David A. Baltrus
dbaltrus@darkwing.uoregon.edu

University of Oregon
Center for Ecology & Evolution
1210 University of Oregon
Eugene, OR 97403-1254 USA
(541) 346-0519

Advisors:
Dr. Patrick Phillips, Center for Ecology & Evolution
Dr. Karen Guillemin, Institute of Molecular Biology

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Research Interests

Genotypic variance is a prerequisite for the action of natural selection. Assuming a heterogeneous starting population, variance may be enhanced by the influx of new mutations or the rearrangement/redistribution of extant genotypes. One can therefore predict that the ability of an organism to adapt to a new environment is restricted by the concreteness of these parameters (which I broadly term genomic fluidity). Numerous processes can be interpreted as influencing genomic fluidity: variability of mutation rates, horizontal gene exchange, transposition, insertion/deletion, phase variation, duplication, and translocations. My research, utilizing theoretical and experimental investigations, primarily attempts to explore how the modification of some of these factors relates to adaptation in novel environments.

Helicobacter pylori infects the stomachs of almost half of the world's population, and is a causative agent of ulceration, chronic gastritis, and adenocarcinoma. Additionally, this pathogen is naturally transformable, sensitive to DNA rearrangements, and possesses an unusual spectrum (summing over all strains) of per locus mutation rates, all of which combine to yield a remarkably fluid genome. In vivo, Helicobacter pylori adheres to human gastric epithelial cells with virulent strains inducing dramatic shifts in host cell morphology (the hummingbird phenotype) as well as extensive cellular damage. After many rounds of selection in the lab, the host range of this bacterium may be expanded to include, with corresponding evolution of infection phenotypes, non-human lineage cell lines. Although H. pylori is not as well characterized as other bacterial systems, two complete genomic sequences as well as extensive molecular tools allow for the genotypic manipulation of the loosely defined genome fluidity phenotype. Thus, this system is a microcosm of bacterial adaptation to a novel environment, albeit somewhat artificial, under which I can manipulate the underlying genetics to determine the effects of individual aspects of genomic fluidity.

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Publications

Cresko WA, Yan YL, Baltrus DA, Amores A, Singer A, Rodriguez-Mari A,
Postlethwait JH. (2003) Genome duplication, subfunction partitioning, and lineage divergence: Sox9
in stickleback and zebrafish. Dev Dyn.228(3):480-9.