Phytotaxa

Cyanobacteria biodiversity remains underexplored despite their ecological importance and potential applications. To address this, we investigated two Leptolyngbya-like strains, LEGE 07170 and LEGE 191244, collected from marine tide pools in Portugal and Morocco using polyphasic approach. Phylogenetic analyses indicates that the strains form a distinct clade with strong statistical support in the Oculatellales order. The 16S rRNA gene identity matrix shows that the maximum shared values with the phylogenetically closest genera Gansulinema, Kaiparowitsia, Shahulinema, Aerofilum and Thermoleptolyngbya is consistently below 94.5%. Morphologically, LEGE 07170 and LEGE 191244 are indistinguishable to each other. Both optical and TEM analyses showed vacuole-like structures at the cells cross-walls and this character morphologically distinguishes these strains from their phylogenetically related genera. The 16S–23S ITS secondary structures also differed the LEGE-CC strains from their closest related genera.

Although species of the order Nostocales have morphological similarities to each other, some Nostoc species have been considered cryptic and are classified in the families Nostocaceae, Nodulariaceae and Aphanizomenaceae. Since then, the phylogenetic and morphological evaluation of Nostoc-like organisms has led to the taxonomic revision of some genera in different families. In the present work a cyanobacterium morphologically identified as Nostoc was isolated from an extreme cold lotic environment, in a high mountain of the Transmexican Volcanic Belt, and was taxonomically and phylogenetically characterized based on a polyphasic approach. Analysis of the 16S rRNA gene sequence references: Reofilinostoc matlalcueyense gen. et sp. nov. Thus, establishing a new genus of the family Nodulariaceae. The morphology of Reofilinostoc in the wild is reminiscent of a mouse ear, it is of 0.4-1.2 cm in length and has a firm cartilaginous texture; colonies can be pale green, brown or dark green in colour. Through a microscopic inspection, the filaments resemble to Komarekiella atlantica, Desikacharya nostocoides and Minunostoc cylindricum. While, the phylogenetic approach yielded similar results and consistently showed that Reofilinostoc matlalcueyense F02 (OR724089) is closely related to D. nostocoides and M. cylindricum in the core clade of Nodulariaceae. This research revealed that some comparisons between genera of Nodulariaceae exhibited similarity values higher than 97%, such as Atlanticothrix vs. Goleter and Cyanocohniella vs. Anabaenopsis. Nevertheless, in comparison to these phylogenetically closer genera, a substantial difference in the length and structure of D1-D1’, Box-B and V3 helix was demostrated; where Reofilinostoc, Desikacharya, and Minunostoc are part of the Nodulariaceae family; leading to the establishment of Reofilinostoc gen. nov., with Reofilinostoc matlalcueyense sp. nov. as the type species.

In this study, novel Calothrix-like strains NUACC09 and NUACC10 were isolated from the surfaces of rocks in Phayao Lake, Thailand. Morphological, molecular and ecological comparisons were investigated to characterize the taxonomic status of these novel strains. Under the light microscope, morphological studies indicated that these two strains were morphologically similar to Calothrix but could be differentiated by production of a non-hyaline hair at the terminal end, a low degree of tapering, twisted or loop-forming filaments, a knotted growth form, intertwined trichomes and presenting more than one trichome within the single sheath. In the 16S rRNA and rbcLX gene phylogenetic tree analyses, our strains formed a monophyletic clade with former freshwater/terrestrial Calothrix-like taxa separating distantly from other Calothrix-like genera. Furthermore, low 16S rRNA gene sequence similarity (<94.9%) to the closely related genera and species delimitation analyses (PTP/bPTP, GMYC, ABGD and ASAP methods) indicated that this clade should be considered as a different cyanobacterial lineage. The phylogenetic tree and secondary structures (D1–D1′, V2, Box-B and V3 helix) based on 16S–23S rRNA ITS regions suggested that multiple species might be contained in this clade. Therefore, here, Phayaothrix was proposed as a novel cyanobacterial genus with Phayaothrix lacustris sp. nov. as the type species following the International Code of Nomenclature for algae, fungi and plants.

