Postdoctoral Fellowship: PRFB: Mechanisms coupling photosynthesis and nitrogen fixation from molecular to ecological scales

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2025. The fellowship supports research and training of the fellow that will contribute to biology in innovative ways. Nitrogen is an important nutrient for photosynthetic plants and algae, but there is often not enough of it in natural and agricultural settings.

Only a few species of bacteria can take abundant nitrogen from the air and turn it into a form that can be used by biological life. This process is called nitrogen fixation. Because of this, most plants and algae get fixed nitrogen from their surroundings, while some form partnerships with nitrogen-fixing bacteria.

This research will study a rare case in which a nitrogen-fixing cyanobacterium has become a permanent part of an alga. It now exists as a special compartment called a “diazoplast.” Having a nitrogen-fixing compartment inside an alga creates unique challenges. The process of nitrogen fixation uses a lot of energy and cannot happen when oxygen is present.

Because of this, it must take place in a low-oxygen space. This research will help us understand the mechanisms that are necessary for the evolution of a nitrogen-fixing compartment inside a photosynthetic cell.

The diazoplast relies on metabolites from the host to fuel nitrogen fixation. The mechanisms responsible for metabolite import into the diazoplast and protection of nitrogenase, the enzyme responsible for nitrogen fixation, from O2 remain unknown. The fellow will identify and test genes of putative importance to diazoplast biology using a combination of cell-based and in vitro assays.

The fellow will employ exometabolite mass spectrometry and in vitro biochemistry assays to assess potential involvement in metabolite exchange with the host, and acetylene reduction assays in engineered E. coli and Synechocystis to assess a supportive role in nitrogen fixation, especially in the presence of O2. Finally, the fellow will use phylogenetic tree analyses and distributions of the identified genes in the TARA Oceans database to analyze the possible effects of microbial interactions and horizontal gene transfer on the evolution of these genes.

Through this project, the fellow will mentor Community College students in primary research internships. Additionally, the fellow will shadow and guest lecture for a faculty at a local Community College and in the fellow’s home state of Hawaii.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.