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Effects of temperature and carbon source on the isotopic fractionations associated with O_2 respiration for ^(17)O/^(16)O and ^(18)O/^(16)O ratios in E. coli

Stolper, Daniel A. and Fischer, Woodward W. and Bender, Michael L. (2018) Effects of temperature and carbon source on the isotopic fractionations associated with O_2 respiration for ^(17)O/^(16)O and ^(18)O/^(16)O ratios in E. coli. Geochimica et Cosmochimica Acta, 240 . pp. 152-172. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20180810-091418004

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Abstract

^(18)O/^(16)O and ^(17)O/^(16)O ratios of atmospheric and dissolved oceanic O_2 are used as biogeochemical tracers of photosynthesis and respiration. Critical to this approach is a quantitative understanding of the isotopic fractionations associated with production, consumption, and transport of O_2 in the ocean both at the surface and at depth. We made measurements of isotopic fractionations associated with O_2 respiration by E. coli. Our study included wild-type strains and mutants with only a single respiratory O_2 reductase in their electron transport chains (either a heme-copper oxygen reductase or a bd oxygen reductase). We tested two common assumptions made in interpretations of O_2 isotope variations and in isotope-enabled models of the O_2 cycle: (i) laboratory-measured respiratory ^(18)O/^(16)O isotopic fractionation factors (^(18)α) of microorganisms are independent of environmental and experimental conditions including temperature, carbon source, and growth rate; And (ii) the respiratory ‘mass law’ exponent, θ, between ^(18)O/^(16)O and ^(17)O/^(16)O, ^(17)α = (^(18)α)^θ, is universal for aerobic respiration. Results demonstrated that experimental temperatures have an effect on both ^(18)α and θ for aerobic respiration. Specifically, lowering temperatures from 37 to 15 °C decreased the absolute magnitude of ^(18)α by 0.0025 (2.5‰), and caused the mass law slope to decrease by 0.005. We propose a possible biochemical basis for these variations using a model of O_2 reduction that incorporates two isotopically discriminating steps: the reversible binding and unbinding of O_2 to a terminal reductase, and the irreversible reduction of that O_2 to water. Finally, we cast our results in a one-dimensional isopycnal reaction-advection-diffusion model, which demonstrates that enigmatic δ^(18)O and Δ^(17)O variations of dissolved O_2 in the dark ocean can be understood by invoking the observed temperature dependence of these isotope effects.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.gca.2018.07.039DOIArticle
ORCID:
AuthorORCID
Stolper, Daniel A.0000-0003-3299-3177
Fischer, Woodward W.0000-0002-8836-3054
Alternate Title:Effects of temperature and carbon source on the isotopic fractionations associated with O2 respiration for 17O/16O and 18O/16O ratios in E. coli
Additional Information:© 2018 Elsevier Ltd. Received 8 March 2018, Accepted 28 July 2018, Available online 10 August 2018. DAS acknowledges funding from a NOAA C&GC postdoctoral fellowship. WWF acknowledges support from the David and Lucile Packard Foundation. We thank J Hemp for providing E. coli mutant strains, and S Kopf for providing us with E. coli NCM and the trace-metal solution. We thank D Sigman, S Kopf, and F Morel for helpful discussions.
Funders:
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)UNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20180810-091418004
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180810-091418004
Official Citation:Daniel A. Stolper, Woodward W. Fischer, Michael L. Bender, Effects of temperature and carbon source on the isotopic fractionations associated with O2 respiration for 17O/16O and 18O/16O ratios in E. coli, Geochimica et Cosmochimica Acta, Volume 240, 2018, Pages 152-172, ISSN 0016-7037, https://doi.org/10.1016/j.gca.2018.07.039. (http://www.sciencedirect.com/science/article/pii/S0016703718304253)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88744
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Aug 2018 16:22
Last Modified:03 Oct 2019 20:09

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