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William H. Wilson - One of the best experts on this subject based on the ideXlab platform.
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the cheshire cat escape strategy of the coccolithophore Emiliania huxleyi in response to viral infection
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Miguel Frada, Ian Probert, Michael J Allen, William H. Wilson, Colomban De VargasAbstract:The coccolithophore Emiliania huxleyi is one of the most successful eukaryotes in modern oceans. The two phases in its haplodiploid life cycle exhibit radically different phenotypes. The diploid calcified phase forms extensive blooms, which profoundly impact global biogeochemical equilibria. By contrast, the ecological role of the noncalcified haploid phase has been completely overlooked. Giant phycodnaviruses (Emiliania huxleyi viruses, EhVs) have been shown to infect and lyse diploid-phase cells and to be heavily implicated in the regulation of populations and the termination of blooms. Here, we demonstrate that the haploid phase of E. huxleyi is unrecognizable and therefore resistant to EhVs that kill the diploid phase. We further show that exposure of diploid E. huxleyi to EhVs induces transition to the haploid phase. Thus we have clearly demonstrated a drastic difference in viral susceptibility between life cycle stages with different ploidy levels in a unicellular eukaryote. Resistance of the haploid phase of E. huxleyi provides an escape mechanism that involves separation of meiosis from sexual fusion in time, thus ensuring that genes of dominant diploid clones are passed on to the next generation in a virus-free environment. These “Cheshire Cat” ecological dynamics release host evolution from pathogen pressure and thus can be seen as an opposite force to a classic “Red Queen” coevolutionary arms race. In E. huxleyi, this phenomenon can account for the fact that the selective balance is tilted toward the boom-and-bust scenario of optimization of both growth rates of calcifying E. huxleyi cells and infectivity of EhVs.
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Proteomic analysis of the EhV-86 virion
Proteome Science, 2008Co-Authors: Michael J Allen, Kathryn Susan Lilley, Julie Howard, William H. WilsonAbstract:Background Emiliania huxleyi virus 86 (EhV-86) is the type species of the genus Coccolithovirus within the family Phycodnaviridae. The fully sequenced 407,339 bp genome is predicted to encode 473 protein coding sequences (CDSs) and is the largest Phycodnaviridae sequenced to date. The majority of EhV-86 CDSs exhibit no similarity to proteins in the public databases.
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complete genome sequence and lytic phase transcription profile of a coccolithovirus
Science, 2005Co-Authors: William H. Wilson, Declan C. Schroeder, Michael J Allen, Matthew T G Holden, Julian Parkhill, B G Barrell, Carol Churcher, N Hamlin, Karen Mungall, Halina NorbertczakAbstract:The genus Coccolithovirus is a recently discovered group of viruses that infect the globally important marine calcifying microalga Emiliania huxleyi. Among the 472 predicted genes of the 407,339–base pair genome are a variety of unexpected genes, most notably those involved in biosynthesis of ceramide, a sphingolipid known to induce apoptosis. Uniquely for algal viruses, it also contains six RNA polymerase subunits and a novel promoter, suggesting this virus encodes its own transcription machinery. Microarray transcriptomic analysis reveals that 65% of the predicted virus-encoded genes are expressed during lytic infection of E. huxleyi.
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virus succession observed during an Emiliania huxleyi bloom
Applied and Environmental Microbiology, 2003Co-Authors: Declan C. Schroeder, Gillian Malin, Matthew J. Hall, William H. WilsonAbstract:Denaturing gradient gel electrophoresis was used as a molecular tool to determine the diversity and to monitor population dynamics of viruses that infect the globally important coccolithophorid Emiliania huxleyi. We exploited variations in the major capsid protein gene from E. huxleyi-specific viruses to monitor their genetic diversity during an E. huxleyi bloom in a mesocosm experiment off western Norway. We reveal that, despite the presence of several virus genotypes at the start of an E. huxleyi bloom, only a few virus genotypes eventually go on to kill the bloom.
