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1.
Arch Microbiol ; 204(6): 291, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35503579

RESUMO

A Gram-stain-negative, rod-shaped bacterial strain DH6T was isolated from fresh water of the Daechung Reservoir during the Microcystis bloom period. The strain grew at pH 6.0-8.5, at temperature 17-40 °C, and at 0-1% (w/v) NaCl concentration. Comparison of 16S rRNA gene sequence indicated that strain DH6T exhibits the highest similarity with Panacibacter ginsenosidivorans Gsoil 1550T (96.6%). The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and average amino acid identity (AAI) values of strain DH6T compared to its related type strains were below 74.2%, 22.3%, and 74.8%, respectively. The predominant fatty acids (> 5.0%) were identified as iso-C17:0 3-OH, iso-C13:0, iso-C15:0, C17:0 2-OH, iso-C11:0, anteiso-C13:0, and iso-C15:1 G. The polar lipid profile contained phosphatidylethanolamine, four unidentified aminolipids, and three unidentified lipids. The respiratory quinone was menaquinone 7 (MK-7). The genomic DNA G + C content was 42.6%. Collectively, strain DH6T should be classified as a novel species within the genus Panacibacter, for which the name Panacibacter microcysteis sp. nov. is proposed. The type strain is DH6T (= KCTC 82471T = LMG 32426T).


Assuntos
Microcystis , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , Ácidos Graxos/análise , Microcystis/genética , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Vitamina K 2/química
2.
Biomed Res Int ; 2022: 2928235, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35434123

RESUMO

In the present study, we evaluated the effects of different environments on the filtering rate (FR), mortality, and biodeposition (BD) of the freshwater mussel Unio douglasiae in bloom waters containing the toxic cyanobacterium Microcystis aeruginosa. The mean FR of 19 selected individuals (shell length, 5.0-9.8 cm) was 0.30 ± 0.03 L g-1 h-1 (range = 0.24-0.35 L g-1 h-1). Shell length was strongly correlated with both net and gross BD of mussels (P < 0.0001). The mean FR was higher in river water (0.405 ± 0.052 L g-1 h-1) than in lake water (0.304 ± 0.051 L g-1 h-1). In contrast, the BD of mussels was higher in RW (0.671 ± 0.609 mg g-1 h-1) than in LW (0.275 ± 0.027 mg g-1 h-1). For algal species, the FR of mussels ranged from 0.114 ± 0.024 to 0.553 ± 0.019 L g-1 h-1. The FR of U. douglasiae was higher in river water (mainly diatoms), whereas BD was higher in lake water (mainly Microcystis). U. douglasiae did not prefer toxic M. aeruginosa, which was significantly accumulated in pseudofaeces and faeces. The maximum FR of U. douglasiae in algal bloom water was recorded at a water temperature of 25°C and water depth of 50 cm. Moreover, the in situ mortality of U. douglasiae was strongly affected by water temperature and nitrogen concentration. Overall, U. douglasiae can enhance water quality in eutrophic areas by removing dominant cyanobacteria, although its removal efficiency depends on environmental parameters and site of introduction.


Assuntos
Bivalves , Cianobactérias , Microcystis , Unionidae , Animais , Água Doce/microbiologia , Humanos
3.
Aquat Toxicol ; 246: 106151, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35390581

RESUMO

Retinoids are newly detected compounds in aquatic ecosystems associated with cyanobacterial water blooms. Their potential health risks are only scarcely described despite numerous detections of all-trans retinoic acid (ATRA) and its derivatives in the environment. Besides the known teratogen ATRA there is only little or no information about their potency and namely their effects in vivo. We characterize ATRA and 8 other retinoids reported to occur in the environment for their bioactivity and teratogenicity using four in vitro reporter gene assays and zebrafish (Danio rerio) embryotoxicity assay. Our results document the ability of these compounds to interfere with retinoid signalling and cause teratogenicity at environmentally relevant levels with EC50 values at nM (hundreds of ng/L) levels and teratogenic indexes ranging from 2.8 (9cis retinoic acid) to 15.8 (retinal). The relative potency of individual compounds for teratogenicity ranged from 0.059 (retinal) to 0.96 (5,6-epoxy ATRA) when compared to ATRA. An environmentally relevant mixture of retinoids was tested showing good predictability of teratogenicity from the in vitro activities and additive toxicity of the mixture. The high teratogenicity of the newly described compounds associated with cyanobacteria presents a concern for developmental stages due to high conservation of the retinoid signalling across vertebrates.


