Planktothrix

Abstract: Microcystins represent an extraordinarily large family of cyclic heptapeptide toxins that are nonribosomally synthesized by various cyanobacteria. Microcystins specifically inhibit the eukaryotic protein phosphatases 1 and 2A. Their outstanding variability makes them particularly useful for studies on the evolution of structure-function relationships in peptide synthetases and their genes. Analyses of microcystin synthetase genes provide valuable clues for the potential and limits of combinatorial biosynthesis. We have sequenced and analyzed 55.6 kb of the potential microcystin synthetase gene (mcy) cluster from the filamentous cyanobacterium Planktothrix agardhii CYA 126. The cluster contains genes for peptide synthetases (mcyABC), polyketide synthases (PKSs; mcyD), chimeric enzymes composed of peptide synthetase and PKS modules (mcyEG), a putative thioesterase (mcyT), a putative ABC transporter (mcyH), and a putative peptide-modifying enzyme (mcyJ). The gene content and arrangement and the sequence of specific domains in the gene products differ from those of the mcy cluster in Microcystis, a unicellular cyanobacterium. The data suggest an evolution of mcy clusters from, rather than to, genes for nodularin (a related pentapeptide) biosynthesis. Our data do not support the idea of horizontal gene transfer of complete mcy gene clusters between the genera. We have established a protocol for stable genetic transformation of Planktothrix, a genus that is characterized by multicellular filaments exhibiting continuous motility. Targeted mutation of mcyJ revealed its function as a gene coding for a O-methyltransferase. The mutant cells produce a novel microcystin variant exhibiting reduced inhibitory activity toward protein phosphatases.

Abstract: Toxic and non-toxic cyanobacterial strains from Anabaena, Aphanizomenon, Calothrix, Cylindrospermum, Nostoc, Microcystis, Planktothrix (Oscillatoria agardhii), Oscillatoria and Synechococcus genera were examined by RFLP of PCR-amplified 16S rRNA genes and 16S rRNA gene sequencing With both methods, high 16S rRNA gene similarity was found among planktic, anatoxin-a-producing Anabaena and non-toxic Aphanizomenon, microcystin-producing and non-toxic Microcystis, and microcystin-producing and non-toxic Planktothrix strains of different geographical origins The respective sequence similarities were 999-100%, 942-999% and 993-100% Thus the morphological characteristics (eg Anabaena and Aphanizomenon), the physiological (toxicity) characteristics or the geographical origins did not reflect the level of 16S rRNA gene relatedness of the closely related strains studied In addition, cyanobacterial strains were fingerprinted with repetitive extragenic palindromic (REP)- and enterobacterial repetitive intergenic consensus (ERIC)-PCR All the strains except two identical pairs of Microcystis strains had different band profiles The overall grouping of the trees from the 16S rRNA gene and the REP- and ERIC-PCR analyses was similar Based on the 16S rRNA gene sequence analysis, four major clades were formed (i) The clade containing filamentous heterocystous cyanobacteria was divided into three discrete groups of Anabaena/Aphanizomenon, Anabaena/Cylindrospermum/ Nodularia/Nostoc and Calothrix strains The three other clades contained (ii) filamentous non-heterocystous Planktothrix, (iii) unicellular non-heterocystous Microcystis and (iv) Synechococcus strains

