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1.
Harmful Algae ; 134: 102623, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38705613

RESUMO

Microcystins release from bloom-forming cyanobacteria is considered a way to gain competitive advantage in Microcystis populations, which threaten water resources security and aquatic ecological balance. However, the effects of microcystins on microalgae are still largely unclear. Through simulated culture experiments and the use of UHPLC-MS-based metabolomics, the effects of two microcystin-LR (MC-LR) concentrations (400 and 1,600 µg/L) on the growth and antioxidant properties of three algae species, the toxic Microcystis aeruginosa, a non-toxic Microcystis sp., and Chlorella vulgaris, were studied. The MC-LR caused damage to the photosynthetic system and activated the protective mechanism of the photosynthetic system by decreasing the chlorophyll-a and carotenoid concentrations. Microcystins triggered oxidative stress in C. vulgaris, which was the most sensitive algae species studied, and secreted more glycolipids into the extracellular compartment, thereby destroying its cell structure. However, C. vulgaris eliminated reactive oxygen species (ROS) by secreting terpenoids, thereby resisting oxidative stress. In addition, two metabolic pathways, the vitamin B6 and the sphingolipid pathways, of C. vulgaris were significantly disturbed by microcystins, contributing to cell membrane and mitochondrial damage. Thus, both the low (400 µg/L) and the high (1,600 µg/L) MC-LR concentration inhibited algae growth within 3 to 7 days, and the inhibition rates increased with the increase in the MC-LR concentration. The above results indicate that the toxin-producing Microcystis species have a stronger toxin tolerance under longer-term toxin exposure in natural water environments. Thus, microcystins participates in interspecific interaction and phytoplankton population regulation and creates suitable conditions for the toxin-producing M. aeruginosa to become the dominant species in algae blooms.


Assuntos
Antioxidantes , Toxinas Marinhas , Microcistinas , Microcystis , Fotossíntese , Microcistinas/metabolismo , Fotossíntese/efeitos dos fármacos , Antioxidantes/metabolismo , Microcystis/efeitos dos fármacos , Microcystis/crescimento & desenvolvimento , Microcystis/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Chlorella vulgaris/metabolismo , Clorofila A/metabolismo
2.
J Hazard Mater ; 470: 134196, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38603907

RESUMO

The secondary outbreak of cyanobacteria after algicide treatment has been a serious problem to water ecosystems. Hydrogen peroxide (H2O2) is an algaecide widely used in practice, but similar re-bloom problems are inevitably encountered. Our work found that Microcystis aeruginosa (M. aeruginosa) temporarily hibernates after H2O2 treatment, but there is still a risk of secondary outbreaks. Interestingly, the dormant period was as long as 20 and 28 days in 5 mg L-1 and 20 mg L-1 H2O2 treatment groups, respectively, but the photosynthetic activity was both restored much earlier (within 14 days). Subsequently, a quantitative imaging flow cytometry-based method was constructed and confirmed that the re-bloom had undergone two stages including first recovery and then re-division. The expression of ftsZ and fabZ genes showed that M. aeruginosa had active transcription processes related to cell division protein and fatty acid synthesis during the dormancy stat. Furthermore, metabolomics suggested that the recovery of M. aeruginosa was mainly by activating folate and salicylic acid synthesis pathways, which promoted environmental stress resistance, DNA synthesis, and cell membrane repair. This study reported the comprehensive mechanisms of secondary outbreak of M. aeruginosa after H2O2 treatment. The findings suggest that optimizing the dosage and frequency of H2O2, as well as exploring the potential use of salicylic acid and folic acid inhibitors, could be promising directions for future algal control strategies.


Assuntos
Peróxido de Hidrogênio , Microcystis , Microcystis/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Ácido Fólico , Ácido Salicílico/farmacologia , Proteínas de Bactérias/genética
3.
J Hazard Mater ; 470: 134241, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38608594

