Protection of nitrogenase from photosynthetic O2 evolution in Trichodesmium: methodological pitfalls and advances over 30 years of research.

The Trichodesmium genus comprises some of the most abundant N₂-fixing organisms in oligotrophic marine ecosystems. Since nitrogenase, the key enzyme for N₂ fixation, is irreversibly inhibited upon O₂ exposure, these organisms have to coordinate their N₂-fixing ability with simultaneous photosynthetic O₂ production. Although being the principal object of many laboratory and field studies, the overall process of how Trichodesmium reconciles these two mutually exclusive processes remains unresolved. This is in part due to contradictory results that fuel the Trichodesmium enigma. In this review, we sift through methodological details that could potentially explain the discrepancy between findings related to Trichodesmium's physiology. In doing so, we exhaustively contrast studies concerning both spatial and temporal nitrogenase protective strategies, with particular attention to more recent insights. Finally, we suggest new experimental approaches for solving the complex orchestration of N₂ fixation and photosynthesis in Trichodesmium.