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Christopher J Gobler - One of the best experts on this subject based on the ideXlab platform.
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3 000 km and 1 500 year presence of Aureococcus anophagefferens reveals indigenous origin of brown tides in china
Molecular Ecology, 2019Co-Authors: Ying Zhong Tang, Yunyan Deng, Aoao Yang, Siheng Lin, Zhaoyang Chai, Christopher J GoblerAbstract:The nonmotile, spherical, picoplanktonic (2-μm-sized) pelagophyte Aureococcus anophagefferens has caused numerous harmful blooms ("brown tides") across global marine ecosystems. Blooms have developed along the east coast of the USA since 1985, a limited number of times in South Africa around 1997, and frequently in China since 2009. As a consequence, the harmful blooms have caused massive losses in aquaculture and coastal ecosystems, particularly mortalities in cultured shellfish. Therefore, whether A. anophagefferens was recently introduced to China via natural/artificial transport of resting stage cells or has been an indigenous species has become a question of profound ecological significance and broad interest, which motivated our extensive investigation on the geographic and historical presence of this species in the seas of China. We applied a combined approach of extensive PCR-based detection and sequencing, germination experiments and monoclonal antibody staining of germlings to samples of surface sediment and sediment core (dated via combined isotopic measurements) collected from all four seas of China, and searched the supplementary data set of a recent Science publication. We discovered that A. anophagefferens does have a resting stage in the sediment, but it also has a wide geographic distribution both in China (covering a range of ~30° in latitude, ~15.7° in longitude and 2.5-3,456 m in water depth; temperate to tropical and coastal to open oceans) and in almost all oceans of the world and a historical presence of >1,500 years in the Bohai Sea, China. The work revealed that A. anophagefferens is not a recently introduced, but an indigenous species in China and has in fact a globally cosmopolitan distribution.
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diversity and dynamics of algal megaviridae members during a harmful brown tide caused by the pelagophyte Aureococcus anophagefferens
FEMS Microbiology Ecology, 2016Co-Authors: Mohammad Moniruzzaman, Yoonja Kang, Christopher J Gobler, Eric R Gann, Gary R Lecleir, Steven W. WilhelmAbstract:Many giant dsDNA algal viruses share a common ancestor with Mimivirus--one of the largest viruses, in terms of genetic content. Together, these viruses form the proposed 'Megaviridae' clade of nucleocytoplasmic large DNA viruses. To gauge Megaviridae diversity, we designed degenerate primers targeting the major capsid protein genes of algae-infecting viruses within this group and probed the clade's diversity during the course of a brown tide bloom caused by the harmful pelagophyte,Aureococcus anophagefferens We amplified target sequences in water samples from two distinct locations (Weesuck Creek and Quantuck Bay, NY) covering 12 weeks concurrent with the proliferation and demise of a bloom. In total, 475 amplicons clustered into 145 operational taxonomic units (OTUs) at 97% identity. One OTU contained 19 sequences with ≥97% identity to AaV, a member of the Megaviridae clade that infects A. anophagefferens, suggesting AaV was present during the bloom. Unifrac analysis showed clear temporal patterns in algal Megaviridae dynamics, with a shift in the virus community structure that corresponded to the Aureococcus bloom decline in both locations. Our data provide insights regarding the environmental relevance of algal Megaviridae members and raise important questions regarding their phylodynamics across different environmental gradients.
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expression of a xanthine permease and phosphate transporter in cultures and field populations of the harmful alga Aureococcus anophagefferens tracking nutritional deficiency during brown tides
Environmental Microbiology, 2014Co-Authors: Louie L Wurch, Christopher J Gobler, Sonya T DyhrmanAbstract:Summary Targeted gene expression using quantitative reverse transcription polymerase chain reaction (qRT-PCR) was employed to track patterns in the expression of genes indicative of nitrogen or phosphorus deficiency in the brown tide-forming alga Aureococcus anophagefferens. During culture experiments, a xanthine/uracil/vitamin C permease (XUV) was upregulated ∼20-fold under nitrogen-deficient conditions relative to a nitrogen-replete control and rapidly returned to nitrogen-replete levels after nitrogen-deficient cells were resupplied with nitrate or ammonium. It was not responsive to phosphorus deficiency. Expression of an inorganic phosphate transporter (PTA3) was enriched ∼10-fold under phosphorus-deficient conditions relative to a phosphorus-replete control, and this signal was rapidly lost upon phosphate resupply. PTA3 was not upregulated by nitrogen deficiency. Natural A. anophagefferens populations from a dense brown tide that occurred in Long Island, NY, in 2009 were assayed for XUV and PTA3 expression and compared with nutrient concentrations over the peak of a bloom. Patterns in XUV expression were consistent with nitrogen-replete growth, never reaching the values observed in N-deficient cultures. PTA3 expression was highest prior to peak bloom stages, reaching expression levels within the range of P-deficient cultures. These data highlight the value of molecular-level assessments of nutrient deficiency and suggest that phosphorus deficiency could play a role in the dynamics of destructive A. anophagefferens blooms.