RESUMO

Artemisinin, a novel plant allelochemical, has attracted attention for its potential selective inhibitory effects on algae, yet to be fully explored. This study compares the sensitivity and action targets of Microcystis aeruginosa (M. aeruginosa) and Chlorella pyrenoidosa (C. pyrenoidosa) to artemisinin algaecide (AMA), highlighting their differences. Results indicate that at high concentrations, AMA displaces the natural PQ at the QB binding site within M. aeruginosa photosynthetic system, impairing the D1 protein repair function. Furthermore, AMA disrupts electron transfer from reduced ferredoxin (Fd) to NADP+ by interfering with the iron-sulfur clusters in the ferredoxin-NADP+ reductases (FNR) domain of Fd. Moreover, significant reactive oxygen species (ROS) accumulation triggers oxidative stress and interrupts the tricarboxylic acid cycle, hindering energy acquisition. Notably, AMA suppresses arginine synthesis in M. aeruginosa, leading to reduced microcystins (MCs) release. Conversely, C. pyrenoidosa counters ROS accumulation via photosynthesis protection, antioxidant defenses, and by regulating intracellular osmotic pressure, accelerating damaged protein degradation, and effectively repairing DNA for cellular detoxification. Additionally, AMA stimulates the expression of DNA replication-related genes, facilitating cell proliferation. Our finding offer a unique approach for selectively eradicating cyanobacteria while preserving beneficial algae, and shed new light on employing eco-friendly algicides with high specificity.


Assuntos
Artemisininas , Chlorella , Microcystis , Fotossíntese , Espécies Reativas de Oxigênio , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Chlorella/efeitos dos fármacos , Chlorella/metabolismo , Artemisininas/farmacologia , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Microcistinas/metabolismo
4.
J Microbiol ; 62(3): 249-260, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38587591

RESUMO

The proliferation of harmful cyanobacterial blooms dominated by Microcystis aeruginosa has become an increasingly serious problem in freshwater ecosystems due to climate change and eutrophication. Microcystis-blooms in freshwater generate compounds with unpleasant odors, reduce the levels of dissolved O2, and excrete microcystins into aquatic ecosystems, potentially harming various organisms, including humans. Various chemical and biological approaches have thus been developed to mitigate the impact of the blooms, though issues such as secondary pollution and high economic costs have not been adequately addressed. Red clays and H2O2 are conventional treatment methods that have been employed worldwide for the mitigation of the blooms, while novel approaches, such as the use of plant or microbial metabolites and antagonistic bacteria, have also recently been proposed. Many of these methods rely on the generation of reactive oxygen species, the inhibition of photosynthesis, and/or the disruption of cellular membranes as their mechanisms of action, which may also negatively impact other freshwater microbiota. Nevertheless, the underlying molecular mechanisms of anticyanobacterial chemicals and antagonistic bacteria remain unclear. This review thus discusses both conventional and innovative approaches for the management of M. aeruginosa in freshwater bodies.


Assuntos
Água Doce , Microcystis , Microcystis/crescimento & desenvolvimento , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Água Doce/microbiologia , Proliferação Nociva de Algas , Eutrofização , Ecossistema , Peróxido de Hidrogênio/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Microcistinas/metabolismo , Fotossíntese , Mudança Climática
5.
J Hazard Mater ; 471: 134373, 2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38678710

RESUMO

The cyanobacterial response to pharmaceuticals is less frequently investigated compared to green algae. Pharmaceuticals can influence not only the growth rate of cyanobacteria culture, but can also cause changes at the cellular level. The effect of diclofenac (DCF) as one of the for cyanobacteria has been rarely tested, and DCF has never been applied with cellular biomarkers. The aim of this work was to test the response of two unicellular cyanobacteria (Synechocystis salina and Microcystis aeruginosa) toward DCF (100 mg L-1) under photoautotrophic growth conditions. Such endpoints were analyzed as cells number, DCF uptake, the change in concentrations of photosynthetic pigments, the production of toxins, and chlorophyll a in vivo fluorescence. It was noted that during a 96 h exposure, cell proliferation was not impacted. Nevertheless, a biochemical response was observed. The increased production of microcystin was noted for M. aeruginosa. Due to the negligible absorption of DCF into cells, it is possible that the biochemical changes are induced by an external signal. The application of non-standard biomarkers demonstrates the effect of DCF on microorganism metabolism without a corresponding effect on biomass. The high resistance of cyanobacteria to DCF and the stimulating effect of DCF on the secretion of toxins raise concerns for environment biodiversity.


