Occurrence of toxic water blooms containing microcystins in a German lake over a three year period

Diversity of hepatotoxic microcystins and bioactive anabaenopeptins in cyanobacterial blooms from Greek freshwaters

Microcystins (MCs) and anabaenopeptins from 26 cyanobacterial bloom samples dominated mainly by the genus Microcystis and collected from seven Greek freshwaters were identified and quantified by high-performance liquid chromatography coupled to a diode array detector. All the samples analyzed contained microcystins; in 27% of the samples anabaenopeptins were detected but not anabaenopeptilide (A). In each sample 1-7 microcystins and up to two anabaenopeptins (anabaenopeptins A and B) were identified. MC-RR and MC-LR were the predominant microcystins, followed by MC-YR. MC-LA and demethylated variants of MC-LR and MC-RR also were present but were not abundant. Total content of microcystin and anabaenopeptin varied from 40 to 2565 microg g(-1) freeze-dried material (mean 674.5 microg g(-1)) and from undetectable to 48 microg g(-1) freeze-dried material (mean 6.2 microg g(-1)), respectively. Qualitative and quantitative variation in the microcystins in the samples indicates there may be geographical trends in the distribution of microcystins. This study reports for the first time (1) the widespread occurrence of several different microcystins in Greek freshwaters and (2) quantitative data on the anabaenopeptins produced in natural cyanobacterial populations.

[ADMAdda5]-microcystins in Planktothrix agardhii strain PH-123 (cyanobacteria)--importance for monitoring of microcystins in the environment

Two major and two minor microcystins (MCYST) were isolated from a hepatotoxic Danish strain of Planktothrix agardhii (Gomont) Anagnostidis et Komárek by reversed-phase high-performance liquid chromatography. The microcystins were characterized by UV spectroscopy, amino acid analysis, fast atom bombardment mass spectrometry (FABMS), and high-resolution FABMS. The major microcystins were further analysed by collisionally induced tandem electrospray ionization MS. The microcystins were found to be demethylated variants of MCYST-HtyR (homotyrosine-arginine) and MCYST-LR (leucine-arginine). The two major microcystins contained an acetyl-demethyl variant (ADMAdda) of 3-amino-9-acetoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (Adda). This is the first report of [ADMAdda5]-microcystins in Planktothrix. The two [ADMAdda5]-microcystins inhibited protein phosphatase activity but showed low cross-reactivity with antibodies of an enzyme-linked immunosorbent assay (ELISA), emphasizing the potential underestimation of the toxicity of natural blooms dominated by Planktothrix when microcystin content is quantified using only an ELISA.

Determination of oligopeptide diversity within a natural population of Microcystis spp. (cyanobacteria) by typing single colonies by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Besides the most prominent peptide toxin, microcystin, the cyanobacteria Microcystis spp. have been shown to produce a large variety of other bioactive oligopeptides. We investigated for the first time the oligopeptide diversity within a natural Microcystis population by analyzing single colonies directly with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The results demonstrate a high diversity of known cyanobacterial peptides such as microcystins, anabaenopeptins, microginins, aeruginosins, and cyanopeptolins, but also many unknown substances in the Microcystis colonies. Oligopeptide patterns were mostly related to specific Microcystis taxa. Microcystis aeruginosa (Kütz.) Kütz. colonies contained mainly microcystins, occasionally accompanied by aeruginosins. In contrast, microcystins were not detected in Microcystis ichthyoblabe Kütz.; instead, colonies of this species contained anabaenopeptins and/or microginins or unknown peptides. Within a third group, Microcystis wesenbergii (Kom.) Kom. in Kondr., chiefly a cyanopeptolin and an unknown peptide were found. Similar patterns, however, were also found in colonies which could not be identified to species level. The significance of oligopeptides as a chemotaxonomic tool within the genus Microcystis is discussed. It could be demonstrated that the typing of single colonies by MALDI-TOF MS may be a valuable tool for ecological studies of the genus Microcystis as well as in early warning of toxic cyanobacterial blooms.

