ISSN:
1432-184X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Toxic cyanobacterial mass occurrences have caused animal poisonings worldwide and may pose a health hazard for humans. Strains of the genus Anabaena are either non-toxic or produce hepatotoxins, microcystins (MCYST), or neurotoxins (such as anatoxin-a). In order to study which growth conditions favor hepatotoxic vs neurotoxic strains and how production of toxins varies, we compared the responses of two microcystin- and two anatoxin-a-producing Anabaena strains in continuous turbidostat cultures, at different temperatures, under growth-limiting light levels. Growth rates consistently remained 〈0.8 divisions per 24 h. Differences were strain-specific and not associated with hepatotoxicity or neurotoxicity. Thus, differential adaptation of strains to temperature and to growth-limiting light levels cannot explain why, in some cyanobacterial water blooms, hepatotoxic strains, and in others, neurotoxic ones become dominant. A statistical analysis of field data showed that the most significant discriminating factors between different types of blooms were the concentrations of dissolved PO4-phosphorus and NO3-nitrogen. Anabaena blooms with unknown neurotoxicity associated with low PO4-phosphorus and high NO3-nitrogen concentrations. Among other Anabaena blooms, the hepatotoxic ones associated with the lowest, and most of the non-toxic ones with higher concentrations of PO4-phosphorus. Anabaena blooms that contained anatoxin-a and hepatotoxic Microcystis blooms showed tendencies towards the highest concentrations of PO4-phosphorus. Non-toxic blooms dominated by genera other than Anabaena occurred over a wide range of growth conditions. In turbidostat cultures, maximal production of microcystins correlated with maximal growth rates. Light regulated the production of MCYST-LR variants, and temperature affected the production of MCYST-RR variants. Anatoxin-a seemed to be produced most under temperatures and light levels slightly suboptimal for growth. Under low light, considerable amounts of extracellular anatoxin-a were detected while microcystins consistently remained intracellular.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002489900105
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