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Tracy A Villareal - One of the best experts on this subject based on the ideXlab platform.
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Summer diatom blooms in the eastern North Pacific gyre investigated with a long-endurance autonomous surface vehicle.
PeerJ, 2018Co-Authors: Emily E Anderson, Cara Wilson, Anthony H Knap, Tracy A VillarealAbstract:Satellite chlorophyll a (chl a) observations have repeatedly noted summertime phytoplankton blooms in the North Pacific subtropical gyre (NPSG), a region of open ocean that is far removed from any land-derived or Ekman upwelling nutrient sources. These blooms are dominated by N2-fixing diatom-cyanobacteria associations of the diatom genera Rhizosolenia Brightwell and Hemiaulus Ehrenberg. Their nitrogen fixing endosymbiont, Richelia intracellularis J.A. Schmidt, is hypothesized to be critical to the development of blooms in this nitrogen limited region. However, due to the remote location and unpredictable duration of the summer blooms, prolonged in situ observations are rare outside of the Station ALOHA time-series off of Hawai’i. In summer, 2015, a proof-of-concept mission using the autonomous vehicle, Honey Badger (Wave Glider SV2; Liquid Robotics, a Boeing company, Sunnyvale, CA, USA), collected near-surface (
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upward nitrate transport by phytoplankton in oceanic waters balancing nutrient budgets in oligotrophic seas
PeerJ, 2014Co-Authors: Tracy A Villareal, Cynthia H Pilskaln, Joseph P Montoya, Mark R DennettAbstract:In oceanic subtropical gyres, primary producers are numerically dominated by small (1–5 µm diameter) pro- and eukaryotic cells that primarily utilize recycled nutrients produced by rapid grazing turnover in a highly effi cient microbial loop. Continuous losses of nitrogen (N) to depth by sinking, either as single cells, aggregates or fecal pellets, are balanced by both nitrate inputs at the base of the euphotic zone and N2-fixation. This input of new N to balance export losses (the biological pump) is a fundamental aspect of N cycling and central to understanding carbon fluxes in the ocean. In the Pacific Ocean, detailed N budgets at the time-series station HOT require upward transport of nitrate from the nutricline (80–100 m) into the surface layer (∼0–40 m) to balance productivity and export needs. However, concentration gradients are negligible and cannot support the fluxes. Physical processes can inject nitrate into the base of the euphotic zone, but the mechanisms for transporting this nitrate into the surface layer across many 10s of m in highly stratified systems are unknown. In these seas, vertical migration by the very largest (10 2 –10 3 µm diameter) phytoplankton is common as a survival strategy to obtain N from sub-euphotic zone depths. This vertical migration is driven by buoyancy changes rather than by flagellated movement and can provide upward N transport as nitrate (mM concentrations) in the cells. However, the contribution of vertical migration to nitrate transport has been diffi cult to quantify over the required basin scales. In this study, we use towed optical systems and isotopic tracers to show that migrating diatom (Rhizosolenia) mats are widespread in the N. Pacific Ocean from 140 ◦ W to 175 ◦ E and together with other migrating phytoplankton (Ethmodiscus, Halosphaera, Pyrocystis, and solitary Rhizosolenia) can mediate time-averaged transport of N (235 µmol N m −2 d −1 ) equivalent to eddy nitrate injections (242 µmol NO − m −2 d −1 ). This upward biotic transport can close N budgets in the upper 250 m of the central Pacific Ocean and together with diazotrophy creates a surface zone where biological nutrient inputs rather than physical processes dominate the new N flux. In addition to these numerically rare large migrators, there is evidence in the literature of ascending behavior
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nitrogen fixation suspension characteristics and chemical composition of Rhizosolenia mats in the central north pacific gyre
Biological oceanography, 2013Co-Authors: Tracy A Villareal, Edward J CarpenterAbstract:AbstractRhizosolenia mats were hand-collected from the central North Pacific gyre in March-April 1989 to examine their suspension properties, composition, and potential for nitrogen fixation by symbionts. Six species of Rhizosolenia were found in 10 different mat combinations. Nitrogen fixation could not be demonstrated either in in situ incubations or under N-poor culture conditions. Measured C: N (7.4 ± 2.8 by atoms) and C: Chi (150 ± 100 by weight) ratios were characteristic of healthy high-light-adapted phytoplankton populations, and this suggests that mat formation is not a senescence-induced phenomenon. Mats accounted for 2–30% of the total chlorophyll a in the upper 10 m and 98% of the biogenic particulate silicate. Positive buoyancy was documented in the aggregates, with an average daytime ascent rate of 3.6 ± 1.8 m h−1. Mats accumulated at the surface under low wind conditions. This study shows that macroscopic diatom associations need not sink. The vertical migration documented in one buoyant no...