Assuntos
Biomarcadores , Clorofila A , Diclofenaco , Microcystis , Synechocystis , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Microcystis/crescimento & desenvolvimento , Diclofenaco/toxicidade , Diclofenaco/metabolismo , Biomarcadores/metabolismo , Synechocystis/metabolismo , Synechocystis/efeitos dos fármacos , Synechocystis/crescimento & desenvolvimento , Clorofila A/metabolismo , Microcistinas/metabolismo , Clorofila/metabolismo , Poluentes Químicos da Água/toxicidade , Poluentes Químicos da Água/metabolismo , Fotossíntese/efeitos dos fármacos , Anti-Inflamatórios não Esteroides/farmacologia
6.
Chemosphere ; 358: 142104, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38653399

RESUMO

Uptake of methylmercury (MeHg), a potent neurotoxin, by phytoplankton is a major concern due to its role as the primary pathway for MeHg entry into aquatic food webs, thereby posing a significant risk to human health. While it is widely believed that the MeHg uptake by plankton is negatively correlated with the concentrations of dissolved organic matter (DOM) in the water, ongoing debates continue regarding the specific components of DOM that exerts the dominant influence on this process. In this study, we employed a widely-used resin fractionation approach to separate and classify DOM derived from algae (AOM) and natural rivers (NOM) into distinct components: strongly hydrophobic, weakly hydrophobic, and hydrophilic fractions. We conduct a comparative analysis of different DOM components using a combination of spectroscopy and mass spectrometry techniques, aiming to identify their impact on MeHg uptake by Microcystis elabens, a prevalent alga in freshwater environments. We found that the hydrophobic components had exhibited more pronounced spectral characteristics associated with the protein structures while protein-like compounds between hydrophobic and hydrophilic components displayed significant variations in both distributions and the values of m/z (mass-to-charge ratio) of the molecules. Regardless of DOM sources, the low-proportion hydrophobic components usually dominated inhibition of MeHg uptake by Microcystis elabens. Results inferred from the correlation analysis suggest that the uptake of MeHg by the phytoplankton was most strongly and negatively correlated with the presence of protein-like components. Our findings underscore the importance of considering the diverse impacts of different DOM fractions on inhibition of phytoplankton MeHg uptake. This information should be considered in future assessments and modeling endeavors aimed at understanding and predicting risks associated with aquatic Hg contamination.


Assuntos
Interações Hidrofóbicas e Hidrofílicas , Compostos de Metilmercúrio , Fitoplâncton , Poluentes Químicos da Água , Compostos de Metilmercúrio/química , Compostos de Metilmercúrio/metabolismo , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/metabolismo , Poluentes Químicos da Água/metabolismo , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Rios/química , Cadeia Alimentar
7.
Aquat Toxicol ; 271: 106918, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38598945

RESUMO

Antibiotics are commonly found in the aquatic environment, which can affect microbial community compositions and activities, and even have potential adverse impacts on human and ecosystem health. The current understanding of the effects of antibiotics on microalgae growth and algal dissolved organic matter (DOM) remains indistinct. To understand the toxic effects of antibiotics on the microalgae, Microcystis aeruginosa was exposed to clarithromycin (CLA) in this study. Cell density determination, chlorophyll content determination, and organic spectrum analysis were conducted to show the effect of CLA exposure on the growth, photosynthetic activity, and organic metabolic processes of Microcystis aeruginosa. The findings revealed that the physiological status of algae could be significantly influenced by CLA exposure in aquatic environments. Specifically, exposure to 1 µg/L CLA stimulated the growth and photosynthetic activity of algal cells. Conversely, CLA above 10 µg/L led to the inhibition of algal cell growth and photosynthesis. Notably, the inhibitory effects intensified with the increasing concentration of CLA. The molecular weight of DOM produced by Microcystis aeruginosa increased when exposed to CLA. Under the exposure of 60 µg/L CLA, a large number of algal cells ruptured and died, and the intracellular organic matter was released into the algal liquid. This resulted in an increase in high molecular weight substances and soluble microbial-like products in the DOM. Exposure to 1 and 10 µg/L CLA stimulated Microcystis aeruginosa to produce more humic acid-like substances, which may be a defense mechanism against CLA. The results were useful for assessing the effects of antibiotic pollution on the stability of the microalgae population and endogenous DOM characteristics in aquatic ecosystems.


Assuntos
Claritromicina , Microcystis , Fotossíntese , Poluentes Químicos da Água , Microcystis/efeitos dos fármacos , Microcystis/crescimento & desenvolvimento , Poluentes Químicos da Água/toxicidade , Fotossíntese/efeitos dos fármacos , Claritromicina/toxicidade , Claritromicina/farmacologia , Microalgas/efeitos dos fármacos , Clorofila/metabolismo , Antibacterianos/toxicidade
8.
ACS Nano ; 18(18): 11828-11836, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38659192

