Group [internal]



Group members.

Individuals interested in undergraduate, graduate, or postdoc research opportunities in the Fischer Group at Caltech are urged to send a brief statement of background and interest. [recruitment]

Woodward W. Fischer [principal investigator]

Professor of Geobiology in Geological and Planetary Sciences. PhD Harvard University. BA Colorado College. I'm often called by my nickname, Woody. My research generally falls in the discipline of Geobiology—combining techniques from field geology, analytical chemistry, and biology— to understand and explore the relationships between of life and Earth surface environments through diverse and fundamental transitions in Earth history. Read a brief interview with Woody.

Preston Cosslett Kemeny

Graduate Student (Hertz NDSEG). AB Princeton University. I am interested in the mutual interactions between the evolution of life and global biogeochemical cycles, as recorded in the stable isotope ratios of natural materials in the geologic record. My research combines fieldwork, experimental measurements, thermodynamic calculations, and numerical models to understand the large-scale geochemical and geobiological processes that generate Earth’s climate, both now and in the past. My current projects include using sulfur isotope ratios to constrain sulfur cycling and fluxes of organic matter in river catchments and using nitrogen isotope ratios to model glacial nutrient dynamics in the Southern Ocean. I am also interested in the physical chemistry underlying isotopic variation, particularly with respect to molecules with multiple isotopic substitutions or which fail to obey canonical mass-law relationships. When outside the lab, I like to hike and talk about science.

Usha Lingappa

Graduate Student (NSF GRFP). BA Hampshire College. I'm broadly interested in manganese, phototrophy, and the biogenesis of proteins critically important for biogeochemical processes in the environment. With Woody Fischer, I'm studying Mn oxidation by Cyanobacteria. This work is both to explore a possible evolutionary stepping stone in the origin of oxygenic photosynthesis based on Mn phototrophy, and also to characterize a previously unappreciated branch of environmental Mn cycling.

John S. Magyar

Research Scientist. PhD, Northwestern University. AB, Dartmouth College. My current work in the Fischer group is focused on biological manganese oxidation related to the evolution of photosystem II. Previously, I was a chemistry professor at Barnard College, Columbia University, where I continue to advise undergraduate research students. We are exploring molecular mechanisms of cold adaptation, specifically in the hydrocarbonoclastic, psychrophilic bacterium Colwellia psychrerythraea. We are also investigating the molecular details of trace metal uptake and homeostasis in environmentally important microorganisms, such as marine phytoplankton and methanogenic archaea. Before Barnard, I was a postdoctoral scholar in chemistry at Caltech (with Harry B. Gray), where I studied electron-transfer kinetics and protein dynamics in cytochrome c. My doctoral research, with Hilary Arnold Godwin, provided important insights into the molecular mechanisms of lead(II) poisoning.

Kyle Metcalfe

Graduate Student (NSF GRFP). BA Pomona College. I’m interested in the microbe-mineral interface and studying the dynamics of biomineralization by microbes in both culture and the environment. Working with Victoria Orphan and Woody Fischer, I’m working on a project focusing on silicate biomineralization of anaerobic methane-oxidizing (AOM) microbial consortia. Microbial silicate biomineralization in non-hydrothermal environments is poorly recognized, but may provide insight into biogeochemical cycles and the physiology and ecology of microbial aggregates and communities. I’m currently characterizing the mineralogy and architecture of silicate shells enveloping AOM consortia with X-ray spectroscopy to understand the function of these biomaterials. Additionally, I have worked with Woody to unravel some of the history preserved in manganese-rich sedimentary rocks.

Christopher Spalding

Graduate Student (NESSF). BA/MSci University of Cambridge. An Astrophysicist by training and practice, I'm working with Konstantin Batygin on the dynamics of planetary systems with a focus on excitation of spin-orbit misalignments in close-in planetary systems. But I'm also leading a somewhat double life as a 'geobiologist' in the Fischer Group. My interests here generally lie in deciphering the influences that have shaped the course of evolution using mathematical techniques. In particular, I have developed an analytical model that quantifies the energetic costs to an organism of building a calcium carbonate shell, and how these costs change as a function of seawater chemistry. The goal is to determine why some groups have been more susceptible than others to extinction during past events of ocean acidification, such as the Permian-Triassic Mass Extinction, and provide some fresh insights into extinction risk for modern fisheries associated with ocean acidification.

