Elizabeth Karr, PhD
Professor and Senior Associate Dean of OU Graduate College
My research program focuses on understanding the mechanisms of gene expression and energy conservation in anaerobic microorganisms. In my lab, we’ve focused on methanoarchaea, syntrophic bacteria, and the human pathogen Clostridioides difficile. The commonality is their role in the decomposition of organic material in anaerobic environments. Anaerobic decomposition is a complex biological process involving a diverse and interacting microbial community. Diverse fermentative bacteria hydrolyze natural polymers such as polysaccharides, proteins, and lipids and ferment the hydrolysis products to acetate and longer chain fatty acids, aromatic acids, CO2, formate, and H2. Next, syntrophic metabolizers degrade fatty and aromatic acids, alcohols, and some amino acids to the methanogenic substrates: H2, formate, and acetate. Lastly, the hydrogenotrophic and acetoclastic methanogens complete the process by converting acetate, formate, and hydrogen to methane and carbon dioxide.
My research group investigates questions around response to environmental change and understanding life under thermodynamic constraints in members of life’s bacterial and archaeal domains using molecular, biochemical, biophysical, genetic, structural, physiological, and traditional microbiological tools. I am interested in key microorganisms involved in methane generation from an environmental perspective, including methanoarchaea and syntrophic bacteria. I am also interested in how the regulation of gene expression contributes to hypervirulence in select strains of the medically important pathogen Clostridiodes difficile.
Dinh, D.M., L.M. Thomas, E. A. Karr. 2023. Crystal structure of putative 3-hydroxypimelyl-CoA dehydrogenase, Hcd1, at 1.78 Å resolution from Syntrophus aciditrophicus strain SB. Acta Cryst. F79, doi: 10.1107/S2053230X23004399.
James, K.L., J.W. Kung, B.R. Crable, H. Mouttaki, J.R. Sieber, H.N. Nguyen, Y. Yang, Y. Xie, J. Erde, N.Q. Wofford, E.A. Karr, J.A. Loo, R.R. Ogorzalek Loo, R.P. Gunsalus and M.J. McInerney*. 2019. Syntrophus aciditrophicus uses the same enzymes in a reversible manner to degrade and synthesize aromatic and alicyclic acids. Environ Microbiol, 21: 1833-1846. doi:10.1111/1462-2920.14601.
James, K.L., L.A. Ríos-Hernández, N.Q. Wofford, H. Mouttaki, J.R. Sieber, C.S. Sheik, H.N. Nguyen, Y.Yang, Y. Xie, J. Erde, L. Rohlin, E.A. Karr, J.A. Loo, R.R. Ogorzalek[1]Loo, G.B. Hurst, R.P. Gunsalus, L.I. Szweda, and M.J. McInerney*. 2016. Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A in Syntrophus aciditrophicus, a New Twist on ATP Formation. mBio 7. doi: 10.1128/mbio.01208-16.
Isom, C.E., S.K. Menon, L.M. Thomas, A.H. West, G.B. Richter-Addo and E.A. Karr. 2016. Crystal structure of a PadR family transcription regulator from hypervirulent Clostridium difficile R20291. BMC Microbiol. 16:231. DOI 10.1186/s12866-016-0850-0.
Karr, E.A. The methanogen-specific transcription factor MsvR regulates the adjacent fpaA-rlp-rub oxidative stress operon in Methanothermobacter thermautotrophicus. J. Bacteriol. 192 5914-5922. doi: 10.1128/JB.00816-10
