Impact of Environmental Factors on the Regulation of Cyanotoxin Production

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Abstract

Cyanobacteria are capable of thriving in almost all environments. Recent changes in climatic conditions due to increased human activities favor the occurrence and severity of harmful cyanobacterial bloom all over the world. Knowledge of the regulation of cyanotoxins by the various environmental factors is essential for effective management of toxic cyanobacterial bloom. In recent years, progress in the field of molecular mechanisms involved in cyanotoxin production has paved the way for assessing the role of various factors on the cyanotoxin production. In this review, we present an overview of the influence of various environmental factors on the production of major group of cyanotoxins, including microcystins, nodularin, cylindrospermopsin, anatoxins and saxitoxins.

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Most cited references 148

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Harmful cyanobacterial blooms: causes, consequences, and controls.

Hans W. Paerl, Timothy Otten (2013)

Cyanobacteria are the Earth's oldest oxygenic photoautotrophs and have had major impacts on shaping its biosphere. Their long evolutionary history (≈ 3.5 by) has enabled them to adapt to geochemical and climatic changes, and more recently anthropogenic modifications of aquatic environments, including nutrient over-enrichment (eutrophication), water diversions, withdrawals, and salinization. Many cyanobacterial genera exhibit optimal growth rates and bloom potentials at relatively high water temperatures; hence global warming plays a key role in their expansion and persistence. Bloom-forming cyanobacterial taxa can be harmful from environmental, organismal, and human health perspectives by outcompeting beneficial phytoplankton, depleting oxygen upon bloom senescence, and producing a variety of toxic secondary metabolites (e.g., cyanotoxins). How environmental factors impact cyanotoxin production is the subject of ongoing research, but nutrient (N, P and trace metals) supply rates, light, temperature, oxidative stressors, interactions with other biota (bacteria, viruses and animal grazers), and most likely, the combined effects of these factors are all involved. Accordingly, strategies aimed at controlling and mitigating harmful blooms have focused on manipulating these dynamic factors. The applicability and feasibility of various controls and management approaches is discussed for natural waters and drinking water supplies. Strategies based on physical, chemical, and biological manipulations of specific factors show promise; however, a key underlying approach that should be considered in almost all instances is nutrient (both N and P) input reductions; which have been shown to effectively reduce cyanobacterial biomass, and therefore limit health risks and frequencies of hypoxic events.

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Toxins of cyanobacteria.

Gerrit J A Speijers, Robrecht van der Wel, Edwige Van der Heiden … (2006)

Blue-green algae are found in lakes, ponds, rivers and brackish waters throughout the world. In case of excessive growth such as bloom formation, these bacteria can produce inherent toxins in quantities causing toxicity in mammals, including humans. These cyanotoxins include cyclic peptides and alkaloids. Among the cyclic peptides are the microcystins and the nodularins. The alkaloids include anatoxin-a, anatoxin-a(S), cylindrospermopsin, saxitoxins (STXs), aplysiatoxins and lyngbyatoxin. Both biological and chemical methods are used to determine cyanotoxins. Bioassays and biochemical assays are nonspecific, so they can only be used as screening methods. HPLC has some good prospects. For the subsequent detection of these toxins different detectors may be used, ranging from simple UV-spectrometry via fluorescence detection to various types of MS. The main problem in the determination of cyanobacterial toxins is the lack of reference materials of all relevant toxins. In general, toxicity data on cyanotoxins are rather scarce. A majority of toxicity data are known to be of microcystin-LR. For nodularins, data from a few animal studies are available. For the alkaloids, limited toxicity data exist for anatoxin-a, cylindrospermopsin and STX. Risk assessment for acute exposure could be relevant for some types of exposure. Nevertheless, no acute reference doses have formally been derived thus far. For STX(s), many countries have established tolerance levels in bivalves, but these limits were set in view of STX(s) as biotoxins, accumulating in marine shellfish. Official regulations for other cyanotoxins have not been established, although some (provisional) guideline values have been derived for microcystins in drinking water by WHO and several countries.

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The Cyanobacterial Hepatotoxin Microcystin Binds to Proteins and Increases the Fitness of Microcystis under Oxidative Stress Conditions

Yvonne Zilliges, Jan-Christoph Kehr, Sven Meissner … (2011)

Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ΔmcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites.

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Journal

Journal ID (nlm-ta): Toxins (Basel)

Journal ID (iso-abbrev): Toxins (Basel)

Journal ID (publisher-id): toxins

Title: Toxins

Publisher: MDPI

ISSN (Electronic): 2072-6651

Publication date (Electronic): 25 June 2014

Publication date Collection: July 2014

Volume: 6

Issue: 7

Pages: 1951-1978

Affiliations

Department of Life Science, Sangmyung University, Seoul 110-743, Korea; E-Mail: iamboopathy@ 123456gmail.com

Author notes

[* ] Author to whom correspondence should be addressed; E-Mail: kijs@ 123456smu.ac.kr ; Tel.: +82-2-2287-5449; Fax: +82-2-2287-0070.

Article

Publisher ID: toxins-06-01951

DOI: 10.3390/toxins6071951

PMC ID: 4113735

PubMed ID: 24967641

SO-VID: 7db31f80-5e20-4269-ad30-b0b4e54a5f51

License:

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

History

Date received : 30 April 2014

Date revision received : 06 June 2014

Date accepted : 17 June 2014

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Impact of Environmental Factors on the Regulation of Cyanotoxin Production

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Most cited references 148

Harmful cyanobacterial blooms: causes, consequences, and controls.

Toxins of cyanobacteria.

The Cyanobacterial Hepatotoxin Microcystin Binds to Proteins and Increases the Fitness of Microcystis under Oxidative Stress Conditions

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