Abstract: 1 Introduction: Cyanotoxins - Research for Environmental Safety and Human Health.- 2 Cyanotoxin Occurrence in Freshwaters.- 2.1 Cyanotoxin Occurrence in Germany.- 2.1.1 The Waterbodies Surveyed for Cyanotoxins in Germany.- 2.1.2 Microcystins and Hepatocyte Toxicity.- 2.1.3 Cyanobacterial Neurotoxins.- 2.2 Comparison of Cyanotoxin Occurrence in Different Countries.- 2.2.1 Toxic Cyanobacterial Blooms of Inland Waters in Southern Norway 1978-1998.- 2.2.2 Toxic Freshwater Cyanobacteria in Denmark.- 2.2.3 Microcystin-LR and Total Microcystins in Cyanobacterial Blooms in the Czech Republic 1993-1998.- 2.2.4 Freshwater Cyanobacteria and their Toxins in Portugal.- 2.2.5 Cyanotoxins and Cyanobacterial Blooms in South Korean Lakes.- 2.2.6 Cyanotoxin Occurrence in Freshwaters - a Summmary of Survey Results from Different Countries.- 2.3 Release and Persistence of Microcystins in Natural Waters.- 3 Factors Controlling Cellular Microcystin Content.- 3.1 Effects of Light and Nutrient Supply on Growth and Microcystin Content of Different Strains of Microcystis aeruginosa.- 3.2 Light-Limited Growth and Microcystin Content of Planktothrix agardhii and Microcystis aeruginosa in Turbidostats.- 3.3 Importance of Energy Charge for Microcystin Production.- 3.4 Characterization of Microcystin Synthetase Genes in Microcystis aeruginosa.- 4 Factors Affecting Cyanotoxin Concentrations in Natural Populations.- 4.1 Microcystin Variants in Microcystis and Planktothrix Dominated Field Samples.- 4.2 Isolation and Characterization of Colony-Forming Microcystis aeruginosa Strains.- 4.3 Environmental Factors an Microcystin Levels in Waterbodies.- 5 Cyanobacterial Toxicity and Human Exposure.- 5.1 Cyanotoxins and Human Health - Overview.- 5.2 Recreational Exposure to Cyanotoxins.- 5.3 Cyanotoxins in Drinking-Water Supplies.- 5.3.1 An Extensive Outbreak of Gastroenteritis Associated with the Toxic Cyanobacterium Planktothrix agardhii (Oscillatoriales, Cyanophyceae) in Scania, South Sweden.- 5.3.2 Cyanobacterial Toxins in Drinking Water: a Canadian Perspective.- 5.3.3 Dissolved Microcystins in Raw and Treated Drinking Water in the Czech Republic.- 5.3.4 Microcystin Analysis in Selected Drinking-Water Supplies in Germany.- 5.3.4.1 Elimination of Microcystins in the Rostock Drinking-Water Treatment Plant.- 5.3.4.2 Elimination of Microcystins at Dortendorf: Conventional Treatment and a Pilot Experimental Treatment System.- 5.3.4.3 Elimination of Microcystins Through Bank Filtration at the Radeburg Reservoir.- 5.3.4.4 Reducing Intake of Microcystins at the Deesbach Reservoir Drinking-Water Abstraction System.- 6 Effects of Microcystis spp. and Selected Cyanotoxins on Freshwater Organisms.- 6.1 Effects of Cyanotoxins on Early Life Stages of Fish and Amphibians.- 6.2 Uptake, Enzyme Effects and Metabolism of Microcystin-LR in Aquatic Organisms.- 6.2.1 Uptake of Microcystin-LR in Aquatic Organisms.- 6.2.2 Effects of Microcystin-LR on Detoxication Enzymes.- 6.2.3 Metabolism of Microcystin-LR in Aquatic Organisms.- 6.3 Changes of Fish Behaviour Affected by Microcystin-LR.- 6.4 Responses of Daphnia galeata fed with Microcystis strains with and without Microcystins.- 7 Toxic Effects and Substances in Cyanobacteria other than Microcystins, Anatoxin-a and Saxitoxins.- 7.1 Peptides and Depsipeptides Produced by Cyanobacteria.- 7.2 Significance of Unidentified Toxic Compounds and Approaches to their Identification.- 7.3 New Cyanobacterial Substances with Bioactive Properties.- 8 Contributions to Toxicity Testing and Toxin Analysis.- 8.1 Testing Cyanobacterial Toxicity with Primary Rat Hepatocyte and Cell-Line Assays.- 8.2 Can the Primary Rat Hepatocyte Assay Replace the Mouse Assay for Microcystin Testing? Validation with "Historic" Samples from the First Survey on Cyanobacterial Toxicity in Germany.- 8.3 Comparative Evaluation of Methods for Assessing Microcystin Concentrations with a Variety of Field Samples.- 8.4 A Fish-Embryo Bioassay for the Assessment of Cyanobacterial Toxicity.- 8.5 Rapid Typing and Structure Determination of Cyanobacterial Peptides Using MALDI-TOF Mass Spectrometry.- 9 Routine Analytical Methods Applied in the German Cyanotox Project.- 9.1 Microcystin Analysis.- 9.2 Cell Counting, Determination of Biovolume and Chlorophyll-a.