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Keywords = microcystin synthetase genes (mcyS)

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11 pages, 1969 KiB  
Article
Two New Strains of Microcystis Cyanobacteria from Lake Baikal, Russia: Ecology and Toxigenic Potential
by Ekaterina Sorokovikova, Irina Tikhonova, Galina Fedorova, Nadezhda Chebunina, Anton Kuzmin, Maria Suslova, Yanzhima Naidanova, Sergey Potapov, Andrey Krasnopeev, Anna Gladkikh and Olga Belykh
Limnol. Rev. 2025, 25(3), 31; https://doi.org/10.3390/limnolrev25030031 - 10 Jul 2025
Viewed by 259
Abstract
Microcystis, a potentially toxigenic cyanobacterium known to form extensive blooms in eutrophic lakes globally, was investigated in the cold oligotrophic Lake Baikal. We report the isolation of two Microcystis strains, Microcystis aeruginosa and M. novacekii, and document the presence of the [...] Read more.
Microcystis, a potentially toxigenic cyanobacterium known to form extensive blooms in eutrophic lakes globally, was investigated in the cold oligotrophic Lake Baikal. We report the isolation of two Microcystis strains, Microcystis aeruginosa and M. novacekii, and document the presence of the latter species in Lake Baikal for the first time. In M. aeruginosa strain BN23, we detected the microcystin synthetase gene mcyE. Liquid chromatography-mass spectrometry revealed the presence of two microcystin variants in BN23, with microcystin-LR, a highly potent toxin, being the dominant form. The concentration of MC-LR reached 540 µg/g dry weight. In contrast, M. novacekii strain BT23 lacked both microcystin synthesis genes and detectable toxins. The habitat waters were characterized as oligotrophic with minor elements of mesotrophy, exhibiting low phytoplankton biomass dominated by the chrysophyte Dinobryon cylindricum (76–77% of biomass), with cyanobacteria contributing 8–10%. The contribution of Microcystis spp. to the total phytoplankton biomass could not be quantified as they were exclusively found in net samples. The water temperature at both sampling stations was ~19 °C, which is considerably lower than optimal for Microcystis spp. and potentially conducive to enhanced microcystin production in toxigenic genotypes. Full article
(This article belongs to the Special Issue Trends in the Trophic State of Freshwater Ecosystems)
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18 pages, 2309 KiB  
Article
Is a Central Sediment Sample Sufficient? Exploring Spatial and Temporal Microbial Diversity in a Small Lake
by Barbara Weisbrod, Susanna A. Wood, Konstanze Steiner, Ruby Whyte-Wilding, Jonathan Puddick, Olivier Laroche and Daniel R. Dietrich
Toxins 2020, 12(9), 580; https://doi.org/10.3390/toxins12090580 - 9 Sep 2020
Cited by 13 | Viewed by 4355
Abstract
(1) Background: Paleolimnological studies use sediment cores to explore long-term changes in lake ecology, including occurrences of harmful cyanobacterial blooms. Most studies are based on single cores, assuming this is representative of the whole lake, but data on small-scale spatial variability of microbial [...] Read more.
(1) Background: Paleolimnological studies use sediment cores to explore long-term changes in lake ecology, including occurrences of harmful cyanobacterial blooms. Most studies are based on single cores, assuming this is representative of the whole lake, but data on small-scale spatial variability of microbial communities in lake sediment are scarce. (2) Methods: Surface sediments (top 0.5 cm) from 12 sites (n = 36) and two sediment cores were collected in Lake Rotorua (New Zealand). Bacterial community (16S rRNA metabarcoding), Microcystis specific 16S rRNA, microcystin synthetase gene E (mcyE) and microcystins (MCs) were assessed. Radionuclide measurements (210Pb, 137Cs) were used to date sediments. (3) Results: Bacterial community, based on relative abundances, differed significantly between surface sediment sites (p < 0.001) but the majority of bacterial amplicon sequence variants (88.8%) were shared. Despite intense MC producing Microcystis blooms in the past, no Microcystis specific 16S rRNA, mcyE and MCs were found in surface sediments but occurred deeper in sediment cores (approximately 1950′s). 210Pb measurements showed a disturbed profile, similar to patterns previously observed, as a result of earthquakes. (4) Conclusions: A single sediment core can capture dominant microbial communities. Toxin producing Microcystis blooms are a recent phenomenon in Lake Rotorua. We posit that the absence of Microcystis from the surface sediments is a consequence of the Kaikoura earthquake two years prior to our sampling. Full article
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24 pages, 7147 KiB  
Article
Morphological and Molecular Identification of Microcystin-Producing Cyanobacteria in Nine Shallow Bulgarian Water Bodies
by Mariana Radkova, Katerina Stefanova, Blagoy Uzunov, Georg Gärtner and Maya Stoyneva-Gärtner
Toxins 2020, 12(1), 39; https://doi.org/10.3390/toxins12010039 - 8 Jan 2020
Cited by 28 | Viewed by 6829
Abstract
The paper presents results from the first application of polyphasic approach in studies of field samples from Bulgaria. This approach, which combined the conventional light microscopy (LM) and molecular-genetic methods (based on PCR amplified fragments of microcystin synthetase gene mcyE), revealed that [...] Read more.
