Identification of photoheterotrophic microorganisms in temperate freshwater lakes

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Fuelled by solar energy and performed by microscopic algae, or phytoplankton, photosynthesis is the primary source of productivity in aquatic ecosystems. However, recent studies suggest that microorganisms with previously unknown capabilities for harnessing solar energy, the so-called photoheterotrophs, are abundant in the oceans and are present in freshwater ecosystems as well. In contrast to algae, which completely depend on chlorophyll-based photosynthesis for their growth, photoheterotrophs use pigments called rhodopsins and bacteriochlorophylls to convert solar energy into a food supplement to their predominant diet of ingested organic matter. The aim of this project is to discover, describe, and document the predominant organisms that make up this unusual group of phytoplankton in temperate freshwater lakes. Due to their light-harvesting capacity and amenability to genetic engineering, photoheterotrophs may be useful in future bioenergy production systems. Research results will provide baseline information for freshwater phytoplankton bioprospecting, in a search for potentially useful microorganisms. The broader impacts of this work also include further development of cutting-edge research technologies, such as the study of a complete genome of a single cell, infrared epifluorescence microscopy for visualizing phytoplankton, and fluorescence-activated cell sorting to isolate and study phytoplankton cells for experiments. One postdoctoral associate and up to three undergraduate students will be trained during the course of the project, with particular effort placed on recruiting Native American students. Wide dissemination of research results will be achieved by workshops and advanced courses to the scientific community, as well as through diverse outreach activities to the general public.