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Nitrogen inputs into the euphotic zone by vertically migrating Rhizosolenia mats
Journal of Plankton Research, 2005Co-Authors: Heather R. Singler, Tracy A VillarealAbstract:Rhizosolenia mats conduct extensive vertical migrations in the oligotrophic central North Pacific (cNP) gyre that permit these diatoms to acquire nitrate at depth and return to the surface for photosynthesis. The ultimate fate of this N within the ecosystem is unknown, but may include remineralization by grazing, loss to depth by sinking biomass, or N excretion by Rhizosolenia mats. Direct release of N by mats into the mixed layer would represent an upward biological pump that circumvents the diffusion barriers and nutrient sinks at the base of the oceanic euphotic zone. We examined Rhizosolenia mat N release along a transect (28-31° N) in the summer of 2002 (Hawaii to California) and 2003 (Hawaii to west of Midway Island) using sensitive fluorometric and chemiluminescence methods. Nitrate, NO 2 - and NH 4 + release was determined. Nitrate and NH 4 + release by the mats occurred in both 2002(22.84 ± 6.04 and 3.69 + 1.74 nmol N μg 1 Chl a h -1 , respectively) and 2003 (23.74 ± 3.54 and 3.60 ± 0.74 nmol N μg -1 Chl a h -1 , respectively). Nitrite release only occurred in the 2003 summer period but occurred in both years when Fe chelators were added. Fv/Fm values decreased westward in 2003 suggesting a gradient of increasing physiological stress towards the west. The various physiological measures are consistent with concurrent Fe stress; however, other possibilities exist Nitrate excretion was the dominant form of N release in both years and provided a substantial addition to the ambient nitrate pool in the mixed layer. Rhizosolenia mat nitrate release supplies at least 4-7% of the nitrate pool on daily basis, and possibly as much as 27%. Rhizosolenia mats are part of a large phytoplankton community that appears to migrate, and rates could be significantly higher. Literature reports suggest little or no nitrification in the upper euphotic zone, and thus biological transport and release of nitrate may be a major source to this region. This N release is uncoupled from upward CO 2 transport and, like N 2 fixation, provides a component of the N pool available for net carbon removal.
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vertical migration by Rhizosolenia spp bacillariophyceae implications for fe acquisition
Journal of Phycology, 2000Co-Authors: Michael R L Mckay, Tracy A VillarealAbstract:Available data support a mechanism of buoyancy-mediated vertical migration by large-sized diatoms of Rhizosolenia spp. as a means to access "new" nitrogen from deep waters. To assess whether phytoplankton simultaneously satisfy their Fe requirements by this mechanism, field samples collected during summer 1996 at stations located along a transect through the central North Pacific gyre were assayed for the presence of flavodoxin and ferredoxin via Western blot analysis. All samples, regardless of their buoyancy status and the station from which they were collected, had accumulated flavodoxin but not ferredoxin. To understand better the significance of the field results, cultures of Rhizosolenia formosa H. Peragallo were grown in the laboratory with varying levels of total Fe (200 nM-10,000 nM). Fe had little effect on the physiological and photochemical parameters measured for each treatment. Growth rates did not exceed 0.17 d-1 and values of Fv /Fm ranged from 0.48 to 0.62. In addition, R. formosa accumulated only flavodoxin at each level of Fe addition. From these results, it appears that for some rhizosolenids, flavodoxin is constitutively expressed. The underlying basis for the constitutive nature of this flavodoxin is unclear at present, although it is likely that it is ultimately related to chronic Fe deficit incurred in natural waters.