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de novo assembly of Aureococcus anophagefferens transcriptomes reveals diverse responses to the low nutrient and low light conditions present during blooms
Frontiers in Microbiology, 2014Co-Authors: Kyle R Frischkorn, Christopher J Gobler, Matthew J Harke, Sonya T DyhrmanAbstract:Transcriptome profiling was performed on four treatments of the harmful algal bloom-forming pelagophyte Aureococcus anophagefferens strain CCMP 1850 to assess responses to common stressors for dense phytoplankton blooms: low inorganic nitrogen concentrations, low inorganic phosphorus concentrations, low light levels, and a replete control. The de novo assemblies of pooled reads from all treatments reconstructed ~ 54,000 transcripts using Trinity, and ~ 31,000 transcripts using ABySS. Comparison to the strain CCMP 1984 genome showed that the majority of the gene models were present in both de novo assemblies and that roughly 95% of contigs from both assemblies mapped to the genome, with Trinity capturing slightly more genome content. Sequence reads were mapped back to the de novo assemblies as well as the gene models and differential expression was analyzed using a Bayesian approach called Analysis of Sequence Counts (ASC). On average, 93% of significantly upregulated transcripts recovered by genome mapping were present in the significantly upregulated pool from both de novo assembly methods. Transcripts related to the transport and metabolism of nitrogen were upregulated in the low nitrogen treatment, transcripts encoding enzymes that hydrolyze organic phosphorus or relieve arsenic toxicity were upregulated in the low phosphorus treatment, and transcripts for enzymes that catabolize organic compounds, restructure lipid membranes, or are involved in sulfolipid biosynthesis were upregulated in the low light treatment. A comparison of this transcriptome to the nutrient regulated transcriptional response of CCMP 1984 identified conserved responses between these two strains. These analyses reveal the transcriptional underpinnings of physiological shifts that could contribute to the ecological success of this species in situ: organic matter processing, metal detoxification, lipid restructuring, and photosynthetic apparatus turnover.
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the ability of the branchiopod artemia salina to graze upon harmful algal blooms caused by alexandrium fundyense Aureococcus anophagefferens and cochlodinium polykrikoides
Estuarine Coastal and Shelf Science, 2013Co-Authors: Alejandra M Marcoval, Ying Zhong Tang, Jeronimo Pan, Christopher J GoblerAbstract:Abstract We present experiments that examined the grazing and survivorship of zooplankton native ( Acartia tonsa ) and non-native ( Artemia salina ) to NY (USA) estuaries when exposed to blooms and cultures of the three harmful algae native to NY, Alexandrium fundyense , Aureococcus anophagefferens (strains CCMP 1850 and CCMP 1984) and Cochlodinium polykrikoides . During experiments with cultures of A. anophagefferens , clearance rates (CR) of A. salina were significantly greater than those of A. tonsa for both algal strains examined. A. salina fed on cultures of C. polykrikoides at higher rates than all phytoplankton species examined, including the control diet ( Rhodomonas salina ), and faster than rates of A. tonsa fed C. polykrikoides . During experiments with A. fundyense , A. salina actively grazed all cell concentrations (250–1500 cells ml −1 ) while A. tonsa did not feed at any concentration. Percent mortality of A. salina and A. tonsa fed A. fundyense for 48 h were 43 ± 7.7% and 72 ± 7.8%, respectively, percentages significantly higher than those of individuals fed all other algal diets. During 25 field experiments using natural blooms of the three HAB species performed across six NY estuaries, A. salina significantly ( p A. anophagefferens , C. polykrikoides , and A. fundyense relative to the control treatments in all but one experiment. The sum of these findings demonstrates that a failure to graze these HABs by the indigenous copepod, A. tonsa , may permit blooms to occur. In addition, the ability of A. salina to graze these HABs at densities that were inhibitory to A. tonsa suggests that A. salina could, in some circumstances, be considered as a part of mitigation strategy for these events.
Steven W. Wilhelm - One of the best experts on this subject based on the ideXlab platform.
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structural and proteomic studies of the Aureococcus anophagefferens virus demonstrate a global distribution of virus encoded carbohydrate processing
Frontiers in Microbiology, 2020Co-Authors: Eric R Gann, Todd B Reynolds, Yuejiao Xian, Paul E Abraham, Robert L Hettich, Chuan Xiao, Steven W. WilhelmAbstract:Viruses modulate the function(s) of environmentally relevant microbial populations, yet considerations of the metabolic capabilities of individual virus particles themselves are rare. We used shotgun proteomics to quantitatively identify 43 virus-encoded proteins packaged within purified Aureococcus anophagefferens Virus (AaV) particles, normalizing data to the per-virion level using a 9.5-A-resolution molecular reconstruction of the 1900-A (AaV) particle that we generated with cryogenic electron microscopy. This packaged proteome was used to determine similarities and differences between members of different giant virus families. We noted that proteins involved in sugar degradation and binding (e.g., carbohydrate lyases) were unique to AaV among characterized giant viruses. To determine the extent to which this virally encoded metabolic capability was ecologically relevant, we examined the TARA Oceans dataset and identified genes and transcripts of viral origin. Our analyses demonstrated that putative giant virus carbohydrate lyases represented up to 17% of the marine pool for this function. In total, our observations suggest that the AaV particle has potential prepackaged metabolic capabilities and that these may be found in other giant viruses that are widespread and abundant in global oceans.
