EGU21-8486, updated on 14 Jun 2023
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

δ13C compositions of bacteriohopanetrol isomers reveal bacterial processes involved in the carbon cycle

Rachel Schwartz-Narbonne1,2, Philippe Schaeffer3, Sabine Lengger4,5, Jerome Blewett4, D. Martin Jones1, Estelle Motsch3, Alex Charlton1, Andrew Crombie6, Scott Hardy2, Muhammad Farhan Ul Haquee7,8, Mike S. M. Jetten9, Deirdre Mikkelsen10, Philippe Normand11, Guylaine H. L. Nuijten9, and Darci Rush1,12
Rachel Schwartz-Narbonne et al.
  • 1School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom of Great Britain – England, Scotland, Wales
  • 2Sheffield Hallam University, Biomolecular Sciences Research Center, Sheffield, United Kingdom of Great Britain – England, Scotland, Wales
  • 3CNRS, Université de Strasbourg, Strasbourg, France
  • 4Organic Geochemistry Unit, University of Bristol, Bristol, United Kingdom of Great Britain – England, Scotland, Wales
  • 5Biogeochemistry Research Centre, University of Plymouth, Plymouth, United Kingdom of Great Britain – England, Scotland, Wales
  • 6School of Biological Science, University of East Anglia, Norwich, United Kingdom of Great Britain – England, Scotland, Wales
  • 7School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom of Great Britain – England, Scotland, Wales
  • 8School of Biological Sciences, University of the Punjab, Lahore, Pakistan
  • 9Department of Microbiology, Radboud University, Nijmegen, the Netherlands
  • 10School of Agriculture and Food Sciences, The University of Queensland, Brisbane Australia
  • 11Ecologie Microbienne, Université de Lyon, Lyon, France
  • 12Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands

Bacteria play key roles in the carbon cycle. In many sediments and peatlands, methanotrophic bacteria consume a portion of released methane, reducing the emissions of this potent greenhouse gas. In marine oxygen minimum zones (OMZ) and other anoxic settings, anaerobic ammonium oxidizing (anammox) bacteria remove bioavailable nitrogen while performing chemoautotrophic carbon fixation. Methanotrophic and anammox bacteria synthesize a wide number of complex bacteriohopanepolyols (BHPs), comprising notably several stereoisomers of bacteriohopanetetrols (BHT), which are used as biomarker lipids.  While BHT-17β(H), 21β(H), 22R, 32R, 33R, 34S (BHT-34S) is ubiquitous in the environment, its 34R stereoisomer (BHT-17β(H), 21β(H), 22R, 32R, 33R, 34R; BHT-34R) has only five known producers: the freshwater anammox genera ‘Candidatus Brocadia’, the aerobic acidic peatland methanotroph Methylocella palustris, the nitrogen-fixing aerobic bacteria Frankia spp., and the aerobic acetic acid-producing bacteria Acetobacter pasteurianus and Komagataeibacter xylinus. BHT-x—another BHT isomer of unknown stereochemistry—has only one known producer, the marine anammox bacteria ‘Candidatus Scalindua’ (Schwartz-Narbonne et al., 2020). The occurrence and extent of these different carbon cycle processes can be assessed by measuring the concentrations of these BHT stereoisomers and changes in their δ13C values (Hemingway et al., 2018; Lengger et al., 2019).However, the 13C fractionation associated with the different carbon assimilation pathways of these bacteria has been minimally assessed, resulting in poorly constrained ranges in δ13C values and difficulty in interpreting isotope results.

We used a gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) method to measure the δ13C of BHT-34S, BHT34R, and BHT-x of cultured bacteria (‘Ca. Scalindua’, ‘Ca. Brocadia’, Methylocella tundrae, Frankia spp., and Komagataeibacter xylinus). These δ13C values were combined with bulk isotopic measurements of the bacterial biomass and δ13C analyses of the bacterial growth substrates to establish carbon isotopic fractionation from substrate to biomass to BHT lipid. We demonstrated that bacteria using different metabolic pathways produced distinct fractionation factors between substrate and BHTs, which potentially allows for distinguishing BHT-34R produced by ‘Ca. Brocadia’ and methanotrophs from other freshwater producers (e.g. in peatlands). Measurement of BHT-specific fractionation factors allowed us to better constrain the contribution of anammox bacteria to fixed carbon in OMZ. This work expands the application of BHT isomers to isotopically identify carbon cycle processes.



Hemingway, Jordon D., et al. "A novel method to measure the 13C composition of intact bacteriohopanepolyols." Organic Geochemistry 123 (2018): 144-147.

Lengger, Sabine K., et al. "Dark carbon fixation in the Arabian Sea oxygen minimum zone contributes to sedimentary organic carbon (SOM)." Global Biogeochemical Cycles 33.12 (2019): 1715-1732.

Schwartz-Narbonne, Rachel, et al. "A unique bacteriohopanetetrol stereoisomer of marine anammox." Organic Geochemistry (2020): 103994.

How to cite: Schwartz-Narbonne, R., Schaeffer, P., Lengger, S., Blewett, J., Jones, D. M., Motsch, E., Charlton, A., Crombie, A., Hardy, S., Haquee, M. F. U., Jetten, M. S. M., Mikkelsen, D., Normand, P., Nuijten, G. H. L., and Rush, D.: δ13C compositions of bacteriohopanetrol isomers reveal bacterial processes involved in the carbon cycle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8486,, 2021.