Intra- and interspecific siderophore cheating in bacteria

该项目的目标是研究有助于维持细菌群落中铁的合作获取的机制。合作获取铁对许多微生物群落的生存至关重要，但它容易受到社会欺诈者的利用，这些人在不付出代价的情况下获得获取铁的好处。合作获取铁广泛存在于微生物群落中，包括对土壤生态、农业和医学具有重要意义的群落。这项工作将提供关于稳定这些社区的条件和情况的重要信息，以及关于如何稳定更复杂的社区的一般信息。这个项目将有助于研究生、本科生和高中生的培训和职业发展。人们已经了解了微生物合作行为的分子机制，如生物膜的形成、毒力和养分的获得。然而，直到最近，微生物学家才开始从社会进化的角度来研究这些行为。本项目的重点是研究假单胞菌中合作获取铁的进化稳定性。几种假单胞菌通过分泌吡咯烷来获得铁，这是一类结构多样化的非核糖体多肽铁载体，由同源受体内化。铜绿假单胞菌和蛋白质假单胞菌之间的种内作弊和非生产者作弊，以及两个假单胞菌和蛋白质假单胞菌之间的作弊，挑战了吡喃甲啶合作进化的稳定性，在这两种欺骗中，蛋白质假单胞菌识别前者产生的吡喃啶，反之亦然。这两个案例都涉及细胞潜在地利用合作生产的吡喃啶，这些细胞可以在不支付成本的情况下获得好处。根据初步的实验和模型数据，假设细菌的生长生理，特别是限制生长速度的营养物质的性质，以及不对称竞争，特别是吡喃佛丁受体的亲和力，是决定作弊成本和收益的两个重要因素。这些假设将通过建模和实验工作相结合的方式进行验证。建模将涉及全基因组代谢模型和动态种群增长模型。实验工作将包括在确定的营养条件下对单一和联合培养物进行批量和恒温生长，以及测量吡喃佛丁受体结合亲和力和表达水平。这些研究将为促进合作获取铁的进化稳定性的机制提供洞察力。合作获取铁和其他微生物的社会行为与自然生态系统有很大的相关性，并对社会性的进化具有普遍意义。研究生、本科生和高中生将接受微生物遗传学、生理学、生物化学、进化生物学和数学建模方面的广泛技能培训。高中生将通过俄勒冈州立大学的暑期实习项目--理工科学徒计划获得招待。

The goal of this project is to study mechanisms that help maintain cooperative iron acquisition in bacterial communities. Cooperative iron acquisition is crucial to the survival of many microbial communities, but it is vulnerable to exploitation by social cheaters that reap the benefits of iron acquisition without paying the cost. Cooperative iron acquisition is widespread in microbial communities, including communities that are important for soil ecology, agriculture, and medicine. This work will provide important information about the conditions and circumstances that stabilize such communities and general information about how more complex communities are stabilized. This project will contribute to the training and career development of students at the graduate, undergraduate and high school levels.Much has been learned about the molecular mechanisms of microbial cooperative behaviors such as biofilm formation, virulence, and nutrient acquisition. However, only recently have microbiologists also begun to investigate these behaviors from the perspective of social evolution. The focus of this project is on the evolutionary stability of cooperative iron acquisition in pseudomonads. Several Pseudomonas species acquire iron by secreting pyoverdines, a structurally diverse class of non-ribosomal peptide siderophores that are internalized by cognate receptors. The evolutionary stability of pyoverdine cooperation is challenged by intraspecific cheating between P. aeruginosa pyoverdine producers and non-producers, and by interspecific cheating between two Pseudomonas species, P. aeruginosa and P. protegens, in which the latter recognizes the pyoverdine produced by the former but not vice versa. Both cases involve the potential exploitation of cooperative pyoverdine production by cells that reap the benefits without paying the costs. Based on preliminary experimental and modeling data, it is hypothesized that bacterial growth physiology, specifically the nature of the growth-rate limiting nutrient, and asymmetric competition, specifically pyoverdine receptor affinity, are two important factors that determine the costs and benefits of cheating. These hypotheses will be tested with a combination of modeling and experimental work. Modeling will involve whole-genome metabolic models and dynamic population growth models. Experimental work will involve batch and chemostat growth of single and co-cultures under defined nutrient conditions, as well as measurements of pyoverdine receptor binding affinities and expression levels. These studies will provide insights into the mechanisms that contribute to the evolutionary stability of cooperative iron acquisition. Cooperative iron acquisition and other microbial social behaviors are of great relevance to natural ecosystems and have implications for the evolution of sociality in general. Graduate, Undergraduate and high school students will be trained in a wide range of skills in microbial genetics, physiology, biochemistry, evolutionary biology, and mathematical modeling. High school students will be hosted through the Apprenticeship for Science and Engineering, a summer internship program at Oregon State University.