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Stenomitos is a recently established cyanobacterial genus, some species of which appear to be cryptic. Here we describe two new species in this genus, Stenomitos kolaensis sp. nov. isolated from the Al-Fe humic podzols of a boreal forest near Nikel town, Murmansk region, Russia and S. hiloensis sp. nov. isolated from a basaltic seep wall on Akeola Road, Hilo, Hawaii, USA. Phylogenetic analyses were conducted on the 16S and 16S-23S ITS rRNA gene regions using Bayesian Inference, and Maximum Likelihood. Phylogenetic analysis of the 16S-23S ITS rRNA region resulted in both S. kolaensis and S. hiloensis forming separate clades from other Stenomitos lineages. Antarctic strains of Stenomitos frigidus (previously reported as “Leptolyngbya frigida”) show that species to be polyphyletic and in need of revision. The structure of the conserved ITS regions (Box-B, D1-D1ʹ, V2 and V3 helices) provided support for separation of the species, and the p-distances among aligned ITS regions further confirmed that a number of species exist within the genus. S. kolaensis and S. hiloensis can be distinguished from other described Stenomitos species (S. rutilans and S. tremulus) by their geographical distribution, habitat preference, 16S rRNA phylogeny, and differences in the secondary structure of the 16S-23S ITS region.

We report draft genomes of two bacterial strains in the genera Hyphobacterium and Reichenbachiella, which are associated with the diatom Cyclotella cryptica strain CCMP332. Genomes from these strains were 2,691,501 bp and 3,325,829 bp in size, respectively, and will be useful for understanding interactions between diatoms and bacteria., We report draft genomes of two bacterial strains in the genera Hyphobacterium and Reichenbachiella, which are associated with the diatom Cyclotella cryptica strain CCMP332. Genomes from these strains were 2,691,501 bp and 3,325,829 bp, respectively, and will be useful for understanding interactions between diatoms and bacteria.

The diatom genus Orthoseira Thwaites (Bacillariophyta) is a ubiquitous taxon in aerial diatom assemblages, with species found globally. Cylindrical cell shape and radial symmetry of this genus has led to its historical placement in the Coscinodiscophyceae ('radial centric' diatoms), but its systematic relationships have remained uncertain. We present a five-gene phylogeny, based on nuclear (nSSU rDNA) and chloroplast (rbcL, psbC, psbA, and psaB) genes to determine the phylogenetic placement of Orthoseira among the diatoms. The concatenated multi-gene phylogenies and nSSU-only gene tree demonstrate that Orthoseira is deeply embedded within a clade of the Mediophyceae ('multipolar centric' diatoms). Throughout all phylogenetic analyses, Orthoseira was shown to be sister to the genera Terpsinoë and Hydrosera. Through comparison of topologies reflecting competing hypotheses about the placement of Orthoseira, it was determined that the hypothesis that Orthoseira, represented here by O. dendroteres and O. roeseana, is a member of the Melosirales should be rejected. Therefore, lack of morphological similarity between Hydrosera, Orthoseira, and Terpsinoë is hypothesized to be the result of changes in habitat preferences that lead to an ancient divergence event between the Orthoseirales and the Hydrosera, Terpsinoë clade.