University of North Dakota Faculty/Staff Newsletter

Biology candidate to present seminar Jan. 28

Brian Darby, a candidate for the Integrative Biology position within the Department of Biology, will present a seminar titled "Soil microfauna as model communities to integrate ecology with genomics" at noon Friday, Jan. 28, in 141 Starcher Hall. Everyone is welcome to attend.

Darby completed his master's thesis and doctoral dissertation at the University of Toledo, Ohio, and University of Vermont, respectively, studying desert soil microfaunal communities. His current work as a post-doctoral researcher is to develop genomic tools for studying biotic interactions and environmental adaptations in a group of soil nematodes closely related to the model organism Caenorhabditis elegans.

Abstract: Soil microfauna, such as nematodes and protozoans, are important but often overlooked components of below ground ecosystems. An integrative approach is necessary for understanding the ecology of soil microfauna because their environment is more complex than can be reproduced in the lab. In essence, functional and structural genomic tools will help us to 'ask the nematodes' what cellular functions are necessary in different environments. Bacterial-feeding nematodes of the family Rhabditidae inhabit soils that are enriched with nitrogen or organic amendments. Enriched soils have a greater concentration, but usually less diversity, of bacteria than non-enriched soils, but it is unknown whether the species composition of bacterial communities influences the species composition of Rhabditidae in the field. Although bacteria are a dietary necessity, there is increasing evidence that some bacteria can be pathogenic to their nematode predators. Several main C. elegans signaling pathways regulate defense-related genes in response to pathogens, including the insulin-like DAF-2/DAF-16, P38 Map-Kinase PMK-1, Toll-like TOL-1, and TGF-â DBL-1 pathways. Prior work has identified a candidate gene list of 204 C. elegans genes that were differentially expressed when exposed to several different soil bacteria. The objective of the current work is to compare the genomic response of native isolated rhabditid species with that of the candidate gene list developed from C. elegans. We have recently sequenced partial transcriptomes of four representative Rhabditidae nematodes from a native tallgrass prairie which we use to measure gene expression profiles on different bacteria. As could be predicted, the proportion of genes with confident homology to C. elegans depends on phylogenetic proximity. However, there are still expressed gene transcripts from native nematode isolates that appear to be lineage-specific and not annotated in any of the phylogenetically proximate species. This genomic information will help us to answer how rhabditid nematodes deal with the bacterial communities that inhabit enriched soil conditions.

-- Jeannie Lewis, Biology, 777-2622,

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