PAST
I earned a Bachelor of Arts, majoring in biology and minoring in chemistry, from the University of Louisville in 1999. Then I joined the laboratory of Terence Marsh as a research associate in the Center for Microbial Ecology at Michigan State University (MSU). There I examined the microbiogeology of continental deep subsurface (below 200 meters) bacteria. A year later I began graduate study at Arizona State University under the guidance of Ferran Garcia-Pichel and James Elser in the Life Sciences School and Jack Farmer in the Earth and Space Exploration School. There I characterized calcifying cyanobacteria which, together with algae, form modern microbialites (microbe-built rocks; a.k.a., stromatolites) and those which inhabit modern endoevaporites (microbe-containing salt deposits) in the Cuatro Cienegas Valley (Mexico). I returned to MSU in 2003 to continue graduate study, entering the Crop and Soil Sciences Department, where I remain to this day. I investigated psychrophiles (cold-thriving organisms; a.k.a., cryophiles) for a year in the laboratory of Michael Thomashow before settling in the laboratory of Richard Lenski.
PRESENT
I am conducting two long-term (thousands of generations) evolution experiments utilizing a well-studied bacterium, Escherichia coli, specifically strain B (E. coli B). This strain is the subject of an ongoing 20-year-long (> 40,000 generations) Long-Term Evolution Experiment (LTEE) established by Richard Lenski in 1988. In one experiment I am attempting to illuminate the evolutionary underpinnings of the dual tolerance of desiccation and radiation exhibited by some organisms, a characteristic epitomized by the bacterium Deinococcus radiodurans. I have experimentally ascertained that E. coli B can survive, albeit with high mortality (> 75 % die), short periods of desiccation (a few tens of minutes) and irradiation (ultraviolet B; a few minutes). Hence, it is sensitive to these stressors (i.e., it barely survives brief exposure to them), but it is not tolerant of them (i.e., it does not survive prolonged exposure to them), making it ideally suited for this experiment. This weakness of E. coli B allows an opportunity for evolutionary adaptations to significantly improve its tolerance of desiccation and radiation. My foremost aim of this experiment is to establish if a de novo evolved tolerance of desiccation can afford tolerance of radiation without ever being previously exposed to radiation and vise versa, therefore advancing insight of a characteristic that permits the survival of organisms in low water, high insolation environments (e.g., equatorial deserts).
In the other experiment I am seeking to elucidate the effects of long-term, static and dynamic nutrient limitation on phenotypic characteristics, primarily the cellular stoichiometry of carbon, nitrogen, and phosphorus. I am propagating populations in a nutritionally static or dynamic medium. This medium, a modified Davis Minimal Medium (buffered with Tris instead of mono- and dibasic phosphate), varies by whether carbon, nitrogen, or phosphorus constantly or alternately limits growth. For example, the growth of some populations is always limited by phosphorus while others experience a cycle in which their growth is limited by phosphorus one day and is unlimited by it the other day. My principal goal of this experiment is to determine if E. coli B can develop a mechanism for storing nitrogen and / or phosphorus and what effect such a possible mechanism has on its cellular carbon : nitrogen : phosphorus stoichiometry, thus furthering knowledge of a process, stoichiometric homeostasis, that influences the ecology and evolution of populations, communities, and ecosystems.
FUTURE
While I appreciate the necessity and enjoy the rewards of laboratory-based work, I greatly miss field-based work,
so I will return to it, integrating my experiences with
experimental evolution and microbiogeology to
better understand microbial systems. Two such systems that still highly
interest me are the previously noted modern microbialites and endoevaporites in Cuatro Cienegas. Other modern microbialites that interest me are those in Pavilion Lake, British Columbia, Canada and those near Lee Stocking Island, Exuma Cays, Bahamas. Other endoevaporites that interest me are those arising from salterns in Guerrero Negro, Baja California Sur, Mexico and those fringing the Red and Dead Seas.
