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The traditional cyanobacterial form-genus Aphanothece was established according to morphological criteria in the middle of the 19th century by Nägeli. It comprises unicellular morphotypes with oval or cylindrical cells arranged irregularly in amorphous mucilaginous colonies. Up to now, more than 80 morphospecies have been described, mostly from various freshwater aquatic habitats. The genus Aphanothece is heterogeneous in the traditional morphological concept as well as according to modern molecular criteria. Therefore, it must be divided into several taxonomic clusters. Generic characteristics, studied by a combination of molecular sequencing of 16S rDNA, ultrastructure, ecology and morphological variation, were investigated in selected strains and populations of type species of the traditional subgenera Aphanothece and Anathece. Distinct differences were found between both of these clusters in their position in the phylogenetic tree, ultrastructure of cells, morphology (size of cells), mucilage structure, life cycles and ecology. They must therefore be separated into two genera, according to both bacteriological and botanical criteria, and placed in different orders (Chroococcales and Synechococcales). Accordingly we describe Anathece, gen. et stat. nov., and transfer to it the type A. clathrata comb. nov. and six other species. Several other morphotypes, originally classified in the genus Aphanothece (but morphologically different from Aphanothece sensu stricto), correspond to the genera Cyanoaggregatum, Cyanogastrum, Gloeobacter, Gloeothece and Halothece. The closest relative of Anathece appears to be Cyanobium. [ABSTRACT FROM AUTHOR]

Selected strains of filamentous Phormidium-like cyanobacteria isolated from two Arctic regions (Ellesmere Island, High Canadian Arctic and Svalbard) and from Antarctica (Antarctic peninsula, South Shetland Islands and South Orkney Islands) were studied. The polyphasic approach used included phenotypic observations of morphological features and genotypic analyses (restriction fragment length polymorphism of 16S rRNA gene, internal transcribed space, 16S rRNA gene sequence analysis). Although genotypes generally correspond to observed morphotypes, the genetic analyses revealed a high degree of biodiversity that could not be unveiled using solely morphological evaluations. According to the phylogenetic analysis, the three clones were divided into two major clades, indicating that the phylogenetic distance between Arct-Ph5/Ant-Ph68 and Ant-Ph58 was so large they belonged to different genera. The polyphyletic position of strains of the genus Phormidium was confirmed by this study, attesting the need to entirely revise classification in this taxon in the future. [ABSTRACT FROM AUTHOR]

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Investigations carried out on Lake Dojran, fYR Macedonia, during the spring-autumn seasons in 2015 have been focused on detecting the degree of eutrophication in the lake, successive algal flora changes in the plankton communities and eventual presence of cyanotoxins (free microcystins) in the water. The obtained results revealed a co-existence of nine Microcystis species in the lake (M. aeruginosa, M. botrys, M. flos-aquae, M. ichthyoblabe, M. novacekii, M. protocystis, M. smithii, M. viridis and M. wesenbergii), with domination of the pan and neo-tropical species M. protocystis, again confirmed in a European lake. Results also corroborate the necessity to change the accepted morphospecies concept into separation of Microcystis taxa as distinct species which are clearly delimited according to their constant morphological features. Toxicity analyses demand for a specific and targeted investigation, since the toxin production and presence depends on many factors, and the toxin dynamics including the highest peaks may be easily overlooked if other issues are in the focus of the performed monitoring. Detected values for free microcystins in the water reached 2.84 µg L-1 microcystin-LR equivalents. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms are commonly associated with high concentrations of nutrients in waters. An exception among the species forming heavy water blooms is Limnoraphis robusta Komárek et al. (Fottea 13:39-52, 2013). Until now, heavy water blooms of this species were found only in tropical, rather oligotrophic waters. Filaments of L. robusta contain diazocytes and thus are able to fix molecular nitrogen during night. This ability gives L. robusta an advantage over other phytoplankters to explore nitrogen-poor habitats. In 2014, filaments of this cyanobacterium appeared also in plankton and periphyton in the Bay of Puno, Lake Titicaca, Peru. Accessible data on water chemistry, chlorophyll a concentration, and phytoplankton composition were compared with those from Lake Atitlán, Guatemala, where this cyanobacterium formed a thick brownish layer on the water surface in 2008, 2009 and 2011. Except for shallow bays, both lakes (Atitlán and Lago Mayor of Titicaca) are still oligotrophic in some periods, and phytoplankton growth is limited by lack of nitrogen. In this paper, we are discussing factors which might allow development of heavy bloom of this cyanobacterium in the Lago Mayor and other clear parts of the Lake Titicaca. [ABSTRACT FROM AUTHOR]

