Copyright © 1993, American Society for Microbiology Physical Genome Map of the Unicellular Cyanobacterium

A physical restriction map of the genome of the cyanobacterium Synechococcus sp. strain PCC 7002 was assembled from AscI, NotI, Sall, and SfiI digests of intact genomic DNA separated on a contour-clamped homogeneous electric field pulsed-field gel electrophoresis system. An average genome size of 2.7 X 106 bp was calculated from 21 Nod, 37 Salf, or 27 SfiI frgments obtained by the digestions. The genomic map was assembled by using three different strategies: linking clone analysis, pulsed-field fragment hybridization, and individual clone hybridization to singly and doubly restriction-digested large DNA fragments. The relative positions of 21 genes or operons were determined, and these data suggest that the gene order is not highly conserved between Synechococcus sp. strain PCC 7002 and Anabaena sp. strain PCC 7120. As a model system for the study of oxygenic photosyn-thesis, cyanobacteria have been used as successful tools to delineate the functional proteins involved in the light and dark reactions of photosynthesis. Several strains of cyano-bacteria have been used in these experiments. These include Synechocystis sp. strain PCC 6803 (28, 43, 47), Anabaena sp. strain PCC 7120 (2), Anacystis nidulans (Synechococcu