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Viral control of Emiliania huxleyi blooms
Journal of Marine Systems, 1996Co-Authors: Gunnar Bratbak, William H. Wilson, Mikal HeldalAbstract:Virus and virus-like particles (VLP) have been observed in all major algal classes. Few host-virus systems of microalgae have until now been brought into culture and extensively studied. For Emiliania huxleyi we have been able to describe viral infection during blooms in mesocosms and in landlocked fjords. Evidence of viral lysis of E. huxleyi during blooms in the North Sea has also been obtained. We have also developed a plaque assay for E. huxleyi virus with which we have been able to isolate a virus that could be propagated in the laboratory. This virus isolate lost its virulence possibly due to defective interfering particles (DI). The sizes of viruses related to E. huxleyi indicate two major groups, one with a particle diameter of 180 nm and one with a head diameter of 140 nm.
Ulf Riebesell - One of the best experts on this subject based on the ideXlab platform.
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The Calcium Carbonate Shell of Emiliania huxleyi Provides Limited Protection Against Viral Infection
Frontiers in Marine Science, 2020Co-Authors: Mathias Haunost, Ulf Riebesell, Lennart T. BachAbstract:Coccolithophores are a group of marine phytoplankton which cover themselves with the coccosphere - a shell composed of numerous calcium carbonate (CaCO3) platelets. They play a pivotal role in the oceanic carbon and calcium carbonate cycles, as they contribute significantly to the marine primary production and account for a large proportion of the pelagic CaCO3 production. Despite more than a century of coccolithophore research, it remains speculative why coccolithophores calcify. However, resolving this question is essential to assess the competitive fitness of this important group in the future ocean where changes in calcification are expected. Here, we used the Emiliania huxleyi – Emiliania huxleyi virus 86 host-virus model system to test the hypothesis that the coccosphere serves as a physical barrier reducing viral infection. Therefore, we removed the coccosphere from living E. huxleyi cells and compared the infection progress relative to calcified cells in a series of 6 experiments under different growth conditions. These experiments showed that the CaCO3 shell provides limited protection directly after cell division when the coccosphere has been shared among the two daughter cells and is therefore permeable for viral particles. However, the coccosphere can reduce viral infection and the protection improves as the number of calcite platelets in the coccosphere increases. Our results indicate that E. huxleyi can reach higher abundances in blooms that are infested with large viruses due to the protective role of the coccosphere. The findings improve our understanding of the ecological role of calcification.
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dissecting the impact of co2 and ph on the mechanisms of photosynthesis and calcification in the coccolithophore Emiliania huxleyi
New Phytologist, 2013Co-Authors: Lennart T. Bach, Declan C. Schroeder, Colin Brownlee, Luke C. M. Mackinder, Kai G. Schulz, Glen L. Wheeler, Ulf RiebesellAbstract:Coccolithophores are important calcifying phytoplankton predicted to be impacted by changes in ocean carbonate chemistry caused by the absorption of anthropogenic CO2. However, it is difficult to disentangle the effects of the simultaneously changing carbonate system parameters (CO2, bicarbonate, carbonate and protons) on the physiological responses to elevated CO2. Here, we adopted a multifactorial approach at constant pH or CO2 whilst varying dissolved inorganic carbon (DIC) to determine physiological and transcriptional responses to individual carbonate system parameters. We show that Emiliania huxleyi is sensitive to low CO2 (growth and photosynthesis) and low bicarbonate (calcification) as well as low pH beyond a limited tolerance range, but is much less sensitive to elevated CO2 and bicarbonate. Multiple up-regulated genes at low DIC bear the hallmarks of a carbon-concentrating mechanism (CCM) that is responsive to CO2 and bicarbonate but not to pH. Emiliania huxleyi appears to have evolved mechanisms to respond to limiting rather than elevated CO2. Calcification does not function as a CCM, but is inhibited at low DIC to allow the redistribution of DIC from calcification to photosynthesis. The presented data provides a significant step in understanding how E. huxleyi will respond to changing carbonate chemistry at a cellular level.
