The Influence of Quorum Sensing and Flow on the Organization of Biofilm Streamers

生物膜是广泛存在于自然界和技术领域的复杂生命系统。例如，生物膜在溪流和湖泊的水净化、矿物加工过程中的环境质量（如矿山排水）、制造过程的质量控制等方面发挥着关键作用。因此，了解生物膜的结构和发育特征具有广泛的意义。在最简单的表征中，生物膜是细菌和聚合物（细胞外基质）的聚集体，它们通常直接附着在表面上。因此，生物膜通常被认为是扁平的细胞垫。然而，在一些系统中已经观察到丝状生物膜或细菌流线，它们附着在表面上，但具有线状结构延伸成流。人们对这些细菌流带的详细结构，以及它们是如何形成和成熟的知之甚少。在大多数被研究的细菌物种中，适当的生物膜形成依赖于群体感应，这是一种细菌细胞间通信的过程，依赖于被称为自诱导剂的信号分子的产生、释放和群体范围内的检测。由于群体感应涉及可扩散分子，因此气流应通过其对扩散和对流过程的影响显著影响各种生化和生物物理过程。此外，与群体感应和进化稳定性相关的一个重要问题是群体感应和细胞外聚合物生产如何在“作弊”细胞的出现中存活下来，这些“作弊”细胞感知但不产生信号。因此，本项目将研究生物膜飘带的生物物理、机械和物理化学特征，这些特征与流体相互作用的方式，以及群体感应（对细菌行为和发育至关重要）如何与流体相互作用，形成和组织飘带。项目团队结合了工程、分子生物学和物理学方面的专业知识，研究将为生物膜飘带的物理学和微生物学提供信息，并将这两个学科结合起来。更广泛的影响：除了在涵盖生物学、工程学和物理学的期刊上发表他们的研究成果外，项目团队还将继续开展多方面的外展活动，包括接待来自不同学科和教育机构的访客，让本科生参与研究并在会议上发表演讲，为本科生、研究生和博士后同事领导专业发展活动。并参与为来自代表性不足群体的年轻研究人员提供指导的项目。此外，团队成员在过去9年中成功地将研究主题融入了他们为孩子和家长所做的“假日”讲座中，并将继续共同开发和呈现。这项研究将对我们对流动中的细菌群落的理解产生直接影响，这在食品加工、水处理、农业管理和其他生物质存在于流动系统的环境中具有广泛的兴趣。

Biofilms are complex living systems that are widespread in nature and technology. For example, biofilms play critical roles in water purification in streams and lakes, environmental quality during mineral processing (e.g. mine drainage), quality control of manufacturing processes, etc. Thus, understanding the structural and developmental features of biofilms has broad implications. In the simplest characterization, biofilms are aggregates of bacteria and polymer (the extracellular matrix), and they are commonly found directly attached to surfaces. Hence, biofilms are generally regarded as flat mats of cells. Nevertheless, filamentous biofilms, or bacterial streamers, that are attached to surfaces but with thread-like structures extending into a flow, have been observed in some systems. Little is known about the detailed structure of these bacterial streamers, or how they form and mature. In most bacterial species studied, proper biofilm formation relies on quorum sensing, a process of bacterial cell-cell communication that depends on the production, release, and population-wide detection of signal molecules called autoinducers. Since quorum sensing involves diffusible molecules, a flow should significantly impact various biochemical and biophysical processes through its impact on diffusion and convection processes. Moreover, one of the important questions relevant to quorum sensing and evolutionary stability is how quorum sensing and extracellular polymer production survive the emergence of "cheater" cells that sense but do not produce a signal. Therefore, this project will address the biophysical, mechanical and physicochemical features of biofilm streamers, the way these characteristics interact with a flow, and how quorum sensing, which is critical to bacterial behavior and development, interacts with the flow to form and organize the streamers. The project team combines expertise in engineering, molecular biology, and physics and the research will inform both the physics and microbiology of biofilm streamers, and the coupling of the two subjects.Broader impacts:, In addition to publishing their findings in journals that span biology, engineering, and physics, the project team will continue their multi-faceted outreach activities, including hosting visitors from different disciplines and educational institutions, engaging undergraduate students in research and giving talks at conferences, leading professional development activities for undergraduate, graduate, and postdoctoral colleagues, and participating in mentoring programs for young researchers from under-represented groups. Also, members of the team have successfully incorporated research themes into "holiday" lectures for children and parents that they have given over the past 9 years and which they will jointly continue to develop and present. This research will have a direct impact on our understanding of bacterial communities in flow, which is of widespread interest in food processing, water treatment, agricultural management, and other settings where biomass is present in flowing systems.