Progress in the nitrogen fixation strategy of Trichodesmium

Abstract:

Tricodesmium, a genus of nitrogen-fixing cyanobacteria, is the most abundant nitrogen-fixing microorganisms in the ocean. They contribute about 42% of marine biological nitrogen fixation and provide a new source of nitrogen to marine ecosystems, driving marine primary productivity and biogeochemical cycles. As a major contributor of new nitrogen in the ocean, Tricodesmium is a group of filamentous nitrogen-fixing cyanobacteria that do not produce heterocysts. Because nitrogenase, the key enzyme of biological nitrogen fixation, is sensitive to oxygen, nitrogen-fixing cyanobacteria usually produce heterocysts or fix nitrogen at night to avoid the inhibitory effects of oxygen on nitrogen-fixing enzymes. The recent studies have discovered that Tricodesmium has a unique nitrogen fixation system, which enables the same filament to complete photosynthesis and nitrogen fixation simultaneously during the daytime and has a complex regulatory mechanism. We review the recent progress in the nitrogen fixation strategy of Tricodesmium and introduce the sophisticated regulatory mechanism between biological nitrogen fixation and photosynthesis. This review helps to deenpen our understanding of the nitrogen fixation mechanism of microorganisms, especially marine cyanobacteria.