Diversity of the cyanobacteria

Abstract

The cyanobacteria are an ancient lineage of photo-oxygenic bacteria. Globally responsible for much of the primary productivity and nitrogen fixation, they are also evolutionarily significant as the photosynthetic members of serial endosymbiotic events leading to the establishment of chloroplasts. Traditionally classified based on morphological characters, recent research revealed an abundance of cryptic diversity evidenced by molecular analyses, most notably the 16S rDNA gene sequence. Explorations of seldom sampled habitats, such as tropics environments, aerophytic habitats, soil crusts, etc., have also revealed a tremendous new diversity of taxa. This increase in the alpha-level diversity, coupled with new molecular techniques, has greatly altered our perceptions of the evolutionary relationships within this clade. Many of the traditional genera have proven to be polyphyletic, but revisions are underway.