CAREER: The impact of spatial-positioning mechanisms on the metabolic interactions and emergent properties of synthetic bacterial communities

微生物构成了地球生物量的很大一部分。在大多数环境中，微生物以相互作用的群落生活。然而，关于微生物世界是如何交流、进化、共享资源以及与其他生物相互作用的，我们知之甚少。该项目将研究细菌如何在微生物群落中定位自己，与邻近细胞合作交换营养，或者从邻居那里窃取营养。这种交叉喂养相互作用影响重要的过程，包括人类健康和元素循环。交叉饲养的群落也可以用来降解污染物，并将可再生资源转化为有用的产品，如生物燃料。因此，该项目的成果将具有广泛的益处，因为它为环境和医学相关性的自然微生物相互作用提供了信息，并为细菌群落工程作为一种造福社会的技术产生了原则。这项研究将涉及地区高中生的直接参与，包括代表性不足的少数民族。通过研究小组和高中教师的合作，更多的高中生将获得研究经验，并将实验带到课堂上。该项目还将产生一个创新的讲故事平台，提供一个直观的框架，在这个框架上，所有年龄段的学习者都可以在新陈代谢和生物化学中交流细节密集、传统上不受欢迎的话题。这个项目将研究细菌如何优化它们在交叉喂养群落中的位置，使合作细胞对抗剥削（欺骗）细胞。目前的理论表明，合作细胞的聚集可以防止作弊。然而，这一理论并没有考虑到细菌用来感知和游向营养物质以及附着在表面和其他细胞上的机制。缺乏关于运动和粘附如何影响代谢相互作用和群落结构的知识不仅阻碍了我们对微生物群落行为的一般理解，而且阻碍了我们设计有用的合成群落的能力。该项目的目的是确定流动性和附着力对交叉取食群落亚种群动态的影响，以及对氢生物燃料生产等紧急特性的影响。该目标将通过实验和计算模拟社区来实现。其中一个群落会将排泄氨的合作者和消耗氨的骗子配对，这是一种单一物种，古红假单胞菌。另一个群落将palustris与大肠杆菌配对，形成专门的交叉饲养关系，其中palustris的铵与大肠杆菌的碳营养物质交换。这种互惠关系也将受到R. palustris骗子的挑战。在每种情况下，运动性和粘附性对合作者和欺骗者的适应性和社区结构的影响将由允许或限制运动性和粘附性的环境和遗传条件决定。因此，该项目将为环境、医疗和工业相关的空间细菌群落行为提供急需的分子理解。

Microbes constitute a large portion of the Earth's biomass. In the majority of environments, microbes live as interacting communities. However, not much is known regarding how microbial worlds communicate, evolve, share resources, and interact with other organisms. This project will address how bacteria position themselves within microbial communities to cooperatively trade nutrients with neighboring cells or alternatively steal nutrients from neighbors. Such cross-feeding interactions influence important processes, including human health and element cycling. Cross-feeding communities can also be harnessed to degrade pollutants and convert renewable resources into useful products, such as biofuels. The results from this project will thus have broad benefits by informing on natural microbial interactions of environmental and medical relevance and by generating principles for the engineering of bacterial communities as a technology to benefit society. This research will involve direct participation of regional high school students, including underrepresented minorities. Additional high school students will gain research experiences through a collaboration between the research team and high school teachers, which will bring experiments to classrooms. This project will also generate an innovative storytelling platform that will provide an intuitive framework upon which to communicate detail-intensive and traditionally unpopular topics in metabolism and biochemistry to learners of all ages. This project will examine how bacteria optimize their location within cross-feeding communities that pit cooperative cells against exploitive (cheater) cells. Current theory indicates that clustering of cooperative cells can keep cheaters at bay. However, this theory does not take into account mechanisms that bacteria use to sense and swim towards nutrients and to adhere to surfaces and other cells. A lack of knowledge on how motility and adhesion influence metabolic interactions and community structure hampers not only our general understanding of microbial community behavior but also our ability to design useful synthetic communities. The objective of this project is to determine the impact of motility and adhesion on subpopulation dynamics in cross-feeding communities and on emergent properties, such as hydrogen biofuel production. The objective will be achieved using both experimental and computationally-simulated communities. One community will pair ammonium-excreting cooperators and ammonium-consuming cheaters of a single species, Rhodopseudomonas palustris. A second community will pair R. palustris with Escherichia coli in an obligate cross-feeding relationship wherein ammonium from R. palustris is exchanged for carbon nutrients from E. coli. This mutualism will also be challenged with an R. palustris cheater. In each case, the effects of motility and adhesion on cooperator and cheater fitness and community structure will be determined using environmental and genetic conditions that either permit or restrict motility and adhesion. This project will thus provide a much-needed molecular understanding of spatial bacterial community behaviors of environmental, medical, and industrial relevance.