The occurrence of cyanobacteria and microcystins in the Hoan Kiem Lake and the Nui Coc reservoir (North Vietnam)
Thi Thuy DuongSabine JähnichenThi Phuong Quynh LeCuong Tu HoTrung Kien HoangTrung Kien NguyenThi Nguyet VuDinh Kim Dang
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Microcystis
Bloom
Dominance (genetics)
Cyanotoxin
Oscillatoria
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ABSTRACT Cyanobacterial mass occurrences in freshwater lakes are generally formed by Anabaena , Microcystis , and Planktothrix , which may produce cyclic heptapeptide hepatotoxins, microcystins. Thus far, identification of the most potent microcystin producer in a lake has not been possible due to a lack of quantitative methods. The aim of this study was to identify the microcystin-producing genera and to determine the copy numbers of microcystin synthetase gene E ( mcyE ) in Lake Tuusulanjärvi and Lake Hiidenvesi in Finland by quantitative real-time PCR. The microcystin concentrations and cyanobacterial cell densities of these lakes were also determined. The microcystin concentrations correlated positively with the sum of Microcystis and Anabaena mcyE copy numbers from both Lake Tuusulanjärvi and Lake Hiidenvesi, indicating that mcyE gene copy numbers can be used as surrogates for hepatotoxic Microcystis and Anabaena . The main microcystin producer in Lake Tuusulanjärvi was Microcystis spp., since average Microcystis mcyE copy numbers were >30 times more abundant than those of Anabaena . Lake Hiidenvesi seemed to contain both nontoxic and toxic Anabaena as well as toxic Microcystis strains. Identifying the most potent microcystin producer in a lake could be valuable for designing lake restoration strategies, among other uses.
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Hepatotoxin
Microcystin-LR
Microcystis aeruginosa
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Cyanobacterial harmful algal blooms (CHABs) are increasing at an alarming rate in different water bodies worldwide. In India, CHAB events in water bodies such as Dal Lake have been sporadically reported with no study done to characterize the cyanobacterial species and their associated toxins. We hypothesized that this Lake is contaminated with toxic cyanobacterial species with the possibility of the presence of cyanotoxin biosynthetic genes. We, therefore, used some of the molecular tools such as 16S ribosomal DNA, PCR, and phylogenetic analysis to explore cyanobacterial species and their associated toxins. A 3-year (2018–2020) survey was conducted at three different sampling sites of Dal Lake namely, Grand Palace Gath (S1), Nigeen basin (S2), and Gagribal basin (S3). Two strains of Dolichospermum sp. AE01 and AE02 (S3 and S1 site) and one strain of Microcystis sp. AE03 (S2 site) was isolated, cultured, and characterized phylogenetically by 16S ribosomal DNA sequencing. The presence of cyanotoxin genes from the isolates was evaluated by PCR of microcystins ( mcyB ), anatoxins ( anaC ), and cylindrospermopsins ( pks ) biosynthesis genes. Results revealed the presence of both mcyB and pks gene in Microcystis sp. AE03, and only anaC gene in Dolichospermum sp. AE02 strain. However, Dolichospermum sp. AE01 strain was not found to harbor any such genes. Our findings, for the first time, reported the coexistence of pks and mcyB in a Microcystis AE03 strain. This study has opened a new door to further characterize the unexplored cyanobacterial species, their associated cyanotoxin biosynthetic genes, and the intervention of high-end proteomic techniques to characterize the cyanotoxins.
Cyanotoxin
Microcystis
Cylindrospermopsin
Microcystis aeruginosa
Strain (injury)
Gene cluster
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Cyanotoxin
Microcystis
Microcystis aeruginosa
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Microcystis
Oscillatoria
Microcystis aeruginosa
Aphanizomenon
Bloom
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Primer (cosmetics)
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Abstract This study was conducted to examine and determine the factors affecting dominance of the blue‐green algal species of genus Microcystis, Anabaena, Oscillatoria and Phormidium from 1988 to 1990 in eutrophic Lake Kasumigaura. The algal dominancy of the three Anabaena species, A. affinis,A. flos‐aquae and A. spiroides, took place in early summer, while the dominance of the Microcystis species, M. aeruginosa, M. viridis and M. wesenbergii, took place from summer to fall. Water samples were collected at Tsuchiura Harbour in Lake Kasumigaura. The correlations between cell numbers of blue‐green algal species and water qualities were investigated. The growth rates of algae in situ were determined. Af. aeruginosa showed the highest increasing growth rate, while Af. viridis was the lowest decay rate in the Microcystis species. M. aeruginosa exhibited high single correlations between water temperature, pH, total chemical oxygen demand (T‐COD) and dissolved chemical oxygen demand (D‐COD). The cell numbers of blue‐green algal species were also compared with each other to know any correlation. The high correlations between the three Anabaena species were observed. Keywords: Microcystis Anabaena Oscillatoria Phormidium succession
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Microcystis aeruginosa
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Microcystis
Nostoc
Arthrospira
Primer (cosmetics)
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Toxic cyanobacterial blooms are increasing in prevalence. Microcystins are the most commonly produced cyanotoxin. Despite extensive research the variables regulating microcystin production remain unclear. Using a RT-QPCR assay that allowed the precise measurement of mcyE transcriptional gene expression and an ELISA that enabled small changes in total microcystin concentrations to be monitored, we demonstrate for the first time that microcystin production is not always constitutive and that significant up- and downregulation in microcystin synthesis can occur on time scales of 2-6 h. Samples were collected over 3 days from a small eutrophic lake during a dense microcystin-producing Microcystis bloom. McyE gene transcripts were detected in only four out of 14 samples. Vicissitudes in both microcystin quotas and extracellular microcystin levels corresponded with changes in mcyE expression. During the period of exalted microcystin synthesis Microcystis sp. cell concentrations increased from 70 000 cells ml(-1) to 4 000 000 cells ml(-1) . These data provide compelling evidence that changes in Microcystis cell concentrations influence microcystin production.
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Cyanotoxin
Bloom
Microcystin-LR
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The South African Hartbeespoort Dam is known for the occurrence of heavy Microcystis blooms. Although a few other cyanobacterial genera have been described, no detailed study on those cyanobacteria and their potential toxin production has been conducted. The diversity of cyanobacterial species and toxins is most probably underestimated. To ascertain the cyanobacterial composition and presence of cyanobacterial toxins in Hartbeespoort Dam, water samples were collected in April 2011. In a polyphasic approach, 27 isolated cyanobacterial strains were classified morphologically and phylogenetically and tested for microcystins (MCs), cylindrospermopsin (CYN), saxitoxins (STXs) and anatoxin-a (ATX) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and screened for toxin-encoding gene fragments. The isolated strains were identified as Sphaerospermopsis reniformis, Sphaerospermopsis aphanizomenoides, Cylindrospermopsis curvispora, Raphidiopsis curvata, Raphidiopsis mediterrranea and Microcystis aeruginosa. Only one of the Microcystis strains (AB2011/53) produced microcystins (35 variants). Forty-one microcystin variants were detected in the environmental sample from Hartbeespoort Dam, suggesting the existence of other microcystin producing strains in Hartbeespoort Dam. All investigated strains tested negative for CYN, STXs and ATX and their encoding genes. The mcyE gene of the microcystin gene cluster was found in the microcystin-producing Microcystis strain AB2011/53 and in eight non-microcystin-producing Microcystis strains, indicating that mcyE is not a good surrogate for microcystin production in environmental samples.
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Microcystis aeruginosa
Cylindrospermopsin
Cyanotoxin
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