Very thin filamentous cyanobacteria are ubiquitous in a wide range of environments. For many years they were traditionally studied according to their morphological properties only. With the introduction of additional taxonomic methods (cytomorphological analyses, molecular sequencing, exact ecological studies, better data about phytogeographical distribution), traditional genera such as Leptolyngbya and Phormidium were found to be polyphyletic. Phormidesmis belonged to a newly formed genus that was supposed to explain the variability of such very thin simple filamentous cyanobacteria. However, even after definition of Phormidesmis based on distinct cytomorphological and phylogenetic traits, the variability within this genus remained unresolved. Here we analyzed 26 Phormidesmis strains to describe the variability within this genus, classified two new species (P. arctica and P. communis) and transferred Leptolyngbya nigrescens into P. nigrescens. A tabular review of Phormidesmis species is included. The diacritical features of all these species are: width up to 1–4 µm, barrel-shaped cells, which can be shorter or slightly longer than wide, with apparent constrictions at the cross-walls. Our study shows that Phormidesmis is a morphologically and genetically well-defined genus with a global distribution. A newly described genus Leptodesmis has significant morphological similarities both with Phormidesmis and Leptolyngbya, however with intermediate phylogenetic position with significant divergence in 16S rRNA gene. Leptodesmis is cryptic both to Phormidesmis and Leptolyngbya. In the initial part of the life cycle resembles Leptolyngbya, the appearance of older trichomes change to Phormidesmis like morphology.

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.

The genus Synechococcus represents an enigmatic group of cyanobacteria with very simple unicellular morphology and polyphyletic evolutionary origin. Here, we describe a new genus based on strain of Synechococcus-like cyanobacterium. The strain was isolated from the peat bog Klin (Slovakia), where it occupies different niches such as hyaline cells of Sphagnum, sheaths of cyanobacteria, dead cells of desmids, carapaces of dead crustaceans, and solitary in detritus. We describe this new genus using a combination of molecular, morphological and ecological features. A phylogeny of the 16S rRNA gene, 16S-23S ITS and rbcL loci showed a separate position of the investigated strain and its close proximity to filamentous cyanobacteria. Therefore, it is a novel lineage of Synechococcus-like cyanobacteria illustrating the polyphyletic nature of the genus Synechococcus. Moreover, the strain exhibits unique morphological and ecological features, which allow us to erect the new monospecific genus Neosynechococcus.

A new species of Hassallia (Cyanobacteria, Nostocales, Microchaetaceae) from a supralittoral tropical marine biotope is described. Hassallia littoralis is a false-branched nostocalean cyanobacterium with caespitose free filaments or with fasciculated individual filaments not in a common sheath. Filaments are mainly heteropolar, bearing mono- and bi-pored heterocysts and isopolar or heteropolar hormogonia. The sheath is often widening, with pronounced rounded terminals. This new species is defined according to molecular, morphological and ecological criteria, considering data from different stages of its life cycle as well as the 16S rRNA partial gene sequence.

Five new species of cyanobacteria, Scytonematopsis maxima, Tolypothrix pseudorexia, Hormoscilla irregularis, Phormidium arthurensis, and Godleya alpina, the last belonging to a new genus, are described from cultured material isolated from the alpine zone of Mt Philistine, New Zealand. Tolypothrix pseudorexia resembles Rexia erecta in formation of upright trichomes on agar, but clearly lacks the ability to divide in two planes that is characteristic of the latter species. Godleya displays characteristics of the Scytonemataceae-isopolar hormogone development and binary branching-but groups with a species of Coleodesmium (Microchaetaceae) in analyses of 16S rDNA, despite its morphological differences, thus conflicting with the current classification system. We also show that material referable to the widely reported species Phormidium autumnale is found in the New Zealand alpine zone; molecular data indicate that this is likely the same organism reported recently from the Hutt River, Wellington, New Zealand, a quite different habitat. In this site, a lowland river, the species may form extensive mats. These have not been seen on Mt Philistine.