Assuntos
Cianobactérias , Microcystis , Poluentes Químicos da Água , Animais , Ecossistema , Retinoides/toxicidade , Teratógenos/toxicidade , Tretinoína/toxicidade , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/genética
4.
Sci Rep ; 12(1): 5655, 2022 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-35383194

RESUMO

The vertical migration and accumulation of Microcystis colonies is a critical process in algal bloom formation. This work explored the effect of wind and light intensity on the vertical migration of Microcystis colonies. The wind-driven currents, light-driven changes in mass density of colonies, and the effect of colony size was coupled to simulate the vertical motion of colonies via Ansys Fluent and MATLAB. Results showed that light causes Microcystis to exhibit a 'day-sinking and night-floating' (d-n) phenomenon, however, wind weakens the phenomenon by forming a turbulent drag force that inhibits the vertical movement of Microcystis. This study proposed a kinetic ratio-based method, that there is a specific equilibrium turbulent kinetic energy and when turbulent kinetic energy of the water body is greater than the equilibrium turbulent kinetic energy, the d-n phenomenon does not occur. For Lake Taihu, the wind-driven turbulent kinetic energy is usually greater than the equilibrium turbulent kinetic energy. Therefore, Microcystis colonies may not exhibit the d-n phenomenon. Our findings provide a new theoretical basis for current process-based models in simulating algal blooms in large shallow lakes.


Assuntos
Microcystis , China , Eutrofização , Lagos , Vento
5.
Artigo em Inglês | MEDLINE | ID: mdl-35446755

RESUMO

A novel bacterial strain, designated MK52T, was isolated from the phycosphere of Microcystis aeruginosa. Strain MK52T is a Gram-stain-negative, pink-pigmented, rod-shaped, strictly aerobic bacterium. In 16S rRNA phylogenetic analysis, the MK52T strain was most closely related to Rhizorhabdus wittichii RW1T (98.66 %) and Rhizorhabdus histidinilytica UM2T (98.51 %). The genomic DNA G+C content of strain MK52T was calculated to be 65.5 mol%. The average nucleotide identity values of strain MK52T with R. wittichii RW1T and R. histidinilytica UM2T were 80.35 and 80.23 %, respectively, with digital DNA-DNA hybridization values of 23.6 and 22.9 %, respectively, and average amino acid identities of 75.59 and 75.79 %, respectively. The major isoprenoid quinone was Q-10, and the predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and sphingoglycolipid. Fatty acid methyl ether analysis showed that summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) was the main cellular fatty acid in strain MK52T. Strain MK52T cells grew at 21-34 °C (optimum, 30 °C), pH 5-8 (optimum, pH 7) and with 0-2 % (w/v) NaCl (optimum, 0.5 % NaCl). Rhizorhabdus phycosphaerae sp. nov. is proposed as a new species (=KCTC 72877T=DSM 111424T) based on its genotypic and phenotypic characteristics.


