Stability of microcystins from cyanobacteria—III. Effect of pH and temperature

Harada, Kenichi; Tsuji, Kiyomi; Watanabe, Mariyo F.; Kondo, Fumio

doi:10.2216/i0031-8884-35-6s-83.1

Cited by 163 publications

(97 citation statements)

References 16 publications

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“…The stable cyclic structure of MC-LR is a real challenge for its removal via abiotic methods, which are generally used in conventional drinking water treatment plants [60]. In addition, MC-LR resists boiling and chemical hydrolysis at neutral pH [61]. Compared to the control which was autoclaved to remove all kind of biological organisms, the water from HLPL presented a MC-LR degradation, leading us to conclude that MC-LR was degraded by indigenous bacteria since no other degrader was brought into the batch culture [62].…”

Section: Degradation Of Mc-lr In Hlpl Watermentioning

confidence: 99%

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

Kansole

Lin

2016

Water

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Abstract:Harmful cyanobacteria blooms may deteriorate freshwater environments, leading to bad water quality that can adversely affect the health of humans, animals, and aquatic life. Many cyanobacteria can produce toxic metabolites, with Microcystin-LR (MC-LR) being the most commonly detected cyanotoxin in fresh water bodies. In this study, a MC-LR degrading Bacillus sp. strain was isolated from Hulupi Lake (HLPL), Taiwan and tested for its degradability of the cyanotoxin. The results showed that the degradation of Microcystin-LR by the isolated Bacillus sp. was temperature-dependent with an optimum MC-LR removal at 37 • C and a first order degradation constant rate for 0.22 day −1 . The degradation rate was also found to increase with decreasing MC-LR concentrations and increasing Bacillus sp. concentrations. Biomolecular monitoring of three types of genes (mlrA, CAAX, and GST) involved in the degradation indicated that mlrA, and CAAX genes were present in the indigenous bacteria in HLPL water samples. However, for the isolated Bacillus sp. strain, only CAAX genes were detected. The absence of the mlrA gene in the isolated Bacillus sp. strain shows that the degradation of MC-LR does not necessarily follow the pathways with mlrA, and can also follow the pathways involved with CAAX type II amino-terminal protease.

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Section: Degradation Of Mc-lr In Hlpl Watermentioning

confidence: 99%

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

Kansole

Lin

2016

Water

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“…Because of their chemical structure, MCs are extremely stable in water and can tolerate radical changes in water chemistry, including pH (Harada and Tsuji, 1998;Harada et al, 1996). Structurally, MCs are monocyclic heptapeptides, containing two variable l-amino acids and two novel d-amino acids: N-methyldehydroalanine (Mdha), which hydrolyses to methylamine, and a unique non-polar-linked amino acid 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid, also known as Adda.…”

Section: Microcystins: Chemical and Biochemical Characteristicsmentioning

confidence: 99%

Guidance values for microcystins in water and cyanobacterial supplement products (blue-green algal supplements): a reasonable or misguided approach?

Dietrich

Hoeger

2005

Toxicology and Applied Pharmacology

323

185

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This article reviews current scientific knowledge on the toxicity and carcinogenicity of microcystins and compares this to the guidance values proposed for microcystins in water by the World Health Organization, and for blue-green algal food supplements by the Oregon State Department of Health. The basis of the risk assessment underlying these guidance values is viewed as being critical due to overt deficiencies in the data used for its generation: (i) use of one microcystin congener only (microcystin-LR), while the other presently known nearly 80 congeners are largely disregarded, (ii) new knowledge regarding potential neuro and renal toxicity of microcystins in humans and (iii) the inadequacies of assessing realistic microcystin exposures in humans and especially in children via blue-green algal food supplements. In reiterating the state-of-the-art toxicology database on microcystins and in the light of new data on the high degree of toxin contamination of algal food supplements, this review clearly demonstrates the need for improved kinetic data of microcystins in humans and for discussion concerning uncertainty factors, which may result in a lowering of the present guidance values and an increased routine control of water bodies and food supplements for toxin contamination. Similar to the approach taken previously by authorities for dioxin or PCB risk assessment, the use of a toxin equivalent approach to the risk assessment of microcystins is proposed. D

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“…monocyclic heptapeptides. MCs share a general structure, cyclo-(-D-Ala 1 -L-X 2 -D-isoMeAsp 3 -L-Z 4 -Adda 5 -D-isoGlu 6 -Mdha 7 ), where D-isoMeAsp is D-erythro-β-methyl-aspartic acid, Mdha is N-methyl-dehydro-alanine, and X and Z in positions two and four are highly variable L-amino acids that determine the suffix in the nomenclature of MCs [3]. For example, microcystin-LR (MC-LR) contains leucine (L) and arginine (R), whereas microcystin-YA (MC-YA) contains tyrosine (Y) and alanine (A).…”

Section: Introductionmentioning

confidence: 99%

“…MCs are extremely stable and resist to common chemical breakdown such as hydrolysis or oxidation under conditions found in most natural water bodies, possibly because of their cyclic structure and novel amino acids [6]. At 40 °C, the half-life of MC-LR is about 3 and 10 weeks at pH 1 and 9, respectively [7]. MCs are also stable under irradiation by sunlight, although sunlight irradiation with pigments contained in cyanobacteria significantly decomposed the toxins by isomerization of a double bond in the Adda side chain; the half-life of photolysis was observed to be about 10 days [8,9].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Microcystin-induced Cytotoxicity and Apoptosis

Chen¹,

Xie

2016

MRMC

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Abstract:In recent years, cyanobacterial blooms have dramatically increased and become an ecological disaster worldwide. Cyanobacteria are also known to produce a wide variety of toxic secondary metabolites, i.e. cyanotoxins. Microcystins (MCs), a group of cyclic heptapeptides, are considered to be one of the most common and dangerous cyanobacterial toxins. MCs can be incorporated into the cells via organic anion transporting polypeptides (Oatps). It's widely accepted that inhibition of protein phosphatases (PPs) and induction of oxidative stress are the main toxic mechanisms of MCs. MCs are able to induce a variety of toxic cellular effects, including DNA damage, cytoskeleton disruption, mitochondria dysfunction, endoplasmic reticulum (ER) disturbance and cell cycle deregulation, all of which can contribute to apoptosis/programmed cell death. This review aimed to summarize the increasing data regarding the intracellular biochemical and molecular mechanisms of MC-induced toxicity and cell death.

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Stability of microcystins from cyanobacteria—III. Effect of pH and temperature

Cited by 163 publications

References 16 publications

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

Guidance values for microcystins in water and cyanobacterial supplement products (blue-green algal supplements): a reasonable or misguided approach?

Mechanisms of Microcystin-induced Cytotoxicity and Apoptosis

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