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Short-term response of the coccolithophore <i>Emiliania huxleyi</i> to abrupt changes in seawater carbon dioxide concentrations
Biogeosciences Discussions, 2009Co-Authors: J. Barcelos E Ramos, M. N. Müller, Ulf RiebesellAbstract:Abstract. The response of the coccolithophore Emiliania huxleyi to rising CO2 concentrations is well documented in acclimated cultures where cells are exposed to the CO2 treatments for several generations prior to the experiment. Extended acclimation times have generally been applied because of the lack of information about time required to reach a new physiological "equilibrium" (acclimation) in response to CO2-induced changes in seawater carbonate chemistry. Here we show that Emiliania huxleyi's short-term response (hours to 1 day) to increasing CO2 is similar to that obtained with acclimated cultures under comparable conditions in earlier studies. At CO2 concentrations ranging from glacial (190 μatm) to projected year 2100 (750 μatm) levels, calcification decreased and organic carbon fixation increased within 8 h after exposing the cultures to the changed CO2 conditions. This led to a decrease in the ratio of CaCO3 to organic carbon production. Our results show that Emiliania huxleyiapidly alters the rates of various essential processes in response to changes in seawater carbonate chemistry, establishing a new physiological (acclimation) "state" within a matter of hours. If this relatively rapid response applies to other phytoplankton species, it may simplify interpretation of studies with natural communities (e.g. mesocosm studies and ship-board incubations), where often it is not feasible to allow for a pre-conditioning phase before starting experimental incubations.
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Short-term response of the coccolithophore Emiliania huxleyi to an abrupt change in seawater carbon dioxide concentrations.
Biogeosciences, 2009Co-Authors: J. Barcelos E Ramos, Marius N Muller, Ulf RiebesellAbstract:The response of the coccolithophore Emiliania huxleyi to rising CO2 concentrations is well documented for acclimated cultures where cells are exposed to the CO2 treatments for several generations prior to the experiment. The exact number of generations required for acclimation to CO2-induced changes in seawater carbonate chemistry, however, is unknown. Here we show that Emiliania hux- leyi's short-term response (26 h) after cultures (grown at 500 µatm) were abruptly exposed to changed CO2 concentra- tions ( 190, 410, 800 and 1500 µatm) is similar to that ob- tained with acclimated cultures under comparable conditions in earlier studies. Most importantly, from the lower CO2 lev- els (190 and 410 µatm) to 750 and 1500 µatm calcification de- creased and organic carbon fixation increased within the first 8 to 14 h after exposing the cultures to changes in carbonate chemistry. This suggests that Emiliania huxleyi rapidly al- ters the rates of essential metabolical processes in response to changes in seawater carbonate chemistry, establishing a new physiological "state" (acclimation) within a matter of hours. If this relatively rapid response applies to other phy- toplankton species, it may simplify interpretation of studies with natural communities (e.g. mesocosm studies and ship- board incubations), where often it is not feasible to allow for a pre-conditioning phase before starting experimental incu- bations.
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Short-term response of the coccolithophore Emiliania huxleyi to an abrupt change in seawater carbon dioxide concentrations.
Biogeosciences, 2009Co-Authors: J. Barcelos E Ramos, Marius N Muller, Ulf RiebesellAbstract:The response of the coccolithophore Emiliania huxleyi to rising CO2 concentrations is well documented for acclimated cultures where cells are exposed to the CO2 treatments for several generations prior to the experiment. The exact number of generations required for acclimation to CO2-induced changes in seawater carbonate chemistry, however, is unknown. Here we show that Emiliania hux- leyi's short-term response (26 h) after cultures (grown at 500 µatm) were abruptly exposed to changed CO2 concentra- tions ( 190, 410, 800 and 1500 µatm) is similar to that ob- tained with acclimated cultures under comparable conditions in earlier studies. Most importantly, from the lower CO2 lev- els (190 and 410 µatm) to 750 and 1500 µatm calcification de- creased and organic carbon fixation increased within the first 8 to 14 h after exposing the cultures to changes in carbonate chemistry. This suggests that Emiliania huxleyi rapidly al- ters the rates of essential metabolical processes in response to changes in seawater carbonate chemistry, establishing a new physiological "state" (acclimation) within a matter of hours. If this relatively rapid response applies to other phy- toplankton species, it may simplify interpretation of studies with natural communities (e.g. mesocosm studies and ship- board incubations), where often it is not feasible to allow for a pre-conditioning phase before starting experimental incu- bations.
Benjamin A. S. Van Mooy - One of the best experts on this subject based on the ideXlab platform.
