Surviving in the absence of air – analysis of the anaerobic hydrogen metabolism of the microalga Chlamydomonas by RNA-Seq and classical approaches

The unicellular green alga Chlamydomonas reinhardtii has emerged as a model for research on photosynthetic biofuel production, especially lipid accumulation and photo-hydrogen evolution. The latter is catalyzed by a very active [FeFe]-hydrogenase, HYDA1, coupled to the photosynthetic electron transport chain via its natural electron donor ferredoxin (1). Despite the profound oxygen sensitivity of HYDA1, hydrogen production takes place in illuminated algal suspensions upon sulfur starvation, to which the cells respond by down-regulating photosynthetic oxygen evolution and establishing hypoxic conditions in the light (2, 3). Though this photo-fermentative metabolism (4) constitutes the vision of producing a clean energy carrier by using the energy of the sun, it is far from being acceptably efficient for industrial use. For a targeted optimization of hydrogen production by Chlamydomonas, a deeper understanding of physiology, biochemistry and gene regulatory events underlying hydrogen production and the anaerobic response is essential. This presentation will summarize the latest advances of research on the [FeFe]-hydrogenase enzyme as well as new insights obtained by whole-genome RNA-sequencing of anaerobic Chlamydomonas cultures.