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Brett A. Neilan - One of the best experts on this subject based on the ideXlab platform.
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genome variation in nine co occurring toxic Cylindrospermopsis Raciborskii strains
Harmful Algae, 2018Co-Authors: Anusuya Willis, Sarah E Ongley, Michele A. Burford, Jason N. Woodhouse, Aaron R Jex, Brett A. NeilanAbstract:Cyanobacteria form harmful algal blooms and are highly adapted to a range of habitats, in part due to their phenotype plasticity. This plasticity is partially the result of co-existence of multiple strains within a single population. The toxic cyanobacterium Cylindrospermopsis Raciborskii has remarkable phenotypic plasticity, strain variation and environmental adaptation resulting in an expansion of its global range. To understand the genetic basis of the high level of plasticity within a C. Raciborskii population, the genomes of nine co-occurring strains were compared. The strains differed in morphology, toxin cell quotas and physiology, despite being obtained from a single water sample. Comparative genomics showed that three coiled strains were 3.9 Mbp in size, with 3544 ± 11 genes, while straight strains were 3.8 Mbp in size, with 3485 ± 20 genes. The core proteome comprised 86% of the genome and consisted of 2891 orthologous groups (OGs), whereas the variable genome comprised ∼14% (847 OGs), and the strain specific genome only ∼1% (433 OGs).There was a high proportion of variable strain-specific genes for the very closely related strains, which may underpin strain differentiation. The variable genes were associated with environmental responses and adaptation, particularly phage defence, DNA repair, membrane transport, and stress, illustrative of the adaptability of the strains in response to environmental and biological stressors. This study shows that high genomic variability exists between co-occurring strains and may be the basis of strain phenotypic differences and plasticity of populations. Therefore management and prediction of blooms of this harmful species requires different approaches to capture this strain variability.
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Intraspecific variation in growth, morphology and toxin quotas for the cyanobacterium, Cylindrospermopsis Raciborskii.
Toxicon : official journal of the International Society on Toxinology, 2016Co-Authors: Anusuya Willis, Brett A. Neilan, Ann W. Chuang, Jason N. Woodhouse, Michele A. BurfordAbstract:Cylindrospermopsis Raciborskii is a bloom forming cyanobacterium with complex population dynamics and toxicity. In January of 2013 a single sample was collected from surface waters in Lake Wivenhoe, Australia, and twenty-four individual trichomes were isolated. Each isolate exhibited differences in growth rate, toxin cell quota and morphology, in the absence of phylogenetic heterogeneity. This study demonstrates substantial intraspecific isolate variation within a small sample and this has implications for understanding the population dynamics of this species.
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understanding the winning strategies used by the bloom forming cyanobacterium Cylindrospermopsis Raciborskii
Harmful Algae, 2016Co-Authors: Michele A. Burford, John Beardall, Anusuya Willis, Sandra M.f.o. Azevedo, Philip T. Orr, Valeria F Magalhaes, Luciana M Rangel, Brett A. NeilanAbstract:The cyanobacterium Cylindrospermopsis Raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. It is of particular concern because strains in some geographic areas are capable of producing toxins with implications for human and animal health. Studies of this species have increased rapidly in the last two decades, especially in the southern hemisphere where toxic strains are prevalent. A clearer picture is emerging of the strategies adopted by this species to bloom and out-compete other species. This species has a high level of flexibility with respect to light and nutrients, with higher temperatures and carbon dioxide also promoting growth. There are two types of toxins produced by C. Raciborskii: cylindrospermopsins (CYNs) and saxitoxins (STXs). The toxins CYNs are constitutively produced irrespective of environmental conditions and the ecological or physiological role is unclear, while STXs appear to serve as protection against high salinity and/or water hardness. It is also apparent that strains of this species can vary substantially in their physiological responses to environmental conditions, including CYNs production, and this may explain discrepancies in findings from studies in different geographical areas. The combination of a flexible strategy with respect to environmental conditions, and variability in strain response makes it a challenging species to manage. Our ability to improve bloom prediction will rely on a more detailed understanding of the complex physiology of this species.
