Toxin production in cyanobacterial mats from ponds on the McMurdo Ice Shelf, Antarctica

Abstract

Cyanobacteria are known to produce hepatotoxic substances, the functional and ecological role of these toxins, however, remains largely unclear. Toxic properties of cyanobacteria collected in Antarctica were investigated to determine whether toxin-producing species can also be found under these environmental conditions. Samples were collected from meltwater ponds on the McMurdo Ice Shelf, Antarctica in the summers of 1997 to 1999. These ponds are colonized by benthic algae and cyanobacterial mats. Oscillatoriales, Nodularia sp., and Nostoc sp. constituted the major taxa in freshwater ponds, while Nostoc sp. was missing from brackish and saline ponds. Samples were taken from either¯oating, submerged or benthic mats, and extracted for in vitro toxicity testing. The presence of toxins was determined by the phosphatase-inhibition assay and by high performance liquid chromatography. The cytotoxic properties of the extracts were investigated in hepatocytes determining 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide metabolism and trypan blue dye exclusion. The results show that all cyanobacterial extracts display phosphatase-inhibiting activity, of which approximately half had signi®cantly greater than 50% inhibiting activity. The presence of nodularin and microcystin-LR was established by high performance liquid chromatography. Cytotoxic properties, independent of the phosphatase inhibiting activity, were also detected. Toxic strains of cyanobacteria can therefore also be found in Antarctica and this ®nding may lead to further insight into potential ecological roles of cyanobacterial phosphatase inhibiting toxins. 7

Widespread Distribution and Identification of Eight Novel Microcystins in Antarctic Cyanobacterial Mats

“…MS alone cannot distinguish between the isobaric N-methyl dehydroanaline and dehydrobutyrine, which is another potential substitution (38). The details of these structural assignments will be published elsewhere but are consistent with the analyses of low-energy collisionally activated ion spectra for similar MC variants identified from Nostoc species and Planktothrix agardhii (25,32,54 (16,18). Using a combination of ELISAs, PP-2A inhibition assay, and LC-MS, MCs were detected in cyanobacterial mats from four distant geographic locations within the Dry Valleys of Eastern Antarctica.…”

“…Various hypotheses have been proposed, including defense against grazers (27), gene regulation (10), allelopathic interactions (44), and intraspecific regulation (39). Recently, relatively low concentrations (Ͻ15 mg/kg MC-LR [dry weight]) of MCs were identified in cyanobacterial mats from meltwater ponds on McMurdo Ice Shelf in Antarctica (16,19). The identification of MCs in these mats provides evidence to dispute some of their putative roles, for example, defense against grazers (16).…”

“…Recently, relatively low concentrations (Ͻ15 mg/kg MC-LR [dry weight]) of MCs were identified in cyanobacterial mats from meltwater ponds on McMurdo Ice Shelf in Antarctica (16,19). The identification of MCs in these mats provides evidence to dispute some of their putative roles, for example, defense against grazers (16). To date, MCs have been identified in Antarctica only from meltwater ponds on Bratina Island, and the extent of their occurrence in other locations in Antarctica was unknown.…”

“…Subsequent multivariant analysis of ARISA profiles allowed the investigation of correlations between community structure, MC production, and geographical locations to be made and enabled the investigation of the influence of water chemistry parameters on cyanobacterial miscellany. , and Na ϩ concentrations and pH) were determined for all samples (except Lake Purgatory) as previously described (16,28). No physicochemical data were collected for hydroterrestrial mats collected in Mier and Marshall valleys.…”

Occurrence and elimination of cyanobacterial toxins in drinking water treatment plants

“…The harmful potential of cyanobacterial toxins for the population is appreciated in many European countries and has been described in many publications (Funari et al, 2000;Hitzfeld et al, 2000b;Thebault et al, 1995;Vasconcelos, 1999). The fact that cyanobacteria are able to exist even in hot springs in volcanic regions (Ward et al, 1998) and in cold and hot deserts such as Antarctica (Hitzfeld et al, 2000a;Wynn-Williams, 2000) or the Atacama desert (Wynn-Williams, 2000) underlines the omnipresence of these organisms. Cyanobacteria are ubiquitous in surface waters worldwide and many species including Microcystis, Nodularia, Cylindrospermopsis, Anabaena, and Aphanizomenon are known to produce toxins such as microcystins (MC), nodularins, cylindrospermopsins, anatoxins, and paralytic shellfish poisons (Landsberg, 2002).…”