Sequence Features of the Genome of a Unicellular Cyanobacterium Synechocystis sp. strain PCC6803

Abstract

Cyanobacteria, which are capable of photoheterotrophic growth, have been used as a model organism for the study of oxygenic photosynthesis, and the structure and biochemical organization of the photosynthetic apparatus have been extensively investigated and compared with those of plant plastids (Bryant, 1994). One advantage of using these microorganisms, especially the unicellular strains, is their transformable characteristic. This permits elucidation of the structure and function of genes by using various genetic engineering procedures. However, information on the genes and on their organization in the genome remains imperative. The physical and genetic maps of cyanobacterial genomes have been constructed for two strains: the heterocyst-forming Anabaena sp. strain PCC7120 (Bancroft, Wolk and Oren, 1989; see also Chapter 47) and the unicellular Synecho-coccus sp. strain PCC7002 (Chen and Widger, 1993). However, not many genes have been characterized in detail. To achieve understanding of the entire genetic system involved in the oxygenic photosynthesis, as well as the general genetic complement carried by a single organism living in a relatively simple environment, we have begun the project of sequencing the entire genome of another unicellular cyanobacterium, Synechocystis sp. strain PCC6803 (Kotani et al., 1994; Kotani et al., 1995, Kaneko et al., 1995). The main reason for the selection of this strain was that the size and GC content of the genome were appropriate for the sequencing project.