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elevated na and ph influence the production and transport of saxitoxin in the cyanobacteria anabaena circinalis awqc131c and Cylindrospermopsis Raciborskii t3
Environmental Microbiology, 2016Co-Authors: Sarah E Ongley, Jasper J L Pengelly, Brett A. NeilanAbstract:Saxitoxins (STX), neurotoxic alkaloids, fall under the umbrella of paralytic shellfish toxins produced by marine dinoflagellates and freshwater cyanobacteria. The genes responsible for the production of STX have been proposed, but factors that influence their expression and induce toxin efflux remain unclear. Here we characterize the putative STX NorM-like MATE transporters SxtF and SxtM. Complementation of the antibiotic-sensitive strain Escherichia coli KAM32 with these transporters decreased fluoroquinolone sensitivity, indicating that while becoming evolutionary specialized for STX transport these transporters retain relaxed specificity typical of this class. The transcriptional response of STX biosynthesis (sxtA) along with that of the STX transporters (sxtM and sxtF from Cylindrospermopsis Raciborskii T3, and sxtM from Anabaena circinalis AWQC131C) were assessed in response to ionic stress. These data, coupled with a measure of toxin intracellular to extracellular ratios, provide an insight into the physiology of STX export. Cylindrospermopsis Raciborskii and Anabaena circinalis exhibited opposing responses under conditions of ionic stress. High Na(+) (10 mM) induced moderate alterations of transcription and STX localization, whereas high pH (pH 9) stimulated the greatest physiological response. Saxitoxin production and cellular localization are responsive to ionic strength, indicating a role of this molecule in the maintenance of cellular homeostasis.
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Elevated Na(+) and pH influence the production and transport of saxitoxin in the cyanobacteria Anabaena circinalis AWQC131C and Cylindrospermopsis Raciborskii T3.
Environmental microbiology, 2015Co-Authors: Sarah E Ongley, Jasper J L Pengelly, Brett A. NeilanAbstract:Saxitoxins (STX), neurotoxic alkaloids, fall under the umbrella of paralytic shellfish toxins produced by marine dinoflagellates and freshwater cyanobacteria. The genes responsible for the production of STX have been proposed, but factors that influence their expression and induce toxin efflux remain unclear. Here we characterize the putative STX NorM-like MATE transporters SxtF and SxtM. Complementation of the antibiotic-sensitive strain Escherichia coli KAM32 with these transporters decreased fluoroquinolone sensitivity, indicating that while becoming evolutionary specialized for STX transport these transporters retain relaxed specificity typical of this class. The transcriptional response of STX biosynthesis (sxtA) along with that of the STX transporters (sxtM and sxtF from Cylindrospermopsis Raciborskii T3, and sxtM from Anabaena circinalis AWQC131C) were assessed in response to ionic stress. These data, coupled with a measure of toxin intracellular to extracellular ratios, provide an insight into the physiology of STX export. Cylindrospermopsis Raciborskii and Anabaena circinalis exhibited opposing responses under conditions of ionic stress. High Na(+) (10 mM) induced moderate alterations of transcription and STX localization, whereas high pH (pH 9) stimulated the greatest physiological response. Saxitoxin production and cellular localization are responsive to ionic strength, indicating a role of this molecule in the maintenance of cellular homeostasis.
Michele A. Burford - One of the best experts on this subject based on the ideXlab platform.
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genome variation in nine co occurring toxic Cylindrospermopsis Raciborskii strains
Harmful Algae, 2018Co-Authors: Anusuya Willis, Sarah E Ongley, Michele A. Burford, Jason N. Woodhouse, Aaron R Jex, Brett A. NeilanAbstract:Cyanobacteria form harmful algal blooms and are highly adapted to a range of habitats, in part due to their phenotype plasticity. This plasticity is partially the result of co-existence of multiple strains within a single population. The toxic cyanobacterium Cylindrospermopsis Raciborskii has remarkable phenotypic plasticity, strain variation and environmental adaptation resulting in an expansion of its global range. To understand the genetic basis of the high level of plasticity within a C. Raciborskii population, the genomes of nine co-occurring strains were compared. The strains differed in morphology, toxin cell quotas and physiology, despite being obtained from a single water sample. Comparative genomics showed that three coiled strains were 3.9 Mbp in size, with 3544 ± 11 genes, while straight strains were 3.8 Mbp in size, with 3485 ± 20 genes. The core proteome comprised 86% of the genome and consisted of 2891 orthologous groups (OGs), whereas the variable genome comprised ∼14% (847 OGs), and the strain specific genome only ∼1% (433 OGs).There was a high proportion of variable strain-specific genes for the very closely related strains, which may underpin strain differentiation. The variable genes were associated with environmental responses and adaptation, particularly phage defence, DNA repair, membrane transport, and stress, illustrative of the adaptability of the strains in response to environmental and biological stressors. This study shows that high genomic variability exists between co-occurring strains and may be the basis of strain phenotypic differences and plasticity of populations. Therefore management and prediction of blooms of this harmful species requires different approaches to capture this strain variability.
