The Experts below are selected from a list of 135 Experts worldwide ranked by ideXlab platform
William H. Gerwick - One of the best experts on this subject based on the ideXlab platform.
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kalkipyrone b a marine cyanobacterial γ pyrone possessing cytotoxic and anti fungal activities
Phytochemistry, 2016Co-Authors: Matthew J Bertin, Ozlem Demirkiran, Gabriel Navarro, Nathan A Moss, John Lee, Gregory M Goldgof, Edgar Vigil, Elizabeth A Winzeler, Fred Valeriote, William H. GerwickAbstract:Bioassay-guided fractionation of two marine cyanobacterial extracts using the H-460 human lung cancer cell line and the OVC-5 human ovarian cancer cell line led to the isolation of three related α-methoxy-β, β'-dimethyl-γ-pyrones each containing a modified alkyl chain, one of which was identified as the previously reported kalkipyrone and designated kalkipyrone A. The second compound was an analog designated kalkipyrone B. The third was identified as the recently reported yoshinone A, also isolated from a marine cyanobacterium. Kalkipyrone A and B were obtained from a field-collection of the cyanobacterium Leptolyngbya sp. from Fagasa Bay, American Samoa, while yoshinone A was isolated from a field-collection of cyanobacteria (cf. Schizothrix sp.) from Panama. One-dimensional and two-dimensional NMR experiments were used to determine the overall structures and relative configurations of the kalkipyrones, and the absolute configuration of kalkipyrone B was determined by (1)H NMR analysis of diastereomeric Mosher's esters. Kalkipyrone A showed good cytotoxicity to H-460 human lung cancer cells (EC50=0.9μM), while kalkipyrone B and yoshinone A were less active (EC50=9.0μM and >10μM, respectively). Both kalkipyrone A and B showed moderate toxicity to Saccharomyces cerevisiae ABC16-Monster strain (IC50=14.6 and 13.4μM, respectively), whereas yoshinone A was of low toxicity to this yeast strain (IC50=63.8μM).
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somamides a and b two new depsipeptide analogues of dolastatin 13 from a fijian cyanobacterial assemblage of lyngbya majuscula and Schizothrix species
Journal of Natural Products, 2001Co-Authors: Lisa M Nogle, Thomas R Williamson, William H. GerwickAbstract:Somamides A (1) and B (2) were isolated from assemblages of the marine cyanobacteria Lyngbya majuscula and Schizothrix sp. from the Fijian Islands. These new depsipeptides are analogous in structure to the cyanobacterial metabolite symplostatin 2 (4) as well as dolastatin 13 (3), originally isolated from Dolabella auricularia, further demonstrating the cyanobacterial origin of the dolastatins.
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Yanucamides A and B, two new depsipeptides from an assemblage of the marine cyanobacteria Lyngbya majuscula and Schizothrix species.
Journal of natural products, 2000Co-Authors: Namthip Sitachitta, R T Williamson, William H. GerwickAbstract:Yanucamides A (1) and B (2) were isolated from the lipid extract of a Lyngbya majuscula and Schizothrix sp. assemblage collected at Yanuca Island, Fiji. The structures of compounds 1 and 2 were determined by spectroscopic methods. Both compounds contain a unique 2,2-dimethyl-3-hydroxy-7-octynoic acid, which has previously been described only as a component of kulolide-1 (3) and kulokainalide-1 (4), metabolites from the marine mollusk Philinopsis speciosa. Thus, the isolation of the yanucamides from this cyanobacterial assemblage supports the hypothesis that the kulolides and related metabolites are of cyanobacterial origin.
Pamela R. Reid - One of the best experts on this subject based on the ideXlab platform.