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Alkenone unsaturation during virus infection of Emiliania huxleyi
Organic Geochemistry, 2017Co-Authors: James M Fulton, Giacomo R Ditullio, B. Jacob Kendrick, Benjamin A. S. Van MooyAbstract:Abstract Alkenones are found in diverse prymnesiophytes including Emiliania huxleyi , which ranges throughout the world ocean. The number of double bonds in alkenones corresponds with growth temperature, and calibrations between sea surface temperature and alkenone unsaturation have been used to establish alkenone unsaturation as a temperature proxy in ancient sediments. Here we report virus infection causes a relative increase in the proportion of diunsaturated alkenones in E. huxleyi strain CCMP 374. As virus infection routinely terminates E. huxleyi blooms in the ocean, it is possible that this contributes to the variance in alkenone-based temperature estimates for core-top sediments.
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temperature induced viral resistance in Emiliania huxleyi prymnesiophyceae
PLOS ONE, 2014Co-Authors: Jacob B Kendrick, Giacomo R Ditullio, Tyler Cyronak, James M Fulton, Benjamin A. S. Van Mooy, Kay D BidleAbstract:Annual Emiliania huxleyi blooms (along with other coccolithophorid species) play important roles in the global carbon and sulfur cycles. E. huxleyi blooms are routinely terminated by large, host-specific dsDNA viruses, (Emiliania huxleyi Viruses; EhVs), making these host-virus interactions a driving force behind their potential impact on global biogeochemical cycles. Given projected increases in sea surface temperature due to climate change, it is imperative to understand the effects of temperature on E. huxleyi’s susceptibility to viral infection and its production of climatically active dimethylated sulfur species (DSS). Here we demonstrate that a 3°C increase in temperature induces EhV-resistant phenotypes in three E. huxleyi strains and that successful virus infection impacts DSS pool sizes. We also examined cellular polar lipids, given their documented roles in regulating host-virus interactions in this system, and propose that alterations to membrane-bound surface receptors are responsible for the observed temperature-induced resistance. Our findings have potential implications for global biogeochemical cycles in a warming climate and for deciphering the particular mechanism(s) by which some E. huxleyi strains exhibit viral resistance.
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novel molecular determinants of viral susceptibility and resistance in the lipidome of Emiliania huxleyi
Environmental Microbiology, 2014Co-Authors: James M Fulton, Jacob B Kendrick, Giacomo R Ditullio, Kay D Bidle, Helen F Fredricks, Assaf Vardi, Benjamin A. S. Van MooyAbstract:Summary Viruses play a key role in controlling the population dynamics of algae, including Emiliania huxleyi, a globally distributed haptophyte with calcite coccoliths that comprise ca. 50% of the sinking carbonate flux from the surface ocean. Emiliania huxleyi viruses (EhVs) routinely infect and terminate E. huxleyi blooms. EhVs are surrounded by a lipid envelope, which we found to be comprised largely of glycosphingolipids (GSLs) with lesser amounts of polar glycerolipids. Infection appears to involve membrane fusion between the virus and host, and we hypothesized that specific polar lipids may facilitate virus attachment. We identified three novel intact polar lipids in E. huxleyi strain CCMP 374 and EhV86, including a GSL with a monosaccharide sialic acid headgroup (sGSL); for all 11 E. huxleyi strains we tested, there was a direct relationship between sGSL content and sensitivity to infection by EhV1, EhV86 and EhV163. In mesocosms, the E. huxleyi population with greatest initial sGSL content had the highest rate of virus-induced mortality. We propose potential physiological roles for sGSL that would be beneficial for growth but leave cells susceptible to infection, thus furthering the discussion of Red Queen-based co-evolution and the cost(s) of sensitivity and resistance in the dynamic E. huxleyi-EhV system.
Toby Tyrrell - One of the best experts on this subject based on the ideXlab platform.
