Cooperation and Cheating in Bacterial Quorum Sensing

细菌群体感应中的合作与作弊

• 批准号: 0843102
• 负责人: Martin Schuster
• 金额: $ 49.5万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-15 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0843102&HistoricalAwards=false
• 关键词: Cooperation; Cheating; Bacterial; Quorum; Sensing

Scientific research. There has been an explosion of research directed at understanding the mechanisms of how bacteria communicate and cooperate to perform a variety of multicellular behaviors. Not until very recently have microbiologists also begun to investigate these behaviors from the perspective of social evolution. Dr. Schuster's long-term goal is to integrate mechanistic and evolutionary approaches to investigate communication, also termed quorum sensing (QS), and cooperation in the model bacterium Pseudomonas aeruginosa. P. aeruginosa communicates via diffusible acyl-homoserine lactone (acyl-HSL) signals to coordinate the expression of hundreds of genes, many of which encode extracellular factors. Acyl-HSL QS is a widespread phenomenon in bacteria and regulates diverse group behaviors such as light production, virulence, and biofilm formation. The specific objective of this project is to conduct a comprehensive characterization of novel forms of social behavior. Initially, the focus will be on the recently discovered signal-blind obligate cheating and re-evolved cooperation phenomenon that the Schuster group identified during an experimental evolution study of P. aeruginosa. The obligate cheaters do not contribute to the production of quorum-controlled public goods because they harbor a loss-of-function mutation in the gene encoding the central QS regulator. Such mutants have been isolated from natural environments suggesting that cheaters arise also in vivo. The re-evolved cooperators emerged from cheaters are predicted to harbor mutations elsewhere in the genome that restore QS-dependent phenotypes. Very little is known about the genetic basis of such transitions from an obligate to an autonomous life style. Candidate mutations in the genome of a re-evolved cooperator point towards a novel regulatory mechanism of QS gene expression. The specific aims of this project are to (1) characterize the mutation(s) and underlying molecular mechanisms responsible for the cheater-to-cooperator conversion, (2) screen environmental P. aeruginosa isolates for the presence of social mutations and determine their frequency within the population, and (3) characterize evolutionary fitness and cooperative behavior of the cheater-turned-cooperator under social and asocial conditions. This research is relevant to the evolution of many bacteria that rely on social traits for evolutionary success, and has important implications for our understanding of the evolution of cooperative behavior across all domains of life. Educational impact. The described project provides excellent educational opportunities for students. Dr. Schuster has and will continue to train graduate and undergraduate students in the laboratory. Dr. Schuster will also provide educational opportunities for high-school students through an established program at Oregon State University. He has found that the incorporation of evolutionary concepts in the study of microbiological problems greatly enhances student curiosity and interest. Most experiments are conceptually and technically straight-forward and are particularly well suited for the engagement of high-school and undergraduate students in the scientific process.

科学研究。针对细菌如何交流和合作执行各种多细胞行为的机制的研究已经出现了爆炸性的增长。直到最近，微生物学家才开始从社会进化的角度来研究这些行为。舒斯特博士的长期目标是整合机械论和进化论的方法来研究交流，也被称为群体感应(QS)，以及在模式细菌铜绿假单胞菌中的合作。铜绿假单胞菌通过可扩散的酰基-高丝氨酸内酯(acyl-HSL)信号来协调数百个基因的表达，其中许多基因编码细胞外因子。酰基-HSL QS是细菌中普遍存在的一种现象，调节着不同的群体行为，如光产生、毒力和生物被膜的形成。这个项目的具体目标是对新的社会行为形式进行全面的表征。最初，重点将放在最近发现的信号盲强制作弊和重新进化的合作现象上，这是Schuster团队在铜绿假单胞菌的实验进化研究中发现的。专制的作弊者不会对群体控制公共产品的生产做出贡献，因为他们在编码中央QS调节器的基因中存在功能缺失突变。这样的突变体已经从自然环境中分离出来，这表明作弊者也在体内出现。从作弊者身上出现的重新进化的合作者被预测在基因组的其他地方隐藏着突变，这些突变恢复了QS依赖的表型。人们对这种从义务生活方式向自主生活方式转变的遗传基础知之甚少。重新进化的合作者基因组中的候选突变指向一种新的QS基因表达调节机制。该项目的具体目标是(1)表征由骗子向合作者转变的突变(S)和潜在的分子机制；(2)筛选环境中存在社会突变的铜绿假单胞菌菌株并确定其在种群中的频率；(3)表征从骗子转变为合作者的社会和非社会条件下的进化适应度和合作行为。这项研究与许多依赖社会特征获得进化成功的细菌的进化有关，并对我们理解生命所有领域的合作行为的进化具有重要意义。对教育的影响。所描述的项目为学生提供了极好的教育机会。舒斯特博士已经并将继续在实验室培训研究生和本科生。舒斯特博士还将通过俄勒冈州立大学的一个既定项目为高中生提供教育机会。他发现，在微生物学问题的研究中融入进化论概念，极大地提高了学生的好奇心和兴趣。大多数实验在概念上和技术上都是直截了当的，特别适合高中生和本科生参与科学过程。