A total of 48 strains of thin, filamentous cyanobacteria in Synechococcales were studied by sequencing 16S rRNA and rpoC1 sequence fragments. We also carefully characterized a subset of these by morphology. Phylogenetic analysis of the 16S rRNA gene data using Bayesian inference of a large Synechococcales alignment (345 OTU’s) was in agreement with the phylogeny based on the rpoC1 gene for 59 OTU’s. Both indicated that the large family-level grouping formerly classified as the Leptolyngbyaceae could be further divided into four family-level clades. Two of these family-level clades have been recognized previously as Leptolyngbyaceae and Prochlorotrichaceae. Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. are proposed for the other two families. The Oculatellaceae was studied in greater detail, and six new genera containing 14 species were characterized and named. These new taxa are: Pegethrix botrychoides, P. olivacea, P. convoluta, P. indistincta, Drouetiella lurida, D. hepatica, D. fasciculata, Cartusia fontana, Tildeniella torsiva, T. nuda, Komarkovaea angustata, Kaiparowitsia implicata, Timaviella obliquedivisa, and T. radians.

A total of 27 strains of Oculatella were isolated, characterized and sequenced, and analysed phylogenetically with an additional environmental clone from the Atacama Desert and 10 strains isolated and sequenced by others. The strains were clearly separated based upon phylogenetic analyses conducted with a concatenated alignment of the 16S rRNA and 16S-23S ITS region of the ribosomal operons in the genus Oculatella. Differences in secondary structure of the conserved domains of the ITS region, as well as comparative analysis of P-distance among ITS regions, served to separate the strains into distinct taxonomic units. Seven new species of Oculatella were described, including four from arid to semi-arid soils (O. atacamensis, O. mojaviensis, O. coburnii, O. neakameniensis) and three from more mesic habitats, including a temperate lake (O. hafneriensis), a desert waterfall (O. cataractarum) and a Hawaiian sea cave (O. kauaiensis). The soil forms show statistically significant morphological differences, but the ranges overlap to a degree that they are not diagnosable by morphology, and these four cryptic species are characterized here using molecular characters. The more mesic species, including the type species from Mediterranean hypogea, O. subterranea, are all morphologically distinct from each other and from all four soil taxa. This report is the first to use solely molecular criteria to distinguish cryptic species of cyanobacteria.

A total of 16 strains phylogenetically placed within the Nostocaceae were found to possess morphological features of the Rivulariaceae and Tolypothrichaceae (tapering trichomes and single false branching, respectively) in addition to their typical Nostocacean features (production of arthrospores in series). These strains formed a strongly supported clade separate from other strains that are phylogenetically and morphologically close. We describe four new species within the genus Roholtiella gen. nov. The four species include three distinguishable morphotypes. Roholtiella mojaviensis and R. edaphica are morphologically distinct from each other and from the other two species, R. fluviatilis and R. bashkiriorum. Roholtiella fluviatilis and R. bashkiriorum are cryptic species with respect to each other. All four species are easily distinguished based on the sequence of the 16S-23S ITS regions, in particular the flanking regions to the conserved Box-B and V3 helices. The species are further established by the elevated p-distance between species that is much reduced among strains within the same species. Calochaete cimrmanii, a recently described tapering species from tropical biomes, is the most likely sister taxon to Roholtiella.

The family Microchaetaceae is a large group of heterocytous cyanobacteria, whose members bear typical morphological features of uniseriate heteropolar filaments never terminated by thin hairs and with simple false branching. However, phylogenetic analyses of the gene for 16S rRNA showed that members of this traditionally morphologically delimited family form several distant groups and therefore the current concept is hereafter indefensible. In this study, we provide reassessment of the status of the family Microchaetaceae based on morphology, ecology, biogeography, and phylogeny of 16S rRNA gene. Thorough examination of strains of the nominate genus Microchaete revealed their affiliation to two groups, Nostocaceae and Rivulariaceae, and their distant position to other traditional members of Microchaetaceae such as Tolypothrix, Hassallia, and Coleodesmium.To reflect the phylogenetic relationships and to accommodate members of the traditional family Microchaetaceae that are clearly not related to any of the Microchaete representatives, we propose establishment of two new families, Tolypothrichaceae and Godleyaceae. Based on both molecular and morphological evidence, we also provide a description of three new species of the genus Fortiea.

Members of the morphologically unusual cyanobacterial family Gomontiellaceae were studied using a polyphasic approach. Cultured strains of Hormoscilla pringsheimii, Starria zimbabweënsis, Crinalium magnum, and Crinalium epipsammum were thoroughly examined, and the type specimen of the family, Gomontiella subtubulosa, was investigated. The results of morphological observations using both light microscopy and transmission electron microscopy were consistent with previous reports and provided evidence for the unique morphological and ultrastructural traits of this family. Analysis of the 16S rRNA gene confirmed the monophyletic origin of non-marine repre-sentatives of genera traditionally classified into this family. The family was phylogenetically placed among other groups of filamentous cyanobacterial taxa. The presence of cellulose in the cell wall was analyzed and confirmed in all cultured Gomontiellaceae members using Fourier transform infrared spectroscopy and fluorescence microscopy. Evaluation of toxins produced by the studied strains revealed the hepatotoxin cylindrospermopsin (CYN) in available strains of the genus Hormoscilla. Production of this compound in both Hormoscilla strains was detected using high-performance liquid chromatography in tandem with high resolution mass spectrometry and confirmed by positive PCR amplification of the cyrJ gene from the CYN biosynthetic cluster. To our knowledge, this is the first report of CYN production by soil cyanobacteria, establishing a previously unreported CYN-producing lineage. This study indicates that cyanobacteria of the family Gomontiellaceae form a separate but coherent cluster defined by numerous intriguing morphological, ultrastructural, and biochemical features, and exhibiting a toxic potential worthy of further investigation.

Abstract:The simple filamentous cyanobacterial genus Geitlerinema is heterogeneous. At least two distinct phylogenetic clades can be derived from the set of most common freshwater Geitlerinema species. Our revision is based on the original description of the type species G. splendidum aka Oscillatoria spendida and on molecular sequencing of morphologically relevant strains. The revised Geitlerinema contains only one species according to morphological similarity with its original description. Consequently, the majority of other freshwater species inferred from molecular sequencing of 16S rRNA gene and 16S-23S ITS analysis (related both genetically and morphologically to G. pseudacutissimum) must be classified as a special taxon on the generic level. The name Anagnostidinema is proposed for this genus, which was selected in memory of the prominent late cyanobacterial specialist Konstantinos Anagnostidis. The genetic position, short review and characteristics of the newly defined genus Anagnostidinema is presented in this paper. The taxonomy of the rest of species (including the marine taxa), which are currently unable to be classified taxonomically with certainty, remain to be resolved in future studies.

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Two populations of Rivularia-like cyanobacteria were isolated from ecologically distinct and biogeographically distant sites. One population was from an unpolluted stream in the Kola Peninsula of Russia, whereas the other was from a wet wall in the Grand Staircase-Escalante National Monument, a desert park-land in Utah. Though both were virtually indistinguishable from Rivularia in field and cultured material, they were both phylogenetically distant from Rivularia and the Rivulariaceae based on both 16S rRNA and rbcLX phylogenies. We here name the new cryptic genus Cyanomargarita gen. nov., with type species C. melechinii sp. nov., and additional species C. calcarea sp. nov. We also name a new family for these taxa, the Cyanomargaritaceae.