Hydrogenases, accessory genes and the regulation of 6NiFe9 hydrogenase biosynthesis in Thiocapsa roseopersicina

The purple (Sulphur) phototrophic bacterium, Thiocapsa roseopersicina BBS contains several [NiFe] hydrogenases, of which two are membrane bound. Mutant T . roseopersicina cells, carrying deletions in both gene clusters showed hydrogenase activity. This activity was located in the cytoplasm. The structural gene cluster hoxEFUYH was identi:ed and sequenced. In addition, genes homologous to hupUV=hoxBC, the hydrogen sensing hydrogenase have been identi:ed and sequenced. Regulation of hydrogenase biosynthesis was studied in detail for HydSL (renamed HynSL). A random mutagenesis system was optimised for T. roseopersicina. One of the mutations was in a gene similar to that coding for the HypF proteins in other organisms. Inactivation of the hypF gene resulted in a 60-fold increase in hydrogen evolution under nitrogen :xing conditions. In addition to hypF, the following accessory genes were identi:ed: hydD, hupK, hypC1, hypC2, hypDE. Characterisation of the corresponding gene products and search for additional accessory genes are in progress. ? 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.