The paper presents results from the first application of polyphasic approach in studies of field samples from Bulgaria. This approach, which combined the conventional light microscopy (LM) and molecular-genetic methods (based on PCR amplified fragments of microcystin synthetase gene mcyE), revealed that almost all microcystin-producers in the studied eutrophic waterbodies belong to the genus Microcystis. During the molecular identification of toxin-producing strains by use of HEPF × HEPR pair of primers, we obtained 57 sequences, 56 of which formed 28 strains of Microcystis, spread in six clusters of the phylogenetic tree. By LM, seven Microcystis morphospecies were identified (M. aeruginosa, M. botrys, M. flos-aquae, M. natans, M. novacekii, M. smithii, and M. wesenbergii). They showed significant morphological variability and contributed from <1% to 98% to the total biomass. All data support the earlier opinions that taxonomic revision of Microcystis is needed, proved the presence of toxigenic strains in M. aeruginosa and M. wesenbergii, and suppose their existence in M. natans. Our results demonstrated also that genetic sequencing, and the use of HEPF × HEPR pair in particular, can efficiently serve in water quality monitoring for identifying the potential risk from microcystins, even in cases of low amounts of Microcystis in the water. Full article
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18 pages, 341 KiB  
Article
Hepatotoxic Seafood Poisoning (HSP) Due to Microcystins: A Threat from the Ocean?
by Katerina Vareli, Walter Jaeger, Anastasia Touka, Stathis Frillingos, Evangelos Briasoulis and Ioannis Sainis
Mar. Drugs 2013, 11(8), 2751-2768; https://doi.org/10.3390/md11082751 - 5 Aug 2013
Cited by 39 | Viewed by 8441
Abstract
Cyanobacterial blooms are a major and growing problem for freshwater ecosystems worldwide that increasingly concerns public health, with an average of 60% of blooms known to be toxic. The most studied cyanobacterial toxins belong to a family of cyclic heptapeptide hepatotoxins, called microcystins. [...] Read more.
Cyanobacterial blooms are a major and growing problem for freshwater ecosystems worldwide that increasingly concerns public health, with an average of 60% of blooms known to be toxic. The most studied cyanobacterial toxins belong to a family of cyclic heptapeptide hepatotoxins, called microcystins. The microcystins are stable hydrophilic cyclic heptapeptides with a potential to cause cell damage following cellular uptake via organic anion-transporting proteins (OATP). Their intracellular biologic effects presumably involve inhibition of catalytic subunits of protein phosphatases (PP1 and PP2A) and glutathione depletion. The microcystins produced by cyanobacteria pose a serious problem to human health, if they contaminate drinking water or food. These toxins are collectively responsible for human fatalities, as well as continued and widespread poisoning of wild and domestic animals. Although intoxications of aquatic organisms by microcystins have been widely documented for freshwater ecosystems, such poisonings in marine environments have only occasionally been reported. Moreover, these poisonings have been attributed to freshwater cyanobacterial species invading seas of lower salinity (e.g., the Baltic) or to the discharge of freshwater microcystins into the ocean. However, recent data suggest that microcystins are also being produced in the oceans by a number of cosmopolitan marine species, so that Hepatotoxic Seafood Poisoning (HSP) is increasingly recognized as a major health risk that follows consumption of contaminated seafood. Full article
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