The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Alena Lukešová - One of the best experts on this subject based on the ideXlab platform.
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Morphological and molecular characterization within 26 strains of the genus Cylindrospermum (Nostocaceae, Cyanobacteria), with descriptions of three new species.
Journal of phycology, 2014Co-Authors: Jeffrey R. Johansen, Markéta Bohunická, Alena Lukešová, Kristýna Hrčková, Melissa A. Vaccarino, Nicholas M. ChesarinoAbstract:Twenty-six strains morphologically identified as Cylindrospermum as well as the closely related taxon Cronbergia siamensis were examined microscopically as well as phylogenetically using sequence data for the 16S rRNA gene and the 16S-23S internal transcribed spacer (ITS) region. Phylogenetic analysis of the 16S rRNA revealed three distinct clades. The clade we designate as Cylindrospermum sensu stricto contained all five of the foundational species, C. maius, C. stagnale, C. licheniforme, C. muscicola, and C. catenatum. In addition to these taxa, three species new to science in this clade were described: C. badium, C. moravicum, and C. pellucidum. Our evidence indicated that Cronbergia is a later synonym of Cylindrospermum. The phylogenetic position of Cylindrospermum within the Nostocaceae was not clearly resolved in our analyses. Cylindrospermum is unusual among cyanobacterial genera in that the morphological diversity appears to be more evident than sequence divergence. Taxa were clearly separable using morphology, but had very high percent similarity among ribosomal sequences. Given the high diversity we noted in this study, we conclude that there is likely much more diversity remaining to be described in this genus.
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Cytotoxic effect of soil cyanobacterial extracts to mammal cell lines YAC-1 and WEHI
Fottea, 2005Co-Authors: Pavel Hrouzek, Jiří Kopecký, Jíří Salát, Blahoslav Maršálek, Alena LukešováAbstract:The cytotoxic effects of ten methanol extracts obtained from soil filamentous cyanobacteria (Anabaena, Calothrix, Nodularia, Cylindrospermum, Tolypothrix and Trichormus) were studied. Two different mammal cell lines (YAC-1, WEHI) were selected for cytotoxicity testing using the MTT test and flow-cytometry (FC). For comparison, the brine shrimp assay (using Artemia as a testing organism) was performed. The composition of extracts was studied using HPLC-MS. Both MTT and FC found the cytotoxic effect in 6 of 10 tested cyanobacterial extracts, but these results did not correlate with those obtained by brine shrimp assay. In Anabaena torulosa and Cylindrospermum sp. the most severe damage was recorded by both methods. In cells treated by the extract of Anabaena torulosa, 100% inhibition was found already after 60-minute exposure. Induction of necrosis was revealed by FC, since all tested cells were marked by propidium iodide indicating disruption of the cellular membrane. Surprisingly, no effects associated with this extract were found for Artemia. In Cylindrospermum sp. both necrotic (80%) and apoptotic (20%) induction was found by FC. The presence of microcystins in these extracts was not proved by HPLC-MS, but several peaks with unknown molecular masses were observed. Thus, the production of new cytotoxins with cytoxicity comparable to microcystin can be expected.
Emily P Balskus - One of the best experts on this subject based on the ideXlab platform.
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a new strategy for aromatic ring alkylation in cylindrocyclophane biosynthesis
Nature Chemical Biology, 2017Co-Authors: Hitomi Nakamura, Erica E Schultz, Emily P BalskusAbstract:Alkylation of aromatic rings with alkyl halides is an important transformation in organic synthesis, yet an enzymatic equivalent is unknown. Here, we report that cylindrocyclophane biosynthesis in Cylindrospermum licheniforme ATCC 29412 involves chlorination of an unactivated carbon center by a novel halogenase, followed by a previously uncharacterized enzymatic dimerization reaction featuring sequential, stereospecific alkylations of resorcinol aromatic rings. Discovery of the enzymatic machinery underlying this unique biosynthetic carbon-carbon bond formation has implications for biocatalysis and metabolic engineering.
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A new strategy for aromatic ring alkylation in cylindrocyclophane biosynthesis.
Nature chemical biology, 2017Co-Authors: Hitomi Nakamura, Erica E Schultz, Emily P BalskusAbstract:Cylindrocyclophane biosynthesis involves an unexpected halogenated intermediate arising from chlorination of an unactivated carbon center by a halogenase, followed by dimerization through stereospecific enzymatic alkylation of resorcinol aromatic rings. Alkylation of aromatic rings with alkyl halides is an important transformation in organic synthesis, yet an enzymatic equivalent is unknown. Here, we report that cylindrocyclophane biosynthesis in Cylindrospermum licheniforme ATCC 29412 involves chlorination of an unactivated carbon center by a novel halogenase, followed by a previously uncharacterized enzymatic dimerization reaction featuring sequential, stereospecific alkylations of resorcinol aromatic rings. Discovery of the enzymatic machinery underlying this unique biosynthetic carbon–carbon bond formation has implications for biocatalysis and metabolic engineering.
