Phylogenetic placement of seven strains of Synechococcales (Cyanobacteria) isolated from desert soils in Zion National Park.

Seven strains of cyanobacteria of the order Synechococcales were isolated from the sandstone derived soil of Zion National Park. These strains were analyzed using 16S rRNA and 16S-23S phylogenetic analysis, percent dissimilarity of the ITS sequence, morphology, and the similarity of the 16S rRNA sequence. One strain was placed within the genus Plectolyngbya, but the Bayesian inference and 16S rRNA similarity analysis support the conclusion that Plectolyngbya should not considered a valid genus, and that it should be integrated into the taxonomically prioritized Leptolybya. Two of the strains were found to be similar to Phormidesmus morphologically, but the Bayesian inference and maximum likelihood indicate that they do not belong in Phormidesmus sensu stricto. These strains also have a low 16S similarity with Phormidesmus, further indicating that these strains warrant a new genus. One of the seven strains were found to be strongly supported as belonging to Stenomitos because it is sister to the type species S. rutilans. This strain was compared to other Stenomitos using the percent dissimilarity in the 16S-23S ITS region and this supported the conclusion this strain is a new species of Stenomitos. The remaining three strains from Zion National Park were found to be highly divergent from other members of Leptolyngbyaceae. Two of the strains were supported as the same species according to their 16S-23S ITS similarity comparison. These two strains were also supported as being an undescribed genus based upon their placement in the Bayesian inference. The third strain was not supported as the same species and was found to not just be supported as a different species, but a different genus from the other strains. These three strains are so dissimilar to other Leptolyngbyaceae that that they may warrant not just a new genus, but a new family. One of these three strains could also represent a case of horizontal gene transfer from an unknown cyanobacterium into Stenomitos since the sequence was isolated from the same test tube as the Stenomitos. However, further investigation is needed to determine if this is a case of horizontal gene transfer, or of contamination by an unidentified strain