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nitrate phosphate ratios and Emiliania huxleyi blooms
Limnology and Oceanography, 2005Co-Authors: Evelyn J Lessard, Agostino Merico, Toby TyrrellAbstract:It has been hypothesized that phosphate limitation classically indicated by NO3:PO4 ratios > 16, is one of the critical factors allowing the coccolithophorid Emiliania huxleyi to bloom. This hypothesis is based on physiological studies showing that E. huxleyi has an exceptionally high affinity for orthophosphate and is able to use organic phosphate. Indeed, E. huxleyi has been found to bloom at high NO3: PO4 ratios in some mesocosm studies and in the oceanic northeast North Atlantic. Recent E. huxleyi blooms on the southeastern Bering Sea shelf, however, occurred under low NO3: PO4 conditions, which is indicative of nitrogen rather than phosphorus stress. A review of field studies of blooms where nitrate and phosphate were measured indicates that NO3: PO4 was in fact frequently low. A survey of most of the areas of the world ocean where satellite-detected E. huxleyi blooms occur also shows that NO3:PO4 ratios are generally low. These observations suggest that E. huxleyi is able to exploit situations where either phosphorus or nitrogen is limiting to competing species. They also indicate that attention should be directed to examining organic nitrogen, organic phosphorus, and ammonium during E. huxleyi blooms to better understand the role macronutrients play in these blooms.
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analysis of satellite imagery for Emiliania huxleyi blooms in the bering sea before 1997
Geophysical Research Letters, 2003Co-Authors: Agostino Merico, Toby Tyrrell, Steve Groom, Chris W Brown, Peter I MillerAbstract:The presence of blooms of the coccolithophore Emiliania huxleyi in the Bering Sea shelf has been studied using satellite imagery in order to ascertain whether its first reported appearance in 1997 is really a new phenomenon for the area. Examination for Emiliania huxleyi blooms in Coastal Zone Color Scanner (CZCS) and Advanced Very High Resolution Radiometer (AVHRR) imagery dating from 1978 to 1996 was performed and the relationship between the presence of Emiliania huxleyi and the Pacific Decadal Oscillation and the El Nino Southern Oscillation was investigated. No evidence of the presence of this species was found in CZCS or AVHRR imagery between 1978 and 1995. AVHRR images reveal that a small coccolithophore bloom was present in summer 1996. Although the blooms of 1997 were unprecedented in extension and intensity, it appears that the Bering Sea ecosystem did not respond as abruptly to atmospheric anomalies as initially reported.
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a modelling study of Emiliania huxleyi in the ne atlantic
Journal of Marine Systems, 1996Co-Authors: Toby Tyrrell, A. H. TaylorAbstract:Intensive (> 10,000 cells ml−1) and extensive (> 100,000 km2) blooms of the coccolithophorid Emiliania huxleyi frequently occur in the NE Atlantic, usually in the months of June and July, and only north of 50°N. This article describes a modelling study of these blooms, with the aim of understanding why they occur. That is to say, which water conditions allow Emiliania huxleyi to become dominant amongst the phytoplankton? Providing answers to these questions in the NE Atlantic, and comparing the results with data from other areas, allows us to tackle the question: what is the ecological niche for Emiliania huxleyi? The model described in this article is a single-layer ID Eulerian phytoplankton seasonal succession model, with detailed representations of physical, chemical and biological forcing functions and interactions. Model assumptions and their derivation from data are described, and sensitivity analyses examine the reliance of model results on individual assumptions. The model results suggest that, in the summer of 1991 in the NE Atlantic, the most likely factors causing the bloom of Emiliania huxleyi were high light (high surface irradiances, shallow stratification) and low phosphate (phosphate limiting rather than nitrate). The model was able to reproduce the observed distributoin of Emiliania huxleyi in the NE Atlantic by assuming that Emiliania huxleyi has similar limitations to other phytoplankton species except that it possesses a competitive advantage at high light and low phosphate.
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Latitudinal and seasonal variations in carbon dioxide and oxygen in the northeast Atlantic and the effects on Emiliania huxleyi and other phytoplankton
Global Biogeochemical Cycles, 1995Co-Authors: Toby Tyrrell, Arnold H. TaylorAbstract:Several cruise programs, such as Transient Tracers in the Ocean (TTO), the Biogeochemical Ocean Flux Study (BOFS), and the Joint Global Ocean Flux Study (JGOFS), have measured physical, chemical, and biological variables in the northeast Atlantic, with the aim of understanding the seasonal variation in oceanic components such as carbon dioxide and oxygen and the role of different factors (e.g., the marine biota) in determining these seasonal variations. For this paper, data from the different cruise programs have been collated, and then three-dimensional (3-D) interpolated surfaces have been plotted in order to illustrate the seasonal and latitudinal changes in these different components. These data-generated plots are then compared with plots generated from the results of the simulation model of Taylor et al. (1991). The model-derived and data-derived plots are shown to be similar, and the model is subsequently used to explain the interaction of the processes underlying the observed variation in pCO2. It is argued that more data needs to be collected at the time of the spring bloom north of 50°N. The plot of carbon dioxide concentration is discussed in relation to the effects of carbon dioxide concentration on phytoplankton growth, as proposed by Riebesell et al.(1993). In addition, it is shown that the distribution of blooms of Emiliania huxleyi in the NE Atlantic (55°–63°N but not farther south) is not coincident with areas of low [CO2], contrary to the hypothesis that Emiliania huxleyi has evolved to be a successful competitor at low [C02].