Z. Obreht - One of the best experts on this subject based on the ideXlab platform.
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Colonization of wheat Triticum vulgare L.) by N2-fixing cyanobacteria: I. A survey of soil cyanobacterial isolates forming associations with roots
New Phytologist, 1991Co-Authors: Miroslav Gantar, Nigel W. Kerby, Peter Rowell, Z. ObrehtAbstract:summary A variety of heterocystous, N2-fixing cyanobacteria, isolated from soils, were identified as members of the genera Nostoc, Anabaena and Cylindrospermum. These isolates were tested for their ability to form associations with the roots of wheat seedlings grown in liquid culture. Two types of associations were recognized: loose associations with cyanobacterial filaments growing between root hairs, which were typical of the Anabaena isolates, and tight associations of microcolonies in intimate association with the root surface, which were restricted to certain Nostoc isolates. Differences in nitrogenase activities of the free-living and associated cyanobacteria, together with the effects of added nitrate, indicate that nitrogenase activity may be influenced by the plant and/or its products.
Hitomi Nakamura - One of the best experts on this subject based on the ideXlab platform.
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a new strategy for aromatic ring alkylation in cylindrocyclophane biosynthesis
Nature Chemical Biology, 2017Co-Authors: Hitomi Nakamura, Erica E Schultz, Emily P BalskusAbstract:Alkylation of aromatic rings with alkyl halides is an important transformation in organic synthesis, yet an enzymatic equivalent is unknown. Here, we report that cylindrocyclophane biosynthesis in Cylindrospermum licheniforme ATCC 29412 involves chlorination of an unactivated carbon center by a novel halogenase, followed by a previously uncharacterized enzymatic dimerization reaction featuring sequential, stereospecific alkylations of resorcinol aromatic rings. Discovery of the enzymatic machinery underlying this unique biosynthetic carbon-carbon bond formation has implications for biocatalysis and metabolic engineering.
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A new strategy for aromatic ring alkylation in cylindrocyclophane biosynthesis.
Nature chemical biology, 2017Co-Authors: Hitomi Nakamura, Erica E Schultz, Emily P BalskusAbstract:Cylindrocyclophane biosynthesis involves an unexpected halogenated intermediate arising from chlorination of an unactivated carbon center by a halogenase, followed by dimerization through stereospecific enzymatic alkylation of resorcinol aromatic rings. Alkylation of aromatic rings with alkyl halides is an important transformation in organic synthesis, yet an enzymatic equivalent is unknown. Here, we report that cylindrocyclophane biosynthesis in Cylindrospermum licheniforme ATCC 29412 involves chlorination of an unactivated carbon center by a novel halogenase, followed by a previously uncharacterized enzymatic dimerization reaction featuring sequential, stereospecific alkylations of resorcinol aromatic rings. Discovery of the enzymatic machinery underlying this unique biosynthetic carbon–carbon bond formation has implications for biocatalysis and metabolic engineering.
Pavel Hrouzek - One of the best experts on this subject based on the ideXlab platform.
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Gene arrangement, functional annotation and domain structure of the puw gene cluster (56.7 kbp) from Cylindrospermum alatosporum CCALA 988.
2014Co-Authors: Jan Mareš, Jan Hájek, Petra Urajová, Jiří Kopecký, Pavel HrouzekAbstract:Gene arrangement, functional annotation and domain structure of the puw gene cluster (56.7 kbp) from Cylindrospermum alatosporum CCALA 988.
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Cytotoxic effect of soil cyanobacterial extracts to mammal cell lines YAC-1 and WEHI
Fottea, 2005Co-Authors: Pavel Hrouzek, Jiří Kopecký, Jíří Salát, Blahoslav Maršálek, Alena LukešováAbstract:The cytotoxic effects of ten methanol extracts obtained from soil filamentous cyanobacteria (Anabaena, Calothrix, Nodularia, Cylindrospermum, Tolypothrix and Trichormus) were studied. Two different mammal cell lines (YAC-1, WEHI) were selected for cytotoxicity testing using the MTT test and flow-cytometry (FC). For comparison, the brine shrimp assay (using Artemia as a testing organism) was performed. The composition of extracts was studied using HPLC-MS. Both MTT and FC found the cytotoxic effect in 6 of 10 tested cyanobacterial extracts, but these results did not correlate with those obtained by brine shrimp assay. In Anabaena torulosa and Cylindrospermum sp. the most severe damage was recorded by both methods. In cells treated by the extract of Anabaena torulosa, 100% inhibition was found already after 60-minute exposure. Induction of necrosis was revealed by FC, since all tested cells were marked by propidium iodide indicating disruption of the cellular membrane. Surprisingly, no effects associated with this extract were found for Artemia. In Cylindrospermum sp. both necrotic (80%) and apoptotic (20%) induction was found by FC. The presence of microcystins in these extracts was not proved by HPLC-MS, but several peaks with unknown molecular masses were observed. Thus, the production of new cytotoxins with cytoxicity comparable to microcystin can be expected.