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internal nitrogen pools shape the infection of Aureococcus anophagefferens ccmp 1984 by a giant virus
Frontiers in Microbiology, 2020Co-Authors: Eric R Gann, Todd B Reynolds, Brennan J Hughes, Steven W. WilhelmAbstract:The pelagophyte Aureococcus anophagefferens blooms annually in shallow bays around the world, where it is hypothesized to outcompete other phytoplankton in part by using alternative nitrogen sources. The high proportion of natural populations that are infected during the late stages of the bloom suggest viruses cause bloom collapse. We hypothesized that the Aureococcus anophagefferens Virus (AaV) infection cycle would be negatively influenced in cultures acclimated to decreasing external nitrogen conditions, but that the real-time external nitrogen concentration would not influence the infection cycle. Cultures acclimated in NO 3 - concentrations (0.0147 mM; N:P = 0.1225) that showed reduced end point cell abundances, forward scatter (a proxy for size) and red fluorescence (a proxy for chlorophyll a), also produced fewer viruses per cell at a slower rate. Decreasing the external concentration of nitrogen post infection did not alter burst size or time to lysis. These data suggest that the nitrogen used for new viral progeny is present within host cells at the time of infection. Flow cytometric data of an infection cycle showed a reduction in red fluorescence around twelve hours post infection, consistent with degradation of nitrogen-rich chloroplasts during the infection cycle. Using cell and virus quota estimates, we determined that A. anophagefferens cells had sufficient nitrogen and carbon for the lower ranges of burst sizes determined but did not contain enough phosphorous. Consistent with this observation, expression of nitrate and sugar transporters did not increase in the publicly available transcriptome data of the infection cycle, while several phosphorus transporters were. Our data demonstrate that dynamics of viruses infecting Aureococcus over the course of a bloom is dictated by the host cell state upon infection, which is set a priori by external nutrient supplies.
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influence of light on the infection of Aureococcus anophagefferens ccmp 1984 by a giant virus
PLOS ONE, 2020Co-Authors: Eric R Gann, Jackson P Gainer, Todd B Reynolds, Steven W. WilhelmAbstract:The pelagophyte Aureococcus anophagefferens has caused recurrent brown tide blooms along the northeast coast of the United States since the mid-1980’s, and more recently spread to other regions of the globe. These blooms, due to the high cell densities, are associated with severe light attenuation that destroys the sea grass beds which provide the basis for many fisheries. Data collected by transmission electron microscopy, PCR, and metatranscriptomic studies of the blooms, support the hypothesis that large dsDNA viruses play a role in bloom dynamics. While a large (~140 nm) icosahedral virus, with a 371 kbp genome, was first isolated more than a decade ago, the constraints imposed by environmental parameters on bloom infection dynamics by Aureococcus anophagefferens Virus, (AaV) remain unknown. To investigate the role light plays in infection by this virus, we acclimated A. anophagefferens to light intensities of 30 (low), 60 (medium) or 90 μmol photons m-2 s-1 (high) and infected cultures at these irradiance levels. Moreover, we completed light shift experiments where acclimated cultures were exposed to even lower light intensities (0, 5, and 15 μmol photons m-2 s-1) consistent with irradiance found during the peak of the bloom when cell concentrations are highest. The abundance of viruses produced per lytic event (burst size) was lower in the low irradiance acclimated cultures compared to the medium and high acclimated cultures. Transferring infected cultures to more-limiting light availabilities further decreased burst size and increased the length of time it took for cultures to lyse, regardless of acclimation irradiance level. A hypothetical mechanism for the reduced efficiency of the infection cycle in low light due to ribosome biogenesis was predicted from pre-existing transcriptomes. Overall, these studies provide a framework for understanding light effects on infection dynamics over the course of the summer months when A. anophagefferens blooms occur.
