Effects of Environmental Factors on Toxicity of a Cyanobacterium (
            <i>Microcystis aeruginosa</i>
            ) under Culture Conditions

Watanabe, Mariyo F.; Oishi, Shogo

doi:10.1128/aem.49.5.1342-1344.1985

Cited by 266 publications

(118 citation statements)

References 8 publications

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“…Previous culture-based studies have shown only a onefold to twofold increase in microcystin quotas when temperatures have been increased in > 5°C increments (e.g. Watanabe and Oishi, 1985). Significant spikes in light intensity were recorded but these did not start until after 1300 h (Fig.…”

Section: Resultsmentioning

confidence: 82%

Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom

Wood

Rueckert

Hamilton

et al. 2011

Environ Microbiol Rep

105

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Toxic cyanobacterial blooms are increasing in prevalence. Microcystins are the most commonly produced cyanotoxin. Despite extensive research the variables regulating microcystin production remain unclear. Using a RT-QPCR assay that allowed the precise measurement of mcyE transcriptional gene expression and an ELISA that enabled small changes in total microcystin concentrations to be monitored, we demonstrate for the first time that microcystin production is not always constitutive and that significant up- and downregulation in microcystin synthesis can occur on time scales of 2-6 h. Samples were collected over 3 days from a small eutrophic lake during a dense microcystin-producing Microcystis bloom. McyE gene transcripts were detected in only four out of 14 samples. Vicissitudes in both microcystin quotas and extracellular microcystin levels corresponded with changes in mcyE expression. During the period of exalted microcystin synthesis Microcystis sp. cell concentrations increased from 70 000 cells ml(-1) to 4 000 000 cells ml(-1) . These data provide compelling evidence that changes in Microcystis cell concentrations influence microcystin production.

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Section: Resultsmentioning

confidence: 82%

Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom

Wood

Rueckert

Hamilton

et al. 2011

Environ Microbiol Rep

105

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“…Traditionally, the regulation of microcystin biosynthesis has been studied using toxin analysis. Earlier studies conducted during the 1980s employed mouse bioassays (e.g., Watanabe and Oishi 1985;van der Westhuizen and Eloff 1985) and with the advancement of analytical and biochemical methodologies at the onset of the 1990s more sophisticated techniques such as nuclear magnetic resonance spectrometry coupled with mass spectrometry (e.g., Sivonen et al 1990), high pressure liquid chromatography (e.g., Sedmak and Kosi 1998), enzyme-linked immunosorbent assays (e.g., Chu et al 1990), and protein phosphatase inhibition assay (e.g., Yoshizawa et al 1990) have been used, which have greatly improved the capability of toxin detection, quantification, and toxicity assessment. However, despite progress, the regulation of microcystin production is still poorly understood, demonstrating that toxin analysis alone is unlikely to be capable of assessing the full extent and complexity of the genetic and biosynthetic regulatory mechanism of microcystin biosynthesis.…”

Section: Discussionmentioning

confidence: 99%

Use of an armored RNA standard to measure microcystin synthetase E gene expression in toxic Microcystis sp. by reverse‐transcription QPCR

Rueckert

Cary

2009

Limnology & Ocean Methods

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Microcystin is a secondary metabolic peptide toxin known to cause hepatotoxicosis and carcinogenicity in vertebrates. It is produced by various bloom-forming cyanobacterial species constituting a serious threat to the quality of freshwater reservoirs worldwide. There is an intense interest to understand the biological function of microcystin and the regulatory mechanism behind its biosynthesis in order to develop strategies for freshwater management. To date, changes in toxin production in response to various environmental parameters have been studied using direct toxin analysis. Despite extensive research over the past two decades, the function of microcystin remains poorly understood. In this study, we developed an alternative method to study the regulation of microcystin production in toxic Microcystis sp. (and alternatively in Anabaena sp.) at the level of gene expression targeting microcystin synthetase E (mcyE) transcripts. We developed a durable and ribonuclease-resistant armored RNA standard to monitor for the integrity of all nucleic acid processing steps including extraction, reverse transcription, amplification, and detection. The armored RNA was designed to consist of the mcyE target matrix with a unique internal probe-binding sequence. To validate the efficacy of the method, we conducted a comprehensive survey of mcyE expression profiling in batch cultures of Microcystis sp. during exponential, linear, and stationary growth phase. Our transcriptional analysis indicates a growth-phase-dependent expression of mcyE, with the maximal level of expression observed during mid-log growth. With progressing age of the cultures, mcyE was gradually down-regulated, with expression levels having declined by more than three orders of magnitude during the stationary growth phase.

