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

Abstract

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.

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.…”

“…3) (54). ADMAdda MC analogues have reported in benthic Nostoc strains from Finland (32,40,41) and Planktothrix agardhii (planktonic) from Denmark (25). This is the first reporting of such variants from Southern Hemisphere cyanobacteria.…”

“…The ADDA-ELISAs used during the present study measure the total amount of ADDA-containing compounds in the sample, with the second ELISA having lower cross-reactivity with free ADDA and nodularin (Lyn Briggs, personal communication). As both ELISAs used antibodies raised against the ADDA moiety, it is very likely that cross-reactivity to ADMAdda variants was low (25) and that therefore the total MCs in these samples were underestimated. Similarly, the LC-MS (MRM) analyses targeting 13 common ADDA-containing MCs did not determine the ADMAdda variants.…”

Discovery of Rare and Highly Toxic Microcystins from Lichen-Associated Cyanobacterium Nostoc sp. Strain IO-102-I

“…strains DUN901, IO-102-I, and 152 synthesized only the rare ADMAdda and DMAdda families of microcystins. Interestingly, ADMAdda is found only in the Nostoc strains (3,40,42) and the single Planktothrix agardhii strain PH-123 (24). DMAdda is found in Nostoc sp.…”

Cyanobacterial hepatotoxins, microcystins and nodularins, in fresh and brackish waters of the Pomeranian Province, northern Poland

“…Cyanobacterial species belonging to the genera Planktothrix (P. agardhii and P. rubescence) commonly occur in the lakes of northern Europe. They are efficient producers of microcystins, especially variants with different degrees and sites of demethylation (Laub et al 2002, Spoof et al 2003, Barco et al 2004). In one strain of Planktothrix isolated from Lake Maxsee (Brandenburg, Germany) Welker et al (2004) detected 11 microcystins, all of them lacking a methyl group on the Asp residue.…”