D. Ellen K. Tarr, Ph.D.

Associate Professor

Midwestern University
Arizona College of Osteopathic Medicine
Department of Microbiology and Immunology
Agave 203D
19555 N. 59th Ave.
Glendale, AZ 85308

Office: (623) 572-3725
e-mail: etarrx@midwestern.edu

Research Gate: https://www.researchgate.net/profile/Ellen_Tarr
Linked In: https://www.linkedin.com/pub/ellen-tarr/15/685/789
ORCID ID: http://orcid.org/0000-0003-1604-4545


B.S. Microbiology University of Iowa 1998
Ph.D. Molecular Microbiology/Immunology Johns Hopkins University 2004


Comparative Immunology of Invertebrate Taxa

While vertebrates have both innate and adaptive immunity, invertebrates have to defend against pathogens using only innate mechanisms.  There is no single, prototypical invertebrate immune system-invertebrate lineages have been diverging for millions of years and have diversified components of their immunity based on encounters with potential pathogens in their specific environments.

Invertebrate defensins

Invertebrates produce several types of antimicrobial peptides that aid in their defense against potential pathogens.  Of these, defensins have been the most studied, but only in a few select taxa.  In the lab, I focus on defensins produced by two invertebrates: the nematode Caenorhabditis elegans and the tardigrade Hypsibius dujardini.  For both species, we are attempting to express recombinant versions of putative defensins that have been identified and test their antimicrobial activity against a panel of bacteria and fungi.  For C. elegans, we will compare activity of the purified peptides with the susceptibility to these microbes of mutant worms that are missing one or more defensins.  We would eventually like to do similar studies with H. dujardini using RNAi methods since knock-out strains are not currently available.  Experiments using these two model systems are then put into a larger context by comparing the protein sequences to those available from a broad range of taxa and experimental results to those previously seen in arthropods and mollusks.  I hope to address several questions using this combination of approaches:

Tardigrade innate immunity

Any immune system must have components that detect potential pathogens, signaling molecules, and effector molecules (such as defensins).  In addition to detailed characterization of tardigrade defensins, I plan to see if tardigrades have homologs of immune components identified in other invertebrates.  Tardigrades are closely related to arthropods and Drosophila has been studied extensively, making it a good starting point for comparison.  A systematic comparison will show which components have been conserved and where there are gaps that may indicate novel components that have evolved in tardigrades.

Selected Publications

Tarr, D.E.K., 2016. Establishing a Reference Array for the CS-αβ Superfamily of Defensive Peptides. BMC Research Notes. 9(1):490.

Tarr, D.E.K., 2016. Commentary: What Research Universities Can Learn from Teaching-Intensive Counterparts. The Chronicle of Higher Education. http://www.chronicle.com/article/What-Research-Universities-Can/237518

Tarr, D.E.K., 2012. Nematode antimicrobial peptides. Invertebrate Survival Journal. 9(1): 122-133.  Invited review. http://www.isj.unimo.it/articoli/ISJ270.pdf

Tarr, D.E.K., 2012. Distribution and characteristics of ABFs, cecropins, nemapores, and lysozymes in nematodes. Developmental and Comparative Immunology 36(3): 502-520.