GENE-TRANSFER AND MANIPULATION IN THE THERMOPHILIC CYANOBACTERIUM SYNECHOCOCCUS-ELONGATUS

DNA can be introduced into the thermophilic cyanobacterium Synechococc us elongatus by electroporation or conjugation. Its genome can be read ily manipulated through integrative transformation or by using promisc uous RSF1010-derived plasmids that can be transferred unaltered betwee n Escherichia coli and Synechococcus elongatus. These vectors can ther efore be used for in vivo studies of cyanobacterial proteins in both m esophilic and thermophilic cyanobacterial backgrounds. As a preliminar y step towards the analysis of structure-function relationships of pho tosystem I (PSI) from this thermophile, the genes encoding the PSI sub units PsaF, PsaL, and PsaK were inactivated and shown to be non-essent ial in S. elongatus. In addition, PSI reaction centres were extracted from a psaL(-) strain exclusively as monometric complexes.