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Jeffrey R Johansen - One of the best experts on this subject based on the ideXlab platform.
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Rivularia halophila sp nov nostocales cyanobacteria the first species of Rivularia described with the modern polyphasic approach
European Journal of Phycology, 2018Co-Authors: Sergei Shalygin, Nicole Pietrasiak, Fernando J Gomez, Cecilia Mlewski, Emmanuelle Gerard, Jeffrey R JohansenAbstract:ABSTRACTNatural populations of a Rivularia-like cyanobacterium were collected from the carbonate deposits of the temporarily flooded littoral zone of a hypersaline, high elevation lake, The Laguna Negra, Andes, Argentina. Subsequently, the cyanobacterial strain PUNA-NP3, named after its origin (Puna Volcanic Plateau) was isolated from these Rivularia-like rounded, pillow-like, black microbial mats. None of the previously described species of the genus Rivularia occupy inland, hypersaline aquatic environments. After morphological examination of this strain, we found clear morphological autapomorphies, such as mucilaginous pads at the bases of the young trichomes, wide trichomes and filaments, and uniquely branched trichomes. Furthermore, based on results from 16S rRNA phylogeny and analysis of the 16S-23S ITS region, PUNA-NP3 was found to be an independent lineage of the evolutionary tree. Based on the combination of ecological, morphological and molecular evidence, we name strain PUNA-NP3 Rivularia haloph...
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CYANOMARGARITA GEN. NOV. (NOSTOCALES, CYANOBACTERIA): CONVERGENT EVOLUTION RESULTING IN A CRYPTIC GENUS
Journal of Phycology, 2017Co-Authors: Sergei Shalygin, Nicole Pietrasiak, Jeffrey R Johansen, Regina Shalygina, Esther Berrendero Gómez, Markéta Bohunická, Jan Mareš, Christopher A. SheilAbstract: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.
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Macrochaete gen. nov. (Nostocales, Cyanobacteria), a taxon morphologically and molecularly distinct from Calothrix
Journal of Phycology, 2016Co-Authors: Esther Berrendero Gómez, Jeffrey R Johansen, Markéta Bohunická, Jan Kaštovský, Kateřina ČapkováAbstract:Historically, the genus Calothrix included all noncolonial, tapered, heterocytous filaments within the cyanobacteria. However, recent molecular phylogenies show that "Calothrix" defined in this sense represents five distinct clades. The type species of Calothrix is marine, with solitary basal heterocytes, no akinetes, and distal ends tapering abruptly into short hairs. We examined the morphology and phylogeny of 45 tapering cyanobacteria in the Rivulariaceae, including freshwater and marine representatives of both Calothrix (35 strains) and its sister taxon Rivularia (10 strains). The marine Calothrix fall into two lineages, but we lack the generitype and so cannot identify the clade corresponding to the type species. The freshwater and soil Calothrix fall into the C. parietina clade and are characterized by having a basal heterocyte, no akinetes, and gradual tapering-but not into a long hyaline hair. Macrochaete gen. nov. is a freshwater taxon sister to the Calothrix lineages but clearly separated from Rivularia. The species in this genus differ morphologically from Calothrix by their ability to produce two heteromorphic basal heterocytes and specific secondary structures of the 16S-23S ITS. An additional feature present in most species is the presence of a distal, long hyaline hair, but this character has incomplete penetrance due to its expression only under specific environmental conditions (low phosphate), and in one species appears to be lost. We recognize three species: M. psychrophila (type species) from cold environments (high mountains, Antarctica), M. santannae from wet walls of subtropical South America, and M. lichenoides, a phycobiont of lichens from Europe.
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Scytonematopsis contorta sp. nov. (Nostocales), a new species from the Hawaiian Islands.
