The ocean’s surface waters are inhabited by a diverse mixture of plankton that drift with tides and currents. Photosynthetic phytoplankton are key components of life on earth: they are at the base of marine food webs and generate half the oxygen on earth. The bacterioplankton are equally important as they break down detritus and release the nutrients for phytoplankton to use. The interactions of phyto- and bacterio-plankton are critical for food webs and productivity in the oceans and yet, we have very little insight into exactly how these two key groups interact. This project will take a critical look at the small-scale interactions of phyto- and bacterio-plankton. We will develop new tools for examining the microscale interactions of these two groups in nature. We will also take members of each group into the lab and grow them together under a variety of conditions to determine if, how and when they benefit from each other, particularly when living in close contact. The outcomes of this project will lead to new insights into the kinds of relationships that are formed by these two key groups and how those relationships help to support healthy marine food webs.
Specifically, we examine microscale energetic and molecular interactions between heterotrophic bacteria and the marine algae by integrating a model system with environmental observations. The three major goals for this study are to (1) Examine changes in growth rate for culturable bacteria and the alga Thalassiosira rotula separately and in co-culture, determining how interactions alter with nutrient limitation and how the energetic costs/ advantages of bacterial motility change in the presence of algae, (2) Develop the novel technique of phycosphere-associated cell sorting to extend these results to natural communities and to determine if the algal phycosphere exerts a selective pressure on bacterial phylotypes, and (3) Examine algal-bacterial interactions through gene expression studies under a range of nutrient conditions. This research will contribute to a more fundamental understanding of the interactions, dynamics, and physiologies of these two dominant players in microbial oceanography in the ocean’s surface waters: heterotrophic bacteria and phytoplankton.
Grant Announcement: “Moore Foundation Awards $774K for Study of Marine Ecology at Microbial Scale”