Abstract
Sulfur deprivation of algal cultures selectively and partially inactivates photosystem II (PSII)-catalyzed O2 evolution, induces anaerobiosis and hydrogenase expression, and results in sustained H2 photoproduction for several days. We show that re-addition of limiting amounts of sulfate (1-10 μM final concentration) to the cultures during the H 2-production phase temporarily reactivates PSII photochemical and O2-evolution activity and re-establishes higher rates of electron transport through the photosynthetic electron transport chain. The reactivation of PSII occurs by de novo D1 protein synthesis, but does not result in the re-establishment of aerobic conditions in the reactor, detectable by dissolved-O2 sensors. However, concomitant H2 photoproduction is inhibited, possibly due to excessive intra-cellular levels of photosynthetically-evolved O2. The partial recovery of electron transport rates correlates with the re-oxidation of the plastoquinone (PQ) pool, as observed by pulse-amplitude modulated (PAM) and fluorescence-induction measurements. These results show that the presence of a more oxidized PQ pool releases some of the down-regulation of electron transport caused by the anaerobic conditions.
Original language | American English |
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Pages (from-to) | 295-305 |
Number of pages | 11 |
Journal | Photosynthesis Research |
Volume | 85 |
Issue number | 3 |
DOIs | |
State | Published - 2005 |
NREL Publication Number
- NREL/JA-590-39363
Keywords
- Biohydrogen,Chlamydomonas reinhardtii
- H photoproduction
- Hydrogenase
- Photosystem II activity
- Sulfur deprivation
- Sulfur re-addition