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Toxins
Special Issues
Biological Functions, Defense and Control of Cyanobacterial Toxins
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Biological Functions, Defense and Control of Cyanobacterial Toxins

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Marine and Freshwater Toxins".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 11298

Special Issue Editor

Prof. Dr. Gan Nanqin

E-Mail Website
Guest Editor
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
Interests: cyanotoxins; biological function; cyanobacterial bloom; eutrophication; global climate change

Special Issue Information

Dear Colleagues,

Harmful cyanobacterial blooms (cyanoHABs) pose a serious threat to water quality in lakes worldwide. The mass development and degradation of senescent cyanoHABs cause foul odors and induce hypoxic conditions, disturbing ecosystem functioning and affecting public water supply and recreational activities, directly affecting social and economic conditions. In recent years, numerous studies have postulated that global climate change will further promote the frequency, intensity and expansion of cyanoHABs in aquatic ecosystems. In addition, cyanoHABs produce a number of toxins (microcystins, cylindrospermopsins, neurotoxins, etc.) that cause damage to the liver or nervous system in humans and other mammals.

A considerable number of journal articles are published annually on cyanobacterial toxins. Frequent outbreaks of cyanobacteria blooms trigger studies assessing the toxicity, and developing knowledge on the toxicology, health effects, and risk assessment of cyanotoxins. The potential ecophysiological role of cyanotoxins is an important aspect that the academic community has also considered. In 2013, 2016 and 2019, the topic “Natural function of cyanotoxins” was discussed at the International Conference on Toxic Cyanobacteria held separately in South Africa, China and Brazil. However, the actual biological role of cyanotoxins and the main drivers that stimulate the cyanotoxin production have not been elucidated clearly, which limits the effective defense strategies to reduce the damages induced by cyanotoxins.

This Special Issue intends to present a collection of studies exploring the biological function of cyanotoxins, including toxin-producing drivers such as temperature, CO2 (global climate change factors), and nutrients (eutrophication), developing new technologies to mitigate cyanobacterial blooms and degrade cyanotoxins. These studies will increase our understanding of the regulation of cyanotoxins in the environment and help to prevent their toxicity and health risk, and will ultimately be helpful for the management of water resources

Prof. Dr. Gan Nanqin
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a double-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • cyanotoxins
  • biological function
  • mitigation
  • degradation
  • eutrophication
  • cyanobacterial bloom
  • global climate change

Published Papers (5 papers)

