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.
