@article{13256a4af79a44178aeb7f129121b7f7,
title = "Biochemical Barriers on the Path to Ocean Anoxia?",
abstract = "The kinetics of microbial respiration suggests that, if excess organic matter is present, oxygen should fall to nanomolar levels in the range of the Michaelis-Menten constants (Km). Yet even in many biologically productive coastal regions, lowest observed O2 concentrations often remain several orders of magnitude higher than respiratory Km values. We propose the hypoxic barrier hypothesis (HBH) to explain this apparent discrepancy. The HBH postulates that oxidative enzymes involved in organic matter catabolism are kinetically limited by O2 at concentrations far higher than the thresholds for respiration. We found support for the HBH in a meta-analysis of 1,137 O2 Km values reported in the literature: the median value for terminal respiratory oxidases was 350nM, but for other oxidase types, the median value was 67mM. The HBH directs our attention to the kinetic properties of an important class of oxygen-dependent reactions that could help explain the trajectories of ocean ecosystems experiencing O2 stress.",
keywords = "Dissolved organic matter, Dissolved organic matter, Ocean respiration, Ocean respiration, Oxygen minimum zones, Oxygenase K",
author = "Stephen Giovannoni and Francis Chan and Edward Davis and Curtis Deutsch and Sarah Wolf",
note = "Funding Information: We thank the reviewers, John Coates and Dave Valentine, for their many useful comments. John Coates offered the important insight that intracellular competition with respiratory oxygenases could contribute to the inhibition of nonrespiratory oxygenases. We are grateful to Adam Schneiderhan for his contributions to early discussions. This work was funded by the National Science Foundation grant DEB-1639033, National Oceanic and Atmospheric Administration (NOAA) grant NA18NOS4780169, a SciRIS award from the Oregon State University College of Science, and a grant from Simons Foundation International. We declare no real or perceived financial conflicts of interest. Funding Information: This work was funded by the National Science Foundation grant DEB-1639033, National Oceanic and Atmospheric Administration (NOAA) grant NA18NOS4780169, a SciRIS award from the Oregon State University College of Science, and a grant from Simons Foundation International. We declare no real or perceived financial conflicts of interest. Publisher Copyright: Copyright {\textcopyright} 2021 Giovannoni et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.",
year = "2021",
month = aug,
day = "1",
doi = "10.1128/mBio.01332-21",
language = "English (US)",
volume = "12",
journal = "mBio",
issn = "2161-2129",
publisher = "American Society for Microbiology",
number = "4",
}