Research Interest
I am interested in microbial diversity and bacterial adaptations to the environment. In particular, 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. I have chosen to study biofilm formation by P. arcticus for several reasons. First, this is a model bacterium in astrobiological research for studying adaptation to cold environments. The more we learn about how and where bacteria can survive on Earth the better prepared we are to look for and recognize microbial life on other planets, a major objective of the NASA Astrobiology Institute. The study of biofilm formation by P. arcticus, which I initiated while completing my postdoctoral studies at Michigan State University as a NASA Astrobiology Institute Postdoctoral Fellow, is one of the first to identify genes important for attachment in extreme cold environments. Second, the genome of P. arcticus has been sequenced and annotated and genetic tools are available to specifically remove genes of interest from the bacterial genome, which is rare for an environmental bacterium. Finally, work with six undergraduate collaborators has 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. We are also investigating the microbial diversity in the Siberian permafrost through culture-dependent and culture-independent methods. We have isolated over 100 bacterial strains using a variety of media, and a set of these isolates is being characterized for the ability to grow at low and high temperatures (-4 C to 37 C), and the ability of these strains to tolerate high salt concentrations. We are also determining if the icl gene (which encodes for isocitrate lyase) of these microorganisms contains known cold-adaptations. A 16S clone library has been generated to study the bacterial diversity through culture-independent methods. Finally, through student led projects in my Environmental Microbiology class, we are beginning to characterize the Wolbachia and Actinomycete populations associated with the ant Formica exsectoides. This ant species forms large mounds found at our Conrad Environmental Research Area (CERA) and we are interested in investigating possible symbiotic relationships between bacteria and this ant species through culture dependent and independent techniques.