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Variations in carbon-to-phosphorus ratios of two Australian strains of Cylindrospermopsis Raciborskii
European Journal of Phycology, 2017Co-Authors: Anusuya Willis, Amanda Jean Posselt, Michele A. BurfordAbstract:The toxic cyanobacterium Cylindrospermopsis Raciborskii can form large blooms in freshwater systems, causing water quality problems. The availability of the essential macronutrient phosphorus (P), ...
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Nitrogen fixation by the diazotroph Cylindrospermopsis Raciborskii (Cyanophyceae)
Journal of phycology, 2016Co-Authors: Anusuya Willis, Ann W. Chuang, Michele A. BurfordAbstract:Nitrogen fixation has been proposed as a mechanism that allows the diazotrophic cyanobacterium, Cylindrospermopsis Raciborskii, to bloom in nitrogen-limited freshwater systems. However, it is unclear whether dinitrogen fixation (N2 fixation) can supplement available dissolved inorganic nitrogen (DIN) for growth, or only provides minimum nitrogen (N) for cell maintenance under DIN deplete conditions. Additionally, the rate at which cells can switch between DIN use and N2 fixation is unknown. This study investigated N2 fixation under a range of nitrate concentrations. Cultures were grown with pretreatments of nitrate replete (single dose 941 μmol NO3- · L-1 ) and N-free conditions and then either received a single dose of 941 μmol NO3- · L-1 (N941), 118 μmol NO3- · L-1 (N118) or 0 N. Heterocysts appeared from days 3 to 5 when treatments of high NO3- were transferred to N free media (N941:N0), and from day 5 in N941 transferred to N118 treatments. Conversely, transferring cells from N0 to N941 resulted in heterocysts being discarded from day 3 and day 5 for N0:N118. Heterocyst appearance correlated with a detectable rate of N2 fixation and up-regulation of nifH gene expression, the discard of heterocysts occurred after sequential reduction of nifH expression and N2 fixation. Nitrate uptake rates were not affected by pretreatment, suggesting no regulation or saturation of this uptake pathway. These data demonstrate that for C. Raciborskii, N2 fixation is regulated by the production or discard of heterocysts. In conclusion, this study has shown that N2 fixation only provides enough N to support relatively low growth under N-limited conditions, and does not supplement available nitrate to increase growth rates.
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Intraspecific variation in growth, morphology and toxin quotas for the cyanobacterium, Cylindrospermopsis Raciborskii.
Toxicon : official journal of the International Society on Toxinology, 2016Co-Authors: Anusuya Willis, Brett A. Neilan, Ann W. Chuang, Jason N. Woodhouse, Michele A. BurfordAbstract:Cylindrospermopsis Raciborskii is a bloom forming cyanobacterium with complex population dynamics and toxicity. In January of 2013 a single sample was collected from surface waters in Lake Wivenhoe, Australia, and twenty-four individual trichomes were isolated. Each isolate exhibited differences in growth rate, toxin cell quota and morphology, in the absence of phylogenetic heterogeneity. This study demonstrates substantial intraspecific isolate variation within a small sample and this has implications for understanding the population dynamics of this species.
