Genetic disruption of both Chlamydomonas reinhardtii [FeFe]-hydrogenases: Insight into the role of HYDA2 in H2 production

► Disruption of the two Chlamydomonas hydrogenase genes (HYDA1 and HYDA2). ► The hydA1-1, hydA2-1 and hydA1-1 hydA2-1 mutants were isolated. ► Both HYDA catalyze H2 production from light and dark pathways. ► hydA2-1 mutant revealed total dark and 25% of photosynthetic wild-type activities. ► Enhanced hydrogenase activity measured following HYDA1 gene rescue.