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Variation of microcystins, cyanobacterial hepatotoxins, in Anabaena spp. as a function of growth stimuli.

Abstract：

:Cyanobacterial hepatotoxins, microcystins, are specific inhibitors of serine/threonine protein phosphatases and potent tumor promoters. They have caused several poisonings of animals and also pose a health hazard for humans through the use of water for drinking and recreation. Different strains of the same cyanobacterial species may variously be nontoxic, be neurotoxic, or produce several microcystin variants. It is poorly understood how the amount of toxins varies in a single strain. This laboratory study shows the importance of external growth stimuli in regulating the levels and relative proportions of different microcystin variants in two strains of filamentous, nitrogen-fixing Anabaena spp. The concentration of the toxins in the cells increased with phosphorus. High temperatures (25 to 30 degrees C), together with the highest levels of light studied (test range, 2 to 100 mumol m-2 s-1), decreased their amount. Different structural variants of microcystins responded differently to growth stimuli. Variants of microcystin (MCYST)-LR correlated with temperatures below 25 degrees C, and those of MCYST-RR correlated with higher temperatures. Nitrogen added into the growth medium and increasing temperatures increased the proportion of microcystin variants demethylated in amino acid 3. All variants remained mostly intracellular. Time was the most important factor causing the release of the toxins into the growth medium. Time, nitrogen added into the growth medium, and light fluxes above 25 mumol m-2 s-1 significantly increased the concentrations of the dissolved toxins. According to the results, it thus seems that the reduction of phosphorus loads in bodies of water might play a role in preventing the health hazards that toxic cyanobacterial water blooms pose, not only by decreasing the cyanobacteria but also by decreasing their toxin content.

journal_name

Appl Environ Microbiol

journal_title

Applied and environmental microbiology

authors

Rapala J,Sivonen K,Lyra C,Niemelä SI

doi

10.1128/AEM.63.6.2206-2212.1997

subject

Has Abstract

pub_date

1997-06-01 00:00:00

pages

2206-12

issue

eissn

0099-2240

issn

1098-5336

journal_volume

pub_type

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Variation of microcystins, cyanobacterial hepatotoxins, in Anabaena spp. as a function of growth stimuli.