RESUMO

As essential primary producers, cyanobacteria play a major role in global carbon and nitrogen cycles. Though the influence of nanoplastics on the carbon metabolism of cyanobacteria is well-studied, little is known about how nanoplastics affect their nitrogen metabolism, especially under environmentally relevant nitrogen concentrations. Here, we show that nitrogen forms regulated growth inhibition, nitrogen consumption, and the synthesis and release of microcystin (MC) in Microcystis aeruginosa exposed to 10 µg/mL amino-modified polystyrene nanoplastics (PS-NH2) with a particle size of 50 nm under environmentally relevant nitrogen concentrations of nitrate, ammonium, and urea. We demonstrate that PS-NH2 inhibit M. aeruginosa differently in nitrate, urea, and ammonium, with inhibition rates of 51.87, 39.70, and 36.69%, respectively. It is caused through the differences in impairing cell membrane integrity, disrupting redox homeostasis, and varying nitrogen transport pathways under different nitrogen forms. M. aeruginosa respond to exposure of PS-NH2 by utilizing additional nitrogen to boost the production of amino acids, thereby enhancing the synthesis of MC, extracellular polymeric substances, and membrane phospholipids. Our results found that the threat of nanoplastics on primary producers can be regulated by the nitrogen forms in freshwater ecosystems, contributing to a better understanding of nanoplastic risks under environmentally relevant conditions.


Assuntos
Microcystis , Nitrogênio , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Microcystis/crescimento & desenvolvimento , Nitrogênio/química , Nitrogênio/metabolismo , Microcistinas/metabolismo , Poliestirenos/química , Tamanho da Partícula , Microplásticos/metabolismo , Nanopartículas/química , Nitratos/metabolismo , Nitratos/química , Ureia/metabolismo , Ureia/química , Ureia/farmacologia
9.
Ecotoxicol Environ Saf ; 277: 116375, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38677071

RESUMO

Eco-friendly reagents derived from plants represent a promising strategy to mitigate the occurrence of toxic cyanobacterial blooms. The use of an amentoflavone-containing Selaginella tamariscina extract (STE) markedly decreased the number of Microcystis aeruginosa cells, thus demonstrating significant anti-cyanobacterial activity. In particular, the Microcystis-killing fraction obtained from pulverized S. tamariscina using hot-water-based extraction at temperatures of 40 °C induced cell disruption in both axenic and xenic M. aeruginosa. Liquid chromatographic analysis was also conducted to measure the concentration of amentoflavone in the STE, thus supporting the potential M. aeruginosa-specific killing effects of STE. Bacterial community analysis revealed that STE treatment led to a reduction in the relative abundance of Microcystis species while also increasing the 16S rRNA gene copy number in both xenic M. aeruginosa NIBR18 and cyanobacterial bloom samples isolated from a freshwater environment. Subsequent testing on bacteria, cyanobacteria, and algae isolated from freshwater revealed that STE was not toxic for other taxa. Furthermore, ecotoxicology assessment involving Aliivibrio fischeri, Daphnia magna, and Danio rerio found that high STE doses immobilized D. magna but did not impact the other organisms, while there was no change in the water quality. Overall, due to its effective Microcystis-killing capability and low ecotoxicity, aqueous STE represents a promising practical alternative for the management of Microcystis blooms.


Assuntos
Microcystis , Extratos Vegetais , Selaginellaceae , Microcystis/efeitos dos fármacos , Selaginellaceae/química , Animais , Extratos Vegetais/farmacologia , Daphnia/efeitos dos fármacos , Proliferação Nociva de Algas , RNA Ribossômico 16S , Água Doce/microbiologia
10.
Sci Total Environ ; 928: 172500, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38631630

RESUMO

The physical and chemical properties of silver nanoparticles (AgNPs) have led to their increasing use in various fields such as medicine, food, and industry. Evidence has proven that AgNPs cause adverse effects in aquatic ecosystems, especially when the release of Ag is prolonged in time. Several studies have shown short-term adverse effects of AgNPs on freshwater phytoplankton, but few studies have analysed the impact of long-term exposures on these populations. Our studies were carried out to assess the effects of AgNPs on growth rate, photosynthesis activity, and reactive oxygen species (ROS) generation on the freshwater green algae Scenedesmus armatus and the cyanobacteria Microcystis aeruginosa, and additionally on microcystin (MC-LR) generation from these cyanobacteria. The tests were conducted both in single-species cultures and in phytoplanktonic communities exposed to 1 ngL-1 AgNPs for 28 days. The results showed that cell growth rate of both single-species cultures decreased significantly at the beginning and progressively reached control-like values at 28 days post-exposure. This effect was similar for the community-cultured cyanobacteria, but not for the green algae, which maintained a sustained decrease in growth rate. While gross photosynthesis (Pg) increased in both strains exposed in single cultures, dark respiration (R) and net photosynthesis (Pn) decreased in S. armatus and M. aeruginosa, respectively. These effects were mitigated when both strains were exposed under community culture conditions. Similarly, the ROS generation shown by both strains exposed in single-species cultures was mitigated when exposure occurred in community cultures. MC-LR production and release were significantly decreased in both single-species and community exposures. These results can supply helpful information to further investigate the potential risks of AgNPs and ultimately help policymakers make better-informed decisions about their utilization for environmental restoration.