Steven J Rowland - One of the best experts on this subject based on the ideXlab platform.
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The Rise of the Rhizosolenid Diatoms
Science, 2004Co-Authors: Jaap S. Sinninghe Damsté, Simon T Belt, Guillaume Masse, Jeanmichel Robert, Steven J Rowland, Gerard Muyzer, Ben Abbas, Sebastiaan W. Rampen, W.guy Allard, J. Michael MoldowanAbstract:The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 ± 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics.
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biosynthesis of unusual monocyclic alkenes by the diatom Rhizosolenia setigera brightwell
Phytochemistry, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J RowlandAbstract:Abstract Novel, polyunsaturated monocyclic sester- and triterpenes isolated from the diatom Rhizosolenia setigera (Brightwell), are biosynthesised mainly via the mevalonate pathway. The experiments involved incubation of the alga with [1- 13 C]acetate, isolation of the alkenes by extraction and silver ion HPLC, followed by determination of the labelling pattern of one of the monocyclic triterpenes by 13 C-NMR spectroscopy. In addition, the extent of 13 C incorporation was also measured by mass spectrometry which revealed that the involvement of the mevalonate route in the biosynthesis of these cyclic compounds was less than for the co-occurring acyclic highly branched isoprenoid alkenes.
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novel monocyclic sester and triterpenoids from the marine diatom Rhizosolenia setigera
ChemInform, 2004Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:The structures of two polyunsaturated monocyclic triterpenes have been elucidated using NMR spectroscopy following their isolation from the common marine diatom, Rhizosolenia setigera. The structure of a related monocyclic sesterterpene is proposed on the basis of mass spectral comparisons with the two monocyclic triterpenes.
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isoprenoid biosynthesis in the diatoms Rhizosolenia setigera brightwell and haslea ostrearia simonsen
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J Rowland, Michel RohmerAbstract:Isoprenoid biosynthesis in the widespread diatomaceous algae, Rhizosolenia setigera (Brightwell) and Haslea ostrearia (Simonsen), results not only in the production of diterpenoids, triterpenoids, and sterols but, unusually for diatoms, also in the production of sesterterpenoids. By using 13C and 2H isotopic labeling techniques followed by NMR and mass spectrometry, specific inhibition of mevalonate (MVA) and methylerythritol (MEP) pathways, and comparison with the natural 13C/12C isotope ratios of the lipids, the different biosynthetic pathways of the sesterterpenes and other isoprenoids have now been determined. Surprisingly, whereas the sesterterpenes (Δ7(20)-haslenes) in R. setigera were made by the MVA pathway, as were the related triterpenoid rhizenes and desmosterol, in H. ostrearia the structurally similar Δ6(17)-haslenes and the major sterol, 24-ethylcholest-5-en-3β-ol, were instead biosynthesized by the MEP route. Phytol was biosynthesized in both diatoms by the MEP route. Subfractionation of R. setigera cells revealed that although phytol was located in the chloroplasts, the haslenes, rhizenes, and sterols were present in the cytoplasm. The observations described here for R. setigera and H. ostrearia show that terpenoid biosynthesis in diatoms is species-dependent and cannot simply be grouped according to structural type. Triterpenes appear to be made by the MVA route as in higher plants, whereas sesterterpenes and sterols can be made by either the MVA or MEP routes. In neither organism were the isoprenoids biosynthesized by leucine metabolism. Sesterterpene and triterpene biosynthesis in diatoms has not been investigated previously.
