CYANOBACTERIAL SYSTEMATICS IN THE GENOMIC ERA

Wood, A. M. 1 , Castenholz, R 1 , and Waterbury, J. B. 21 Department of Biology, University of Oregon, Eugene, OR 97403 USA; 2 Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA Over the last thirty years, cyanobacteria have become widely represented in culture collections. This has facilitated description of taxa based on biochemical, morphological, and genetic bases. Sequence data for 16S rDNA,DNA:DNA hybridization, and multi‐gene sequence data are permitting rapid, phylogenetically meaningful revision of large form‐genera (e.g. Synechococcus, Oscillatoria), and demonstrating the difficulties of using the botanical system of classification for identifying cyanobacteria. At present, much effort is being devoted to combining genetic characterization with traditional polyphasic approaches based on morphology and physiology in order to develop a phylogenetic treatment of cyanobacterial taxonomy. In the meantime, whole genome sequences of representatives of at least eight cyanobacterial strains from a variety of morphological types are complete or nearly complete. The results of these genome projects are demonstrating that knowledge of the complete genome facilitates taxonomic comparisons in which subtle aspects of genetic relationships and evolutionary history can be inferred. Evolution of shared characters and evidence for character loss give insight into the ecological forces that shape diversification within a lineage as well as information about the molecular mechanisms of evolution. Given the relative ease with which prokaryotic genomes can be sequenced, the rapid pace of technological development in sequencing and bioinformatics, and the informative power of complete genome sequences, it is not unreasonable to strive for a taxonomy of the cyanobacteria that is ultimately based on complete genome sequences.