Assuntos
Água Doce , Nanopartículas Metálicas , Microcystis , Fitoplâncton , Scenedesmus , Prata , Poluentes Químicos da Água , Nanopartículas Metálicas/toxicidade , Prata/toxicidade , Fitoplâncton/efeitos dos fármacos , Microcystis/efeitos dos fármacos , Scenedesmus/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Microcistinas/toxicidade , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo
11.
Environ Sci Pollut Res Int ; 31(19): 28754-28763, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38558345

RESUMO

Fenoxaprop-p-ethyl (FE) is one of the typical aryloxyphenoxypropionate herbicides. FE has been widely applied in agriculture in recent years. Human health and aquatic ecosystems are threatened by the cyanobacteria blooms caused by Microcystis aeruginosa, which is one of the most common cyanobacteria responsible for freshwater blooming. Few studies have been reported on the physiological effects of FE on M. aeruginosa. This study analyzed the growth curves, the contents of chlorophyll a and protein, the oxidative stress, and the microcystin-LR (MC-LR) levels of M. aeruginosa exposed to various FE concentrations (i.e., 0, 0.5, 1, 2, and 5 mg/L). FE was observed to stimulate the cell density, chlorophyll a content, and protein content of M. aeruginosa at 0.5- and 1-mg/L FE concentrations but inhibit them at 2 and 5 mg/L FE concentrations. The superoxide dismutase and catalase activities were enhanced and the malondialdehyde concentration was increased by FE. The intracellular (intra-) and extracellular (extra-) MC-LR contents were also affected by FE. The expression levels of photosynthesis-related genes psbD1, psaB, and rbcL varied in response to FE exposure. Moreover, the expressions of microcystin synthase-related genes mcyA and mcyD and microcystin transportation-related gene mcyH were significantly inhibited by the treatment with 2 and 5 mg/L FE concentrations. These results might be helpful in evaluating the ecotoxicity of FE and guiding the rational application of herbicides in modern agriculture.


Assuntos
Herbicidas , Toxinas Marinhas , Microcystis , Oxazóis , Microcystis/efeitos dos fármacos , Herbicidas/toxicidade , Antioxidantes/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Propionatos , Expressão Gênica/efeitos dos fármacos , Microcistinas
12.
Sci Total Environ ; 866: 161375, 2023 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-36621494

RESUMO

Antibiotics and microplastics (MPs) inevitably coexist in natural waters, but their combined effect on aquatic organisms is still ambiguous. This study investigated the individual and combined toxicity of chloramphenicol (CAP) and micro-polystyrene (mPS) particles to Microcystis aeruginosa by physiological biomarkers, related gene expression, and molecular dynamics simulation. The results indicated that both individual and joint treatments threatened algal growth, while combined toxicity was higher than the former. Photosynthetic pigments and gene expression were inhibited by single CAP and mPS exposure, but CAP dominated and aggravated photosynthetic toxicity in combined exposure. Additionally, mPS damaged cell membranes and induced oxidative stress, which might further facilitate the entry of CAP into cells during co-exposure. The synergistic effect of CAP and mPS might be explained by the common photosynthetic toxicity target of CAP and mPS as well as oxidative stress. Furthermore, the molecular dynamics simulation revealed that CAP altered conformations of photosynthetic assembly protein YCF48 and SOD enzyme, and competed for functional sites of SOD, thus disturbing photosynthesis and antioxidant systems. These findings provide useful insights into the combined toxicity mechanism of antibiotics and MPs as well as highlight the importance of co-pollutant toxicity in the aquatic environment.


