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

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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.