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understanding the winning strategies used by the bloom forming cyanobacterium Cylindrospermopsis Raciborskii
Harmful Algae, 2016Co-Authors: Michele A. Burford, John Beardall, Anusuya Willis, Sandra M.f.o. Azevedo, Philip T. Orr, Valeria F Magalhaes, Luciana M Rangel, Brett A. NeilanAbstract:The cyanobacterium Cylindrospermopsis Raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. It is of particular concern because strains in some geographic areas are capable of producing toxins with implications for human and animal health. Studies of this species have increased rapidly in the last two decades, especially in the southern hemisphere where toxic strains are prevalent. A clearer picture is emerging of the strategies adopted by this species to bloom and out-compete other species. This species has a high level of flexibility with respect to light and nutrients, with higher temperatures and carbon dioxide also promoting growth. There are two types of toxins produced by C. Raciborskii: cylindrospermopsins (CYNs) and saxitoxins (STXs). The toxins CYNs are constitutively produced irrespective of environmental conditions and the ecological or physiological role is unclear, while STXs appear to serve as protection against high salinity and/or water hardness. It is also apparent that strains of this species can vary substantially in their physiological responses to environmental conditions, including CYNs production, and this may explain discrepancies in findings from studies in different geographical areas. The combination of a flexible strategy with respect to environmental conditions, and variability in strain response makes it a challenging species to manage. Our ability to improve bloom prediction will rely on a more detailed understanding of the complex physiology of this species.
Glen R Shaw - One of the best experts on this subject based on the ideXlab platform.
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Factors affecting akinete differentiation in Cylindrospermopsis Raciborskii (Nostocales, Cyanobacteria)
Freshwater Biology, 2005Co-Authors: David Moore, Mark O'donohue, C. M. Garnett, Christa Critchley, Glen R ShawAbstract:1. Cylindrospermopsis Raciborskii is a potentially toxic freshwater cyanobacterium which can produce akinetes (reproductive spores) that on germinating can contribute to future populations. To further understand factors controlling the formation of these specialised cells, the effects of diurnal temperature fluctuations (magnitude and frequency), in combination with different light intensities and phosphorus concentrations were investigated under laboratory conditions. 2. Akinete differentiation was affected by the frequency of temperature fluctuations. Maximum akinete concentrations were observed in cultures that experienced multiple diurnal temperature fluctuations. 3. Akinete concentrations increased with increasing magnitude of temperature fluctuation. A maximum akinete concentration was achieved under multiple diurnal temperature fluctuations with a magnitude of 10degreesC (25degreesC to 15degreesC). 4. A fourfold increase in light intensity (25-100 mumol m(-2) s(-1)) resulted in an approximate 14-fold increase in akinete concentration. 5. High filterable reactive phosphorus (FRP) concentrations (> 70 mug L-1) in the medium, combined with a multiple diurnal temperature fluctuation of 10degreesC, supported the development of the highest akinete concentration.
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MORPHOLOGICAL CHANGES DURING AKINETE GERMINATION IN Cylindrospermopsis Raciborskii (NOSTOCALES, CYANOBACTERIA)
Journal of Phycology, 2004Co-Authors: David Moore, Glen B. Mcgregor, Glen R ShawAbstract:The occurrence of the cyanobacterium Cylindrospermopsis Raciborskii (Woloszynska) Seenayya and Subba Raju is a global water quality issue. The misidentification of C. Raciborskii in the past is a major concern for water quality users, considering the reported cases of human and livestock poisonings associated with the cyanobacterium. Many of the available taxonomic descriptions for this species provide little or no detail of the morphology of early developmental phases that may assist with identification. Therefore, typifying the morphological changes throughout the entire life cycle for such a species requires urgent attention. In this study, five distinct morphological phases identified using a new culturing technique are reported for the process of akinete germination in C. Raciborskii. Before the terminal emergence of three to four cell germlings through a ruptured akinete envelope (phase 3), mature akinetes (phase 1) elongated and the endospore separated from the akinete envelope (phase 2). After the association with the envelope was lost, four-cell germlings (phase 4a) matured into young trichomes of more than four cells (phase 4b). Throughout the process of germination, internal granular structures decreased in size and were irregular in shape in germlings and young trichomes. The culturing technique, which used a Sedgwick-Rafter cell, was successful in its application but was limiting in that the development of young trichomes after phase 4b could not be monitored.
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Extraction and purification of the zwitterions cylindrospermopsin and deoxycylindrospermopsin from Cylindrospermopsis Raciborskii.