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Living Dendrolitic Microbial Mats in Hamelin Pool, Shark Bay, Western Australia
MDPI AG, 2018Co-Authors: Erica P. Suosaari, Stanley M. Awramik, Pamela R. Reid, John F. Stolz, Kathleen GreyAbstract:Hamelin Pool, Shark Bay, Western Australia, is home to the largest and most diverse assemblage of living marine stromatolites, with shapes and sizes comparable to ancient structures. A recent field-intensive program revealed seasonally ephemeral occurrences of modern dendrolitic microbial mats forming in intertidal, low energy settings. Dominated by filamentous cyanobacteria, dendrolitic microbial mats are formed when filaments provide a supporting framework as a result of gliding mobility, to build a shrubby morphology. Dendrolites, known throughout the rock record, refer to macroscopic microbialites with mesostuctures composed of unlaminated arborescent structures called shrubs. In these modern examples, thick filaments of Lyngbya aestuarii form the “trunk” of the bush, with finer filaments of Lyngbya fragilis, Phormidium sp. and Schizothrix sp. forming the “branches” These biologically-influenced dendrolitic structures provide insight into the complex interplay of microbial communities and the environment, broadening our understanding of shrub and dendrolite formation throughout the rock record
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ooid accreting diatom communities from the modern marine stromatolites at highborne cay bahamas
2010Co-Authors: Jonathan Franks, Pamela R. Reid, Rebecca J Aspden, Graham J C Underwood, David M Paterson, Lee Prufertbebout, John F. StolzAbstract:The modern marine stromatolites at Highborne Cay, Bahamas are inhabited by diverse surface microbial communities. Although these communities are most often dominated by cyanobacteria (e.g., Schizothrix gebeleinii, Solentia sp., Oscillatoria sp. etc.), diatoms can be abundant and have been implicated in stromatolite biogenesis. We have identified two distinct surface diatom communities involved in sediment deposition: (1) a thick (0.5–1 cm) yellow surface layer (yellow fur) of the stalked diatoms Licmophora remulus, L. paradoxa, and Striatella unipunctata, and (2) a colorless cohesive surface layer (“pustular blanket”) formed by a tube-forming diatom with individual cells resembling Navicula. The stalks could be labeled with a lectin–FITC conjugate and observed with confocal scanning laser microscopy (CSLM). Ooids were seen trapped within a well-developed network of stalks at the surface and clusters of stalks oriented vertical to the surface were found to penetrate the subsurface to a depth of several centimeters. Interestingly, the tubular structures formed by the naviculid species did not stain with the lectin–FITC conjugate. Nevertheless, manual manipulations of the sediment indicated that this diatom community also trapped ooids. Rapid sediment accretion could be attributed to these two diatom surface communities. Observations over the past decade as well as intensive monitoring over a 3-year period (2005–2007) indicate, however, that these surface diatom communities occur only at particular times of the year and do not survive burial. In addition, the surface layer of diatom-trapped ooids readily erodes unless stabilized by subsequent infiltration of extracellular polymeric substances (EPS) secreting cyanobacteria (e.g., S. gebeleinii). These observations suggest a limited contribution of diatoms to stromatolite biogenesis.
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tem analysis of microbial mediated sedimentation and lithification in modern marine stromatolites
American Mineralogist, 2001Co-Authors: John F. Stolz, Timothy N Feinstein, Joshua Salsi, Pieter T Visscher, Pamela R. ReidAbstract:Three sedimentary processes are involved in the growth of living stromatolites at Highborne Cay, Bahamas: (1) trapping of oolitic sands, (2) formation of surface micritic crusts, and (3) formation of fused-grain laminae. The microbial role in each process was investigated by examining the stromatolites using transmission electron microscopy. Species composition and physiological state of the bacteria were discerned by ultrastructure. A well-dispersed population of Schizothrix gebeleinii was observed in rapidly accreting surface layers. Their filaments produce copious quantities of amorphous exopolymer and condensed sheath that surround individual, and pairs of cells. Both fresh and degraded sheaths are, however, devoid of carbonate precipitates. This suggests that the primary roles of S. gebeleinii are the trapping and binding of unconsolidated sediment and the production of extra-cellular polymeric secretions. Surface micritic layers are composed primarily of needle-shaped crystals of aragonite. The uppermost surface of the micritic crust is coated with a biofilm comprised primarily of small Gram negative bacteria (i.e., sulfate reducing bacteria) that range in size from 250 to 500 nm in diameter and up to 1 μm in length. Empty cyanobacterial sheaths and occasional Gram positive spores were also observed. Thin sections through resin-casts of ooid microborings in the fused-grain laminae show cells of the endolithic cyanbacterium Solentia sp. and evidence of an organic matrix. The micritic crusts and fused-grain layers became lithified laminae that were preserved at depth, although the organisms that formed them were not. This suggests that morphological remains of these organisms (i.e., microfossils) in ancient stromatolites should not be expected.
Dale G. Nagle - One of the best experts on this subject based on the ideXlab platform.