Vlada Stamenkovic

Simons Collaboration on the Origins of Life Fellow at Caltech/JPL. PhD University of Muenster & European Space Agency. MSc ETH Zurich. I am a theoretical physicist and planetary scientist who explores the fundamental principles that determine the interior and surface evolution of rocky planets and the hidden connections between the co-evolution of planets and life - from deep to modern time. I currently focus on connecting the fundamental principles of thermodynamics to the time-dependent ability of a planet to create nutrients, redox gradients, and investigate what these results mean for the origins and the definition of life on Earth, Mars and beyond. You can check out my work here.

Mark Torres

Texaco/AGEP Postdoctoral Scholar. PhD University of Southern California. BA Pitzer College. Broadly, my research focuses on the biogeochemical cycles of carbon, oxygen and sulfur with the intention of understanding the links between physical transport processes and chemical reactions. For this work, I combine laboratory experiments, field measurements, and numerical models. At Caltech, I am focusing my attention on questions related to the multiscale storage and transport of particulate organic carbon. I also maintain an active interest in the relationships between erosion, hydrology, and chemical weathering.

Elizabeth Trower

Agouron Postdoctoral Scholar. PhD Stanford. BS Caltech. My research is broadly focused on chemical sediments: I’m interested in building a better mechanistic understanding of how a diverse range of chemical sediments form so that we can more effectively apply them as geobiological and environmental proxies. My work combines observations from the field, lab experiments, petrography, and high resolution in situ geochemistry. I’m currently investigating the effects of abrasion during sediment transport on the textures present chemical sediments including ooids and stromatolites. I’m also interested in the geologic history of silica as a chemical sediment and the secular evolution of the silica cycle – I’m exploring ways to use Si isotope geochemistry to quantify the various sinks of the silica cycle over time.

Xingchen (Tony) Wang

Simons Foundation Postdoctoral Fellow on the Origins of Life. PhD Princeton University. BS, Nanjing University. My research is focused on the cycling of nitrogen in the modern and past oceans. As a part of this effort, I develop and apply new methods to analyze the isotopic composition of nitrogen in fossils (e.g. corals and stromatolites) as well as in modern marine environments (e.g. reefs). I also employ calculations from simple mathematical models to quantitatively interpret these data. At Caltech I am working with Alex Sessions, Jess Adkins, and Woody Fischer on ocean biogeochemical changes over a broad range of timescales throughout the Earth history, ranging from the Archean to the Quaternary intervals.

Lewis Ward

Graduate Student (NSF GRFP, NESSF). BA Harvard University. I'm interested in the evolution of metabolic pathways that affect biogeochemical cycles and the resulting interactions between organisms and their environment. I’m currently working with Woody Fischer to understand the evolution of nitrogen cycling processes by microorganisms, processes of microbial iron-oxidation as it relates to Precambrian iron formations, and the evolution of phototrophy in the phylum Chloroflexi. By combining approaches from diverse fields, I hope to gain an understanding of how biological and geological processes have interacted to shape the nitrogen cycle through time, and how it has interacted with other important biogeochemical cycles such as those of oxygen and iron.


Kristin Bergmann (former graduate student, now faculty at MIT)

Renata Cummins (former graduate student, now at Risk Management Solutions)

Seth Finnegan (former postdoc, now at UC Berkeley, Dept. of Integrative Biology)

Aya Gerpheide (former undergraduate, Oxy, now Artist, Los Angeles, CA)

Itay Halevy (former postdoc, now at Weizmann Institute, Dept. of Environmental Sciences)

James Hemp (former postdoc, now at University of Utah, School of Medicine)

Jena Johnson (former graduate student, Clauser Prize winner, now at CU Boulder)

Carina Lee (former staff, PhD at UCR, now postdoc at UC Berkeley)

Ariel Liu (former high school student, Troy, now at Stanford University)

Hanna Liu (former undergraduate, now at UCI School of Medicine)

Allison Maker (former undergraduate, now at University of Washington, Dept. of Biochemistry)

Noah Planavsky (former postdoc, now at Yale, Dept. of Geology & Geophysics)

Nikhita Poole (former high school student, now at Caltech)

Chris Reinhard (former postdoc, now at Georgia Tech Dept. of Earth and Atmospheric Sciences)

Sarah Slotznick (former graduate student, now Miller Postdoctoral Fellow at Berkeley)

Kevin Sutherland (former undergraduate, now at MIT/WHOI)

Elizabeth Trembath-Reichert (former graduate student, now NASA NPP at WHOI)

Jon Wilson (former postdoc, now at Haverford College, Dept. of Biology)

Rebecca Zentmyer (former staff)

Past SURF and MURF students.

Allison Maker (Caltech '15), Juliet Su (Caltech '16), Aya Gerpheide (Oxy '14), Hanna Liu (Caltech '11), Haley Barnes (Caltech '12).