Phylogenetic relationship of Arthrospira, Phormidium, and Spirulina strains from Kenyan and Indian waterbodies.

Morphological and genetic diversity of cultured cynobacterial strains of species of the genera Arthrospira, Spirulina and Phormidium from two geographically different regions and habitats (Kenyan saline-alkaline lakes and Indian freshwater bodies) were investigated. Light microscopy observations were used to determine morphological diversity of the cyanobacteria. Three independent molecular techniques, sequencing of 16S rRNA gene, internally transcribed spacer region between 16S and 23S rDNA (ITS) and the phycocyanin locus (PC-IGS) were conducted for the examination of phylogenetic relationship. Despite differences in morphology and habitats the Kenyan and Indian Arthrospira strains belong to the same cluster in phylogenetic trees of the 16S rDNA (AY575923-AY575932) or PC-IGS (AY575937-AY575946). The DNA similarity in both methods was 100%. In the ITS tree, the two Indian Arthrospira strains PD1998/pus (AY575930) and PD2002/ana (AY575932) form their own sub-cluster. The Phormidium strain AB2002/07 (AY575933) from Lake Nakuru, Kenya is included in the Arthrospira cluster in the ITS tree and very closely related in the 16S and PC-IGS trees. Based on 16S rDNA and PC-IGS phylogeny the sequences of the Spirulina strains form a separate cluster distinct from the Arthrospira cluster. The Kenyan and Indian Spirulina subsalsa strains show a considerable genetic variability as similarities in 16S rRNA gene sequence is 91.5% only. Molecular characterizations of cyanobacterial strains in the present study demonstrate that several distinct morphotypes may be genetically similar and vice versa.