Assuntos
Cloranfenicol , Microcystis , Poliestirenos , Poluentes Químicos da Água , Antibacterianos/toxicidade , Cloranfenicol/toxicidade , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Microplásticos/toxicidade , Simulação de Dinâmica Molecular , Plásticos , Poliestirenos/toxicidade , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/toxicidade
13.
Toxins (Basel) ; 14(2)2022 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-35202155

RESUMO

Blooms of harmful cyanobacteria Microcystis aeruginosa lead to an adverse effect on freshwater ecosystems, and thus extensive studies on the control of this cyanobacteria's blooms have been conducted. Throughout this study, we have found that the two bacteria Aeromonas bestiarum HYD0802-MK36 and Pseudomonas syringae KACC10292T are capable of killing M. aeruginosa. Interestingly, these two bacteria showed different algicidal modes. Based on an algicidal range test using 15 algal species (target and non-target species), HYD0802-MK36 specifically attacked only target cyanobacteria M. aeruginosa, whereas the algicidal activity of KACC10292T appeared in a relatively broad algicidal range. HYD0802-MK36, as a direct attacker, killed M. aeruginosa cells when direct cell (bacterium)-to-cell (cyanobacteria) contact happens. KACC10292T, as an indirect attacker, released algicidal substance which is located in cytoplasm. Interestingly, algicidal activity of KACC10292T was enhanced according to co-cultivation with the host cyanobacteria, suggesting that quantity of algicidal substance released from this bacterium might be increased via interaction with the host cyanobacteria.


Assuntos
Aeromonas/química , Toxinas Bacterianas/toxicidade , Proliferação Nociva de Algas/efeitos dos fármacos , Herbicidas/toxicidade , Microcystis/efeitos dos fármacos , Pseudomonas syringae/química
14.
J Nat Prod ; 84(6): 1772-1779, 2021 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-34033480

RESUMO

Induced water hyacinth with purple roots (PRWH) exerts a significant inhibitory effect on the growth of blue-green algae. Interestingly, its chemical constituents differ from those of wild-type water hyacinth and have not yet been reported. This study aimed to explore the chemical constituents of PRWH and its bioactive components serving as allelopathic agents against blue-green algae. Phytochemical investigation of the bioactive ethyl acetate fraction of a crude methanol extract from PRWH led to the isolation of 56 compounds, including 11 new phenylphenalene derivatives. The structures of these compounds were elucidated by comprehensive analyses through NMR, HRMS, and X-ray techniques. Bioactivity evaluation against Microcystis aeruginosa indicated that compounds 7, 12, 15, 37, 39, 45, and 47 potently inhibited blue-green algae growth.


Assuntos
Alelopatia , Eichhornia/química , Microcystis/efeitos dos fármacos , Extratos Vegetais/farmacologia , China , Estrutura Molecular , Compostos Fitoquímicos/farmacologia , Raízes de Plantas/química
15.
Aquat Toxicol ; 235: 105826, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33862333

RESUMO

Norfloxacin is one of the widely used antibiotics, often detected in aquatic ecosystems, and difficultly degraded in the environment. However, how norfloxacin affects the photosynthetic process of freshwater phytoplankton is still largely unknown, especially under varied light conditions. In this study, we investigated photosynthetic mechanisms of Microcystis aeruginosa in responses to antibiotic norfloxacin (0-50 µg/L) for 72 h under low (LL; 50 µmol photons m-2 s-1) and high (HL; 250 µmol photons m-2 s-1) growth light regimes. We found that environmentally related concentrations of norfloxacin inhibited the growth rate and operational quantum yield of photosynthesis system II (PSII) of M. aeruginosa more under HL than under LL, suggesting HL increased the toxicity of norfloxacin to M. aeruginosa. Further analyses showed that norfloxacin deactivated PSII reaction centers under both growth light regimes with increased minimal fluorescence yields only under HL, suggesting that norfloxacin not only damaged reaction centers of PSII, but also inhibited energy transfer among phycobilisomes in M. aeruginosa under HL. However, non-photosynthetic quenching decreased in the studied species by norfloxacin exposure under both growth light regimes, suggesting that excess energy might not be efficiently dissipated as heat. Also, we found that reactive oxygen species (ROS) content increased under norfloxacin treatments with a higher ROS content under HL compared to LL. In addition, HL increased the absorption of norfloxacin by M. aeruginosa, which could partly explain the high sensitivity to norfloxacin of M. aeruginosa under HL. This study firstly reports that light can strongly affect the toxicity of norfloxacin to M. aeruginosa, and has vitally important implications for assessing the toxicity of norfloxacin to aquatic microorganisms.