Fottea, 2011Co-Authors: Melissa A. Vaccarino, Jeffrey R JohansenAbstract:Scytonematopsis Kiseleva is a poorly known cyanobacterial genus with a widespread, mostly tropical distribution. A new species, S. contorta, is described from the Hawaiian Island of Oahu based on morphological and molecular evidence. The new species was found growing on rock in damp aerial habitats proximal to streams and waterfalls. It differs in several regards to the other 14 species, in particular in its pronounced ability to produce a spirally contorted trichome within a single filament. The phylogenetic placement of the genus is uncertain. It is associated with both Rivularia and Calothrix species in the Rivulariaceae, and is distant from the Scytonemataceae, where it has traditionally been placed. However, the relationship of these taxa is unresolved, as there was very little support for the deeper nodes of the phylogeny.
Allan Pentecost - One of the best experts on this subject based on the ideXlab platform.
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photosynthesis and calcification of the stromatolitic freshwater cyanobacterium Rivularia
European Journal of Phycology, 2010Co-Authors: Allan Pentecost, Ulrich FrankeAbstract:Planar optodes and microelectrodes have been used to locate photosynthetic activity in calcified Rivularia biasolettiana and R. haematites. Maximum photosynthesis, measured as oxygen concentration and pH, occurred in the upper 1–3 mm of the colony, coinciding with a region of calcification. Stoichiometric calculations indicate that photosynthesis could account for almost all of the calcification within this region but further calcification was identified deeper within the colonies where photosynthesis was negligible. Overall, it was estimated that a maximum of 14% of the calcium carbonate within the colonies could have been formed as a direct result of photosynthesis.
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raman spectroscopy and light microscopy of a modern and sub fossil microstromatolite Rivularia haematites cyanobacteria nostocales
International Journal of Astrobiology, 2002Co-Authors: Allan Pentecost, Howell G M EdwardsAbstract:A study of Rivularia stromatolites demonstrated seasonal and non-seasonal banding patterns of calcification, ‘sun-screen’ scytonemin pigment and nitrogen-fixing heterocysts. Calcification was controlled by seasonal events with abiogenic ‘winter’ deposition and biogenic ‘summer’ deposition. Scytonemin was produced as a series of complex bands, probably as a response to summer Atlantic weather systems. Its production was also correlated in part with the appearance of heterocysts. The heterocysts were produced in bands, the pattern of which was probably controlled by an internal regulatory system. Raman spectra of modern and ancient (up to 4000 year old) Rivularia showed that scytonemin and carotenoid pigment can persist in dried material for >100 yr. The 4000 year old fossils did not reveal any useful biomarkers.
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Significance of the biomineralizing microniche in a lyngbya (cyanobacterium) travertine
Geomicrobiology Journal, 1995Co-Authors: Allan PentecostAbstract:Observations of the spatial arrangement of Lyngbya (Phormidium) incrustatum tri‐chomes in a travertine crust allowed prediction of the frequency of four types of microniche favorable for photosynthetically induced calcification. The most frequent type of microniche occurred at “cross‐over”; points where two trichomes made contact at a single point. Such points occurred very frequently (∼6000/mm2 travertine). Microniches more favorable to photocalcification consist of groups of three or more trichomes lying side by side, enclosing narrow tubes of interstitial water. These configurations were far less frequent and their effects would be negligible in Lyngbya travertines. In the calcified cyanobacteria Rivularia and Schizothrix such configurations may be much more common. The existence of such microniches demonstrated that regions favorable for photocalcification occur in travertine‐encrusted cyanobac‐terial mats and may initiate carbonate precipitation. However, the bulk of the carbonate precipitated in suc...
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Field relationships between scytonemin density, growth, and irradiance in cyanobacteria occurring in low illumination regimes
Microbial Ecology, 1993Co-Authors: Allan PentecostAbstract:In situ measurements of ultraviolet (UV) irradiance, carbon fixation, and scytonemin pigmentation were made on Scytonema populations from contrasting localities in England. Significant negative correlations were obtained between the following variate pairs: pigmentation and UV irradiance; pigmentation and carbon fixation rate. A significant positive correlation was found between pigmentation and sheath thickness. The negative correlation between pigmentation and UV irradiance was unexpected and appeared contrary to the results of previous studies, which indicated a positive correlation between the variates and the recognition of scytonemin as a radiation shield. However, by considering how radiation damage is related to cell division and the water relations of the sites investigated, it was shown that scytonemin is still functioning as a radiation shield, even in shaded sites. Rivularia colonies produced scytonemin only upon their upper, sun-exposed surfaces and were positively correlated with UV irradiance. This paper also describes the successful use of some new and inexpensive techniques to measure pigments in cyanobacterium sheaths, and integrated in situ UV-irradiance.