Declan C. Schroeder - One of the best experts on this subject based on the ideXlab platform.
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dissecting the impact of co2 and ph on the mechanisms of photosynthesis and calcification in the coccolithophore Emiliania huxleyi
New Phytologist, 2013Co-Authors: Lennart T. Bach, Declan C. Schroeder, Colin Brownlee, Luke C. M. Mackinder, Kai G. Schulz, Glen L. Wheeler, Ulf RiebesellAbstract:Coccolithophores are important calcifying phytoplankton predicted to be impacted by changes in ocean carbonate chemistry caused by the absorption of anthropogenic CO2. However, it is difficult to disentangle the effects of the simultaneously changing carbonate system parameters (CO2, bicarbonate, carbonate and protons) on the physiological responses to elevated CO2. Here, we adopted a multifactorial approach at constant pH or CO2 whilst varying dissolved inorganic carbon (DIC) to determine physiological and transcriptional responses to individual carbonate system parameters. We show that Emiliania huxleyi is sensitive to low CO2 (growth and photosynthesis) and low bicarbonate (calcification) as well as low pH beyond a limited tolerance range, but is much less sensitive to elevated CO2 and bicarbonate. Multiple up-regulated genes at low DIC bear the hallmarks of a carbon-concentrating mechanism (CCM) that is responsive to CO2 and bicarbonate but not to pH. Emiliania huxleyi appears to have evolved mechanisms to respond to limiting rather than elevated CO2. Calcification does not function as a CCM, but is inhibited at low DIC to allow the redistribution of DIC from calcification to photosynthesis. The presented data provides a significant step in understanding how E. huxleyi will respond to changing carbonate chemistry at a cellular level.
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Novel virus dynamics in an Emiliania huxleyi bloom
Journal of Plankton Research, 2009Co-Authors: George Sorensen, Andrea C. Baker, Colin B. Munn, Matthew J. Hall, Declan C. SchroederAbstract:Diel studies of an Emiliania huxleyi bloom within a mesocosm revealed a highly dynamic associated viral community, changing on small times scales of hours.
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complete genome sequence and lytic phase transcription profile of a coccolithovirus
Science, 2005Co-Authors: William H. Wilson, Declan C. Schroeder, Michael J Allen, Matthew T G Holden, Julian Parkhill, B G Barrell, Carol Churcher, N Hamlin, Karen Mungall, Halina NorbertczakAbstract:The genus Coccolithovirus is a recently discovered group of viruses that infect the globally important marine calcifying microalga Emiliania huxleyi. Among the 472 predicted genes of the 407,339–base pair genome are a variety of unexpected genes, most notably those involved in biosynthesis of ceramide, a sphingolipid known to induce apoptosis. Uniquely for algal viruses, it also contains six RNA polymerase subunits and a novel promoter, suggesting this virus encodes its own transcription machinery. Microarray transcriptomic analysis reveals that 65% of the predicted virus-encoded genes are expressed during lytic infection of E. huxleyi.
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virus succession observed during an Emiliania huxleyi bloom
Applied and Environmental Microbiology, 2003Co-Authors: Declan C. Schroeder, Gillian Malin, Matthew J. Hall, William H. WilsonAbstract:Denaturing gradient gel electrophoresis was used as a molecular tool to determine the diversity and to monitor population dynamics of viruses that infect the globally important coccolithophorid Emiliania huxleyi. We exploited variations in the major capsid protein gene from E. huxleyi-specific viruses to monitor their genetic diversity during an E. huxleyi bloom in a mesocosm experiment off western Norway. We reveal that, despite the presence of several virus genotypes at the start of an E. huxleyi bloom, only a few virus genotypes eventually go on to kill the bloom.