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Research

16 pages, 2751 KiB  
Article
Revealing Physiochemical Factors and Zooplankton Influencing Microcystis Bloom Toxicity in a Large-Shallow Lake Using Bayesian Machine Learning
by Xiaoxiao Wang, Lan Wang, Mingsheng Shang, Lirong Song and Kun Shan
Toxins 2022, 14(8), 530; https://doi.org/10.3390/toxins14080530 - 2 Aug 2022
Cited by 4 | Viewed by 1712
Abstract
Toxic cyanobacterial blooms have become a severe global hazard to human and environmental health. Most studies have focused on the relationships between cyanobacterial composition and cyanotoxins production. Yet, little is known about the environmental conditions influencing the hazard of cyanotoxins. Here, we analysed [...] Read more.
Toxic cyanobacterial blooms have become a severe global hazard to human and environmental health. Most studies have focused on the relationships between cyanobacterial composition and cyanotoxins production. Yet, little is known about the environmental conditions influencing the hazard of cyanotoxins. Here, we analysed a unique 22 sites dataset comprising monthly observations of water quality, cyanobacterial genera, zooplankton assemblages, and microcystins (MCs) quota and concentrations in a large-shallow lake. Missing values of MCs were imputed using a non-negative latent factor (NLF) analysis, and the results achieved a promising accuracy. Furthermore, we used the Bayesian additive regression tree (BART) to quantify how Microcystis bloom toxicity responds to relevant physicochemical characteristics and zooplankton assemblages. As expected, the BART model achieved better performance in Microcystis biomass and MCs concentration predictions than some comparative models, including random forest and multiple linear regression. The importance analysis via BART illustrated that the shade index was overall the best predictor of MCs concentrations, implying the predominant effects of light limitations on the MCs content of Microcystis. Variables of greatest significance to the toxicity of Microcystis also included pH and dissolved inorganic nitrogen. However, total phosphorus was found to be a strong predictor of the biomass of total Microcystis and toxic M. aeruginosa. Together with the partial dependence plot, results revealed the positive correlations between protozoa and Microcystis biomass. In contrast, copepods biomass may regulate the MC quota and concentrations. Overall, our observations arouse universal demands for machine-learning strategies to represent nonlinear relationships between harmful algal blooms and environmental covariates. Full article
(This article belongs to the Special Issue Biological Functions, Defense and Control of Cyanobacterial Toxins)
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18 pages, 3814 KiB  
Article
Assessment of the Appearance and Toxin Production Potential of Invasive Nostocalean Cyanobacteria Using Quantitative Gene Analysis in Nakdong River, Korea
by Yong-Jin Kim, Hae-Kyung Park and In-Soo Kim
Toxins 2022, 14(5), 294; https://doi.org/10.3390/toxins14050294 - 21 Apr 2022
Cited by 3 | Viewed by 1948
Abstract
Invasive nostocalean cyanobacteria (INC) were first reported in tropical regions and are now globally spreading rapidly due to climate change, appearing in temperate regions. INC require continuous monitoring for water resource management because of their high toxin production potential. However, it is difficult [...] Read more.
Invasive nostocalean cyanobacteria (INC) were first reported in tropical regions and are now globally spreading rapidly due to climate change, appearing in temperate regions. INC require continuous monitoring for water resource management because of their high toxin production potential. However, it is difficult to analyze INC under a microscope because of their morphological similarity to nostocalean cyanobacteria such as the genus Aphanizomenon. This study calculates the gene copy number per cell for each target gene through quantitative gene analysis on the basis of genus-specific primers of genera Cylindrospermopsis, Sphaerospermopsis, and Cuspidothrix, and the toxin primers of anatoxin-a, saxitoxin, and cylindrospermopsin. In addition, quantitative gene analysis was performed at eight sites in the Nakdong River to assess the appearance of INC and their toxin production potential. Genera Cylindrospermopsis and Sphaerospermopsis did not exceed 100 cells mL−1 at the maximum, with a low likelihood of related toxin occurrence. The genus Cuspidothrix showed the highest cell density (1759 cells mL−1) among the INC. Nakdong River has potential for the occurrence of anatoxin-a through biosynthesis by genus Cuspidothrix because the appearance of this genus coincided with that of the anatoxin-a synthesis gene (anaF) and the detection of the toxin by ELISA. Full article
(This article belongs to the Special Issue Biological Functions, Defense and Control of Cyanobacterial Toxins)
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14 pages, 2938 KiB  
Article
Optimization of Biodegradation Characteristics of Sphingopyxis sp. YF1 against Crude Microcystin-LR Using Response Surface Methodology
by Isaac Yaw Massey, Tangjian Peng, Cai Danping and Fei Yang
Toxins 2022, 14(4), 240; https://doi.org/10.3390/toxins14040240 - 27 Mar 2022
Cited by 4 | Viewed by 2040
Abstract
Sphingopyxis sp. YF1 has proven to be efficient in biodegrading microcystin (MC)-leucine (L) and arginine (R) (MC-LR); however, the optimal environmental factors to biodegrade the toxin have not been investigated. In this study, the biodegrading characteristics of strain YF1 against MC-LR were assessed [...] Read more.
