2001b). For the actual screening procedure, the authors made use of the well-known fact that PSII and PSI are preferentially

excitable by click here different light qualities. The algal colonies were adapted to state 2 by preferentially exciting PSII with light of λ = 620 nm. Vice versa, the cells were forced into state 1 by exciting PSI with light of λ = 695 nm (Kruse et al. 1999). By utilizing such a fluorescence image-based screening system to identify C. reinhardtii cells deficient in state transitions and subsequent analyses of the H2 yields of the identified strains, Kruse et al. (2005) found C. reinhardtii strain Stm6. This strain was shown to be deficient in MOC1, which is related to a mitochondrial transcription termination factor (mTERF) (Schönfeld et al. 2004). The phenotype of

strain Stm6 includes, besides being blocked in state 1, sensitivity toward high light, drastic changes in composition and function of the mitochondrial respiratory chain and the accumulation of large amounts of starch (Schönfeld et al. 2004; Kruse et al. 2005). Most interestingly with regard of the purpose of this study, C. reinhardtii strain Stm6 shows a higher H2 evolution than its parental strain (C. reinhardtii CC-1618) both after a dark–light shift and upon S deprivation (Kruse et al. 2005). It is unclear yet, which of the single altered characteristics of the strain or a combination of all of them leads to the higher H2 yields. However, this study Cobimetinib is a nice example of how the study on the H2 metabolism of photosynthetic microorganisms

can benefit from techniques established in order to analyze photosynthesis. Conclusion Photobiological H2 production by unicellular green algae has become an important research field because of its potential to be applied in renewable energy production. In addition, the research already done has shown that the analysis of this fascinating metabolism also contributed Tau-protein kinase to a deeper understanding of photosynthesis, since the latter is drastically re-directed, especially in S-deprived H2-producing microalgae. Investigations on this re-organization in bioenergetics and metabolism benefited strongly from new techniques designed in order to analyze photosynthesis, as the screening for algal mutant strains with an altered H2 metabolism mostly depends on its coupling to the photosynthetic electron transport chain. On the other hand, methods to induce and analyze H2 production in green algae described in this article might help in characterizing the photosynthetic apparatus of the cells under special environmental conditions and/or in mutant strains with useful alterations in the characteristics of their photosynthesis.