Assuntos
Antibacterianos/toxicidade , Microcystis/fisiologia , Norfloxacino/toxicidade , Complexo de Proteína do Fotossistema II/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Antibacterianos/farmacologia , Clorofila/metabolismo , Ecossistema , Fluorescência , Luz , Microcystis/efeitos dos fármacos , Norfloxacino/metabolismo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo
16.
Ecotoxicol Environ Saf ; 208: 111575, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396101

RESUMO

Microplastics (MPs) have aroused widespread concern due to their extensive distribution in aquatic environments and adverse effects on aquatic organisms. However, the underlying toxicity of different kinds of MPs on freshwater microalgae has not been examined in detail. In this study, we investigated the effects of polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) MPs on the growth of Microcystis aeruginosa, as well as on its toxin production and oxidative stress. We found that all three kinds of MPs had an obvious inhibition effect on the growth of M. aeruginosa. Considering the results of antioxidant-related indicators, the activity of superoxide dismutase (SOD) and catalase (CAT), and cell membrane integrity were greatly affected with exposure to PVC, PS and PE MPs. Moreover, the content of intracellular (intra-) and extracellular (extra-) microcystins (MCs) had a noticeable increase due to the presence of PVC, PS, and PE MPs. Finally, according to the comprehensive stress resistance indicators, the resistance of M. aeruginosa to three MPs followed the order: PE (3.701)> PS (3.607)> PVC (2.901). Our results provide insights into the effects of different kinds of MPs on freshwater algae and provide valuable data for risk assessment of different types of MPs.


Assuntos
Microcystis/fisiologia , Microplásticos/toxicidade , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Catalase/metabolismo , Água Doce , Microalgas/efeitos dos fármacos , Microcistinas , Microcystis/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Plásticos/toxicidade , Polietileno , Poliestirenos/toxicidade , Cloreto de Polivinila/toxicidade , Superóxido Dismutase/metabolismo
17.
Ecotoxicol Environ Saf ; 208: 111664, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396174

RESUMO

Recently, the pollution of microplastics (MPs) in the global freshwater environment has become increasingly problematic, but there are few studies on the freshwater environment risks of MPs. The present study, therefore, has investigated the single and combined effects of MPs and lead (Pb) on the freshwater algal Microcystis aeruginosa. Results showed that Pb-only (>0.05 mg·L-1) promoted the growth of algal cells, while MPs-only (1 mg L-1) resulted in growth inhibition. However, compared with the corresponding concentration of Pb-only groups, the growth of algal cells was promoted in MPs + Pb treatments. MPs-only and Pb-only (0.5 mg L-1) both reduced the content of photosynthetic pigments and affected algal photosynthesis. The MPs-only treatment and MPs + Pb2+ (no pretreatment, 0.5 mg L-1 Pb2+) treatments showed significant cell aggregation. At the same time, MPs-only caused a significant increase in bound extracellular polysaccharides (bEPS), while 0.5 mg L-1 Pb reduced bEPS. Furthermore, under high Pb stress (0.5 mg L-1), the effects of combined MPs and Pb on chlorophyll content, antioxidant enzyme activity (peroxidase (POD), catalase (CAT)), and damage to algal cells were less compared to individual effects, and the combination of MPs and Pb had a synergistic effect on promoting aggregations of M. aeruginosa. These results demonstrate that single and combined effects of MPs and Pb can induce differential responses in the freshwater algal M. aeruginosa, which can have a significant impact on aquatic ecosystems.


Assuntos
Água Doce/microbiologia , Chumbo/toxicidade , Microcystis/efeitos dos fármacos , Microplásticos/toxicidade , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Clorofila/metabolismo , Sinergismo Farmacológico , Ecossistema , Água Doce/química , Microcystis/crescimento & desenvolvimento , Microcystis/metabolismo , Fotossíntese/efeitos dos fármacos
18.
Ecotoxicol Environ Saf ; 211: 111894, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33472108

