The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Beatriz Díez - One of the best experts on this subject based on the ideXlab platform.
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physiological and gene expression responses to nitrogen regimes and temperatures in mastigocladus sp strain chp1 a predominant thermotolerant cyanobacterium of hot springs
Systematic and Applied Microbiology, 2017Co-Authors: Estrella M Alcaman, Monica Vasquez, Jaime Alcorta, Birgitta Bergman, Martin F Polz, Beatriz DíezAbstract:Cyanobacteria are widely distributed primary producers with significant implications for the global biogeochemical cycles of carbon and nitrogen. Diazotrophic cyanobacteria of subsection V (Order Stigonematales) are particularly ubiquitous in photoautotrophic microbial mats of hot springs. The Stigonematal cyanobacterium strain CHP1 isolated from the Porcelana hot spring (Chile) was one of the major contributors of the new nitrogen through nitrogen fixation. Further morphological and genetic characterization verified that the strain CHP1 belongs to Stigonematales, and it formed a separate clade together with other thermophiles of the genera Fischerella and Mastigocladus. Strain CHP1 fixed maximum N2 in the light, independent of the temperature range. At 50°C nifH gene transcripts showed high expression during the light period, whereas the nifH gene expression at 45°C was arrhythmic. The strain displayed a high affinity for nitrate and a low tolerance for high ammonium concentrations, whereas the narB and glnA genes showed higher expression in light and at the beginning of the dark phase. It is proposed that Mastigocladus sp. strain CHP1 would represent a good model for the study of subsection V thermophilic cyanobacteria, and for understanding the adaptations of these photoautotrophic organisms inhabiting microbial mats in hot springs globally.
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The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat
ISME Journal, 2016Co-Authors: María Estrella Alcamán, Birgitta Bergman, Camila Fernandez, Antonio Delgado, Beatriz DíezAbstract:Cyanobacteria from Subsection V (Stigonematales) are important components of microbial mats in non-acidic terrestrial hot springs. Despite their diazotrophic nature (N2 fixers), their impact on the nitrogen cycle in such extreme ecosystems remains unknown. Here, we surveyed the identity and activity of diazotrophic cyanobacteria in the neutral hot spring of Porcelana (Northern Patagonia, Chile) during 2009 and 2011–2013. We used 16S rRNA and the nifH gene to analyze the distribution and diversity of diazotrophic cyanobacteria. Our results demonstrate the dominance of the heterocystous genus Mastigocladus (Stigonematales) along the entire temperature gradient of the hot spring (69–38 °C). In situ nitrogenase activity (acetylene reduction), nitrogen fixation rates (cellular uptake of 15N2) and nifH transcription levels in the microbial mats showed that nitrogen fixation and nifH mRNA expression were light-dependent. Nitrogen fixation activities were detected at temperatures ranging from 58 °C to 46 °C, with maximum daily rates of 600 nmol C2H4 cm−2 per day and 94.1 nmol N cm−2 per day. These activity patterns strongly suggest a heterocystous cyanobacterial origin and reveal a correlation between nitrogenase activity and nifH gene expression during diurnal cycles in thermal microbial mats. N and C fixation in the mats contributed ~3 g N m−2 per year and 27 g C m−2 per year, suggesting that these vital demands are fully met by the diazotrophic and photoautotrophic capacities of the cyanobacteria in the Porcelana hot spring.
Janelle R Thompson - One of the best experts on this subject based on the ideXlab platform.