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infection by a giant virus aav induces widespread physiological reprogramming in Aureococcus anophagefferens ccmp1984 a harmful bloom algae
Frontiers in Microbiology, 2018Co-Authors: Mohammad Moniruzzaman, Eric R Gann, Steven W. WilhelmAbstract:While viruses with distinct phylogenetic origins and different nucleic acid types can infect and lyse eukaryotic phytoplankton, "giant" dsDNA viruses have been found to be associated with important ecological processes, including the collapse of algal blooms. However, the molecular aspects of giant virus-host interactions remain largely unknown. Aureococcus anophagefferens virus (AaV), a giant virus in the Mimiviridae clade, is known to play a critical role in regulating the fate of brown tide blooms caused by the pelagophyte Aureococcus anophagefferens. To understand the physiological response of A. anophagefferens CCMP1984 upon AaV infection, we studied the transcriptomic landscape of this host-virus pair over an entire infection cycle using a RNA-sequencing approach. A massive transcriptional response of the host was evident as early as 5 min post-infection, with modulation of specific processes likely related to both host defense mechanism(s) and viral takeover of the cell. Infected Aureococcus showed a relative suppression of host-cell transcripts associated with photosynthesis, cytoskeleton formation, fatty acid, and carbohydrate biosynthesis. In contrast, host cell processes related to protein synthesis, polyamine biosynthesis, cellular respiration, transcription, and RNA processing were overrepresented compared to the healthy cultures at different stages of the infection cycle. A large number of redox active host-selenoproteins were overexpressed, which suggested that viral replication and assembly progresses in a highly oxidative environment. The majority (99.2%) of annotated AaV genes were expressed at some point during the infection cycle and demonstrated a clear temporal-expression pattern and an increasing relative expression for the majority of the genes through the time course. We detected a putative early promoter motif for AaV, which was highly similar to the early promoter elements of two other Mimiviridae members, indicating some degree of evolutionary conservation of gene regulation within this clade. This large-scale transcriptome study provides insights into the Aureococcus cells infected by a giant virus and establishes a foundation to test hypotheses regarding metabolic and regulatory processes critical for AaV and other Mimiviridae members.
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infection by a giant virus induces widespread physiological reprogramming in Aureococcus anophagefferens a harmful bloom algae
bioRxiv, 2018Co-Authors: Mohammad Moniruzzaman, Eric R Gann, Steven W. WilhelmAbstract:While viruses with distinct phylogenetic origins and different nucleic acid types can infect and lyse eukaryotic phytoplankton, "giant" dsDNA viruses have been found to be associated with important ecological processes, including the collapse of algal blooms. However, the molecular aspects of giant virus - host interactions remain largely unknown. AaV, a giant virus in the Mimiviridae clade, is known to play a critical role in regulating the fate of brown tide blooms caused by the pelagophyte Aureococcus anophagefferens . To understand the physiological response of A. anophagefferens CCMP1984 upon AaV infection, we studied the transcriptomic landscape of this host-virus pair over an entire infection cycle using a RNA-sequencing approach. A massive transcriptional reprogramming of the host was evident as early as 5 min post-infection, with modulation of specific processes likely related to both host defense mechanism(s) and viral takeover of the cell. Infected Aureococcus showed a relative suppression of host-cell transcripts associated with photosynthesis, cytoskeleton formation, fatty acid and carbohydrate biosynthesis. In contrast, host cell processes related to protein synthesis, polyamine biosynthesis, cellular respiration, transcription and RNA processing were overrepresented compared to the healthy cultures at different stages of the infection cycle. A large number of redox active host-selenoproteins were overexpressed, which suggested that viral replication and assembly progresses in a highly oxidative environment. The majority (99.2%) of annotated AaV genes were expressed at some point during the infection cycle and demonstrated a clear temporal-expression pattern and an increasing relative expression for the majority of the genes through the time course. We detected a putative early promoter motif for AaV, which was highly similar to the early promoter elements of two other Mimiviridae members, indicating some degree of evolutionary conservation of gene regulation within this clade. This large-scale transcriptome study provides the insight into the Aureococcus "virocell", and establishes a foundation to test hypotheses regarding metabolic and regulatory processes critical for AaV and other Mimiviridae members.
Sonya T Dyhrman - One of the best experts on this subject based on the ideXlab platform.
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expression of a xanthine permease and phosphate transporter in cultures and field populations of the harmful alga Aureococcus anophagefferens tracking nutritional deficiency during brown tides
Environmental Microbiology, 2014Co-Authors: Louie L Wurch, Christopher J Gobler, Sonya T DyhrmanAbstract:Summary Targeted gene expression using quantitative reverse transcription polymerase chain reaction (qRT-PCR) was employed to track patterns in the expression of genes indicative of nitrogen or phosphorus deficiency in the brown tide-forming alga Aureococcus anophagefferens. During culture experiments, a xanthine/uracil/vitamin C permease (XUV) was upregulated ∼20-fold under nitrogen-deficient conditions relative to a nitrogen-replete control and rapidly returned to nitrogen-replete levels after nitrogen-deficient cells were resupplied with nitrate or ammonium. It was not responsive to phosphorus deficiency. Expression of an inorganic phosphate transporter (PTA3) was enriched ∼10-fold under phosphorus-deficient conditions relative to a phosphorus-replete control, and this signal was rapidly lost upon phosphate resupply. PTA3 was not upregulated by nitrogen deficiency. Natural A. anophagefferens populations from a dense brown tide that occurred in Long Island, NY, in 2009 were assayed for XUV and PTA3 expression and compared with nutrient concentrations over the peak of a bloom. Patterns in XUV expression were consistent with nitrogen-replete growth, never reaching the values observed in N-deficient cultures. PTA3 expression was highest prior to peak bloom stages, reaching expression levels within the range of P-deficient cultures. These data highlight the value of molecular-level assessments of nutrient deficiency and suggest that phosphorus deficiency could play a role in the dynamics of destructive A. anophagefferens blooms.
