Disruption of the uptake hydrogenase gene, but not of the bidirectional hydrogenase gene, leads to enhanced photobiological hydrogen production by the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120.
In order to determine the effects of the deletion of hydrogenase genes on nitrogenase-based photobiological H(2) productivity by heterocystous N(2)-fixing cyanobacteria, we have constructed three hydrogenase mutants from Anabaena sp. PCC 7120: hupL(-) (deficient in the uptake hydrogenase), hoxH(-) (deficient in the bidirectional hydrogenase), and hupL(-)/ hoxH(-) (deficient in both genes). The hupL(-) mutant produced H(2) at a rate four to seven times that of the wild-type under optimal conditions. The hoxH(-) mutant produced significantly lower amounts of H(2) and had slightly lower nitrogenase activity than wild-type. H(2) production by the hupL(-)/ hoxH(-) mutant was slightly lower than, but almost equal to, that of the hupL(-) mutant. The efficiency of light energy conversion to H(2) by the hupL(-) mutant at its highest H(2) production stage was 1.2% at an actinic visible light intensity of 10 W/m(2) (PAR) under argon atmosphere. These results indicate that deletion of the hupL gene could be employed as a source for further improvement of H(2) production in a nitrogenase-based photobiological H(2) production system.
Masukawa
H
H
Department of Biology, School of Education and Division of Pure and Applied Physics, Graduate School of Science and Engineering, Waseda University, Nishiwaseda, Shinjuku, Tokyo 169-8050, Japan.
Mochimaru
M
M
Sakurai
H
H
D017033:Anabaena / Q000201:enzymology* / Q000254:growth & development; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000032:analysis; D017353:Gene Deletion; D005798:Genes, Bacterial; D006859:Hydrogen / Q000378:metabolism*; D008027:Light; D008957:Models, Genetic; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006859:Hydrogen; D010088:Oxidoreductases; C021376:hydrogen dehydrogenase; C091789:HupL protein, Anabaena; D009591:Nitrogenase