Environmental toxicology, 2001Co-Authors: Ross Norris, P. Senogles, Robyn K. Chiswell, Geoffrey K Eaglesham, Glen R Shaw, Alan A. Seawright, M J Smith, B. Davis, Michael R MooreAbstract:The hepatotoxin cylindrospermopsin (CYN) has been isolated from the cyanobacterium Cylindrospermopsis Raciborskii (C. raci.). Efforts to study this toxin have been hampered by the time-consuming requirement to extract it from cultures of the organism. It is usually extracted from lyophilized cells collected from a laboratory culture. Our preliminary work suggested far more of the toxin is available in solution in the culture media than in the cells collected. We have therefore investigated the use of commercially available solid phase extraction sorbents to extract CYN from culture media in which C. raci. has been grown. A range of reverse phase and ion-exchange sorbents were tested across a range of pHs for their ability to retain CYN without success. Subsequently, graphitized carbon cartridges were found to retain CYN strongly. Elution with 5% formic acid in methanol allowed the CYN to be regained for final purification by HPLC. Deoxy-CYN, an analog of CYN can also be extracted using this procedure.
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deoxycylindrospermopsin an analog of cylindrospermopsin from Cylindrospermopsis Raciborskii
Environmental Toxicology, 1999Co-Authors: Ross Norris, Robyn K. Chiswell, Greg Pierens, Geoffrey K Eaglesham, Glen R Shaw, Alan A. Seawright, M J Smith, Michael R MooreAbstract:Cylindrospermopsin (CYN) is a hepatotoxic alkaloid found in the blue-green alga Cylindrospermopsis Raciborskii (C. Raciborskii). Data indicating CYN alone does not account for the toxicity of freeze dried cultures of C. Raciborskii have been presented recently. In an attempt to explain these data, we have purified and characterized the structure of an analog of CYN, deoxycylindrospermopsin (deoxy-CYN). Three mice dosed intraperitoneally (IP) with 0.8 mg/kg of deoxy-CYN showed no toxicity after 5 days. Comparison with the toxicity of CYN (5 day median lethal dose approximately 0.2 mg/kg IF) and its relative abundance in C. Raciborskii suggest deoxy-CYN does not contribute significantly to the toxicity of C. Raciborskii. The additional toxicity of freeze dried C. Raciborskii over pure CYN, therefore, remains unexplained. (C) 1999 by John Wiley & Sons, Inc.
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The oral toxicity for mice of the tropical cyanobacterium Cylindrospermopsis Raciborskii (Woloszynska)
Environmental Toxicology, 1999Co-Authors: Alan A. Seawright, Robyn K. Chiswell, Ross Norris, Glen R Shaw, Michael R Moore, Christopher C. Nolan, M J SmithAbstract:Exposure of humans and domestic animals to Cylindrospermopsis Raciborskii and its associated toxin cylindrospermopsin in their drinking water will normally be by ingestion. Studies of the cyanobacterium to date have involved dosing mice by the intraperitoneal route, which excludes the possible influence on its toxicity of the alimentary tract barrier. In the present study, outbred MF1 male mice were fasted overnight and then given a single oral dose suspended in normal saline of freeze-dried C. Raciborskii culture containing 0.2% cylindrospermopsin. The median lethal dose was in the range 4.4-6.9 mg/kg alkaloid equivalent, Death occurred from 2 to 6 days after dosing, and pathological changes included marked fatty liver, often with periacinar coagulative necrosis, acute renal tubular necrosis, atrophy of the thymic cortex and the lymphoid follicles in the spleen, subepicardial and myocardial hemorrhages, and multiple ulcerations of the esophageal part of the gastric mucosa. The syndrome was consistent with that already reported for cylindrospermopsin dosed parenterally. (C) 1999 by John Wiley & Sons, Inc.
Christopher P Saint - One of the best experts on this subject based on the ideXlab platform.
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Multiplex PCR assay for Cylindrospermopsis Raciborskii and cylindrospermopsin-producing cyanobacteria.
