Skip to content

Research at St Andrews

Molybdenum isotope fractionation by cyanobacterial assimilation during nitrate utilization and N2 fixation

Research output: Contribution to journalArticle


Aubrey Lea Zerkle, K. Scheiderich, J. A. Maresca, L. J. Liermann, S. L. Brantley

School/Research organisations


We measured the delta 98Mo of cells and media from molybdenum (Mo) assimilation experiments with the freshwater cyanobacterium Anabaena variabilis, grown with nitrate as a nitrogen (N) source or fixing atmospheric N-2. This organism uses a Mo-based nitrate reductase during nitrate utilization and a Mo-based dinitrogenase during N-2 fixation under culture conditions here. We also demonstrate that it has a high-affinity Mo uptake system (ModABC) similar to other cyanobacteria, including marine N-2-fixing strains. Anabaena variabilis preferentially assimilated light isotopes of Mo in all experiments, resulting in fractionations of -0.2 parts per thousand to -1.0 parts per thousand +/- 0.2 parts per thousand between cells and media (epsilon(cells-media)), extending the range of biological Mo fractionations previously reported. The fractionations were internally consistent within experiments, but varied with the N source utilized and for different growth phases sampled. During growth on nitrate, A. variabilis consistently produced fractionations of -0.3 +/- 0.1 parts per thousand (mean +/- standard deviation between experiments). When fixing N-2, A. variabilis produced fractionations of -0.9 +/- 0.1 parts per thousand during exponential growth, and -0.5 +/- 0.1 parts per thousand during stationary phase. This pattern is inconsistent with a simple kinetic isotope effect associated with Mo transport, because Mo is likely transported through the ModABC uptake system under all conditions studied. We present a reaction network model for Mo isotope fractionation that demonstrates how Mo transport and storage, coordination changes during enzymatic incorporation, and the distribution of Mo inside the cell could all contribute to the total biological fractionations. Additionally, we discuss the potential importance of biologically incorporated Mo to organic matter-bound Mo in marine sediments.



Original languageEnglish
Pages (from-to)94-106
Number of pages13
Issue number1
Publication statusPublished - Jan 2011

    Research areas


Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. Anaerobic nitrogen cycling on a Neoarchean ocean margin

    Mettam, C. W., Zerkle, A. L., Claire, M., Prave, A. R., Poulton, S. W. & Junium, C. K., 1 Dec 2019, In : Earth and Planetary Science Letters. 527, 115800.

    Research output: Contribution to journalArticle

  2. Nitrates as a potential N Supply for microbial ecosystems in a hyperarid Mars analog system

    Shen, J., Zerkle, A. L., Stueeken, E. E. & Claire, M., 19 Oct 2019, In : Life. 9, 4, 20 p., 79.

    Research output: Contribution to journalArticle

  3. Ammonium availability in the Late Archaean nitrogen cycle

    Yang, J., Junium, C., Grassineau, N., Nisbet, E., Izon, G. J., Mettam, C. W., Martin, A. & Zerkle, A. L., Jul 2019, In : Nature Geoscience. 12, 7, p. 553-557 6 p.

    Research output: Contribution to journalArticle

  4. Nitrate Reduction

    Zerkle, A. L., 23 Jun 2019, Encyclopedia of Astrobiology. Gargaud, M. (ed.). Berlin, Heidelberg: Springer

    Research output: Chapter in Book/Report/Conference proceedingChapter

Related by journal

  1. Exploring cycad foliage as an archive of the isotopic composition of atmospheric nitrogen

    Kipp, M. A., Stüeken, E. E., Gehringer, M. M., Sterelny, K., Scott, J. K., Forster, P. I., Strömberg, C. A. E. & Buick, R., 26 Nov 2019, In : Geobiology. Early View

    Research output: Contribution to journalArticle

  2. Biogeochemical probing of microbial communities in a basalt-hosted hot spring at Kverkfjöll volcano, Iceland

    Cousins, C. R., Fogel, M., Bowden, R., Crawford, I., Boyce, A., Cockell, C. & Gunn, M., Sep 2018, In : Geobiology. 16, 5, p. 507-521

    Research output: Contribution to journalArticle

  3. Tracking the rise of eukaryotes to ecological dominance with zinc isotopes

    Isson, T., Love, G., Dupont, C., Reinhard, C., Zumberge, A., Asael, D., Gueguen, B., McCrow, J., Gill, B., Owens, J., Rainbird, R., Rooney, A., Zhao, M-Y., Stueeken, E. E., Konhauser, K., John, S., Lyons, T. & Planavsky, N., Jul 2018, In : Geobiology. 16, 4, p. 341-352

    Research output: Contribution to journalArticle

  4. Environmental niches and metabolic diversity in Neoarchean lakes

    Stueeken, E. E., Buick, R., Anderson, R. E., Baross, J. A., Planavsky, N. J. & Lyons, T. W., Nov 2017, In : Geobiology. 15, 6, p. 767-783

    Research output: Contribution to journalArticle

  5. Sulphur cycling in a Neoarchean microbial mat

    Meyer, N. R., Zerkle, A. L. & Fike, D. A., May 2017, In : Geobiology. 15, 13, p. 353-365 13 p.

    Research output: Contribution to journalArticle

ID: 51056618