Morphological and molecular characterization of selected desert soil cyanobacteria: Three species new to science including Mojavia pulchra gen. et sp nov.

Four Nostocacean species from desert soils of the western United States, including the phycobiont of the lichen Collema tenax, were studied. Our strains could be forced into morphospecies previously described from Europe, but phylogenetic analysis indicated that they belonged in separate, distinct, and previously undescribed taxa. Partial 16S rRNA sequences of the strains CM1-VF10, CM1-VF14, CNP-AK1 and JT2-VF2 were determined and aligned with published Nostoc sequences from GenBank and our lab, as well as other Nostocales. All aligned sequences were analysed using parsimony, distance, and maximum likelihood methods, and trees based on three separate data sets were generated. Full 16S-23S internal transcribed spacer (ITS) regions were also characterized for our strains, and secondary structures of the ITS region were compared among these and N. commune and N. punctiforme. Intragenomic variability was documented among ITS regions in different operons for these taxa. One of the four strains (JT2-VF2) is distinct from Nostoc by both morphological and molecular criteria and is described as Mojavia pulchra gen. et sp. nov. Two other strains (CM1-VF10 and CM1-VF14) are described as Nostoc indistinguendum sp. nov. and Nostoc desertorum sp. nov., respectively. According to both morphological and molecular characteristics, the phycobiont of C. tenax is not N. commune, N. sphaericum or N. punctiforme as variously suggested in the lichenological literature, and the older name for this taxon, Nostoc lichenoides, is consequently validated in this paper.