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Welcome to the Zhang Geomicrobiology and Biogeochemistry Lab

The Zhang laboratory seeks to understand microbial nutrient and energy transfer in past and present environments.  Our interdisciplinary approach, which draws inspiration from culture-based microbiology, molecular microbial ecology, and stable isotope geochemistry, is imbued by strong consideration of microbial metabolism at cellular and community scales and involves research in both laboratory and field settings.

Metalloproteins are a central theme in our research as they catalyze nearly all energy transfers in biology. Despite their importance, much remains to be understood about what controls metalloprotein activity in the environment. This fundamentally limits our ability to address changes in climate, elemental cycling, and the energy landscape. We believe that viewing metalloprotein activity in the context of broader metabolic fluxes within and between cells will aid in resolving long-standing questions in microbial biogeochemistry.

Opportunities for microbe lovers at both graduate and post-doc levels are available!  Postdoc positions are available for benthic N2 fixation, methane,and alternative nitrogenase related projects.  Undergrads interested in gaining research experience should take a look at summer internships in the Zhang lab funded by the Princeton Environment Institute (see 

Please contact for more information.

Contact Information:
Princeton University, Department of Geosciences, M47 Guyot Hall, Princeton NJ 08544
Phone:  (609) 258-2489


Laboratory News

Monday, Dec 9, 2019

One of the environmental questions Zhang is exploring is why methane, a significant greenhouse gas, is increasing in the atmosphere.

Thursday, Nov 21, 2019

A huge congratulations to Dr. Shannon Haynes, who successfully completed and defended her Ph.D.

Wednesday, Sep 11, 2019

Researchers in the Zhang Lab began their...

Friday, Aug 9, 2019

Meet the Zhang Group summer interns!

Recent Publications

  • Effect of iron limitation on the isotopic composition of cellular and released fixed nitrogen in Azotobacter vinelandii

    D.L. McRose; A. Lee; S.H. Kopf; O. Baars; A.M.L. Kraepiel; D.M. Sigman; F.M.M. Morel; X. Zhang

    Most biological nitrogen transformations have characteristic kinetic isotope effects used to track these processes in modern and past environments. The isotopic fractionation associated with nitrogen fixation, the only biological source of fixed nitrogen (N), provides a particularly important constraint for studies of nitrogen cycling. Nitrogen...

  • Genetic, structural, and functional diversity of low and high-affinity siderophores in strains of nitrogen fixing: Azotobacter chroococcum

    X. Zhang; O. Baars; F. M.M. Morel

    © 2019 The Royal Society of Chemistry. To increase iron (Fe) bioavailability in surface soils, microbes secrete siderophores, chelators with widely varying Fe affinities. Strains of the soil bacterium Azotobacter chroococcum (AC), plant-growth promoting rhizobacteria used as agricultural inoculants, require high Fe concentrations for aerobic...

  • Molybdenum threshold for ecosystem-scale alternative vanadium nitrogenase activity in boreal forests

    Romain Darnajoux; Nicolas Magain; Marie Renaudin; François Lutzoni; Jean-Philippe Bellenger; Xinning Zhang

    Biological nitrogen fixation (BNF) by microorganisms associated with cryptogamic covers, such as cyanolichens and bryophytes, is a primary source of fixed nitrogen in pristine, high-latitude ecosystems. On land, low molybdenum (Mo) availability has been shown to limit BNF by the most common form of nitrogenase (Nase), which requires Mo in its...

  • Crochelins: Siderophores with an Unprecedented Iron-Chelating Moiety from the Nitrogen-Fixing Bacterium Azotobacter chroococcum

    O. Baars; X. Zhang; M. I. Gibson; A. T. Stone; F. M.M. Morel; M. R. Seyedsayamdost

    Microbes use siderophores to access essential iron resources in the environment. Over 500 siderophores are known, but they utilize a small set of common moieties to bind iron. Azotobacter chroococcum expresses iron‐rich nitrogenases, with which it reduces N2. Though an important agricultural inoculant, the structures of its iron‐binding...