Control of Stability of Shewanella oneidensis MR-1 Biofilms

人们认为，自然界中的大多数微生物存在于生物膜中，这些生物膜在几乎任何水界面的生物或非生物表面上发育。这些表面相关的、结构化的微生物群落具有医学和环境重要性。成熟生物膜的稳定性和弹性是由两个相互关联的细胞过程控制的：附着和脱离。然而，分离和附着的潜在分子机制在很大程度上是未知的。该项目探索了对分离/依恋过程的生理、遗传和生化理解的第一步。希瓦氏菌（Shewanella oneidensis） MR-1是一种重要的地球化学微生物，它与生物膜中含铁和含锰的土壤矿物质进行代谢相互作用，可作为这些研究的模式微生物。多层方法涉及分离的生理学研究，包括能量和细胞混合实验。这项研究的预期结果应该为微生物脱离生物膜的分子机制提供基本的见解。虽然过去已经研究了生物膜形成的初始过程，但控制已建立的生物膜的稳定性及其长期存活的重要问题尚未得到解决。这些研究将揭示决定生物膜稳定性的一些重要的生理、机制和遗传原理。更广泛的影响这项研究将产生微生物生物膜生物学的基础知识，并教育研究生和本科生以及更广泛的社区。这个实验室有吸引和留住少数民族的记录（实验室70%是女性，33%是少数民族）。PI每年教授三门环境微生物学课程，包括一门新的大二研讨会“环境与人类健康”。整个实验室的活动在几个层面上产生了更广泛的影响。PI在过去四年中担任马萨诸塞州伍兹霍尔MBL“微生物多样性课程”的联合主任；2003/04年担任NRC/NAS“未来使用和生产氢的替代方案和战略”委员会成员；PI是Sound Vision制作《DNA档案》的科学顾问委员会成员；自2000年起担任斯坦福生物膜研究中心主任，自2002年起担任年度“西海岸细菌生理学家会议”的共同组织者。自2003年起担任斯坦福大学环境工程与科学项目协调员。此外，自2004年秋季以来，该实验室一直在与圣何塞技术博物馆合作，建立一个关于“自然界中的微生物及其在水处理中的作用”的展览单元。该实验室的成员在“Synopsys硅谷科技冠军赛”、“女孩为改变”活动中担任评委，并在东帕洛阿尔托高中辅导学生。诸如此类的活动将在当前项目中继续进行。本研究旨在从生理学和分子生物学的角度理解微生物的附着、分离以及两种状态之间的过渡，并以一叶草为模型系统。此外，研究结果也将为应用环境和医学领域对微生物生物膜进行管理提供有益的依据。例如，通常需要防止或控制有利于废水和地下水处理的生物膜的溶解，而管道、船舶的腐蚀以及牙齿（龋齿）、龈下袋和导管上医学上有害的生物膜的形成可以通过工程操纵微生物脱离生理学来减轻（或防止）。因此，本研究不仅具有基础意义，而且具有应用意义。

Intellectual MeritMost microbes in nature are believed to exist in biofilms that develop on biotic or abiotic surfaces at almost any aqueous interface. These surface-associated, structured microbial communities are of medical and environmental importance. Stability and resilience of mature biofilms is controlled by two interrelated cellular processes: attachment and detachment. However, the underlying molecular mechanism(s) of detachment and attachment are largely unknown. This project explores the first steps towards a physiological, genetic and biochemical understanding of the detachment/attachment processes. Shewanella oneidensis MR-1, a geochemically important microbe that metabolically interacts with Fe- and Mn-containing soil minerals in biofilms serves as model microbe for these studies. The multi-tiered approach involves physiological studies on detachment including energetic and cell mixing experiments. The results expected from this research should provide fundamental insights into the molecular mechanism(s) of microbial detachment from biofilms. While the initial processes of biofilm formation have been investigated in the past, the important questions of the control of stability of established biofilms and their long-term survival have not been addressed. These studies will reveal some important physiological, mechanistic, and genetic principles of determining biofilm stability.Broader ImpactThis research will generate fundamental knowledge on the biology of microbial biofilms and educate graduate and undergraduate students and the broader community. This laboratory has a record of attracting and retaining minorities (70% of the lab are female, 33% ethnic minority). The PI teaches on an annual basis three courses in Environmental Microbiology including a new sophomore seminar on "Environment and Human Health." The broader impact of the activities of the entire lab is on several levels. The PI served for the last four years as co-director of the MBL "Microbial Diversity Course" in Woods Hole, MA; served 2003/04 as a member on the NRC/NAS committee on "Alternatives and Strategies for Future Use and Production of Hydrogen"; the PI has been on the scientific advisory board of Sound Vision for the production of "The DNA Files"; has served since 2000 as the director of the Stanford Biofilm Research Center, since 2002 as co-organizer of the annual "West Coast Bacterial Physiologists' Meeting", Asilomar, CA; and since 2003 as the program coordinator of Stanford's Environmental Engineering and Science Program. In addition, since the fall of 2004, this laboratory has been working with the San Jose Museum of Technology to establish an exhibition module on "Microbes in Nature and their Role in Water Treatment". Members of this laboratory have been active as judges in the "Synopsys Silicon Valley Science and Technology Championship", in "Girls for a Change", and in tutoring East Palo Alto High School students. Activities such as these will continue throughout the current project.Expected significance of proposed researchThis research seeks to provide a physiological and molecular understanding of microbial attachment, detachment, and the transitioning between both states using S. oneidensis as a model system. In addition, the results will also serve as a useful basis for the applied environmental and medical fields to manage microbial biofilms. For example, the dissolution of biofilms beneficial for wastewater and groundwater treatment often needs to be prevented or controlled, whereas corrosion of pipes, ships, as well as formation of medically detrimental biofilms on teeth (caries), subgingival pockets, and catheters could be mitigated (or prevented) by engineered manipulation of the microbial detachment physiology. Therefore, this research is not only of fundamental but also applied relevance.