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de novo assembly of Aureococcus anophagefferens transcriptomes reveals diverse responses to the low nutrient and low light conditions present during blooms
Frontiers in Microbiology, 2014Co-Authors: Kyle R Frischkorn, Christopher J Gobler, Matthew J Harke, Sonya T DyhrmanAbstract:Transcriptome profiling was performed on four treatments of the harmful algal bloom-forming pelagophyte Aureococcus anophagefferens strain CCMP 1850 to assess responses to common stressors for dense phytoplankton blooms: low inorganic nitrogen concentrations, low inorganic phosphorus concentrations, low light levels, and a replete control. The de novo assemblies of pooled reads from all treatments reconstructed ~ 54,000 transcripts using Trinity, and ~ 31,000 transcripts using ABySS. Comparison to the strain CCMP 1984 genome showed that the majority of the gene models were present in both de novo assemblies and that roughly 95% of contigs from both assemblies mapped to the genome, with Trinity capturing slightly more genome content. Sequence reads were mapped back to the de novo assemblies as well as the gene models and differential expression was analyzed using a Bayesian approach called Analysis of Sequence Counts (ASC). On average, 93% of significantly upregulated transcripts recovered by genome mapping were present in the significantly upregulated pool from both de novo assembly methods. Transcripts related to the transport and metabolism of nitrogen were upregulated in the low nitrogen treatment, transcripts encoding enzymes that hydrolyze organic phosphorus or relieve arsenic toxicity were upregulated in the low phosphorus treatment, and transcripts for enzymes that catabolize organic compounds, restructure lipid membranes, or are involved in sulfolipid biosynthesis were upregulated in the low light treatment. A comparison of this transcriptome to the nutrient regulated transcriptional response of CCMP 1984 identified conserved responses between these two strains. These analyses reveal the transcriptional underpinnings of physiological shifts that could contribute to the ecological success of this species in situ: organic matter processing, metal detoxification, lipid restructuring, and photosynthetic apparatus turnover.
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proteome changes driven by phosphorus deficiency and recovery in the brown tide forming alga Aureococcus anophagefferens
PLOS ONE, 2011Co-Authors: Louie L Wurch, Erin M Bertrand, Mak A Saito, Benjamin A S Van Mooy, Sonya T DyhrmanAbstract:Shotgun mass spectrometry was used to detect proteins in the harmful alga, Aureococcus anophagefferens, and monitor their relative abundance across nutrient replete (control), phosphate-deficient (2P) and 2P refed with phosphate (P-refed) conditions. Spectral counting techniques identified differentially abundant proteins and demonstrated that under phosphate deficiency, A. anophagefferens increases proteins involved in both inorganic and organic phosphorus (P) scavenging, including a phosphate transporter, 59-nucleotidase, and alkaline phosphatase. Additionally, an increase in abundance of a sulfolipid biosynthesis protein was detected in 2P and P-refed conditions. Analysis of the polar membrane lipids showed that cellular concentrations of the sulfolipid sulphoquinovosyldiacylglycerol (SQDG) were nearly two-fold greater in the 2P condition versus the control condition, while cellular phospholipids were approximately 8-fold less. Transcript and protein abundances were more tightly coupled for gene products involved in P metabolism compared to those involved in a range of other metabolic functions. Comparison of protein abundances between the 2P and P-refed conditions identified differences in the timing of protein degradation and turnover. This suggests that culture studies examining nutrient starvation responses will be valuable in interpreting protein abundance patterns for cellular nutritional status and history in metaproteomic datasets.
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niche of harmful alga Aureococcus anophagefferens revealed through ecogenomics
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Christopher J Gobler, Louie L Wurch, Sonya T Dyhrman, Steven W. Wilhelm, Dianna L Berry, Asaf Salamov, Alexei Lobanov, Yan Zhang, Jackie L Collier, Adam B KustkaAbstract:Harmful algal blooms (HABs) cause significant economic and ecological damage worldwide. Despite considerable efforts, a comprehensive understanding of the factors that promote these blooms has been lacking, because the biochemical pathways that facilitate their dominance relative to other phytoplankton within specific environments have not been identified. Here, biogeochemical measurements showed that the harmful alga Aureococcus anophagefferens outcompeted co-occurring phytoplankton in estuaries with elevated levels of dissolved organic matter and turbidity and low levels of dissolved inorganic nitrogen. We subsequently sequenced the genome of A. anophagefferens and compared its gene complement with those of six competing phytoplankton species identified through metaproteomics. Using an ecogenomic approach, we specifically focused on gene sets that may facilitate dominance within the environmental conditions present during blooms. A. anophagefferens possesses a larger genome (56 Mbp) and has more genes involved in light harvesting, organic carbon and nitrogen use, and encoding selenium- and metal-requiring enzymes than competing phytoplankton. Genes for the synthesis of microbial deterrents likely permit the proliferation of this species, with reduced mortality losses during blooms. Collectively, these findings suggest that anthropogenic activities resulting in elevated levels of turbidity, organic matter, and metals have opened a niche within coastal ecosystems that ideally suits the unique genetic capacity of A. anophagefferens and thus, has facilitated the proliferation of this and potentially other HABs.