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Stable carbon and oxygen isotope composition of calcites associated with modern freshwater cyanobacteria and algae
Geomicrobiology Journal, 1990Co-Authors: Allan Pentecost, Baruch SpiroAbstract:Abstract The composition of carbon and oxygen stable isotopes was determined for calcite associated with the freshwater cyanobacteria Homoeothrix Crustacea, Phormidium incrustatum, and Rivularia haematites and the green alga Gongrosira incrustans in a UK travertine‐depositing stream. The δ13C values of Rivularia calcites deposited in summer were significantly higher than those deposited during winter. This was interpreted as the result of photosynthetic activity within colonies. The δ13C values were similar for the three cyanobacterium species studied, and colonies of Homoeothrix sampled over a 531‐m length of stream showed progressive downstream enrichment of 13C (2.0‰). This resulted from CO2 degassing of the downstream water, augmented during summer by bryophyte photosynthesis. Subsequent deposition of calcite takes place irrespective of photosynthetic activity of the algae and may blur the isotopic characteristics in older colonies and fossil assemblages.
Andre Pascal - One of the best experts on this subject based on the ideXlab platform.
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lamination of swampy rivulets Rivularia haematites stromatolites in a temperate climate
Sedimentary Geology, 2001Co-Authors: Christiane Caudwell, Jacques Lang, Andre PascalAbstract:Abstract Swampy-rivulets Rivularia haematites (D.C.) Agardh stromatolites were collected from the same site on the Plateau de Langres (Chaugey, France) over a seven year period. Specimens were studied in thin sections, in culture media under varying conditions of temperature and illumination, and by scanning electron microscope (SEM) in order to investigate the processes of calcification and lamination. New SEM observations confirm the polycrystalline structure of the ‘lamellae’ reported by the authors and show that the crystals composing these lamellae are elongate and aligned in the same direction as the filaments linked by them. The lamellae were also isolated in transverse sections under SEM and found to correspond to what under the light microscope appear to be ‘honeycomb’ structures. The diameter of alveoli can be the same as that of a ‘false branching’; their walls, formed by the outer sheath, have a dense network of microfibrils. These observations confirm the formation of calcitic lamellae at the false branching points and in contact with the microfibrils of the outer sheath. Confirmation of earlier hypotheses was sought through observation in thin section of the stromatolites collected over seven years. Micritic dark laminae are thought to form in three stages: (i) formation of a dark lamina by formation of a false branching zone in the wet season, (ii) initial calcification in this zone as microsparitic and sparitic lamellae during even a short dry spell, and (iii) subsequent bacterial micritization of the lamellae during an extended warm, dry season. The sparitic light laminae form around the hair-bearing regions. Lamination was first considered with regard to the annual radial growth rate of R. haematites. The thin section may display either a single dark lamina for two years’ growth, or a dark lamina thicker than the annual growth rate. Examination of local meteorological data accounts for the first phenomenon by a wet spell of more than 13 months and the second by a warm, dry period of one month. It may therefore take several years for a couplet to form as growth of the cyanobacterial colony is influenced by climatic variations. The different calcification phenomena were also correlated with dry spells. These interpretations are consistent with results obtained by experiments.