Assuntos
Microcystis , Sphingomonadaceae , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Microcystis/genética , Fosfolipídeos/química , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Cloreto de Sódio , Sphingomonadaceae/genética
6.
Appl Environ Microbiol ; 88(9): e0246421, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35438519

RESUMO

Cyanobacterial harmful algal blooms (cyanoHABs) degrade freshwater ecosystems globally. Microcystis aeruginosa often dominates cyanoHABs and produces microcystin (MC), a class of hepatotoxins that poses threats to human and animal health. Microcystin toxicity is influenced by distinct structural elements across a diversity of related molecules encoded by variant mcy operons. However, the composition and distribution of mcy operon variants in natural blooms remain poorly understood. Here, we characterized the variant composition of mcy genes in western Lake Erie Microcystis blooms from 2014 and 2018. Sampling was conducted across several spatial and temporal scales, including different bloom phases within 2014, extensive spatial coverage on the same day (2018), and frequent, autonomous sampling over a 2-week period (2018). Mapping of metagenomic and metatranscriptomic sequences to reference sequences revealed three Microcystis mcy genotypes: complete (all genes present [mcyA-J]), partial (truncated mcyA, complete mcyBC, and missing mcyD-J), and absent (no mcy genes). We also detected two different variants of mcyB that may influence the production of microcystin congeners. The relative abundance of these genotypes was correlated with pH and nitrate concentrations. Metatranscriptomic analysis revealed that partial operons were, at times, the most abundant genotype and expressed in situ, suggesting the potential biosynthesis of truncated products. Quantification of genetic divergence between genotypes suggests that the observed strains are the result of preexisting heterogeneity rather than de novo mutation during the sampling period. Overall, our results show that natural Microcystis populations contain several cooccurring mcy genotypes that dynamically shift in abundance spatiotemporally via strain succession and likely influence the observed diversity of the produced congeners. IMPORTANCE Cyanobacteria are responsible for producing microcystins (MCs), a class of potent and structurally diverse toxins, in freshwater systems around the world. While microcystins have been studied for over 50 years, the diversity of their chemical forms and how this variation is encoded at the genetic level remain poorly understood, especially within natural populations of cyanobacterial harmful algal blooms (cyanoHABs). Here, we leverage community DNA and RNA sequences to track shifts in mcy genes responsible for producing microcystin, uncovering the relative abundance, expression, and variation of these genes. We studied this phenomenon in western Lake Erie, which suffers annually from cyanoHAB events, with impacts on drinking water, recreation, tourism, and commercial fishing.


Assuntos
Cianobactérias , Microcystis , Cianobactérias/genética , Ecossistema , Genótipo , Lagos/microbiologia , Microcistinas/genética , Microcistinas/metabolismo , Microcystis/genética , Microcystis/metabolismo , Óperon
7.
Ecotoxicol Environ Saf ; 237: 113546, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35468443

RESUMO

Hydrogen peroxide (H2O2) is an environmentally friendly algaecide with good prospects for cyanobacterial bloom control. In this study, 0.2-1.5 mg L-1 of H2O2 was applied to an aquatic microcosm containing cyanobacteria, bacteria, and eukaryotic phytoplankton at the early cyanobacterial growth stage·H2O2 generated hormesis in cyanobacteria at 0.2 mg L-1; significantly (p < 0.05) inhibited cyanobacterial growth, cyanobacterial photosynthesis, and microcystin production at 0.5-1.5 mg L-1; and effectively prevented the formation of cyanobacterial bloom without generating adverse effects on eukaryotic phytoplankton at 1.0 and 1.5 mg L-1. Application of 0.5-1.5 mg L-1 H2O2 directly inhibited the abundance of five typical bloom-forming cyanobacterial genera (Microcystis, Anabeana, Synechococcus, Nostoc, and Oscillatoria), which were negatively correlated with four bacterial genera (Actinotalea, Flavobacterium, Fluviicola, and Exiguobacterium) and five eukaryotic phytoplankton genera (Cyclotella, Desmodesmus, Dinobryon, Fragilaria, and Mychonastes) and positively correlated with six proteobacterial genera (Brevundimonas, Devosia, Limnohabitans, Porphyrobacter, Pseudomonas, and Rhodobacter). After application of 1.0 and 1.5 mg L-1 H2O2 for 15 days, H2O2-treated groups showed significantly (p < 0.05) different prokaryotic community structures from that of the control group at the bloom stage (15th day), while eukaryotic community structures in H2O2-treated groups remained stable and showed high similarity with that of the control group at a non-bloom stage (5th day). Application of low-dose H2O2 during the early cyanobacterial growth stage could effectively prevent the formation of cyanobacterial blooms without disrupting non-target organisms.


