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EDUCATION
1998 B.S. Biology, Pacific Lutheran University
2005 Ph.D. Microbiology and Molecular Genetics, Michigan State University
RESEARCH INTERESTS
The nature and variety of interactions between species influence the traits that are likely to evolve and the ecological role of each species involved. I am interested in understanding how the nature of interactions between microbes are influenced by ecological variables and how these relationships influence the course of microbial evolution.
Previously, I investigated an antagonistic interaction between the bacterial predator Myxococcus xanthus and two prey species: Escherichia coli and Micrococcus luteus. I described the effects of three ecological variables (prey species, surface hardness, and prey-patch density) on the ability of M. xanthus to kill its prey. I showed that evolution of M. xanthus in the absence of prey could lead to losses in predatory ability. Finally, I demonstrated that the density of prey patches in the environment could predictably influence the degree of evolutionary improvement in searching ability in M. xanthus.
I am now studying a novel mutualistic interaction between a bacteria and an archaea. Unlike the interspecies interaction I previously studied, these two organisms must cooperate with one another in order to obtain energy for growth and survival under specific conditions. They accomplish this cooperation by the transfer of hydrogen from one species (Desulfovibrio) to the other (Methanococcus). This transfer allows Desulfovibrio to gain energy from metabolism of lactate, and provides Methanococcus with the hydrogen that it needs to obtain energy.
There are a variety of interesting ecological and evolutionary questions about mutualistic interspecies interactions that I am interested in addressing in this system, including:
- What are the initial steps involved in adaptation to a mutualistic interaction and how are these steps similar to or different from adaptation to stressful environments?
- Does adaptation to a mutualistic interaction require genetic changes that limit the ability of either species to survive alone in appropriate conditions?
- What are the population dynamics of each species in a mutualism, and how are these dynamics affected by the presence of a third species that is a predator or that is capable of competing with Desulfovibrio to provide hydrogen to Methanococcus?
- Will either species eventually evolve to exploit the other by taking resources from the mutualism without reciprocating?
CURRENT PROJECTS
Environmental Stress Pathway Project (GTL:Genomics)
SELECTED PUBLICATIONS
Stolyar S, Van Dien S, Hillesland KL, Pinel N, Lie T, Leigh J, Stahl D. Flux balance modeling of a syntrophic association between Desulfovibrio vulgaris and the hydrogenotrophic methanogen Methanococcus maripaludis. Submitted to Molecular Systems Biology
Velicer GJ, Hillesland KL. (2007, projected) Why cooperate? The ecology and evolution of myxobacteria. In: Multicellularity and Differentiation Among the Myxboacteria and Their Neighbors, HB Kaplan & D
Whitworth, editors. American Society for Microbiology Press.
Hillesland KL , Lenski RE, Velicer GJ. Prey-patch density affects
evolution of predatory searching in Myxococcus xanthus. In preparation
Hillesland KL , Lenski RE, Velicer GJ. Decline in predatory performance
during evolution in the absence of prey. In preparation
Hillesland KL , Lenski RE, Velicer GJ. Ecological variables affecting
predatory success in Myxococcus xanthus. In press at Microbial Ecology
Hillesland KL , Velicer GJ. (2005) Resource level affects relative
performance of the two motility systems of Myxococcus xanthus. Microbial
Ecology 49: 558-566
Velicer GJ, Stredwick KL . (2002) Experimental social evolution with
Myxococcus xanthus. Antonie von Leeuwenhoek 81: 155-164
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