Getting to know the response of different groups of aquatic organisms tested in altered thermal environments to environmental conditions makes it possible to understand processes of adaptation and limitation factors such as temperature and light. Field sites were located in three thermally abnormal lakes (cooling system of power plants), in eastern part of Wielkopolska region (western Poland): Pątnowskie, Wąsosko-Mikorzyńskie and Licheńskie. Water temperatures of these lakes do not fall below 10°C throughout the year, and the surface water temperature in spring is about 20˚C. In this study, we investigated the species structure of the spring phytoplankton community in a temperature gradient and analyzed diversity of periphyton collected from alien species (Vallisneria spiralis) and stones. 94 taxa belonging to 56 genera of algae (including phytoplankton and periphyton) were determined. The highest number of algae species were observed among Chlorophyta (49), Bacillariophyceae (34) and Cyanobacteria (6). In spite of important differences in temperature in the investigated lakes, taxonomic composition of phytoplankton was comparable. Thermophilic species: Glochidinium penardiforme and Cylindrospermopsis raciborskii were found in the species structure (blooms were not observed). The obtained data also showed that the biotic surface of Vallisneria spiralis was a better substrate for Bacillariophyceae colonization than stones. The examination in the spring season of these thermally altered lakes, indicated the taxonomic composition of phytoplankton typical for eutrophic reservoirs (not heated). There was no replacement of any phytoplankton groups which are characteristic for spring conditions, even if there were changes in the competition dynamics. [ABSTRACT FROM AUTHOR]

Lake benthic cyanobacteria and algae are distributed along a depth gradient. At the extremes of the gradient, irradiance is a selecting factor because of excess (UV exposure in shallow waters) or extreme reduction (light limitation at the bottom of the euphotic zone). We tested whether, how, and to what extent epilithic cyanobacteria assemblages change with depth in a carbonate meromictic lake (Lake Tovel, southeastern Alps) that undergoes marked water-level fluctuations. Fixed stations were placed along a transect at 2- to 3-m depth intervals from 0 to 24 m and were sampled by SCUBA divers. Three depth-distribution zones were identified based on the composition of cyanobacterial assemblages and primary benthic algal pigments: shallow, middepth, and deep. The autecological traits of the cyanobacteria indicators identified by indicator value (IndVal) analysis suggested that the shallow, mid-depth, and deep zones were disturbed by water-level fluctuations, highly stable with favorable growth conditions, and severely light-limited, respectively. The shallow zone was colonized mainly by pseudaerial cyanobacteria and by UV-resisting phenoecodemes with yellow-brown sheaths (scytonemin). Shannon-Wiener diversity was highest in the shallow zone, probably because taxa characteristic of periodically inundated habitats mixed with lacustrine taxa. The most unique morphospecies were in the lower part of the mid-depth and in the deep zone. These species frequently had colorless sheaths or pink-red-violet cell contents. We found clear patterns in the depth distribution of benthic cyanobacteria and algal pigments that indicated adaptation to the principal evolutionary pressures at the extremes of the depth gradient: water-level fluctuation and light attenuation. These features have implications for quality assessments, biodiversity inventories, and identification of areas affected by water-level fluctuations. [ABSTRACT FROM AUTHOR]

The aims of this work were to study cyanobacterial isolates resembling the genus Hydrocoryne using a combination of morphology and phylogeny of 16S r RNA and nifH sequences and to investigate genes involved in cyanotoxin and protease inhibitor production. Four new cyanobacterial strains, isolated from biofilm samples collected from King George Island, Antarctica, were studied. In terms of morphology, these new strains share traits similar to true Anabaena morphotypes (benthic ones), whereas phylogenetic analysis of their 16S r RNA gene sequences grouped them with the sequence of the type species Hydrocoryne spongiosa (H. Schwabe ex Bornet and Flahault 1886-1888), but not with sequences of the type species from the genus Anabaena. This cluster is the sister group of Anabaena morphotypes isolated only from the Gulf of Finland. In addition, this cluster is related to two other clusters formed by sequences of Anabaena isolated from different sites. Partial nifH genes were sequenced from two strains and the phylogenetic tree revealed that the Antarctic nifH sequences clustered with sequences from Anabaena. Furthermore, two strains were tested, using PCR with specific primers, for the presence of genes involved in cyanotoxins (microcystin and saxitoxin) and protease inhibitor (aeruginosin, and cyanopeptolin). Only cyanopeptolin was amplified using PCR. These four Hydrocoryne strains are the first to be isolated and sequenced from Antarctica, which improves our knowledge on this poorly defined cyanobacterial genus. [ABSTRACT FROM AUTHOR]