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etude experimentale de la lamination des stromatolithes a Rivularia haematites en climat tempere edification des lamines micritiques
Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule A-sciences De La Terre Et Des Planetes, 1997Co-Authors: Christiane Caudwell, Jacques Lang, Andre PascalAbstract:The lamination of Rivularia haematites stromatolites (D.C.) Agardh was studied experimentally for 7 years. Micritic laminae are found to form in three stages: biological formation of dark laminae during the wet season, microsparitic calcification of these laminae in the form of clearly individualized polycrystalline aggregates and, finally, micritization of the latter by bacterial action. These three stages develop over 2 to 3 years. The occurrence of transverse, longitudinal and circular microfibrils in the outer sheath is thought to explain the nucleation and the three-dimensional structure of the microsparitic crystals of the dark laminae and of the polycrystalline aggregates.
B. A. Whitton - One of the best experts on this subject based on the ideXlab platform.
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Seasonal changes in ambient phosphate and phosphatase activities of the cyanobacterium Rivularia atra in intertidal pools at Tyne Sands, Scotland
Hydrobiologia, 1996Co-Authors: J. M. Yelloly, B. A. WhittonAbstract:(i) A study was made of Rivularia atra at a sheltered bay in S-E. Scotland, where it is frequent in summer in pools of the upper eulittoral. Monthly measurements of water chemistry and phosphate activities were made at the same stage in the tidal cycle during April 1992–October 1993, together with other short intensive studies. (ii) Drift seaweed deposited at high tide levels (>4.9 m) released high concentrations of inorganic nutrients to adjacent pools, where the water sometimes exceeded 6000 µg l^−1 PO_4−P. Combined inorganic N was, however, always low and the N:P ratio fell to 0.001–0.003:1 (by weight) in August, when the temperature was relatively high: much N was lost to the atmosphere as ammonia. (iii) Total P concentrations in the Rivularia pools (mostly covered by 4.5–4.8 m tides) were much lower than in the drift seaweed pools, but similar to the sea, though with higher % organic P in the former (means of 50% v. 28%): total N concentrations were much lower in the Rivularia pools than in seawater, leading to a very low N:P for most of the time. Aqueous organic P tended to increase (in summer) during the period between tidal cover, even in pools lacking input drainage, suggesting that much of the organic P may be autochthonous. (iv) All 9 Rivularia pools showed high concentrations of P in June in one or both years. At the same time the Rivularia colonies formed abundant hormogonia, followed 4–8 weeks later by a marked increase in macroscopically obvious colonies. (v) Assays of ‘surface’ phosphomonoesterase activity by Rivularia colonies showed different results according to whether p-nitrophenyl phosphate (pNPP) or 4-methylumbelliferyl phosphate (4-MUP) was used as substrate. Both substrates indicated obvious activity at intervals during the year. Using pNPP, activity was very low in June, usually followed by a very high value in July or August; use of 4-MUP showed a different response, with a high value one or two months later than with pNPP.
Pilar Mateo - One of the best experts on this subject based on the ideXlab platform.
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Nitrogen fixation in a non-heterocystous cyanobacterial mat from a mountain river.
Scientific Reports, 2016Co-Authors: Esther Berrendero, Elvira Perona, Virginia Loza, Eduardo Fernández Valiente, Claudia L. Gómez, M. Ángeles Muñoz-martín, Pilar MateoAbstract:In situ nitrogen fixation was investigated in a cyanobacterial mat growing on the bed of rocks of the Muga River, Spain. The filamentous non-heterocystous cyanobacterium Schizothrix dominated the mat, showing nitrogenase activity in the light at similar rates to those found in nearby heterocystous Rivularia colonies. N2 fixation in the light was significantly increased by an inhibitor of PSII and oxygen evolution, DCMU (3-[3,4-dichlorophenyl]-1,1-dimethylurea), and anaerobic conditions. However, no nitrogenase activity was found in the dark. Addition of fructose as a respiratory substrate induced nitrogenase activity in samples incubated under aerobic conditions in the dark but not in anaerobic conditions. Microelectrode oxygen profiles showed internal microaerobic microzones where nitrogen fixation might concentrate. Analyses of the 16S rRNA gene revealed only the presence of sequences belonging to filamentous non-heterocystous cyanobacteria. nifH gene diversity showed that the major phylotypes also belonged to this group. One of the three strains isolated from the Schizothrix mat was capable of fixing N2 and growing in the absence of combined N. This was consistent with the nifH gene analysis. These results suggest a relevant contribution of non-heterocystous cyanobacteria to nitrogen fixation in these mats.
