Nitrifier adaptation to low energy flux controls inventory of reduced nitrogen in the dark ocean

• DOI: 10.1073/pnas.1912367117
• Publication Date: 2020-02-18T23:16:01Z
• Authors: Yao Zhang; Wei Qin; Lei Hou; Emily J. Zakem; Xianhui Wan; Zihao Zhao; Li Liu; Kristopher A. Hunt; Nianzhi Jiao; Shuh-Ji Kao; Kai Tang; Xiabing Xie; Jiaming Shen; Yufang Li; Mingming Chen; Xiaofeng Dai; Chang Liu; Wenchao Deng; Minhan Dai; Anitra E. Ingalls; David A. Stahl; Gerhard J. Herndl
• Keywords: Carbon fixation

Ammonia oxidation to nitrite and its subsequent nitrate provides energy the two populations of nitrifying chemoautotrophs in energy-starved dark ocean, driving a coupling between reduced inorganic nitrogen (N) pools production new organic carbon (C) ocean. However, relationship flux C fluxes N steps remains unclear. Here, we show that, despite orders-of-magnitude difference cell abundances ammonia oxidizers oxidizers, sustain similar bulk N-oxidation rates throughout deep waters with similarly high affinities for under increasing substrate limitation, thus maintaining overall homeostasis oceanic nitrification pathway. Our observations confirm theoretical predictions redox-informed ecosystem model. Using balances from this model, suggest that consistently low concentrations are maintained when have their loss proportional maximum growth rates. The stoichiometric relations indicate threefold fourfold higher C-fixation efficiency per mole oxidized by compared due nearly identical apparent energetic requirements fixation populations. We estimate rate chemoautotrophic amounts ∼1 × 10 13 ∼2 mol year globally through 14