CO2 fixation and photoevolution of H2 and O2 in a mutant of Chlamydomonas lacking photosystem I

Photosystem I Is Indispensable for Photoautotrophic Growth, CO2 Fixation, and H2 Photoproduction inChlamydomonas reinhardtii

“…However, photosynthetic CO 2 fixation and photoautotrophic growth were recently reported (1, 2) in two PS I-deficient mutants, B4 and F8, both of which are nuclear mutants deficient in the trans-splicing of the psaA mRNA (1,10,11). Using a gas flow apparatus, Greenbaum et al (1) were able to measure an evolution of O 2 coupled to CO 2 fixation or to H 2 evolution.…”

“…Using a gas flow apparatus, Greenbaum et al (1) were able to measure an evolution of O 2 coupled to CO 2 fixation or to H 2 evolution. The amount of CO 2 fixed by these mutant strains was roughly equivalent to that measured in wild-type (WT) cells.…”

“…The discovery of cytochromes b and f led to the concept that they served as intermediaries between the two photosystems, which operated in series to achieve linear electron transfer from H 2 O to NADP ϩ (5). The essence of this "Z-scheme" model is that photosystem II (PS II) 1 accomplishes the oxidation of water and the reduction of plastoquinone and cytochromes but is unable to reduce ferredoxin or NADP ϩ ; photosystem I (PS I) is required for the reduction of NADP ϩ and the oxidation of cytochrome f through the mediation of the soluble protein plastocyanin. Although other explanations have been proffered for the enhancement effect and photosystem cooperativity (6), the Z-scheme is strongly supported by experimental data (7) and is currently considered as the "central dogma" of oxygenic photosynthesis (8,9).…”

Solar photoproduction of hydrogen. IEA technical report of the IEA Agreement of the Production and Utilization of Hydrogen

“…Thus genetic engineering will be required to reduce the size of the antenna chlorophyll pool to allow higher irradiances to be used. A recent paper by Greenbaum et al (1995) shows promise that higher efficiencies (perhaps approaching 15-20%) may be possible in certain mutants of Chlamydomonas reinhardii algae, which lack Photosystem I.…”

Photosynthetic Hydrogen and Oxygen Production by Green Algae

“…It has recently been reported (Greenbaum et al, 1995;Lee et al, 1996) that mutants of the green alga Chlamydomonas reinhardtii that lack detectable levels of the Photosystem I (PS I) reaction center are capable of sustained simultaneous photoevolution of H, and 0,, CO, reduction and photoautrophic growth. The data indicated that under some circumstances PS 11 alone is sufficient to generate reductant capable of driving hydrogen evolution and CO, fixation, not of course that the 2-scheme is universally wrong.…”