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nutrient regulated transcriptional responses in the brown tide forming alga Aureococcus anophagefferens
Environmental Microbiology, 2011Co-Authors: Louie L Wurch, Christopher J Gobler, Sheean T Haley, Elizabeth D Orchard, Sonya T DyhrmanAbstract:Summary Long-SAGE (serial analysis of gene expression) was used to profile the transcriptome of the brown tide-forming alga, Aureococcus anophagefferens, under nutrient replete (control), and nitrogen (N) and phosphorus (P) deficiency to understand how this organism responds at the transcriptional level to varying nutrient conditions. This approach has aided A. anophagefferens genome annotation efforts and identified a suite of genes upregulated by N and P deficiency, some of which have known roles in nutrient metabolism. Genes upregulated under N deficiency include an ammonium transporter, an acetamidase/formamidase and two peptidases. This suggests an ability to utilize reduced N compounds and dissolved organic nitrogen, supporting the hypothesized importance of these N sources in A. anophagefferens bloom formation. There are also a broad suite of P-regulated genes, including an alkaline phosphatase, and two 5′-nucleotidases, suggesting A. anophagefferens may use dissolved organic phosphorus under low phosphate conditions. These N- and P-regulated genes may be important targets for exploring nutrient controls on bloom formation in field populations.
Julie Laroche - One of the best experts on this subject based on the ideXlab platform.
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the role of the picoeukaryote Aureococcus anophagefferens in cycling of marine high molecular weight dissolved organic nitrogen
Limnology and Oceanography, 2003Co-Authors: Gry Mine Berg, Daniel J. Repeta, Julie LarocheAbstract:Environmental evidence suggests that Aureococcus anophagefferens(Pelagophyceae), a eukaryotic picoplankton that blooms in coastal seawaters, can outcompete other organisms because of its ability to use abundant dissolved organic nitrogen (DON). To test this hypothesis, we isolated A. anophagefferens in axenic culture and monitored its growth on high‐molecular weight (HMW) DON collected from sediment pore waters, a putative source for DON in bays where blooms occur. HMW DON originating from pore water had a substantially higher protein content than surface seawater DON. We found that A. anophagefferens could deplete 25‐36% of the available nitrogen in cultures with HMW DON as the sole source of nitrogen and that this corresponded well with the protein fraction in pore-water HMW DON. High rates of cell surface peptide hydrolysis and no detectable N-acetyl polysaccharide hydrolysis, together with the high percentage of hydrolyzable amino acids compared to hydrolyzable aminosugars present in the HMW DON, pointed to the protein fraction as the more likely source of nitrogen used for growth. Whether or not nitrogen scavenging from protein is a common mechanism in phytoplankton is at present unknown but needs to be investigated.
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The role of the picoeukaryote Aureococcus anophagefferens in cycling of marine high-molecular weight dissolved organic nitrogen
2003Co-Authors: Gry Mine Berg, Daniel J. Repeta, Julie LarocheAbstract:Environmental evidence suggests that Aureococcus anophagefferens (Pelagophyceae), a eukaryotic picoplankton that blooms in coastal seawaters, can outcompete other organisms because of its ability to use abundant dissolved organic nitrogen (DON). To test this hypothesis, we isolated A. anophagefferens in axenic culture and monitored its growth on high–molecular weight (HMW) DON collected from sediment pore waters, a putative source for DON in bays where blooms occur. HMW DON originating from pore water had a substantially higher protein content than surface seawater DON. We found that A. anophagefferens could deplete 25–36 % of the available nitrogen in cultures with HMW DON as the sole source of nitrogen and that this corresponded well with the protein fraction in pore-water HMW DON. High rates of cell surface peptide hydrolysis and no detectable N-acetyl polysaccharide hydrolysis, together with the high percentage of hydrolyzable amino acids compared to hydrolyzable aminosugars present in the HMW DON, pointed to the protein fraction as the more likely source of nitrogen used for growth. Whether or not nitrogen scavenging from protein is a common mechanism in phytoplankton is at present unknown but needs to be investigated. Intense blooms of Aureococcus anophagefferens, or brown tides, were first observed in 1985 at three separat
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Dissolved organic nitrogen hydrolysis rates in axenic cultures of Aureococcus anophagefferens (Pelagophyceae) : comparison with heterotrophic bacteria
Applied and environmental microbiology, 2002Co-Authors: Gry Mine Berg, Daniel J. Repeta, Julie LarocheAbstract:The marine autotroph Aureococcus anophagefferens (Pelagophyceae) was rendered axenic in order to investigate hydrolysis rates of peptides, chitobiose, acetamide, and urea as indicators of the ability to support growth on dissolved organic nitrogen. Specific rates of hydrolysis varied between 8 and 700% of rates observed in associated heterotrophic marine bacteria.
