Iron conservation by reduction of metalloenzyme inventories in the marine diazotroph Crocosphaera watsonii
Author(s)Saito, Mak A.; Bertrand, Erin M.; Dutkiewicz, Stephanie; Bulygin, Vladimir V.; Moran, Dawn M.; Monteiro, Fanny Meline; Follows, Michael J.; Valois, Frederica W.; Waterbury, John B.; ... Show more Show less
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The marine nitrogen fixing microorganisms (diazotrophs) are a major source of nitrogen to open ocean ecosystems and are predicted to be limited by iron in most marine environments. Here we use global and targeted proteomic analyses on a key unicellular marine diazotroph Crocosphaera watsonii to reveal large scale diel changes in its proteome, including substantial variations in concentrations of iron metalloproteins involved in nitrogen fixation and photosynthesis, as well as nocturnal flavodoxin production. The daily synthesis and degradation of enzymes in coordination with their utilization results in a lowered cellular metalloenzyme inventory that requires ~40% less iron than if these enzymes were maintained throughout the diel cycle. This strategy is energetically expensive, but appears to serve as an important adaptation for confronting the iron scarcity of the open oceans. A global numerical model of ocean circulation, biogeochemistry and ecosystems suggests that Crocosphaera’s ability to reduce its iron-metalloenzyme inventory provides two advantages: It allows Crocosphaera to inhabit regions lower in iron and allows the same iron supply to support higher Crocosphaera biomass and nitrogen fixation than if they did not have this reduced iron requirement.
DepartmentMassachusetts Institute of Technology. Center for Global Change Science; Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Proceedings of the National Academy of Sciences
National Academy of Sciences (U.S.)
Saito, M. A., E. M. Bertrand, S. Dutkiewicz, V. V. Bulygin, D. M. Moran, F. M. Monteiro, M. J. Follows, F. W. Valois, and J. B. Waterbury. “Iron Conservation by Reduction of Metalloenzyme Inventories in the Marine Diazotroph Crocosphaera Watsonii.” Proceedings of the National Academy of Sciences 108, no. 6 (January 19, 2011): 2184–2189.
Final published version