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Tumonoic acids, novel metabolites from a cyanobacterial assemblage of Lyngbya majuscula and Schizothrix calcicola.
Journal of natural products, 1999Co-Authors: George G. Harrigan, Wesley Y. Yoshida, Richard E. Moore, Hendrik Luesch, Dale G. Nagle, Jason S. Biggs, Peter U. Park, Valerie J. PaulAbstract:Five new metabolites have been isolated from a lyngbyastatin 1- and dolastatin 12-producing assemblage of Lyngbya majuscula and Schizothrix calcicola collected at Tumon Bay, Guam. Structure elucidation employed 2D NMR techniques and chemical derivatization. These compounds have been assigned the trivial names tumonoic acids A (2), B (1), and C (5); methyl tumonoate A (3), and methyl tumonoate B (4). Compounds 1 and 4 were also found in a lyngbyastatin 1-producing strain of L. majuscula from Guam.
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isolation structure determination and biological activity of dolastatin 12 and lyngbyastatin 1 from lyngbya majuscula Schizothrix calcicola cyanobacterial assemblages
Journal of Natural Products, 1998Co-Authors: George G. Harrigan, Susan L Mooberry, Wesley Y. Yoshida, Richard E. Moore, Valerie J. Paul, Dale G. Nagle, Jason S. Biggs, Peter U. Park, Thomas H CorbettAbstract:Lyngbyastatin 1 (1a), a new cytotoxic analogue of dolastatins 12 (2a) and 11 (4), was isolated as an inseparable mixture with its C-15 epimer (1b) from extracts of a Lyngbya majuscula/Schizothrix calcicola assemblage and a L. majuscula strain collected near Guam. Dolastatin 12 (2a) was also encountered as an inseparable mixture with its C-15 epimer (2b) in L. majuscula/S. calcicola assemblages. At least one of the compounds in each mixture appeared to exist in solution as a mixture of slowly interconverting conformers resulting in broadened signals in 1H NMR spectra. Structure elucidation therefore relied principally on mass spectroscopy and chemical degradation studies. Both 1ab and 2ab proved toxic with only marginal or no antitumor activity when tested against colon adenocarcinoma #38 or mammary adenocarcinoma #16/C. Both 1ab and 2ab were shown to be potent disrupters of cellular microfilament networks.
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Ypaoamide, a new broadly acting feeding deterrent from the marine cyanobacterium Lyngbya majuscula
Tetrahedron Letters, 1996Co-Authors: Dale G. Nagle, Valerie J. Paul, Mary Ann RobertsAbstract:Ypaoamide, a new herbivore antifeedent metabolite, was isolated from the extract of a mixed cyanobacteria assemblage which was composed of Schizothrix calcicola and Lyngbya majuscula. The structure was determined spectroscopically by interpretation of 2D-NMR experiments, including HMBC and NOESY, and by comparison with model compounds. Isolated cells of the L. majuscula produced ypaoamide in laboratory culture.
Nugues M. - One of the best experts on this subject based on the ideXlab platform.
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Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curac¸ao
'Springer Science and Business Media LLC', 2018Co-Authors: Brocke H.j., Piltz B., Herz Nicole, Abed R.m.m., Palinska K.a., John Uwe, Haan J, De Beer Dirk, Nugues M.Abstract:Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We assessed the cyanobacterial diversity of BCMs at four coral reef sites in Curac¸ao, Southern Caribbean. In addition, nitrogen fixation rates of six common mats were measured. Microscopic examinations showed 22 cyanobacterial species, all from the order Oscillatoriales. Species diversity was similar among sites despite differences in overall BCM abundance. Dominant mats were primarily composed of Hydrocoleum glutinosum, Oscillatoria bonnemaisonii or Lyngbya majuscula. However, some mats exhibited highly variable species composition despite consistent macroscopic appearance. 16S rRNA-based phylogeny revealed similar species as those identified by microscopy, with additional sequences of unicellular (Xenococcus and Chroococcidiopsis) and heterocystous (Rivularia and Calothrix) cyanobacteria. Vice versa, morphotypes of Tychonema, Schizothrix and Dichothrix were found by microscopy only. The detection of similar species at the same sites in a study conducted 40 years ago indicates that changes in environmental conditions over these years may have favored indigenous species to bloom, rather than facilitated the introduction and proliferation of invasive species. Nitrogen fixation rates of mats were 3–10 times higher in the light than in the dark. The highest areal nitrogen fixation rate (169.1 mg N m-2 d-1) was recorded in the cyanobacterial patch dominated by O. bonnemaisonii. A scale-up of nitrogen fixation at a site with 26% BCM cover at 7 m depth yielded an aerial rate of 13 mg N m-2 reef d-1, which exceeds rates reported in open ocean blooms of Trichodesmium in the Caribbean. Our results suggest that the Caribbean basin is not only a hotspot for planktonic nitrogen fixation, but also for benthic nitrogen fixation. Because BCMs fix vast amounts of nitrogen, their proliferation will strongly alter the nitrogen budget of coral reefs