Cyanobacteria are well adapted to freezing and desiccation; they have been proposed as possible survivors of comprehensive Antarctic glaciations. Filamentous types from the order Oscillatoriales, especially the species Phormidium autumnale Kützing ex Gomont 1892, have widely diverse morphotypes that dominate in Antarctic aquatic microbial mats, seepages, and wet soils. Currently little is known about the dispersion of cyanobacteria in Antarctica and of their population history. We tested the hypothesis that cyanobacteria survived Antarctic glaciations directly on site after the Gondwana breakup by using the relaxed and strict molecular clock in the analysis of the 16 S r RNA gene. We estimated that the biogeographic history of Antarctic cyanobacteria belonging to P. autumnale lineages has ancient origins. The oldest go further back in time than the breakup of Gondwana and originated somewhere on the supercontinent between 442 and 297 Ma. Enhanced speciation rate was found around the time of the opening of the Drake Passage ( c. 31-45 Ma) with beginning of glaciations ( c. 43 Ma). Our results, based primarily on the strains collected in maritime Antarctica, mostly around James Ross Island, support the hypothesis that long-term survival took place in glacial refuges. The high morphological diversification of P. autumnale suggested the coevolution of lineages and formation of complex associations with different morphologies, resulting in a specific endemic Antarctic cyanobacterial flora. [ABSTRACT FROM AUTHOR]

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 representatives 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 FROM AUTHOR]

[Display omitted] • Tenebriella – a new geographically widespread Oscillatoria -like genus. • Further step in the revisions of the old polyphyletic genus Oscillatoria. • Two new species based on the combination of morphological and molecular data. Oscillatoria has long been known to be polyphyletic. After recent resequencing of the reference strain for this genus, many Oscillatoria -like groups phylogenetically distant from the type species O. princeps remained unresolved. Here we describe one of these groups as a new genus Tenebriella. Most of the studied strains originate from Central Europe, where they are able to form prominent microbial mats. Despite the overall Oscillatoria -like morphology, Tenebriella can be distinguished by darker trichomes and forms a separate monophyletic clade in phylogenies inferred from the 16S rRNA gene and two additional loci (rpoC1 , rbcLX). Within Tenebriella we recognize two new species differing from each other by morphological and ecological characteristics. First species does not fit any known taxon description, and thus is described as a new species T. amphibia. The latter one corresponds with the information available for Oscillatoria curviceps Agardh ex Gomont, and thus new combination T. curviceps is proposed. The phylogenetic analyses of the 16S–23S ITS region together with the comparison of the hypothetical secondary structures confirmed recognition of these two species and additionally revealed presence of a morphologically cryptic species Tenebriella sp. The results corroborate frequent recurrence of convergent morphotypes in the evolution of cyanobacteria and justify further exploration even of the intensively studied European freshwaters using molecular phylogenetics to discover new and ecologically relevant taxa. [ABSTRACT FROM AUTHOR]

Simple trichal types constitute a group of cyanobacteria with an abundance of novel, often cryptic taxa. Here, we investigated material collected from wet surface-soil in a saline environment in Petchaburi Province, central Thailand. A morphological comparison of the isolated strain with similar known species, as well as its phylogenetic and species delimitation analyses based on the combined datasets of other related organisms, especially simple trichal cyanobacteria, revealed that the material of this study represented an independent taxon. Using a multifaceted method, we propose that this material represents a new genus, Thainema gen. nov., belonging to the family Leptolyngbyaceae, with the type species Thainema salinarum sp. nov. This novel taxon shares similar ecological habitats with strains previously placed in the same lineage., Competing Interests: The authors have declared that no competing interests exist.