Environmental toxicology, 2003Co-Authors: Kim M Fergusson, Christopher P SaintAbstract:Water bodies are routinely monitored for the presence of potentially toxic cyanobacteria; however, the methodology for confirming toxicity is currently complex and expensive. Here we describe the application of gene-based technology to rapidly identify cylindrospermopsin-producing cyanobacteria, specifically, Cylindrospermopsis Raciborskii. A multiplex polymerase chain reaction (PCR) test was developed that simultaneously identified polyketide synthase (pks) and peptide synthetase (ps) determinants associated with cylindrospermopsin production and distinguished C. Raciborskii from other cylindrospermopsin-producing cyanobacteria of the species Anabaena bergii and Aphanizomenon ovalisporum, by targeting the rpoC1 gene. Twenty-one C. Raciborskii, 5 A. bergii, 10 Aph. ovalisporum isolates and 3 environmental samples all yielded PCR results consistent with their toxicological status, as assessed by high-performance liquid chromatography coupled to mass spectrometry or matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, and C. Raciborskii was always correctly identified. The PCR test is a rapid, reliable, and economical way of assessing the toxic potential of cyanobacterial blooms formed by these organisms.
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multiplex pcr assay for Cylindrospermopsis Raciborskii and cylindrospermopsin producing cyanobacteria
Environmental Toxicology, 2003Co-Authors: Kim M Fergusson, Christopher P SaintAbstract:Water bodies are routinely monitored for the presence of potentially toxic cyanobacteria; however, the methodology for confirming toxicity is currently complex and expensive. Here we describe the application of gene-based technology to rapidly identify cylindrospermopsin-producing cyanobacteria, specifically, Cylindrospermopsis Raciborskii. A multiplex polymerase chain reaction (PCR) test was developed that simultaneously identified polyketide synthase (pks) and peptide synthetase (ps) determinants associated with cylindrospermopsin production and distinguished C. Raciborskii from other cylindrospermopsin-producing cyanobacteria of the species Anabaena bergii and Aphanizomenon ovalisporum, by targeting the rpoC1 gene. Twenty-one C. Raciborskii, 5 A. bergii, 10 Aph. ovalisporum isolates and 3 environmental samples all yielded PCR results consistent with their toxicological status, as assessed by high-performance liquid chromatography coupled to mass spectrometry or matrix-assisted laser desorption ionization–time-of-flight mass spectrometry, and C. Raciborskii was always correctly identified. The PCR test is a rapid, reliable, and economical way of assessing the toxic potential of cyanobacterial blooms formed by these organisms. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 120–125, 2003.
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Identification of genes implicated in toxin production in the cyanobacterium Cylindrospermopsis Raciborskii
Environmental toxicology, 2001Co-Authors: Mark A. Schembri, Brett A. Neilan, Christopher P SaintAbstract:Cylindrospermopsis Raciborskii is a bloom-forming cyanobacterium found in both tropical and temperate climates which produces cylindrospermopsin, a potent hepatotoxic secondary metabolite. This organism is notorious for its association with a significant human poisoning incident on Palm Island, Australia, which resulted in the hospitalization of 148 people. We have screened 13 C. Raciborskii isolates from various regions of Australia and shown that both toxic and nontoxic strains exist within this species. No association was observed between geographical origin and toxin production. Polyketide synthases (PKSs) and peptide synthetases (PSs) are enzymes involved in secondary metabolite biosynthesis in cyanobacteria. Putative PKS and PS genes from C. Raciborskii strains AWT205 and CYP020B were identified by PCR using degenerate primers based on conserved regions within each gene. Examination of the strain-specific distribution of the PKS and PS genes in C. Raciborskii isolates demonstrated a direct link between the presence of these two genes and the ability to produce cylindrospermopsin. Interestingly, the possession of these two genes was also linked. They were also identified in an Anabaena bergii isolate that was demonstrated to produce cylindrospermopsin. Taken together, these data suggest a likely role for these determinants in secondary metabolite and toxin production by C. Raciborskii.
Philip T. Orr - One of the best experts on this subject based on the ideXlab platform.
