Homeostasis of Prokaryotes in Natural Environments

磷是生物体中最丰富的元素之一，但在地球表面并不丰富。科学家和医学从业者对生物需要多少磷有一个大致的概念，但他们并不真正知道多少磷是太少，多少是太多。当这种基本元素过多或过少时，生物体、群落和生态系统如何发生根本性变化？这是一个重要的问题，因为在过去的世纪里，人类已经用过量的磷和氮使陆地和水生生态系统肥沃。另一方面，生物如何应对环境中缺乏磷的问题？有机体是否能够用砷（一种通常被认为有毒的元素）代替磷？这些问题的答案对于理解生命如何在早期地球上相对贫磷的世界中起源和进化具有重要意义。拟议的研究的目标是了解生物体如何调节其生物量磷组成的环境中，磷的可用性极高，极低和/或极其可变。能够储存过量的磷有多重要，能够用更少的磷“凑合”有多重要？这些问题将通过研究从受农业影响的上中西部湖泊中分离出来的细菌来检验。核心假设是，富磷环境选择生长迅速且不能改变其所需磷量的细菌，而贫磷环境选择生长缓慢且可以改变其所需磷量的细菌。这两种细菌的能力也将被检查，看看它们是否可以取代砷磷。当这两种细菌的“味道”都存在于环境中时会发生什么，这对它们的群落和生态系统中的其他生物有什么影响？更广泛的影响：这项工作将培训本科生、研究生和博士后研究员。一名研究生和博士后研究员将与PI一起研究该项目的研究重点，以及在明尼苏达州罗切斯特的马约诊所开发的转型计划，称为InSciedOut。在InSciedOut项目中，科学家直接与小学教师和学生合作，制定基于项目的科学课程。此外，该项目的细菌分离株将用于明尼苏达大学实用基因组学的新课程。外联活动将侧重于明尼苏达国际中心重大决策系列讲座的一系列讲座，重点是微生物和海洋。

Phosphorus is one of the most abundant elements in living organisms but it is not very abundant on the Earth's surface. Scientists and medical practitioners have a general idea of how much is required by living things, but they do not really know how much phosphorus is too little and how much is too much. How do organisms, communities and ecosystems fundamentally change when there is too much or too little of this essential element present? This is an important issue because for the past century, humans have fertilized both terrestrial and aquatic ecosystems with excessive quantities of phosphorus as well as nitrogen. On the other hand, how do organisms deal with a lack of phosphorus in the environment? Are organisms able to substitute arsenic, an element that is typically thought to be toxic, for phosphorus? The answers to these questions have important implications for understanding how life originated and evolved on the early Earth in a relatively phosphorus-poor world. The goal of the proposed study is to understand how organisms regulate their biomass phosphorus composition in environments where phosphorus availability is extremely high, extremely low and/or extremely variable. How important is it to be able to store excess phosphorus and how important is it to be able to 'make do' with less? These questions will be examined by studying bacteria isolated from lakes in the agriculturally impacted upper Midwest. The central hypothesis is that phosphorus-rich environments select for bacteria that grow fast and are not able to vary the amount of phosphorus they require whereas phosphorus-poor environments select for bacteria that grow slowly and can vary the amount of phosphorus they require. The ability of both of these kinds of bacteria will also be examined to see if they can substitute arsenic for phosphorus. What happens when both of these 'flavors' of bacteria are present in the environment and what are the implications of this for other organisms in their community and in ecosystems?Broader impacts: This work will train undergraduates, a graduate student and a post-doctoral fellow. A graduate student and post-doctoral fellow will work with the PI both on the research-focused aspects of this project as well as a transformational program that was developed at the Mayo Clinic in Rochester, MN called InSciedOut. In the InSciedOut program, scientists work directly with elementary school teachers and students on a project-based science curriculum. Also, the bacterial isolates from this project will be used in a new course on Practical Genomics at the University of Minnesota. Outreach activities will be focused on a set of lectures focused on microbes and the oceans for the Minnesota International Center's Great Decisions Lecture Series.