A hydrogen-producing, hydrogenase-free mutant strain of Nostoc punctiforme ATCC 29133

The hupL gene, encoding the uptake hydrogenase large subunit, in Nostoc sp. strain ATCC 29133, a strain lacking a bidirectional hydrogenase, was inactivated by insertional mutagenesis. Recombinant strains were isolated and analysed, and one hupL− strain, NHM5, was selected for further study. Cultures of NHM5 were grown under nitrogen-fixing conditions and H2 evolution under air was observed using an H2 electrode.