THE FRESHWATER CYANOBACTERIUM PLANKTOTHRIX SP. FP1: MOLECULAR IDENTIFICATION AND DETECTION OF PARALYTIC SHELLFISH POISONING TOXINS

Abstract

A filamentous cyanobacterium, belonging to the Order of Oscillatoriales, was found to be responsible for a toxic algal bloom in Lake Varese, Italy, during the summer of 1997. Morphological characters, as well as near complete 16S rRNA gene sequencing, revealed that the dominant species of the bloom was most closely related to the genus Planktothrix. In addition, genetic analysis of the phycocyanin operon of Planktothrix sp. FP1 revealed a novel primary structure, previously undescribed within the cyanobacteria, which was used as a genetic marker for rapid detection and identification of this toxic strain. The occurrence of saxitoxin (STX), a principal toxin in paralytic shellfish poisoning (PSP), was confirmed in the natural bloom sample by both pre-column and post-column derivatization high-performance liquid chromatography (HPLC) analyses, and eventually by liquid chromatography/mass spectrometry (LC/MS). The toxicity of this field sample was also revealed by electrophysiological assays in which the extract inhibited 90% of the voltage-dependent Na current in human neuroblastoma cells at the STX concentration of 80 nM. The cultured strain showed a lower physiologic activity than the bloom sample (67% blockage of Na current at a toxin concentration of 200 nM), and STX was detected only by pre-column HPLC, indicating the presence of a compound structurally close to STX. Chemical and molecular genetic analyses performed here add Planktothrix sp. FP1 to the growing list of diverse cyanobacterial species capable of synthesizing STX and its related compounds.

Taxonomy and production of paralytic shellfish toxins by the freshwater cyanobacteriumAphanizomenon gracileLMECYA40

“…Our results are difficult to compare with other reports of PST production by cyanobacteria since toxicity values are often given as STX equivalents mg 71 dry weight (Negri et al, 1997;Yin et al, 1997;Lagos et al, 1999;Pomati et al, 2000;Ferreira et al, 2001;Kass & Henriksen, 2000;Pereira et al, 2000) and the relationship between dry weight and cell number is not easily established. Assuming that PST concentrations similar to those estimated from the cultured A. gracile can also be found in natural freshwater environments, small volumes of water could contain PST amounts comparable to those used as limit enforcements for harvesting and consumption of shellfish in marine environments (80 mg of STX equivalents per 100 g of shellfish).…”

“…Several freshwater bloom-forming cyanobacteria have been recognized as producers of paralytic shellfish toxin (PST) in Australia, Europe, North and South America (Humpage et al, 1994;Carmichael et al, 1997;Lagos et al, 1999;Pomati et al, 2000). Here we report evidence of PST production in a clonal strain of Aphanizomenon gracile, a bloom-forming species with a worldwide distribution.…”

“…However, this might have been due to the relatively low cell densities of the organisms involved in toxin production that were present in the natural water. Several authors have reported the death of wild and domestic animals following extensive neurotoxic blooms (Sawyer et al, 1968;Negri et al, 1995;Pomati et al, 2000) but the cell densities and PST concentrations found in the natural water samples were always higher than those observed in Crato reservoir. We note, however, that the toxic strain LMECYA40 could reach densities above 10 8 cells ml 71 in culture, and this species has been observed locally in some natural reservoirs to reach these densities (Pereira, unpublished).…”

“…Attention has been focused mainly on hepatotoxins as these have been shown to be potent inhibitors of protein phosphatases leading to tumour promotion (Falconer, 1991(Falconer, , 1996Nishiwaki-Matsushima et al, 1992). Many acute poisonings of domestic animals and wildlife have also been reported (Sawyer et al, 1968;Edwards et al, 1992;Negri et al, 1995;Henriksen et al, 1997;Pomati et al, 2000). Among the different types of neurotoxins found in cyanobacteria, the saxitoxins (STXs) are the most potent group.…”

Health hazards for terrestrial vertebrates from toxic cyanobacteria in surface water ecosystems

“…Saxitoxins have been recently identified in five freshwater cyanobacterial species: Aphanizomenon flos-aquae [37,57,70,95], Anabaena circinalis [54,83], Lyngbya wollei [14,91,130] Cylindrospermopsis raciborskii [66] and Planktothrix sp. [96]. STXs were also identified in Danish freshwater field extracts without unambiguous identification of toxin-producing species (Anabaena lemmermannii being very common in these lakes) [60].…”