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understanding the winning strategies used by the bloom forming cyanobacterium Cylindrospermopsis Raciborskii
Harmful Algae, 2016Co-Authors: Michele A. Burford, John Beardall, Anusuya Willis, Sandra M.f.o. Azevedo, Philip T. Orr, Valeria F Magalhaes, Luciana M Rangel, Brett A. NeilanAbstract:The cyanobacterium Cylindrospermopsis Raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. It is of particular concern because strains in some geographic areas are capable of producing toxins with implications for human and animal health. Studies of this species have increased rapidly in the last two decades, especially in the southern hemisphere where toxic strains are prevalent. A clearer picture is emerging of the strategies adopted by this species to bloom and out-compete other species. This species has a high level of flexibility with respect to light and nutrients, with higher temperatures and carbon dioxide also promoting growth. There are two types of toxins produced by C. Raciborskii: cylindrospermopsins (CYNs) and saxitoxins (STXs). The toxins CYNs are constitutively produced irrespective of environmental conditions and the ecological or physiological role is unclear, while STXs appear to serve as protection against high salinity and/or water hardness. It is also apparent that strains of this species can vary substantially in their physiological responses to environmental conditions, including CYNs production, and this may explain discrepancies in findings from studies in different geographical areas. The combination of a flexible strategy with respect to environmental conditions, and variability in strain response makes it a challenging species to manage. Our ability to improve bloom prediction will rely on a more detailed understanding of the complex physiology of this species.
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Nutrient-related changes in the toxicity of field blooms of the cyanobacterium, Cylindrospermopsis Raciborskii.
FEMS microbiology ecology, 2014Co-Authors: Michele A. Burford, Anusuya Willis, Rati Sinha, Timothy W. Davis, Philip T. Orr, Brett A. NeilanAbstract:Nutrients have the capacity to change cyanobacterial toxin loads via growth-related toxin production, or shifts in the dominance of toxic and nontoxic strains. This study examined the effect of nitrogen (N) and phosphorus on cell division and strain-related changes in production of the toxins, cylindrospermopsins (CYNs) by the cyanobacterium, Cylindrospermopsis Raciborskii . Two short-term experiments were conducted with mixed phytoplankton populations dominated by C. Raciborskii in a subtropical reservoir where treatments had nitrate (NO3), urea (U) and inorganic phosphorus (P) added alone or in combination. Cell division rates of C. Raciborskii were only statistically higher than the control on day 5 when U and P were co-supplied. In contrast, cell quotas of CYNs (QCYNS) increased significantly in treatments where P was supplied, irrespective of whether N was supplied, and this increase was not necessarily related to cell division rates. Increased QCYNS did correlate with an increase in the proportion of the cyrA toxin gene to 16S genes in the C. Raciborskii- dominated cyanobacterial population. Therefore, changes in strain dominance are the most likely factor driving differences in toxin production between treatments. Our study has demonstrated differential effects of nutrients on cell division and strain dominance reflecting a C. Raciborskii population with a range of strategies in response to environmental conditions.
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increased incidence of Cylindrospermopsis Raciborskii in temperate zones is climate change responsible
Water Research, 2012Co-Authors: Rati Sinha, Michele A. Burford, Leanne A. Pearson, Timothy W. Davis, Philip T. Orr, Brett A. NeilanAbstract:The bloom-forming, toxic cyanobacterium, Cylindrospermopsis Raciborskii exhibits global distribution. In recent years both the occurrence and dominance of this species, particularly in temperate regions, has increased. Whilst this may be due to increased sensitivity of analytical detection methods or more rigorous sampling routines, it is possible that this expansion has been assisted by a number of changing conditions in these environments. The geographical expansion of both the organism and toxin production can be attributed to phenomena such as eutrophication and climate change. In this review, we discuss the occurrence of C. Raciborskii with respect to current literature against the backdrop of increasing global temperatures. Critically, we identify a concerning trend between the geographical spread of this organism and global climate change.
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Increased incidence of Cylindrospermopsis Raciborskii in temperate zones – Is climate change responsible?
Water research, 2011Co-Authors: Rati Sinha, Michele A. Burford, Leanne A. Pearson, Timothy W. Davis, Philip T. Orr, Brett A. NeilanAbstract:The bloom-forming, toxic cyanobacterium, Cylindrospermopsis Raciborskii exhibits global distribution. In recent years both the occurrence and dominance of this species, particularly in temperate regions, has increased. Whilst this may be due to increased sensitivity of analytical detection methods or more rigorous sampling routines, it is possible that this expansion has been assisted by a number of changing conditions in these environments. The geographical expansion of both the organism and toxin production can be attributed to phenomena such as eutrophication and climate change. In this review, we discuss the occurrence of C. Raciborskii with respect to current literature against the backdrop of increasing global temperatures. Critically, we identify a concerning trend between the geographical spread of this organism and global climate change.