David A Caron - One of the best experts on this subject based on the ideXlab platform.
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immunofluorescence flow cytometry technique for enumeration of the brown tide alga Aureococcus anophagefferens
Applied and Environmental Microbiology, 2008Co-Authors: Beth Stauffer, Rebecca A. Schaffner, Catherine E Wazniak, David A CaronAbstract:A new immunologically based flow cytometry (IFCM) technique was developed to enumerate Aureococcus anophagefferens, a small pelagophyte alga that is the cause of “brown tides” in bays and estuaries of the mid-Atlantic states along the U.S. coast. The method utilizes a monoclonal antibody conjugated to fluorescein isothiocyanate (FITC-MAb) to label the surface of A. anophagefferens cells which are then detected and enumerated by using a flow cytometer. Optimal conditions for FITC-MAb staining, including solution composition, incubation times, and FITC-MAb concentrations, were determined. The FITC-MAb method was tested for cross-reactivity with nontarget, similarly sized, photoautotrophic protists, and the method was compared to an enzyme-linked immunosorbent assay (ELISA) using the same MAb. Comparisons of the IFCM technique to traditional microscopy enumeration of cultures and spiked environmental samples showed consistent agreement over several orders of magnitude (r2 > 0.99). Comparisons of the IFCM and ELISA techniques for enumerating cells from a predation experiment showed a substantial overestimation (up to 10 times higher) of the ELISA in the presence of consumers of A. anophagefferens, presumably due to egested cell fragments that retained antigenicity, using the ELISA method, but were not characterized as whole algal cells by the IFCM method. Application of the IFCM method to environmental “brown-tide” samples taken from the coastal bays of Maryland demonstrated its efficacy in resolving A. anophagefferens abundance levels throughout the course of a bloom and over a large range of abundance values. IFCM counts of the brown-tide alga from natural samples were consistently lower than those obtained using the ELISA method and were equivalent to those of the polyclonal immunofluorescence microscopy technique, since both methods discriminate intact cells. Overall, the IFCM approach was an accurate and relatively simple technique for the rapid enumeration of A. anophagefferens in natural samples over a wide range of abundance values (103 to 106 cells ml−1).
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Feeding behavior and development of Acartia tonsa nauplii on the brown tide alga Aureococcus anophagefferens
Journal of Plankton Research, 2008Co-Authors: Jillian K. Smith, David J. Lonsdale, Christopher J. Gobler, David A CaronAbstract:Toxic attributes of the brown tide alga Aureococcus anophagefferens affect the ability of benthic and protistan grazers to control blooms. Yet, little is known regarding the effect of A. anophagefferens on a dominant component of the microzooplankton community, copepod nauplii. This study describes the grazer–prey relationship between nauplii of the calanoid copepod Acartia tonsa and A. anophagefferens. Four laboratory experiments using varying proportions of A. anophagefferens (2–4 mm) and a control alga, Isochrysis galbana (4–6 mm), were conducted to test the effects of A. anophagefferens isolate 1708 during exponential and stationary growth phases and A. anophagefferens isolate 1850 (exponential phase only) on naupliar grazing and development. A fifth experiment compared the effects of A. anophagefferens with an equal-sized control alga, Micromonas pusilla (1–3 mm). Isolate 1708 (exponential or stationary) as a single food item did not suppress naupliar ingestion rates (ng C nauplius 21 day 21 ) when compared to I. galbana. No ingestion was detected on isolate 1850 when offered alone, suggesting that this isolate may be more harmful to nauplii. Overall, nauplii selectively grazed on I. galbana over A. anophagefferens in mixed diets, but size-selection could not be ruled out as selective feeding was not apparent in mixtures with M. pusilla. Both isolates of A. anophagefferens delayed naupliar development. Our results indicate that Acartia tonsa nauplii can graze on A. anophagefferens, and can potentially help suppress brown tides. However, the efficacy of grazing control by copepods will vary with availability of alternate food sources and toxicity of the A. anophagefferens strain(s) comprising the population.