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effects of auxosporulation on distributions of c25 and c30 isoprenoid alkenes in Rhizosolenia setigera
Phytochemistry, 2002Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:Abstract The effect of life cycle on the distributions of C 25 and C 30 highly branched isoprenoid (HBI) alkene lipids has been investigated for the marine diatom Rhizosolenia setigera . The concentrations of the C 30 compounds are largely independent of the cell volume, though the ratios of the individual isomers possessing five and six double bonds show a dependence on the position of the cell during its life cycle, especially during auxosporulation. In contrast to the C 30 pseudo-homologues, the C 25 isomers are not always detected in cultures of R. setigera . The biosynthesis of the C 25 HBIs would appear to result from the onset of auxosporulation, with further changes to their distributions taking place after this phase, including the formation of more unsaturated isomers. The results of this investigation may be used in part to explain the large variations in these lipids reported previously.
Guillaume Masse - One of the best experts on this subject based on the ideXlab platform.
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The Rise of the Rhizosolenid Diatoms
Science, 2004Co-Authors: Jaap S. Sinninghe Damsté, Simon T Belt, Guillaume Masse, Jeanmichel Robert, Steven J Rowland, Gerard Muyzer, Ben Abbas, Sebastiaan W. Rampen, W.guy Allard, J. Michael MoldowanAbstract:The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 ± 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics.
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biosynthesis of unusual monocyclic alkenes by the diatom Rhizosolenia setigera brightwell
Phytochemistry, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J RowlandAbstract:Abstract Novel, polyunsaturated monocyclic sester- and triterpenes isolated from the diatom Rhizosolenia setigera (Brightwell), are biosynthesised mainly via the mevalonate pathway. The experiments involved incubation of the alga with [1- 13 C]acetate, isolation of the alkenes by extraction and silver ion HPLC, followed by determination of the labelling pattern of one of the monocyclic triterpenes by 13 C-NMR spectroscopy. In addition, the extent of 13 C incorporation was also measured by mass spectrometry which revealed that the involvement of the mevalonate route in the biosynthesis of these cyclic compounds was less than for the co-occurring acyclic highly branched isoprenoid alkenes.
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novel monocyclic sester and triterpenoids from the marine diatom Rhizosolenia setigera
ChemInform, 2004Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:The structures of two polyunsaturated monocyclic triterpenes have been elucidated using NMR spectroscopy following their isolation from the common marine diatom, Rhizosolenia setigera. The structure of a related monocyclic sesterterpene is proposed on the basis of mass spectral comparisons with the two monocyclic triterpenes.
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isoprenoid biosynthesis in the diatoms Rhizosolenia setigera brightwell and haslea ostrearia simonsen
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J Rowland, Michel RohmerAbstract:Isoprenoid biosynthesis in the widespread diatomaceous algae, Rhizosolenia setigera (Brightwell) and Haslea ostrearia (Simonsen), results not only in the production of diterpenoids, triterpenoids, and sterols but, unusually for diatoms, also in the production of sesterterpenoids. By using 13C and 2H isotopic labeling techniques followed by NMR and mass spectrometry, specific inhibition of mevalonate (MVA) and methylerythritol (MEP) pathways, and comparison with the natural 13C/12C isotope ratios of the lipids, the different biosynthetic pathways of the sesterterpenes and other isoprenoids have now been determined. Surprisingly, whereas the sesterterpenes (Δ7(20)-haslenes) in R. setigera were made by the MVA pathway, as were the related triterpenoid rhizenes and desmosterol, in H. ostrearia the structurally similar Δ6(17)-haslenes and the major sterol, 24-ethylcholest-5-en-3β-ol, were instead biosynthesized by the MEP route. Phytol was biosynthesized in both diatoms by the MEP route. Subfractionation of R. setigera cells revealed that although phytol was located in the chloroplasts, the haslenes, rhizenes, and sterols were present in the cytoplasm. The observations described here for R. setigera and H. ostrearia show that terpenoid biosynthesis in diatoms is species-dependent and cannot simply be grouped according to structural type. Triterpenes appear to be made by the MVA route as in higher plants, whereas sesterterpenes and sterols can be made by either the MVA or MEP routes. In neither organism were the isoprenoids biosynthesized by leucine metabolism. Sesterterpene and triterpene biosynthesis in diatoms has not been investigated previously.
