Education
| BS | Biochemistry | University of Wisconsin | Madison, Wis. |
| PhD | Biochemistry | University of Wisconsin | Madison, Wis. |
Research Area
Enzymology, physiology and genomics of biological nitrogen fixation and related metabolic activities.
Research Description
Biochemical regulation of Bradyrhizobium japonicum during symbiotic development.
Current Projects
Biochemical and genetic regulation of the metabolic processes that are required for symbiotic nitrogen fixation is the focus of this research program. Rhizobium-leguminous plant symbioses are unique associations in which both the bacteria and the plant undergo complex metabolic and morphological changes. My laboratory is attempting to identify these processes and to elucidate the mechanisms by which these changes are controlled. The primary goal is to determine which factors, genetic and/or biochemical, limit nitrogen fixation and thus plant growth and development. After these limitations are defined, the appropriate generic alterations will then be attempted to enhance plant productivity.
Specific projects include:
- Genomic analysis using oligonucleotide microarrays of the Bradyrhizobium japonicum genome
- Proteomic analysis of the proteins expressed during symbiotic development; and
- Metabolic analysis using 13C-NMR and combined chromatographic/mass spectral analyses.
A recent focus of the laboratory has been the elucidation of malate metabolism by the symbiotic form of B. japonicum which are referred to as bacteroids and the role of alanine excretion by bacteroids. Malate is the primary compound provided to the bacterorid by the plant and is believed to be metabolized via the citric acid cycle, but we have shown that neither α-ketoglutarate dehydrogenase nor isocitrate dehydrogenase are required for symbiotic nitrogen fixation. Thus, the pathway of malate metabolism to provide energy for reduction of atmospheric dinitrogen remains to be determined. Recently, we have shown that alanine, not ammonium, is the principle nitrogen compound provided to the plant by the bacteroid. The metabolism of B. japonicum is being characterized via DNA microarray and proteomic analysis.
Notable Honors and Service
- Associate Chair, MU Department of Biochemistry
- Frederick B. Mumford Award for Outstanding Faculty, 2018
- Fellow, American Association for the Advancement of Science, 2017
- William T. Kemper Fellowship for Excellence in Teaching, 2000
- Faculty Technology Teaching Grant, 1995
- Member, Gamma Sigma Delta, 1995
- CAFNR Outstanding Advisor Award, 1994
- Alumni Faculty Development Incentive Award, 1993
- CAFNR Teaching Award, Biochemistry Unit, 1993
- Gamma Sigma Delta Teaching Award, 1983
- Herman Frasch Foundation Research Fellow, 1981-86
Selected Publications
Strodtman KN, Frank S, Stevenson S, Thelen JJ, Emerich DW. (2018). Proteomic Characterization of Bradyrhizobium diazoefficiens Bacteroids Reveals a Post-Symbiotic, Hemibiotrophic-Like Lifestyle of the Bacteria within Senescing Soybean Nodules. Int J Mol Sci. 19(12). doi: 10.3390/ijms19123947. [PubMed]
Franck S, Strodtman KN, Qiu J, Emerich DW. (2018). Transcriptomic Characterization of Bradyrhizobium diazoefficiens Bacteroids Reveals a Post-Symbiotic, Hemibiotrophic-Like Lifestyle of the Bacteria within Senescing Soybean Nodules. Int J Mol Sci. 19(12). doi: 10.3390/ijms19123918. [PubMed]
Strodtman KN, Stevenson SE, Waters JK, Mawhinney TP, Thelen JJ, Polacco JC, Emerich DW. (2017). The Bacteroid Periplasm in Soybean Nodules Is an Interkingdom Symbiotic Space. Mol Plant Microbe Interact. 30(12):997-1008. doi: 10.1094/MPMI-12-16-0264-R. [PubMed]
Davis-Richardson AG, Russell JT, Dias R, McKinlay AJ, Canepa R, Fagen JR, Rusoff KT, Drew JC, Kolaczkowski B, Emerich DW, Triplett EW. (2016). Corrigendum: Integrating DNA Methylation and Gene Expression Data in the Development of the Soybean-Bradyrhizobium N2-Fixing Symbiosis. Front Microbiol. 7:952. doi: 10.3389/fmicb.2016.00952. eCollection 2016. [PubMed]
Davis-Richardson AG, Russell JT, Dias R, McKinlay AJ, Canepa R, Fagen JR, Rusoff KT, Drew JC, Kolaczkowski B, Emerich DW, Triplett EW. (2016). Integrating DNA Methylation and Gene Expression Data in the Development of the Soybean-Bradyrhizobium N2-Fixing Symbiosis. Front Microbiol. 7:518. doi: 10.3389/fmicb.2016.00518. eCollection 2016. Erratum in: Front Microbiol. 2016;7:952. [PubMed]
Emerich DW, Krishnan HB. (2014). Symbiosomes: temporary moonlighting organelles. Biochem J. 460(1):1-11. doi: 10.1042/BJ20130271. Review. [PubMed]