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Immunofluorescence Flow Cytometry Technique for Enumeration of the Brown-Tide Alga, Aureococcus anophagefferens
2008Co-Authors: Beth A. Stauffer, Catherine Wazniak, Rebecca A. Schaffner, David A CaronAbstract:A new immunologically based flow cytometry (IFCM) technique was developed to enumerate Aureococcus anophagefferens, a small pelagophyte alga that is the cause of “brown tides ” in bays and estuaries of the mid-Atlantic states along the U.S. coast. The method utilizes a monoclonal antibody conjugated to fluorescein isothiocyanate (FITC-MAb) to label the surface of A. anophagefferens cells which are then detected and enumerated by using a flow cytometer. Optimal conditions for FITC-MAb staining, including solution com-position, incubation times, and FITC-MAb concentrations, were determined. The FITC-MAb method was tested for cross-reactivity with nontarget, similarly sized, photoautotrophic protists, and the method was compared to an enzyme-linked immunosorbent assay (ELISA) using the same MAb. Comparisons of the IFCM technique to traditional microscopy enumeration of cultures and spiked environmental samples showed consistent agreement over several orders of magnitude (r2> 0.99). Comparisons of the IFCM and ELISA techniques for enumerating cells from a predation experiment showed a substantial overestimation (up to 10 times higher) of the ELISA in the presence of consumers of A. anophagefferens, presumably due to egested cell fragments that retained antigenicity, using the ELISA method, but were not characterized as whole algal cells by the IFCM method. Application of the IFCM method to environmental “brown-tide ” samples taken from the coastal bays of Maryland demonstrated its efficacy in resolving A. anophagefferens abundance levels throughou
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role of zooplankton in the onset and demise of harmful brown tide blooms Aureococcus anophagefferens in us mid atlantic estuaries
Aquatic Microbial Ecology, 2006Co-Authors: Sarah N Deonarine, Darcy J Lonsdale, Christopher J Gobler, David A CaronAbstract:Harmful brown tides caused by the pelagophyte Aureococcus anophagefferens have occurred in mid-Atlantic estuaries for 2 decades. Low grazing rates by microzooplankton have been implicated as a possible cause of these events, but no study to date has concurrently quantified zoo- plankton population densities and zooplankton grazing rates of A. anophagefferens cells. We con- ducted field studies from 2002 to 2004 to quantify grazing on the brown tide alga A. anophagefferens by meso-, micro-, and nanozooplankton, while concurrently establishing the composition of the plankton community. Research sites included an estuary that experienced an intense brown tide (Chincoteague Bay, Maryland (MD); 2004: 2 × 10 6 cells ml -1 ) and one that experienced sporadic blooms (Quantuck Bay, New York (NY); 2002: 8 × 10 5 cells ml -1 ; 2003 and 2004: <3 × 10 4 cells ml -1 ). The MD site was dominated by small autotrophs (<5 µm), such as A. anophagefferens and other picoeukaryotes, and small heterotrophs, such as Paulinella ovalis, while the NY site hosted a range of large and small autotrophs and zooplankton. Experiments indicated that small zooplankton (3 to 5 µm) were consumers of A. anophagefferens at bloom and non-bloom locations. However, dilution experiments documented active grazing on most picoplankton except A. anophagefferens in MD, while grazing rates on the brown tide alga in NY were comparable to grazing rates on the total phyto- plankton community and other picoplankton. Experimental enrichment of estuarine waters with mesozooplankton indicated a preferential avoidance of A. anophagefferens by grazers during intense blooms, but active consumption during non-bloom conditions. Differences in the effect of grazing between sites suggest that zooplankton may be controlling brown tides in NY, but allowing blooms to form due to low grazing pressure in MD. These findings further suggest that the zooplank- ton community in NY has changed from one which formerly avoided the consumption of A. anopha- gefferens to one which currently contributes to top-down control of brown tides.
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assessment of brown tide blooms caused by Aureococcus anophagefferens and contributing factors in new jersey coastal bays 2000 2002
Harmful Algae, 2004Co-Authors: Mary Downes Gastrich, David A Caron, Richard G Lathrop, Scott Haag, Michael P Weinstein, Michael Danko, Rebecca A. SchaffnerAbstract:Abstract A 3 year study (2000–2002) in Barnegat Bay-Little Egg Harbor (BB/LEH), New Jersey (USA), was conducted by the New Jersey Department of Environmental Protection, Division of Science Research and Technology (DSRT) in cooperation with several partners to assess brown tide blooms in coastal waters in NJ. Water samples were collected by boat and helicopter at coastal stations from 2000 to 2002 along with field measurements. Aureococcus anophagefferens were enumerated and associated environmental factors were analyzed. A. anophagefferens abundances were classified using the Brown Tide Bloom Index and mapped, along with salinity and temperature parameters, to their geo-referenced location using the ArcView GIS. The highest A. anophagefferens abundances (>106 cells ml−1), including category 3 blooms (≥200,000 cells ml−1) and category 2 blooms (≥35,000 to ≤200,000 cells ml−1), recurred during each of the 3 years of sampling and covered significant geographic areas of the estuary, especially in Little Egg Harbor. While category 3 blooms were generally associated with warmer water temperatures (>16 °C) and higher salinity (>25–26 ppt), these factors were not sufficient alone to explain the timing or distribution of A. anophagefferens blooms. There was no significant relationship between brown tide abundances and dissolved organic nitrogen measured in 2002 but this was consistent with other studies. Extended drought conditions, with corresponding low freshwater inputs and elevated bay water salinities, occurring during this time were conducive to blooms. A. anophagefferens abundances were well above the reported levels that have been reported to cause negative impacts on shellfish. It was shown that over 50% of the submerged aquatic vegetation (SAV) habitat located in Barnegat Bay/Little Egg Harbor was categorized as having a high frequency of category 2 or 3 blooms for all 3 years.
