Mutants of the Cyanobacterium Anahaena variahilts Altered in Hydrogenase Activities

Abstract

Two mutants of the cyanobacterium Anabaena variabilis impaired in the utilization or formation of molecular hydrogen have been obtained by nitroso-guanidine mutagenesis. Cultures of both mutants did not show alterations in the growth characteristics or in the hetero-cysts frequency but evolved molecular hydrogen from nitrogenase with enhanced rates. Activity measurements in extracts showed that one mutant (PK84) did not perform Na2S204-dependent H2-formation and was, therefore, unable to express an active bidirectional hydro-genase. Both mutants (PK84. PK17R) were characterized by lower activity of phenazine-methosulphate-dependent H2-uptake when extracts were assayed from younger cultures. In older cells, particularly when grown with nitrate in the medium, this H2-uptake activity was, however, enhanced. Both mutants are likely affected in regulatory hydrogenase genes. The mutant PK84 offers perspectives for potential applications in solar energy conversion programs. © 1995, Walter de Gruyter. All rights reserved.