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“…The global relevance of MCs and Microcystis has led to dedicated efforts toward elucidating the role of this toxin in cyanobacteria metabolism and the factors regulating its biosynthesis. A good number of studies have shown that nutrients (Rapala et al 1997;Orr and Jones 1998;V ezie et al 2002;Xu et al 2010), temperature (Watanabe and Oishi 1985; Am e and Wunderlin 2005; Davis et al 2009), light (Kaebernick et al 2000;Kardinaal et al 2007;Leblanc Renaud et al 2011), andpH (Van Der Westhuizen andEloff 1983;Kr€ uger et al 2012) affect cyanobacterial growth and microcystin production in various ways. Results from many of these studies are rather contradictory; hence the precise biological function of MCs and the factors regulating its production are still contentious.…”

Section: Introductionmentioning

confidence: 99%

Comparison of cyanobacterial microcystin synthetase (mcy) E gene transcript levels, mcy E gene copies, and biomass as indicators of microcystin risk under laboratory and field conditions

2014

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Increased incidences of mixed assemblages of microcystin-producing and nonproducing cyanobacterial strains in freshwater bodies necessitate development of reliable proxies for cyanotoxin risk assessment. Detection of microcystin biosynthetic genes in water blooms of cyanobacteria is generally indicative of the presence of potentially toxic cyanobacterial strains. Although much effort has been devoted toward elucidating the microcystin biosynthesis mechanisms in many cyanobacteria genera, little is known about the impacts of co-occurring cyanobacteria on cellular growth, mcy gene expression, or mcy gene copy distribution. The present study utilized conventional microscopy, qPCR assays, and enzyme-linked immunosorbent assay to study how competition between microcystin-producing Microcystis aeruginosa CPCC 299 and Planktothrix agardhii NIVA-CYA 126 impacts mcyE gene expression, mcyE gene copies, and microcystin concentration under controlled laboratory conditions. Furthermore, analyses of environmental water samples from the Missisquoi Bay, Quebec, enabled us to determine how the various potential toxigenic cyanobacterial biomass proxies correlated with cellular microcystin concentrations in a freshwater lake. Results from our laboratory study indicated significant downregulation of mcyE gene expression in mixed cultures of M. aeruginosa plus P. agardhii on most sampling days in agreement with depressed growth recorded in the mixed cultures, suggesting that interaction between the two species probably resulted in suppressed growth and mcyE gene expression in the mixed cultures. Furthermore, although mcyE gene copies and McyE transcripts were detected in all laboratory and field samples with measureable microcystin levels, only mcyE gene copies showed significant positive correlations (R2 > 0.7) with microcystin concentrations, while McyE transcript levels did not. These results suggest that mcyE gene copies are better indicators of potential risks from microcystins than McyE transcript levels or conventional biomass proxies, especially in water bodies comprising mixed assemblages of toxic and nontoxic cyanobacteria.

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Effects of Environmental Factors on Toxicity of a Cyanobacterium ( Microcystis aeruginosa ) under Culture Conditions

Cited by 266 publications

References 8 publications

Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom

Switching toxin production on and off: intermittent microcystin synthesis in a Microcystis bloom

Use of an armored RNA standard to measure microcystin synthetase E gene expression in toxic Microcystis sp. by reverse‐transcription QPCR

Comparison of cyanobacterial microcystin synthetase (mcy) E gene transcript levels, mcy E gene copies, and biomass as indicators of microcystin risk under laboratory and field conditions

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