Toxin characterisation and identification of a Microcystis flos-aquae strain from a Spanish drinking-water reservoir

Abstract

The Santillana reservoir, a drinking-water supply in the central part of Spain, was monitored weekly from June to November of 1997 for cyanobacteria and microcystins (MCs) in plankton biomass. Several blooms appeared, some of them with a high MC content. Large changes in both phytoplankton biomass and MCs were observed in a short time period, but not in a concomitant way. We have characterised one Microcystis strain, UAM97, that seemed to dominate a bloom, and with an unusually high MC content. The results obtained strongly indicate that Microcystis UAM97 is a M. flos-aquae strain, containing 4 major MCs: MC-LR, MC-LF, MC-LW, and MC-LY. Species assignment is supported by morphology and molecular criteria. Molecular identification was based on comparison of 16S-23S rDNA internal transcribed spacer (ITS) sequences from Microcystis UAM97 and three other collection Microcystis strains. MCs were characterised by amino acid analysis and combined high performance liquid chromatography and mass spectrometry (HPLC/MS) techniques. This report is the first on a M. flos-aquae strain dominating a toxic bloom in Spanish waterbodies.