Abstract
Gloeobacter violaceus PCC 7421 is a unicellular cyanobacterium containing distinctive characteristics. This strain lacks thylakoids, and the light-harvesting and photosynthetic apparatuses are associated with the cytoplasmic membrane. The 16S rDNA sequence shows that it is branched at the base of the cyanobacterial phylogenetic tree. These features support the idea that Gloeobacter holds ancestral characters for oxygenic photosynthesis. To reveal the genetic background responsible for characteristics of Gloeobacter and evolution of oxygenic photosynthesis, we determined the nucleotide sequence of the entire genome. The genome consisted of a circular chromosome of 4,659,019 bp long with an average GC content of 62%. The genome comprises 4430 potential protein-encoding genes. Forty-one percent of the genes showed sequence similarity to genes of known function. Comparison of the assigned gene components with those of other cyanobacteria has unveiled distinctive features that reflect the phylogenetic distance between them.
