Alex Bradley, PhD

Associate Professor
Earth and Planetary Sciences

Plant and Microbial Biosciences Program
Evolution, Ecology and Population Biology Program


  • Organic & isotope geochemistry, geobiology, microbiology

  • Examination of modern and ancient biogeochemical cycles; the coevolution of life and the Earth.

Research Abstract:

I am a biogeochemist interested the ways in which the evolution of life on Earth and the evolution of the Earth`s environment have affected one another over the course of Earth history.

Our laboratory uses the tools of organic geochemistry to try to understand how organic structures synthesized by living organisms can be preserved over geological time spans, and record information about the organisms and ecosystems from which they derive. We also use light stable isotope geochemistry to try to understand characteristics regarding the biogeochemical cycling of carbon, hydrogen, nitrogen, oxygen, and sulfur.

One component of this work involves the application of organic and isotope geochemistry to samples such as modern microbial mats to understand how these communities function and what information about them has the capability of being preserved in the rock record. We also examine ancient accumulations of material, such as core records from lake sediments, to try to understand how environments have changed over time. In both cases we use the organic and isotope information to make inferences about modern and ancient ecosystems.

The other component of this work involves conducting experiments to better determine exactly what kind of information is being recorded in the molecules we study. For example, we try to understand the genes and metabolic networks that underlie the production of organic structures used as biomarkers, and that control the isotopic fractionation between reactants and products. Through experiments in genetics, physiology, and evolution, we hope to better constrain the types of information that we can acquire from the rock record, and understand the limits of our knowledge.

Selected Publications:

Bradley AS, Leavitt, WD, Schmidt, M, Knoll, AH, Girguis, PR, Johnston, DT. Patterns of microbial sulphur isotope fractionation at low sulphate concentrations. in review

Leavitt, WD, Halevy, I, Bradley, AS, Johnston, DT. Influence of sulphate reduction rates on the Phanerozoic sulphur isotope record. Proceedings of the National Academy of Sciences 2013, 110: 11244-11249

Lincoln, SA, Bradley, AS, Newman, SA, Summons, RE. Archaeal and bacterial glycerol dialkyl glycerol tetraether lipids in chimneys of the Lost City Hydrothermal Field. Organic Geochemistry 2011 60: 45-53.

Bradley AS, Leavitt WD and Johnston DT. Revisiting the dissimilatory sulfate reduction pathway, Geobiology 2011 9: 446-457.

Wankel SD, Germanovich L, Lilley MD, Genc G, DiPerna CJ, Bradley AS, Olson EJ, Lowell RP, Girguis PR. Influence of subsurface biosphere on geochemical fluxes from diffuse hydrothermal fluids. Nature Geoscience 2011 4: 461-468.

Bradley AS, Pearson A, Saenz JP and Marx CJ. Adenosylhopane: the first intermediate in hopanoid side chain biosynthesis. Organic Geochemistry 2010 41: 1075-1081.

Bradley AS and Summons RE. Multiple origins of methane at the Lost City Hydrothermal Field. Earth and Planetary Science Letters 2010 297: 34-41.

Bradley AS, Fredricks H, Hinrichs K-U, Summons RE. Structural diversity of diether lipids in carbonate chimneys at the Lost City Hydrothermal Field. Organic Geochemistry 2009 40:1169-1178.

Last Updated: 8/9/2013 2:51:45 PM

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