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Our Research Focus

Research in our laboratory group focuses on how microorganisms control the availability of nitrogen, a critical element in all life as we know it. Nitrogen, a major plant nutrient, is transformed from one form to another by microorganisms, and moves between habitats. A large reservoir of nitrogen on Earth resides in the air we breath: 80% of the atmosphere is nitrogen gas. Nitrogen gas, or dinitrogen (2 nitrogen atoms triple bonded together) has historically been thought to be unavailable to most organisms, in particular the eukaryotic plants and animals. Many diverse prokaryotic microorganisms have the ability to fix nitrogen from the atmosphere into a biologically available form. Biological nitrogen fixation is catalyzed by an enzyme, called nitrogenase. Since most of the microorganisms in the natural environment have yet to be cultivated, we study the microorganisms in the environment that fix nitrogen by looking for the genes and proteins involved in nitrogen fixation. And recently our work has focused more on the cultivated species, Braarudosphaera bigelowii, the first discovered eukaryotic nitrogen fixing organism. This broadly distributed species of marine eukaryotic phytoplankton contains a nitrogen-fixing organelle, or nitroplast, formerly known as UCYN-A or Candidatus Atelocyanobacterium thalassa. 

Latest Publications

Many partnerships have been formed between nitrogen-fixing microbes and carbon-fixing eukaryotes that need nitrogen to grow. The possibility of a eukaryote with a nitrogen-fixing organelle derived from endosymbiosis, which is called a nitroplast, has been speculated. Studying a marine alga with a cyanobacterial endosymbiont, Coale et al. used soft x-ray tomography to visualize cell morphology and division of the alga, revealing a coordinated cell cycle in which the endosymbiont divides and is split evenly, similar to the situation for plastids and mitochondria in these cells (see the Perspective by Massana). Proteomics revealed that a sizable fraction of the proteins in this structure are encoded by and imported from the alga, including many that are essential for biosynthesis, cell growth, and division. These results offer a fascinating view into the transition from an endosymbiont into a bona fide organelle. —Michael A. Funk


Simons Foundation
U.S. National Science Foundation
Gordon and Betty Moore Foundation
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