Gene transfer and manipulation in the thermophilic cyanobacterium Synechococcus elongatus

DNA can be introduced into the thermophilic cyanobacterium Synechococcus elongatus by electroporation or conjugation. Its genome can be readily manipulated through integrative transformation or by using promiscuous RSF1010-derived plasmids that can be transferred unaltered between Escherichia coli and Synechococcus elongatus. These vectors can therefore be used for in vivo studies of cyanobacterial proteins in both mesophilic and thermophilic cyanobacterial backgrounds. As a preliminary step towards the analysis of structure-function relationships of photosystem I (PSI) from this thermophile, the genes encoding the PSI subunits PsaF, PsaL, and PsaK were inactivated and shown to be non-essential in S. elongatus. In addition, PSI reaction centres were extracted from a psaL- strain exclusively as monomeric complexes.