Quantifying oxygen management and temperature and light dependencies of nitrogen fixation by Crocosphaera watsonii
Name
mSphere-2019-Inomura-e00531-19.full.pdf
Description
Published version
Size
2.86 MB
Format
Adobe PDF
Checksum (MD5)
a4afe4df6b4a8a6490130a7d606ce23f
Author(s)
Gauglitz, Julia M.
Follows, Michael J
Date Issued
December 2019
Journal
mSphere
Publisher
American Society for Microbiology
Citation
Inomura, Keisuke et al. “Quantifying oxygen management and temperature and light dependencies of nitrogen fixation by Crocosphaera watsonii.” mSphere 4 (2019): e00531-19 © 2019 The Author(s)
Version
Final published version
Abstract
Crocosphaera is a major dinitrogen (N2)-fixing microorganism, providing bioavailable nitrogen (N) to marine ecosystems. The N2-fixing enzyme nitrogenase is deactivated by oxygen (O2), which is abundant in marine environments. Using a cellular scale model of Crocosphaera sp. and laboratory data, we quantify the role of three O2 management strategies by Crocosphaera sp.: size adjustment, reduced O2 diffusivity, and respiratory protection. Our model predicts that Crocosphaera cells increase their size under high O2. Using transmission electron microscopy, we show that starch granules and thylakoid membranes are located near the cytoplasmic membranes, forming a barrier for O2. The model indicates a critical role for respiration in protecting the rate of N2 fixation. Moreover, the rise in respiration rates and the decline in ambient O2 with temperature strengthen this mechanism in warmer water, providing a physiological rationale for the observed niche of Crocosphaera at temperatures exceeding 20°C. Our new measurements of the sensitivity to light intensity show that the rate of N2 fixation reaches saturation at a lower light intensity (∼100 μmol m-2 s-1) than photosynthesis and that both are similarly inhibited by light intensities of 500 μmol m-2 s-1. This suggests an explanation for the maximum population of Crocosphaera occurring slightly below the ocean surface.
MIT Department
Massachusetts Institute of Technology. Department of Biology
Woods Hole Oceanographic Institution
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Terms of Use
Creative Commons Attribution 4.0 International license
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1128/mSphere.00531-19
