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Department Chair, Biological Chemistry
I am interested in microbial diversity and bacterial adaptations to the environment. I currently work with undergraduate researchers on two research projects.
I study the survival strategies of one bacterium, Psychrobacter arcticus, which was isolated in 2000 by Vishnivetskaya and colleagues at Michigan State University, from a Siberian permafrost core that has been dated 20,000 to 40,000 years old. The Siberian permafrost is an extreme environment because of the low temperatures, low nutrient availability and small amount of unfrozen water. In the Siberian permafrost from which P. arcticus was isolated, the only unfrozen water is found as thin films surrounding organic and mineral particles. I hypothesize that P. arcticus is able to attach to surfaces in the permafrost and this attachment will provide the bacterium with access to unfrozen water, ultimately increasing survivability in the permafrost environment. What we will learn from this study will not only enhance research of microbes in extreme environments, but also may shed light on a key family of adhesins, some of which have been implicated in human disease as important factors in maintenance of infection. The current focus of my laboratory is to investigate the ability of P. arcticus to form biofilms under a variety of environmental conditions and to identify the genes necessary for attachment of the bacterium to surfaces. Six undergraduate collaborators have generated a mutant P. arcticus library, yielding four mutations mapping to one gene, which render the strains unable to form biofilms at levels equivalent to wild type. This protein encoded by this gene, which I refer to as Cat1 (cold attachment protein1 and cat1 for the corresponding gene), belongs to a family of proteins, many thought to be important for bacterial pathogenesis. We are currently characterizing the role of Cat1 in biofilm formation as well as identifying and characterizing other genes involved in biofilm formation by P. arcticus, and characterizing the role of calcium in biofilm formation.
I also study the microbial diversity found in hog manure and the antiobiotic resistance profiles in the manure, in farm soil in which the manure has been spread, and in sediment from streams into which the CAFO farms drain. Grinnell College resides in an area of Iowa that is full of concentrated animal feeding operations (CAFOs) and we would like to determine if and how these CAFOs are impacting our environment. We work with a local farmer who operates four hog CAFOs in Poweshiek County. We have been provided full access to the manure pits, farm fields onto which the manure is applied annually and streams into which farm tiles drain. Three undergraduates have participated in this project thus far and have focused attention on Escherichia coli and Enterococcus isolates and their resistance profiles. Through culture-independent techniques we are determing the presence of resistance genes in each environment. This work is also integrated into my Environmental Microbiology and Microbial Pathogenesis courses.