Impact of metabolism and temperature on 2H ∕ 1H fractionation in lipids of the marine bacterium Shewanella piezotolerans WP3
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Published:2023-04-14
Issue:7
Volume:20
Page:1491-1504
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Chen Xin,Zhao Weishu,Dong Liang,Jian Huahua,Liang Lewen,Wang Jing,Wang Fengping
Abstract
Abstract. Compound-specific hydrogen isotopes have increasingly been used as a powerful
proxy for investigating biogeochemical cycles and climate change over the
past 2 decades. Understanding the hydrogen isotope in extant organisms is
fundamental for us to interpret such isotope signals preserved in natural
environmental samples. Here, we studied the controls on hydrogen isotope
fractionation between fatty acids and growth water by an Fe-reducing
heterotrophic marine bacterium Shewanella piezotolerans WP3 growing on different organic substrates,
including N-acetyl-D-glucosamine (GlcNac), glucose, acetate, pyruvate,
L-alanine, and L-glutamate. Meanwhile, we also evaluated the impact of growth
temperature on the hydrogen isotope composition of fatty acids using GlcNac
as the sole organic substrate. Our results show that the abundance-weighted mean
fatty-acid / water fractionations (εFA/water) display
considerable variations for cultures grown on different substrates.
Specifically, WP3 yielded the most 2H-enriched fatty acids growing on
L-glutamate and pyruvate with an εFA/water of 52 ± 14 ‰ and 44 ± 4 ‰, respectively,
and exhibited 2H depletion using GlcNac (−76 ± 1 ‰) and glucose (−67 ± 35 ‰)
as sole carbon sources and relatively small fractionations on acetate (23 ± 3 ‰) and L-alanine (−4 ± 9 ‰). Combined with metabolic model analysis, our
results indicate that the central metabolic pathways exert a fundamental
effect on the hydrogen isotope composition of fatty acids in heterotrophs.
Temperature also has an obvious influence on the δ2H values of
fatty acids, with strong 2H depletion at an optimal growth temperature
(−23 ± 2 ‰ and −23 ‰ growing at
15 and 20 ∘C, respectively) and relatively small
fractionations at non-optimal temperatures (4 ± 5 ‰, −4 ± 12 ‰, and 15 ± 41 ‰ at 4, 10, and 25 ∘C,
respectively). We hypothesized that this may be associated with
temperature-induced enzyme activity for nicotinamide adenine dinucleotide phosphate (NADPH) production. This study helps understand the controlling factors of hydrogen isotope fractionation by
marine bacteria, laying the foundation for further interpreting the hydrogen
isotope signatures of lipids as an important proxy to decode the
biogeochemical cycles and ecological changes in marine sediments.
Funder
National Natural Science Foundation of China China Postdoctoral Science Foundation Shanghai Jiao Tong University National Key Research and Development Program of China
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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