Dr. Matthew Posewitz is a Research Professor at the Colorado School of Mines and a visiting Research Scientist at NREL. His research is focused on the study of photosynthetic organisms capable of producing H2. His current research is aimed at identifying genes that influence H2 photoproduction in the green alga Chlamydomonas reinhardtii. Recently, these studies resulted in the discovery of the [FeFe]-hydrogenase assembly genes, which are essential for the formation of an active [FeFe]-hydrogenase and are conserved among organisms containing [FeFe]-hydrogenase enzymes (see Posewitz et al., J. Biol. Chem. 279, 25711–25720, 2004). These studies have subsequently led to the ability to heterologously express these unique enzymes, which are among the most efficient H2-generating catalysts known. This advance will accelerate the ability of scientists to generate and test recombinant enzymes for improved functionality and to further characterize [FeFe]-hydrogenase enzymes. Moreover, this research identified a C. reinhardtii mutant that is unable to accumulate intracellular starch and found that hydrogenase transcription and hydrogen production are attenuated in this mutant. This research established the importance of starch accumulation to H2 production in this alga (see Posewitz et al., Plant Cell 16, 2151–2163, 2004).
Additional research projects include: 1) Changes in cellular gene transcription in wild-type and mutant cultures of C. reinhardtii adapted to conditions that promote H2 production (in collaboration with Arthur Grossman's laboratory at Stanford University), 2) Screening collections of microalgae for robust organisms capable of efficient H2 photoproduction (in collaboration with Charles Dismukes, and Ed Steifel, Princeton University; Robert Bidigare, University of Hawaii; Eric Hegg, University of Utah; and Donald Bryant, Pennsylvania State University), 3) Development of gene shuffling techniques to increase the diversity of [FeFe]-hydrogenases.
- Posewitz, M.C., King, P.W., Smolinksi, S.L., Smith, R.D., Ginley, A.R., Ghirardi, M.L., Seibert, M. (2005). "Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii." Biochemical Society Transactions (33); pp. 102-104.
- Ghirardi, M.L., King, P.W., Posewitz, M.C., Maness, P.C., Fedorov, A., Kim, K., Cohen, J., Schulten, K., and Seibert, M. (2005). "Approaches to developing biological H(2)-photoproducing organisms and processes." Biochem Soc. Trans. (33); pp. 70-72.
- Cohen, J., Kim, K., Posewitz, M., Ghirardi, M.L., Schulten, K., Seibert, M., King, P. (2005). "Molecular dynamics and experimental investigation of H2 and O2 diffusion in [Fe]-hydrogenase." Biochemical Society Transactions (33); pp. 80-82.
- Posewitz, M.C., Smolinski, S.L., Melis, A., Kanakagiri, S., Seibert, M., Ghirardi, M.L. (2004). "Disruption of an isoamylase gene in Chlamydomonas reinhardtii attenuates hydrogen production and starch accumulation." Plant Cell (16); pp. 2151-2163.
- Posewitz, M.C., King, P.W., Smolinski, S.L., Zhang, L., Seibert, M., and Ghirardi, M.L. (2004). "Discovery of Two Novel Radical S-adenosylmethionine Proteins Required for the Assembly of an Active [Fe] hydrogenase." J. Biol. Chem. (279); pp. 25711-25720.
- Forestier, M., King P., Zhang, L., Posewitz, M., Schwarzer S., Happe, T., Ghirardi, M.L., Seibert M. (2003). "Expression of two [Fe]-hydrogenases in Chlamydomonas reinhardtii under anaerobic conditions." European Journal of Biochemistry (270); pp. 2750-2758.