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effects of auxosporulation on distributions of c25 and c30 isoprenoid alkenes in Rhizosolenia setigera
Phytochemistry, 2002Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:Abstract The effect of life cycle on the distributions of C 25 and C 30 highly branched isoprenoid (HBI) alkene lipids has been investigated for the marine diatom Rhizosolenia setigera . The concentrations of the C 30 compounds are largely independent of the cell volume, though the ratios of the individual isomers possessing five and six double bonds show a dependence on the position of the cell during its life cycle, especially during auxosporulation. In contrast to the C 30 pseudo-homologues, the C 25 isomers are not always detected in cultures of R. setigera . The biosynthesis of the C 25 HBIs would appear to result from the onset of auxosporulation, with further changes to their distributions taking place after this phase, including the formation of more unsaturated isomers. The results of this investigation may be used in part to explain the large variations in these lipids reported previously.
Simon T Belt - One of the best experts on this subject based on the ideXlab platform.
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The Rise of the Rhizosolenid Diatoms
Science, 2004Co-Authors: Jaap S. Sinninghe Damsté, Simon T Belt, Guillaume Masse, Jeanmichel Robert, Steven J Rowland, Gerard Muyzer, Ben Abbas, Sebastiaan W. Rampen, W.guy Allard, J. Michael MoldowanAbstract:The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 ± 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics.
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biosynthesis of unusual monocyclic alkenes by the diatom Rhizosolenia setigera brightwell
Phytochemistry, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J RowlandAbstract:Abstract Novel, polyunsaturated monocyclic sester- and triterpenes isolated from the diatom Rhizosolenia setigera (Brightwell), are biosynthesised mainly via the mevalonate pathway. The experiments involved incubation of the alga with [1- 13 C]acetate, isolation of the alkenes by extraction and silver ion HPLC, followed by determination of the labelling pattern of one of the monocyclic triterpenes by 13 C-NMR spectroscopy. In addition, the extent of 13 C incorporation was also measured by mass spectrometry which revealed that the involvement of the mevalonate route in the biosynthesis of these cyclic compounds was less than for the co-occurring acyclic highly branched isoprenoid alkenes.
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novel monocyclic sester and triterpenoids from the marine diatom Rhizosolenia setigera
ChemInform, 2004Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:The structures of two polyunsaturated monocyclic triterpenes have been elucidated using NMR spectroscopy following their isolation from the common marine diatom, Rhizosolenia setigera. The structure of a related monocyclic sesterterpene is proposed on the basis of mass spectral comparisons with the two monocyclic triterpenes.
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isoprenoid biosynthesis in the diatoms Rhizosolenia setigera brightwell and haslea ostrearia simonsen
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Guillaume Masse, Simon T Belt, Steven J Rowland, Michel RohmerAbstract:Isoprenoid biosynthesis in the widespread diatomaceous algae, Rhizosolenia setigera (Brightwell) and Haslea ostrearia (Simonsen), results not only in the production of diterpenoids, triterpenoids, and sterols but, unusually for diatoms, also in the production of sesterterpenoids. By using 13C and 2H isotopic labeling techniques followed by NMR and mass spectrometry, specific inhibition of mevalonate (MVA) and methylerythritol (MEP) pathways, and comparison with the natural 13C/12C isotope ratios of the lipids, the different biosynthetic pathways of the sesterterpenes and other isoprenoids have now been determined. Surprisingly, whereas the sesterterpenes (Δ7(20)-haslenes) in R. setigera were made by the MVA pathway, as were the related triterpenoid rhizenes and desmosterol, in H. ostrearia the structurally similar Δ6(17)-haslenes and the major sterol, 24-ethylcholest-5-en-3β-ol, were instead biosynthesized by the MEP route. Phytol was biosynthesized in both diatoms by the MEP route. Subfractionation of R. setigera cells revealed that although phytol was located in the chloroplasts, the haslenes, rhizenes, and sterols were present in the cytoplasm. The observations described here for R. setigera and H. ostrearia show that terpenoid biosynthesis in diatoms is species-dependent and cannot simply be grouped according to structural type. Triterpenes appear to be made by the MVA route as in higher plants, whereas sesterterpenes and sterols can be made by either the MVA or MEP routes. In neither organism were the isoprenoids biosynthesized by leucine metabolism. Sesterterpene and triterpene biosynthesis in diatoms has not been investigated previously.