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Phosphatase activities of cyanobacteria as indicators of nutrient status in a Pyrenees river
Hydrobiologia, 2010Co-Authors: Pilar Mateo, Esther Berrendero, Elvira Perona, Virginia Loza, Brian A. WhittonAbstract:There is increasing evidence that fluvial systems are influenced by anthropogenic factors, and disturbance due to pollution and other human interference gives rise to specific problems. It is now imperative that we develop and apply novel and effective ways which allow us to monitor water quality. The present study was planned as part of a programme to develop biological monitoring methods to assess nutrient characteristics of upland calcareous streams and rivers. Phototrophs respond to environmental changes over a period of time, so organisms sampled at one time can potentially provide almost as much information about nutrients in the water as a number of individual chemical measurements. Phosphatase activity is often a good indicator of phosphorus limitation, and field materials could be used to study changes in nutrients dynamics. The calcareous River Muga, north-east Spain, at a site 10 km downstream from its source in the Pyrenees, was therefore chosen for the present study of surface phosphatase activities of the main cyanobacterial communities at different seasons to assess P limitation and establish the suitability of this method for use in monitoring catchment processes. Here we report seasonal changes of phosphatase activity in field populations of Schizothrix coriacea, Rivularia biasolettiana, Tolypothrix distorta var. penicillata and Nostoc verrucosum. All four cyanobacteria showed marked surface phosphomonoesterase and phosphodiesterase activity on each sampling period. Michaelis-Menten kinetic studies showed similar K m values for the four species suggesting similar affinity for organic P substrates. Light had no effect on phosphatase activities, indicating that there is no need to consider this factor in short-term field assays. However, there was an increase in phosphomonoesterase activity of Rivularia with rise in temperature over the range 10–35°C, which suggests adaptation to the frequent temperature changes in nature. Phosphorus limitation seems the main chemical factor influencing phototrophs in R. Muga. Combined observations on macroscopically visible phototrophs with assays of surface phosphatase activity provide a valuable means of assessing long-term changes in a catchment.
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genetic and morphological characterization of Rivularia and calothrix nostocales cyanobacteria from running water
International Journal of Systematic and Evolutionary Microbiology, 2008Co-Authors: Esther Berrendero, Elvira Perona, Pilar MateoAbstract:In this study, a polyphasic approach was adopted to investigate natural freshwater (river and stream) samples of Rivularia colonies and isolated strains of cyanobacteria with a high degree of trichome tapering (genera Rivularia and Calothrix). Analysis of the phycocyanin (PC) operon and the intervening intergenic spacer (cpcBA-IGS) and 16S rRNA gene sequences were used for genetic characterization. In addition, a molecular fingerprinting method, temperature-gradient gel electrophoresis, which allows sequence-dependent separation of PCR products, was used to assess genotypic diversity in environmental samples and isolated strains. The results showed a high variability of the PC-IGS among the genotypes that was not associated with the morphologies observed. This study underlines the importance of choosing a low-nutrient-content culture medium, especially one with a low phosphorus concentration, for studying typical morphological features of Rivularia for taxonomic purposes. Molecular fingerprinting methods and morphological analyses confirmed the diversity in Rivularia colonial structure and trichome features corresponding to genetic diversity within a single colony. Phylogenetic analysis of cpcBA-IGS was largely consistent with that obtained from 16S rRNA gene sequence analysis and confirmed the high level of divergence between genotypes. The sequences of Rivularia and Calothrix from this study and database sequences showed great heterogeneity and were clearly not monophyletic. The results of this genetic and morphological study of field samples and fresh isolates indicated that the current classification of these genera needs to be revised.