Sphingopyxis sp. YF1 has proven to be efficient in biodegrading microcystin (MC)-leucine (L) and arginine (R) (MC-LR); however, the optimal environmental factors to biodegrade the toxin have not been investigated. In this study, the biodegrading characteristics of strain YF1 against MC-LR were assessed under diverse environmental factors, including temperature (20, 30 or 40 °C), pH (5, 7 or 9) and MC-LR concentration (1, 3 or 5 µg/mL). Data obtained from the single-factor experiment indicated that MC-LR biodegradation by strain YF1 was temperature-, pH- and MC-LR-concentration-dependent, and the maximal biodegradation rate occurred at 5 µg/mL/h. Proposing Box-Behnken Design in response surface methodology, the influence of the three environmental factors on the biodegradation efficiency of MC-LR using strain YF1 was determined. A 17-run experiment was generated and carried out, including five replications performed at the center point. The ANOVA analysis demonstrated that the model was significant, and the model prediction of MC-LR biodegradation was also validated with the experimental data. The quadratic statistical model was established to predict the interactive effects of the environmental factors on MC-LR biodegradation efficiency and to optimize the controlling parameters. The optimal conditions for MC-LR biodegradation were observed at 30 °C, pH 7 and 3 µg/mL MC-LR, with a biodegradation efficiency of 100% after 60 min. The determination of the optimal environmental factors will help to unveil the detailed biodegradation mechanism of MC-LR by strain YF1 and to apply it into the practice of eliminating MC-LR from the environment. Full article
(This article belongs to the Special Issue Biological Functions, Defense and Control of Cyanobacterial Toxins)
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22 pages, 2066 KiB  
Article
Widespread Distribution and Adaptive Degradation of Microcystin Degrader (mlr-Genotype) in Lake Taihu, China
by Chenlin Hu, Yanxia Zuo, Liang Peng, Nanqin Gan and Lirong Song
Toxins 2021, 13(12), 864; https://doi.org/10.3390/toxins13120864 - 3 Dec 2021
Cited by 5 | Viewed by 2726
Abstract
Microbial degradation is an important route for removing environmental microcystins (MCs). Here, we investigated the ecological distribution of microcystin degraders (mlr-genotype), and the relationship between the substrate specificity of the microcystin degrader and the profile of microcystin congener production in the [...] Read more.
Microbial degradation is an important route for removing environmental microcystins (MCs). Here, we investigated the ecological distribution of microcystin degraders (mlr-genotype), and the relationship between the substrate specificity of the microcystin degrader and the profile of microcystin congener production in the habitat. We showed that microcystin degraders were widely distributed and closely associated with Microcystis abundance in Lake Taihu, China. We characterized an indigenous degrader, Sphingopyxis N5 in the northern Lake Taihu, and it metabolized six microcystin congeners in increasing order (RR > LR > YR > LA > LF and LW). Such a substrate-specificity pattern was congruent to the order of the dominance levels of these congeners in northern Lake Taihu. Furthermore, a meta-analysis on global microcystin degraders revealed that the substrate-specificity patterns varied geographically, but generally matched the profiles of microcystin congener production in the degrader habitats, and the indigenous degrader typically metabolized well the dominant MC congeners, but not the rare congeners in the habitat. This highlighted the phenotypic congruence between microcystin production and degradation in natural environments. We theorize that such congruence resulted from the metabolic adaptation of the indigenous degrader to the local microcystin congeners. Under the nutrient microcystin selection, the degraders might have evolved to better exploit the locally dominant congeners. This study provided the novel insight into the ecological distribution and adaptive degradation of microcystin degraders. Full article
(This article belongs to the Special Issue Biological Functions, Defense and Control of Cyanobacterial Toxins)
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16 pages, 1853 KiB  
Article
Biodegradation of Nodularin by a Microcystin-Degrading Bacterium: Performance, Degradation Pathway, and Potential Application
by Mengxuan Yuan, Qin Ding, Rongli Sun, Juan Zhang, Lihong Yin and Yuepu Pu
Toxins 2021, 13(11), 813; https://doi.org/10.3390/toxins13110813 - 18 Nov 2021
Cited by 1 | Viewed by 2214
Abstract
Currently, studies worldwide have comprehensively recognized the importance of Sphingomonadaceae bacteria and the mlrCABD gene cluster in microcystin (MC) degradation. However, knowledge about their degradation of nodularin (NOD) is still unclear. In this study, the degradation mechanism of NOD by Sphingopyxis sp. m6, [...] Read more.
Currently, studies worldwide have comprehensively recognized the importance of Sphingomonadaceae bacteria and the mlrCABD gene cluster in microcystin (MC) degradation. However, knowledge about their degradation of nodularin (NOD) is still unclear. In this study, the degradation mechanism of NOD by Sphingopyxis sp. m6, an efficient MC degrader isolated from Lake Taihu, was investigated in several aspects, including degradation ability, degradation products, and potential application. The strain degraded NOD of 0.50 mg/L with a zero-order rate constant of 0.1656 mg/L/d and a half-life of 36 h. The average degradation rate of NOD was significantly influenced by the temperature, pH, and initial toxin concentrations. Moreover, four different biodegradation products, linear NOD, tetrapeptide H-Glu-Mdhb-MeAsp-Arg-OH, tripeptide H-Mdhb-MeAsp-Arg-OH, and dipeptide H-MeAsp-Arg-OH, were identified, of which the latter two are the first reported. Furthermore, the four mlr genes were upregulated during NOD degradation. The microcystinase MlrA encoded by the mlrA gene hydrolyzes the Arg-Adda bond to generate linear NOD as the first step of NOD biodegradation. Notably, recombinant MlrA showed higher degradation activity and stronger environmental adaptability than the wild strain, suggesting future applications in NOD pollution remediation. This research proposes a relatively complete NOD microbial degradation pathway, which lays a foundation for exploring the mechanisms of NOD degradation by MC-degrading bacteria. Full article
(This article belongs to the Special Issue Biological Functions, Defense and Control of Cyanobacterial Toxins)
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