RESUMO

Enantiomers of chiral fungicides usually display different toxic effects on nontarget organisms in the surrounding environment, although there are rare reports on the enantioselective toxicity of metconazole (MEZ) to aquatic organisms, such as Microcystis flos-aquae (M. flos-aquae). To explore the enantioselective toxicity of MEZ in algae, the impact of various concentrations (0.001, 0.003, 0.01, 0.03 and 0.1 mg/L) of MEZ on M. flos-aquae over 8 days was investigated. Significant differences were observed between the four enantiomers in chlorophyll a (Chl a) contents, carotenoids, photochemical efficiency (Fv/Fm), rapid light-response curves (RLCs), utilization efficiency of light energy (α) and protein contents during treatment time. MEZ can enantioselectively stimulate the chlorophyll fluorescence parameters (RLCs, Fv/Fm and α) and carotenoid and Chl a contents of M. flos-aquae, especially at low concentrations (0.001 or 0.003 mg/L). At high concentrations of 0.03 or 0.1 mg/L, the chlorophyll fluorescence parameters (RLCs, Fv/Fm and α), protein and Chl a contents of M. flos-aquae exposed to cis-enantiomers were lower than those of M. flos-aquae exposed to trans-enantiomers. These observations indicated that the enantiomers of MEZ pose different toxicities to M. flos-aquae, with the cis-enantiomers more toxic than the trans-enantiomers. These results are beneficial for understanding the enantioselective effects of MEZ enantiomers on nontarget organisms and helpful for evaluating their eco-environment risk.


Assuntos
Fungicidas Industriais/toxicidade , Microcystis/fisiologia , Fotossíntese/efeitos dos fármacos , Triazóis/toxicidade , Clorofila A , Microcystis/efeitos dos fármacos , Estereoisomerismo
19.
J Hazard Mater ; 406: 124722, 2021 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-33296757

RESUMO

Antibiotic contaminants could promote the formation of harmful cyanobacterial blooms through hormetic stimulation, but the mechanisms underlying these stimulatory effects remain unclear. This study investigated the biochemical, transcriptomic, and proteomic responses of a dominant bloom-forming cyanobacterium, Microcystis aeruginosa, to a five-component mixture of frequently detected antibiotics at current contamination levels. The growth rate of M. aeruginosa presented a U-shaped dose-response to 50-500 ng L-1 of mixed antibiotics. Alterations in the transcriptome of M. aeruginosa suggested the excitation of both photosynthesis and carbon metabolism, increasing energy generation in response to oxidative stress induced by low-dose antibiotics, and thus contributing to the significant (p < 0.05) increase in growth rate, Fv/Fm, and cell density. Comparison between transcriptomic and proteomic responses further confirmed the action mode of the mixed antibiotics. Proteins and their corresponding genes related to ROS scavenging, photosynthesis, carbon fixation, electron transport, oxidative phosphorylation, and biosynthesis, showed consistent expression tendencies in response to 200 ng L-1 of mixed antibiotics, which were credible action targets of mixed antibiotics in M. aeruginosa. Mixed antibiotics stimulated microcystin synthesis by upregulating a microcystin synthetase and its encoding gene (mcyC), which could increase the hazard of M. aeruginosa in aquatic environments.


Assuntos
Antibacterianos/farmacologia , Microcistinas/biossíntese , Microcystis , Microcystis/efeitos dos fármacos , Microcystis/genética , Proteoma , Transcriptoma
20.
J Hazard Mater ; 409: 124518, 2021 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-33191018

RESUMO

Moxifloxacin (MOX) and gatifloxacin (GAT) are fourth-generation fluoroquinolone antibiotics that are frequently detected in surface water environments and pose a threat to aquatic organisms. However, research into their toxicity to Microcystis aeruginosa, a cyanobacterium, has thus far been limited. In the present study, we investigated the effects of these antibiotics on M. aeruginosa growth, photosynthesis, oxidative stress, and microcystin (MC) release. The results of the 96 h EC50 values of MOX and GAT were 60.34 and 25.30 µg/L, respectively, and the risk quotients calculated indicated that these antibiotics could pose considerable ecological risks at actual environmental concentrations. Photosynthetic fluorescence intensity was shown to decline markedly, and Fv/Fm significantly decreased without any evidence of recovery, suggesting that the organism's photosystems were irreversibly damaged. Chlorophyll a and carotenoid content decreased, whereas the ratio of carotenoids to chlorophyll a increased, indicating that carotenoids were less susceptible to damage than chlorophyll a. The reactive oxygen species and malondialdehyde content significantly increased, as well as the superoxide dismutase and catalase activities, indicating that exposure caused serious oxidative stress. Additionally, MC release increased. These results demonstrate that the environmental risks posed by MOX and GAT should be given serious consideration, particularly as their use is increasing.


Assuntos
Gatifloxacina/farmacologia , Microcistinas/metabolismo , Microcystis , Moxifloxacina/farmacologia , Antioxidantes , Clorofila , Clorofila A , Microcystis/efeitos dos fármacos , Microcystis/metabolismo , Fotossíntese
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