The importance of surface-active metabolites (biosurfactants) in bacterial social behaviours

在它们的自然生态系统中，细菌作为微生物群落存在，在那里它们利用细胞间相互作用和通信的复杂系统来适应不断变化的环境条件。细菌作为社会有机体的概念正在深刻地改变我们对微生物学的看法。** 生物膜是细菌在自然环境中生长的首选模式，也是微生物群落的最佳研究实例，有助于细菌在不利条件下生存。生物膜在生物技术和医学领域的重要性日益明显。**«群集运动»，一种对鞭毛细菌的社会行为知之甚少，被认为与鉴定涉及多细胞活动的基因和机制有关。铜绿假单胞菌是社会微生物学研究中研究最广泛的细菌物种。我们先前已经揭示了铜绿假单胞菌的群集运动、生物膜形成和细胞间通讯的一些机制。此外，我们还广泛研究了细胞外润湿和趋化剂（称为鼠李糖脂）的产生，这是独特的群集表型所需的特殊细菌特征。我们最近已经确定了一个混合感觉系统，是正常的群集运动的关键，这是独立的鼠李糖脂生产。值得注意的是，这种感觉系统似乎参与介导群集运动和生物膜发育的表达，特别是通过检测表面。因为生活在表面上的细菌与群集细菌有几个共同的特征，我们假设群集运动反映了生物膜发展的基本方面。两个主要的工作假设将推动这一社会微生物学研究：（1）鼠李糖脂作为一种机制，促进细菌扩散/生态系统定植。我们的初步结果表明，限制生长条件促进了鼠李糖脂的产生，从而支持了新生态位的分散/增强定植的益处，（2）专门响应表面上生长的特定感觉通路调节了群集运动所需的调节机制。这项拟议的研究项目旨在通过研究群集运动作为微生物社会行为的模型，进一步提高我们对细菌多细胞功能的理解。我们正在使用一种多方面的方法，主要基于微生物生理学功能基因组学和化学生物学的结合，以深入了解群集运动并确定其意义。知识的获得也有助于揭示控制细菌生物膜建立的途径。

In their natural ecosystems, bacteria persist as microbial communities, where they exploit elaborate systems of intercellular interaction and communication to adapt to changing environmental conditions. The concept of bacteria as social organisms is profoundly altering our views of microbiology. ******Biofilms, the preferred modes of growth of bacteria in the natural environment and the best-studied examples of microbial communities, help bacteria to survive under unfavourable conditions. The importance of biofilms in the biotechnological and medical fields is increasingly evident. ******«Swarming motility», a poorly understood social behaviour of flagellated bacteria is believed to be relevant to the identification of genes and mechanisms involved in multicellular activities. The ubiquitous and extremely versatile Pseudomonas aeruginosa is the most widely studied bacterial species in sociomicrobiology research. We have previously revealed a number of mechanisms involved in swarming motility, biofilm formation and intercellular communication in P. aeruginosa. Furthermore, we have extensively investigated the production of extracellular wetting and chemotactic agents called rhamnolipids, a special bacterial feature required for the unique swarming phenotype.******We have recently identified an hybrid sensory system that is key to normal swarming motility, and that is independent of rhamnolipid production. Significantly, this sensory system appears involved in mediating the expression of swarming motility and biofilm development specifically by detection of surfaces.******Because bacteria living on a surface share several features with swarming bacteria, we hypothesize that swarming motility reflects fundamental aspects of biofilm development. Two principal working hypotheses will drive this sociomicrobiology investigation: (1) rhamnolipids function as a mechanism promoting bacteria dispersal/ecosystem colonization. Our preliminary results suggest that production of rhamnolipids is promoted by restricting growth conditions, thus supporting the benefit of dispersion/enhanced colonization of new niches, (2) Specific sensory pathways specially responding to growth on a surface modulate the regulatory mechanisms required for swarming motility.******This proposed research project aims at further improve our understanding of the multicellular functions of bacteria through the study of swarming motility as a model microbial social behaviour. We are using a multi-faceted approach, primarily based on a combination of microbial physiology functional genomics, and chemical biology, to gain insight into swarming motility and determine its significance. Knowledge gain also contributes to reveal avenues to control the establishment of bacterial biofilms.