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Morphological, genetic, chemical and ecophysiological characterisation of two Microcystis aeruginosa isolates from the Vistula Lagoon, Southern Baltic

100%

Mazur-Marzec H. , Browarczyk-Matusiak G. , Forycka K. , Kobos J. , Plinski M.

nr 1

127-146

The Vistula Lagoon (southern Baltic Sea) is a shallow and highly eutrophic water body, with frequent blooms of cyanobacteria dominated by Microcystis and Anabaena species. Two Microcystis strains, MK10.10 and MAKR0205, isolated from the lagoon were characterised in this work. The morphology of the isolates differed significantly with respect to cell size and their ability to form aggregates. Based on the 16S rRNA sequence and 16S-23S internal transcribed spacer (ITS) sequence, both isolates were classified as Microcystis aeruginosa. However, only one isolate, MK10.10, possessed the mcy genes responsible for microcystin biosynthesis and only this strain produced microcystins. The effects of environmental factors, such as light, temperature and salinity, on toxin production turned out to be minor. Under the culture conditions used in the experiments, the biomass of the toxic MK10.10 was always lower. Hybrid quadrupole-time-of-flight liquid chromatography/tandem mass spectrometry (QTOF-LC/MS/MS) was used to elucidate the structure of the microcystin (MC) variants produced by MK10.10. Based on molecular ion and fragmentation spectra, the toxins were identified as MC-LR, MC-VR and MC- HIlR. Our study confirmed that some morphological criteria could be useful in preliminarily assessing the potential toxicity of a Microcystis bloom.

Toxic cyanobacteria strains in lowland dam reservoir [Sulejow Res., Central Poland]: amplification of mcy genes for detection and identification

100%

Mankiewicz-Boczek J. , Urbaniak M. , Romanowska-Duda Z. , Izydorczyk K.

nr 2

Excessive eutrophication causes the growth of microcystin-producing Cyanobacteria and leads to an increased human health risk. This paper reports the analyses of Cyanobacteria toxigenicity (the degree of potential toxicity) in lowland dam reservoir (Sulejów Reservoir, Central Poland) by the use of PCR-based methods. The reservoir (area 22 km², mean depth 3.3 m) is very eutrophic water body permanently blooming with blue-green algae (mainly Microcystis aeruginosa). For identification of cyanobacterial genus the 16S rRNA region was used. Cyanobacterial genus was detected during the whole monitoring period in summer 2003. The potential toxicity of cyanobacteria was determined by amplification of selected mcyA,B,E genes in the microcystin biosynthesis pathway. All of the analyzed genes were detected at the beginning of the growing season during low cyanobacterial biomass (0.67 mg l⁻¹). 89% of the samples were found to be positive for mcyA detection. Early detection of mcy genes at the beginning of summer preceded a period of the highest microcystins concentration (2.91 µg l⁻¹ in maximum) and toxicity established by ELISA (enzyme-linked immunosorbent assay – enables determination of microcystins concentration) and PPIA (protein phosphatase inhibition assay – enables estimation of microcystins toxicity). We show that toxigenic (potentially toxic) strains of cyanobacteria occurred in Sulejów Reservoir throughout the summer and genetic markers were effective in early identification of microcystin-producing genera. Application of molecular methods in parallel with toxicity testes can provide complete information to prevent any human health risk.