Bacterial physiology highlighted by the δ13C fractionation of bacteriohopanetetrol isomers

Schwartz-Narbonne, Rachel, Schaeffer, Philippe, Lengger, Sabine K., Blewett, Jerome, Jones, D. Martin, Motsch, Estelle, Crombie, Andrew, Jetten, Mike S.-M., Mikkelsen, Deirdre, Normand, Philippe, Nuijten, Guylaine H. l., Pancost, Richard D. and Rush, Darci (2023) Bacterial physiology highlighted by the δ13C fractionation of bacteriohopanetetrol isomers. Organic Geochemistry, 181. ISSN 0146-6380

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Lipid biomarkers, such as the various bacteriohopanetetrol (BHT) isomers studied here, are useful tools in tracing bacterially mediated nitrogen and carbon cycle processes affecting greenhouse gas emissions, including the anaerobic oxidation of ammonia. Three BHT isomers occur commonly in the environment. By gas chromatography, BHT-34S elutes first; it is produced by numerous bacteria. The two later eluting isomers are more constrained in their origin. The marine anammox bacteria ‘Ca. Scalindua’ is the only known producer of a BHT isomer of unknown stereochemistry (BHT-x), making BHT-x a diagnostic biomarker in anoxic marine settings. The BHT-34R isomer is produced by three freshwater aerobic heterotrophic producers (Frankia spp., Acetobacter pasteurianus, and Komagataeibacter xylinus), a freshwater serine-cycle (Type II) methanotroph (Methylocella palustris), and the freshwater anammox ‘Ca. Brocadia’, which makes the detection of freshwater anammox using BHT-34R more complicated. We investigated whether the source of BHT-34R in freshwater environments could be ascertained via its δ 13C value. We used conventional on-column gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) (as opposed to high temperature GC-C-IRMS) to determine the δ 13C composition of acetylated BHT isomers in cultured bacteria and bacterial enrichments. We combined these with bulk biomass and substrate δ 13C compositions to establish carbon isotopic fractionation factors. The two anammox genera had large fractionation factors from dissolved inorganic carbon (DIC) to biomass (Δ 13C biomass – DIC = –43.8 to –26.4 ‰) and to BHTs (Δ 13C BHT – DIC = –53.8 to –38.2 ‰), which clearly distinguished them from the freshwater aerobic heterotrophic producers (Δ 13C biomass – substrate = –2.3 to –0.1 ‰; Δ 13C BHT – substrate = –12.8 to 5.2 ‰). Methylocella assimilated mainly carbon from DIC, rather than from methane, into its biomass and BHT, and previous work suggested this assimilation comes with relatively small fractionation. Thus, in peatlands, the BHT δ 13C values of Methylocella would not reflect the low δ 13C values of biogenic methane. Consequently, the presence of BHT-34R with low δ 13C values relates to ‘Ca. Brocadia’ and presents a novel tool to trace anammox in freshwater environments.

Item Type: Article
Additional Information: Data availability: Data will be made available on request. Funding information: Funding was obtained through Natural Environment Research Council (NERC), United Kingdom project ANAMMARKS (NE/N011112/1) awarded to DR, SIAM, Netherlands 024002002 awarded to MJ. SKL was supported by Rubicon fellowship nr. 825.14.014 from the Netherlands Organization for Scientific Research (NWO), Netherlands. ATC was supported by a Leverhulme Trust Early Career Fellowship (ECF-2016-626). RSN was supported by the Community for Analytical Measurement Science through a 2021 CAMS ECR Fellowship Award funded by the Analytical Chemistry Trust Fund ( | |, as well as by the Summer Studentship scheme jointly run by the British Mass Spectrometry Society (BMSS) and the Chromatographic Society (ChromSoc), with funding provided in this instance by the Chromatographic Society, and the Royal Society of Chemistry Analytical Chemistry Trust Fund Summer Studentship scheme. The authors declare no competing financial or non-financial interests.
Uncontrolled Keywords: anammox,bacteriohopanepolyols,bacteriohopanetetrols,carbon isotopes,carbon-13,hopanoids,lipid biomarkers,methanotroph,geochemistry and petrology,sdg 14 - life below water ,/dk/atira/pure/subjectarea/asjc/1900/1906
Faculty \ School: Faculty of Science > School of Biological Sciences
Faculty of Science > School of Environmental Sciences
UEA Research Groups: Faculty of Science > Research Groups > Molecular Microbiology
Related URLs:
Depositing User: LivePure Connector
Date Deposited: 18 May 2023 11:31
Last Modified: 31 May 2023 12:31
DOI: 10.1016/j.orggeochem.2023.104617

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