Identification of the region of cyanobacterial plasmid pDU1 necessary for replication in Anabaena sp. strain M-131.

Shuttle vectors based on plasmid pDU1 from Nostoc sp. strain PCC7524 are able to replicate both in Escherichia coli and in strains of Anabaena and Nostoc spp. Derivatives partially deleted in the pDU1 portion were tested for their ability to replicate in Anabaena sp. strain M-131. Plasmid pRL6HE containing a 1.75-kb HindIII-ScaI fragment of pDU1 replicated stably in that cyanobacterium and also in Anabaena sp. strain PCC7120. Plasmid pRL6HC, containing an even smaller HpaI-ScaI fragment (1.3 kb) replicated in Anabaena sp. strain M-131 but not in Anabaena sp. strain PCC7120. Similarly, when the 1.75-kb fragment of pDU1 was transferred from pRL6HE to another vector (pRL40 delta), the resulting plasmids replicated in Anabaena sp. strain M-131 but not in Anabaena sp. strain PCC7120.