Anaerobic adaptation in a Chlamydomonas reinhardtii mutant lacking hydrogenase activity

Alexandra Dubini1,3, Florence Mus2, Michael Seibert1, Matthew C. Posewitz3, and Arthur R. Grossman2

1National Renewable Energy Laboratory, Golden, CO; 2Carnegie Institute of Washington, Stanford, CA; 3Colorado School of Mines, Golden, CO.

The green alga Chlamydomonas reinhardtii has an extensive network of fermentation pathways that are used during acclimation to anaerobiosis. As part of an effort to develop an informed model of algal metabolism during anoxia, we examined the metabolic and regulatory adaptations used during anaerobiosis in a Chlamydomonas mutant where H2 production has been eliminated by disruption of an [FeFe]-hydrogenase maturation protein. In this mutant, the accumulation of succinate increases and CO2 levels decrease relative to the parental control. These data are consistent with decreased metabolic flux through the pyruvate-ferredoxin oxidoreductase (PFR) pathway and increased activity of the enzymes required for anoxic succinate production. In the absence of hydrogenase activity, an increase in succinate suggests the need to oxidize NADH and that hydrogenase activity during anaerobiosis in wild-type cells modulates NADH levels. In this study, we examine putative succinate production pathways and investigate the role of hydrogenase activity in fermentation. These data, combined with microarray analyses continue to illustrate the metabolic flexibility of Chlamydomonas during anoxia and implications for modulation of Chlamydomonas for enhanced H2 production are discussed.

e-mail address of presenting author: alexandra_dubini@nrel.gov