Comparative study of cyanobacteria of desert and semi-desert crusts of two different continents: Africa (Ethiopia) and North America (USA)

Cyanobacterial flora of microbiotic crusts of the Ethiopian Rift Valley System and the Great Basin in Idaho and Oregon were studied. Nine species of cyanobacteria were identified and morphologically characterized from the microbiotic crusts of the Rift Valley in Ethiopia. These included one species of Chroococcales, five species of Oscillatoriales, and three species of Nostocales. Similar studies were made for the microbiotic crusts of the Great Basin of Idaho and Oregon. A total of six morphospecies were morphologically characterized and identified, three species of Oscillatoriales, and three in Nostocales, were recorded in the regions. The cyanobacterial flora of the two continents was compared based on their molecular and morphological differences. Partial sequence data of the 16S rRNA gene (∼85%) (Small sub-unit rRNA gene) and the 16S-23S ITS (Internal Transcribed Spacer) genes were obtained for all taxa from the Rift System and for selected morphospecies of cyanobacteria of the Great Basin. Based on the sequence data provided, morphospecies of cyanobacteria of the two continents tend to show variation in their phylogeny. The ITS regions of morphospecies of cyanobacteria of the two continents were also compared in relation to the D1-D1', V2, and box B helices. Based on morphological, ecophysiological and molecular data; four new species of cyanobacteria were defined from microbiotic crusts of the Rift Valley of Ethiopia. Among these new species, one belongs to Chroococcales, one belongs to Oscillatoriales, and two belong to Nostocales.