Co-occurrence of non-toxic (cyanopeptolin) and toxic (microcystin) peptides in a bloom of Microcystis sp. from a Chilean lake

A cyanobacterial bloom occurring in 1998 in lake Tres Pascualas (Concepción/Chile) was found to be dominated by Microcystis sp. The bloom contained both non-toxic (cyanopeptolin-type) and hepatotoxic (microcystin-type) peptides. Cyanopeptolin structure of the non-toxic peptides (called cyanopeptolin VW-1 and VW-2, respectively) was revealed by matrix assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS) of whole cells, showing dominant molecular ions at m/z = 975 and m/z 995, respectively. On post source decay (PSD), both cyanopeptolins showed fragments deriving from Ahp-Phe-MTyr (3-amino-6-hydroxy-2-piperidone), the characteristic partial structure of cyanopeptolins. The amounts of each of the two cyanopeptolins could only roughly be estimated to be >0.1% of bloom material dry weight. In addition the blooms contained microcystins (20 microg/g bloom dry weight as determined by RP-HPLC, 13 microg/g according to ELISA determination). MALDI-TOF-MS revealed several structural variants of microcystin: MCYST-RR (microcystin with Arg and Arg, indicated by m/z 1,038 and confirmed by PSD revealing a m/z = 135 fragment deriving from the Adda side chain, MCYST-FR (microcystin with Phe and Arg, indicated by m/z = 1,015). The presence of [Asp(3)]-MCYST-LR (microcystin with Leu and Arg, Asp non-methylated, indicated by m/z 981), and [Asp(3)]-MCYST-YR (microcystin with Tyr and Arg, Asp non-methylated, indicated by m/z 1,031) were likely. The relative amounts of the peptides varied between February, April, and May. Whole cell extracts from the bloom material revealed specific enzyme inhibitory activities. The serin-proteases trypsin, plasmin, elastase were inhibited, assumable due to the cyanopeptolins found. Elastase and the cysteine-protease papain were not inhibited, inhibitions of protein kinase and glutathione S-transferase (GST) were low. Strong inhibition was observed with protein-phosphatase-1, likely due to the microcystins present in the samples.

Generation of antibodies directed against the low-immunogenic peptide-toxins microcystin-LR/RR and nodularin

The preparation of antibodies against the liver toxin microcystin, as described here, is of major importance for its detection and purification in food and water, and for a therapeutic approach to neutralize the toxin by passive immunization. Microcystin-LR (MLR) and microcystin-RR (MRR) were purified from cyanobacterial cell materials by extraction, Sephadex LH-20-, ODS silica gel-, ionic exchange and RP-HPLC-chromatography. In order to reduce the toxicity for parenteral administration, microcystins were coupled by the carbodiimide method to poly-L-lysine (PLL(50.000)). Mice and rabbits were immunized with the conjugates in the presence of two lipopeptide immunoadjuvants (P(3)CSK(4) and P(3)CS-T(h)). High MLR-specific antibody levels were observed after parenteral coadministration of antigen and lipopeptides, whereas no anti-MLR antibodies were obtained with free microcystin or the microcystin-PLL(50.000)-conjugate in the absence of lipopeptide. In oral immunization, coadministration of antigen and adjuvants resulted in an accelerated development of anti MLR-specific antibodies and high antibody levels. Using the antisera, we could detect different microcystins and nodularin down to a concentration range of 10-50 ng/ml by a competitive inhibition ELISA; detection of microcystins in crude cell preparations was also possible. Furthermore, microcystins from different sources could be detected and discriminated from cyclic cyanopeptolines.

Microcystin in cyanobacterial blooms in a Chilean lake

Cyanobacterial blooms dominated by Microcystis sp. occurred in lake Rocuant ("marisma", near Concepción/Chile) in February 1995 and 1996. In the bloom samples collected in both years the hepatotoxin microcystin was detected by RP-HPLC in both samples and in the sample of 1995 also by a toxicity assay using primary rat hepatocytes. In the bloom of 1995, the microcystin content of the dry bloom biomass was determined to be 130 micrograms/g on the basis of the RP-HPLC peak area and 800 micrograms/g on the basis of the rat hepatotoxicity assay, respectively. In the bloom of 1996, RP-HPLC analysis revealed a microcystin content of 8.13 micrograms/g bloom material dry weight. In this year no hepatotoxicity was measured using a concentration range up to 0.8 mg (d. w.) of bloom material per ml in the rat hepatotoxicity assay. This is the first report on the detection of microcystins in Chilean water bodies.