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insights from the draft genome of the subsection v Stigonematales cyanobacterium hapalosiphon sp strain mrb220 associated with 2 mib production
Standards in Genomic Sciences, 2016Co-Authors: Shu Harn Te, Janelle R ThompsonAbstract:A non-axenic unialgal culture containing a Subsection V (Stigonematales) cyanobacterium, Hapalosiphon strain MRB 220, was obtained from a benthic freshwater algal mat through multiple transfers following growth in sterile media. Physiological characterization demonstrated the culture was capable of nitrogen-fixation and production of the off flavor compound 2-methylisoborneol (2-MIB). Total DNA isolated from this culture was sequenced using Illumina HiSeq and de novo assembled into contigs. The genome of MRB 220 was separated from co-occurring heterotrophic bacteria using sequence homology and compositional approaches, and its purity was confirmed based on best BLAST hit classification and principle component analysis of the tetranucleotide frequencies of fragmented contigs. The genome of ~7.4 Mbp contains 6,345 protein coding genes with 4,320 of these having functional prediction including predicted pathways for biosynthesis of the secondary metabolite welwitindolinone. Analyses of 16S rRNA gene and whole genome sequence average nucleotide identity indicated close relatedness of MRB 220 to the genera Hapalosiphon and Fischerella within the order Stigonematales. Microscopic examination showed that MRB 220 formed heterocystous branched filaments, thereby supporting identification of strain MRB 220 as a morphospecies of Hapalosiphon. Availability of the draft genome of Hapalosiphon strain MRB 220 enables future work to elucidate the pathway and dynamics for biosynthesis of 2-MIB and other secondary metabolites and understand the ecology and physiology of Stigonematales cyanobacteria in tropical freshwaters.
Birgitta Bergman - One of the best experts on this subject based on the ideXlab platform.
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physiological and gene expression responses to nitrogen regimes and temperatures in mastigocladus sp strain chp1 a predominant thermotolerant cyanobacterium of hot springs
Systematic and Applied Microbiology, 2017Co-Authors: Estrella M Alcaman, Monica Vasquez, Jaime Alcorta, Birgitta Bergman, Martin F Polz, Beatriz DíezAbstract:Cyanobacteria are widely distributed primary producers with significant implications for the global biogeochemical cycles of carbon and nitrogen. Diazotrophic cyanobacteria of subsection V (Order Stigonematales) are particularly ubiquitous in photoautotrophic microbial mats of hot springs. The Stigonematal cyanobacterium strain CHP1 isolated from the Porcelana hot spring (Chile) was one of the major contributors of the new nitrogen through nitrogen fixation. Further morphological and genetic characterization verified that the strain CHP1 belongs to Stigonematales, and it formed a separate clade together with other thermophiles of the genera Fischerella and Mastigocladus. Strain CHP1 fixed maximum N2 in the light, independent of the temperature range. At 50°C nifH gene transcripts showed high expression during the light period, whereas the nifH gene expression at 45°C was arrhythmic. The strain displayed a high affinity for nitrate and a low tolerance for high ammonium concentrations, whereas the narB and glnA genes showed higher expression in light and at the beginning of the dark phase. It is proposed that Mastigocladus sp. strain CHP1 would represent a good model for the study of subsection V thermophilic cyanobacteria, and for understanding the adaptations of these photoautotrophic organisms inhabiting microbial mats in hot springs globally.
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The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat
ISME Journal, 2016Co-Authors: María Estrella Alcamán, Birgitta Bergman, Camila Fernandez, Antonio Delgado, Beatriz DíezAbstract:Cyanobacteria from Subsection V (Stigonematales) are important components of microbial mats in non-acidic terrestrial hot springs. Despite their diazotrophic nature (N2 fixers), their impact on the nitrogen cycle in such extreme ecosystems remains unknown. Here, we surveyed the identity and activity of diazotrophic cyanobacteria in the neutral hot spring of Porcelana (Northern Patagonia, Chile) during 2009 and 2011–2013. We used 16S rRNA and the nifH gene to analyze the distribution and diversity of diazotrophic cyanobacteria. Our results demonstrate the dominance of the heterocystous genus Mastigocladus (Stigonematales) along the entire temperature gradient of the hot spring (69–38 °C). In situ nitrogenase activity (acetylene reduction), nitrogen fixation rates (cellular uptake of 15N2) and nifH transcription levels in the microbial mats showed that nitrogen fixation and nifH mRNA expression were light-dependent. Nitrogen fixation activities were detected at temperatures ranging from 58 °C to 46 °C, with maximum daily rates of 600 nmol C2H4 cm−2 per day and 94.1 nmol N cm−2 per day. These activity patterns strongly suggest a heterocystous cyanobacterial origin and reveal a correlation between nitrogenase activity and nifH gene expression during diurnal cycles in thermal microbial mats. N and C fixation in the mats contributed ~3 g N m−2 per year and 27 g C m−2 per year, suggesting that these vital demands are fully met by the diazotrophic and photoautotrophic capacities of the cyanobacteria in the Porcelana hot spring.