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effects of auxosporulation on distributions of c25 and c30 isoprenoid alkenes in Rhizosolenia setigera
Phytochemistry, 2002Co-Authors: Simon T Belt, Guy W Allard, Guillaume Masse, Jeanmichel Robert, Steven J RowlandAbstract:Abstract The effect of life cycle on the distributions of C 25 and C 30 highly branched isoprenoid (HBI) alkene lipids has been investigated for the marine diatom Rhizosolenia setigera . The concentrations of the C 30 compounds are largely independent of the cell volume, though the ratios of the individual isomers possessing five and six double bonds show a dependence on the position of the cell during its life cycle, especially during auxosporulation. In contrast to the C 30 pseudo-homologues, the C 25 isomers are not always detected in cultures of R. setigera . The biosynthesis of the C 25 HBIs would appear to result from the onset of auxosporulation, with further changes to their distributions taking place after this phase, including the formation of more unsaturated isomers. The results of this investigation may be used in part to explain the large variations in these lipids reported previously.
W W C Gieskes - One of the best experts on this subject based on the ideXlab platform.
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novel polyunsaturated n alkenes in the marine diatom Rhizosolenia setigera
FEBS Journal, 2000Co-Authors: Jaap Sinninghe S Damste, Stefan Schouten, W I C Rijpstra, Ellen C Hopmans, H Peletier, W W C Gieskes, Jan A J GeenevasenAbstract:Four previously unknown n-C25 and n-C27 heptaenes of the marine diatom Rhizosolenia setigera were isolated and identified using NMR spectroscopy. They possess six methylene interrupted (Z)-double bonds starting at C-3 and an additional terminal or n-2 (Z)-double bond. Structural and stable carbon isotopic evidence suggests that these polyenes are biosynthesized by chain elongation of the C22:6n-3 fatty acid, followed by decarboxylation and introduction of double bonds at specific positions.
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structural identification of the c25 highly branched isoprenoid pentaene in the marine diatom Rhizosolenia setigera
Organic Geochemistry, 1999Co-Authors: J Sinninghe S Damste, Stefan Schouten, W I C Rijpstra, Ellen C Hopmans, H Peletier, W W C Gieskes, Jan A J GeenevasenAbstract:2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-2,5E,9E,13-tetraene I possessing a C25 highly branched isoprenoid skeleton has been isolated from the marine diatom Rhizosolenia setigera and identified by 1H and 13C NMR spectroscopy.
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a c25 highly branched isoprenoid alkene and c25 and c27 n polyenes in the marine diatom Rhizosolenia setigera
Organic Geochemistry, 1999Co-Authors: J Sinninghe S Damste, Stefan Schouten, W I C Rijpstra, H Peletier, M J E C Van Der Maarel, W W C GieskesAbstract:A North Atlantic strain of the marine diatom Rhizosolenia setigera was examined for the presence of hydrocarbons. This strain biosynthesizes a highly branched isoprenoid (HBI) C25 pentaene, in contrast to Australian strains of R. setigera which produce HBI C30 alkenes. The more widespread occurrence of C25 HBI alkenes compared to their C30 counterparts in sea water and sediments may reflect the fact that C25 HBI alkenes occur both in Haslea and R. setigera. The North Atlantic R. setigera strain also biosynthesizes C25 and C27 n-polyenes with six or seven double bonds in relatively high amounts. Their carbon number distribution was found to depend on growth temperature. These lipids may be the precursors for C25 and C27 2-n-alkylthiophenes, which are important organosulfur compounds in sediments from palaeo upwelling regions. The distribution of these thiophenes may have potential for reconstruction of palaeo sea surface temperatures.