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Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curacao
'Springer Science and Business Media LLC', 2018Co-Authors: Brocke H., Piltz B., Herz N., Abed R., Palinska K., John U., Den Haan J., De Beer D., Nugues M.Abstract:Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We assessed the cyanobacterial diversity of BCMs at four coral reef sites in Curacao, Southern Caribbean. In addition, nitrogen fixation rates of six common mats were measured. Microscopic examinations showed 22 cyanobacterial species, all from the order Oscillatoriales. Species diversity was similar among sites despite differences in overall BCM abundance. Dominant mats were primarily composed of Hydrocoletan glutinosum, Oscillatoria bonnemaisonii or Lyngbya majuscula. However, some mats exhibited highly variable species composition despite consistent macroscopic appearance. 16S rRNA-based phylogeny revealed similar species as those identified by microscopy, with additional sequences of unicellular (Xenococcus and Chroococcidiopsis) and heterocystous (Rivularia and Calothrix) cyanobacteria. Vice versa, morphotypes of Tychonema, Schizothrix and Dichothrix were found by microscopy only. The detection of similar species at the same sites in a study conducted 40 years ago indicates that changes in environmental conditions over these years may have favored indigenous species to bloom, rather than facilitated the introduction and proliferation of invasive species. Nitrogen fixation rates of mats were 3-10 times higher in the light than in the dark. The highest areal nitrogen fixation rate (169.1 mg N m(-2) d(-1)) was recorded in the cyanobacterial patch dominated by O. bonnemaisonii. A scale-up of nitrogen fixation at a site with 26% BCM cover at 7 m depth yielded an aerial rate of 13 mg N m(-2) reef d(-1), which exceeds rates reported in open ocean blooms of Trichodesmiun in the Caribbean. Our results suggest that the Caribbean basin is not only a hotspot for planktonic nitrogen fixation, but also for benthic nitrogen fixation. Because BCMs fix vast amounts of nitrogen, their proliferation will strongly alter the nitrogen budget of coral reefs
Ulrich Nubel - One of the best experts on this subject based on the ideXlab platform.
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phylogenetic and morphological diversity of cyanobacteria in soil desert crusts from the colorado plateau
Applied and Environmental Microbiology, 2001Co-Authors: Ferran Garciapichel, Alejandro Lopezcortes, Ulrich NubelAbstract:We compared the community structures of cyanobacteria in four biological desert crusts from Utah’s Colorado Plateau developing on different substrata. We analyzed natural samples, cultures, and cyanobacterial filaments or colonies retrieved by micromanipulation from field samples using microscopy, denaturing gradient gel electrophoresis, and sequencing of 16S rRNA genes. While microscopic analyses apparently underestimated the biodiversity of thin filamentous cyanobacteria, molecular analyses failed to retrieve signals for otherwise conspicuous heterocystous cyanobacteria with thick sheaths. The diversity found in desert crusts was underrepresented in currently available nucleotide sequence databases, and several novel phylogenetic clusters could be identified. Morphotypes fitting the description of Microcoleus vaginatus Gomont, dominant in most samples, corresponded to a tight phylogenetic cluster of probable cosmopolitan distribution, which was well differentiated from other cyanobacteria traditionally classified within the same genus. A new, diverse phylogenetic cluster, named “Xeronema,” grouped a series of thin filamentous Phormidium-like cyanobacteria. These were also ubiquitous in our samples and probably correspond to various botanical Phormidium and Schizothrix spp., but they are phylogenetically distant from thin filamentous cyanobacteria from other environments. Significant differences in community structure were found among soil types, indicating that soil characteristics may select for specific cyanobacteria. Gypsum crusts were most deviant from the rest, while sandy, silt, and shale crusts were relatively more similar among themselves.