Jeffrey R. Johansen - One of the best experts on this subject based on the ideXlab platform.
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Aetokthonos hydrillicola gen. et sp. nov.: Epiphytic cyanobacteria on invasive aquatic plants implicated in Avian Vacuolar Myelinopathy
2016Co-Authors: Susan B Wilde, Jeffrey R. Johansen, Dayton H. Wilde, Peng Jiang, Bradley A, Rebecca S. HaynieAbstract:Research into the taxonomy of a novel cyanobacterial epiphyte in locations where birds, most notably Bald eagle and Ameri-can coots, are dying from a neurologic disease (Avian Vacuolar Myelinopathy—AVM) has been ongoing since 2001. Field investigations revealed that all sites where birds were dying had extensive invasive aquatic vegetation with dense colonies of an unknown cyanobacterial species growing on the underside of leaves. Morphological evaluation indicated that this was a true-branching, heterocystous taxon falling within the former order Stigonematales. However, 16S rRNA gene sequence demonstrated that it did not match closely with any described genus or species. More recent sequence analysis of the 16S rRNA gene and associated ITS region from additional true branching species resulted in a unique phylogenetic placement distant from the other clades of true-branching cyanobacteria. Light, epifluorescent, and transmission and scanning electron micrographs confirm the novel characteristics of this species, which is true-branching form with uniseriate basal filaments. It is encased within a firm sheath and has heterocytes both within the filaments and at the tips of the branches. The species is in a new genus of uncertain family assignment, and is herein named Aetokthonos hydrillicola gen. et sp. nov
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Mastigocladus laminosus (Stigonematales, Cyanobacteria): phylogenetic relationship of strains from thermal springs to soil-inhabiting genera of the order and taxonomic implications for the genus
Phycologia, 2008Co-Authors: Jan Kaštovský, Jeffrey R. JohansenAbstract:Abstract The morphology, ecology, life cycles, ultrastructure and sequences of the 16S rRNA gene of four cyanobacteria strains from different localities putatively identified as Mastigocladus laminosus were studied. Our strains fall into three separate clades, and conclusions based on “classical” taxonomical methods correspond with conclusions based on sequences of the 16S rRNA gene. According to all methods used, M. laminosus sensu stricto includes true branching strains from thermal springs only, and the genus Mastigocladus is separated from all soil species in the genus Fischerella. The genera Mastigocladus and Fischerella have a confused taxonomic history because the generitype of both taxa was collected from Karlovy Vary Hot Spring within 15 years of the description of each. Strains with other ecological (nonthermal locality) or morphological characteristics (thermal habitat but unbranched forms) belong to different genera. We begin the revision process by moving Mastigocladus laminosus var. indica t...
Alton L Boynton - One of the best experts on this subject based on the ideXlab platform.
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Microcystin-LA from a blue-green alga belonging to the Stigonematales
Phytochemistry, 1992Co-Authors: Michèle R. Prinsep, Faith R. Caplan, Richard E. Honkanen, Gregory M L Patterson, Richard E. Moore, Alton L BoyntonAbstract:Abstract Microcystin-LA accounts for the protein phosphatase (types 1, 2A and 3) inhibitory activity of the terrestrial blue-green alga Hapalosiphon hibernicus BZ-3-1.
