细胞生长的能力。细菌素的产生和分泌对环境应激源的反应可以赋予生产者在与同一生态位中存在的其他细菌竞争时的明显生态优势，或者作为一种可能的机制，在遗传能力状态下从其他物种获得DNA。选择变形链球菌作为模型是因为它与生物膜的生活方式相关，我的总体目标是回答以下问题：细菌素等微生物生长调节剂是否在生物膜的竞争、生物多样性和生态适宜性中发挥作用？我的实验室的研究(过去和正在进行的)表明，作为对环境扰动的反应，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。使用最先进的技术来阐明生物膜的生理和基因活性，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. **