Assuntos
Cianobactérias , Microcystis , Eutrofização , Peróxido de Hidrogênio/farmacologia , Lagos , Fotossíntese , Fitoplâncton
8.
Sheng Wu Gong Cheng Xue Bao ; 38(4): 1589-1601, 2022 Apr 25.
Artigo em Chinês | MEDLINE | ID: mdl-35470629

RESUMO

Gas vesicles are a unique class of gas-filled protein nanostructures which are commonly found in cyanobacteria and Halobacterium. The gas vesicles may scatter sound waves and generate harmonic signals, which enabled them to have the potential to become a novel ultrasound contrast agent. However, the current hypertonic cracking method for isolating gas vesicles contains tedious operational procedures and is of low yield, thus not suitable for large-scale application. To overcome these technical challenges, we developed a rapid and efficient method for isolating gas vesicles from Microcystis. The new H2O2-based method increased the yield by three times and shortened the operation time from 24 hours to 7 hours. The H2O2 method is not only suitable for isolation of gas vesicles from laboratory-cultured Microcystis, but also suitable for colonial Microcystis covered with gelatinous sheath. The gas vesicles isolated by H2O2 method showed good performance in ultrasound contrast imaging. In conclusion, this new method shows great potential for large-scale application due to its high efficiency and wide adaptability, and provides technical support for developing gas vesicles into a biosynthetic ultrasonic contrast agent.


Assuntos
Cianobactérias , Microcystis , Meios de Contraste , Peróxido de Hidrogênio , Proteínas/química
9.
Plant Signal Behav ; 17(1): 2058256, 2022 12 31.
Artigo em Inglês | MEDLINE | ID: mdl-35379075

RESUMO

To study the allelopathic effect of the extracts of Landoltia punctata, the changes of cell density of Microcystis aeruginosa were measured. The anti-algae allelopathic effect of different organic solvent extracts of L. punctata was evaluated, and the physiological, biochemical indexes were determined to discuss the mechanism of algal inhibition. The results showed that the petroleum ether, dichloromethane and ethyl acetate extracts showed various inhibitory effects on M. aeruginosa. Among them, ethyl acetate extract was the most strongly allelopathic part with the semi-effect concentration(EC50) of 59.6 mg L-1, the central polarity part of inhibitory activity. The contents of chlorophyll a(Chl a) and phycobiliproteins(PBPs) of M. aeruginosa were decreased under the concentration of 200 mg L-1 ethyl acetate extract, which indicated that the photosynthesis of M. aeruginosa was inhibited. The consent of microcystins was lower compared to control under 200 mg L-1. The contents of superoxide dismutase(SOD), malondialdehyde(MDA) and hydrogen peroxide(H2O2) of cell pellets were firstly increased and then decreased, which suggested that the algal cells were seriously damaged by oxidation. The results indicated that the extracts of L. punctata had inhibitory effect on M. aeruginosa, and the ethyl acetate extract was the central part of the inhibitory substances, which affected photosynthesis and caused peroxidation damage to inhibit cell proliferation. These findings will be helpful for exploration and application of allelopathic effects of L. punctata in harmful algae control.


Assuntos
Araceae , Microcystis , Clorofila A , Peróxido de Hidrogênio , Malondialdeído
10.
Toxins (Basel) ; 14(3)2022 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-35324698

RESUMO

Bloom-forming cyanobacteria produce and release odorous compounds and pose threats to the biodiversity of aquatic ecosystem and to the drinking water supply. In this study, the concentrations of ß-cyclocitral in different bacterial growth phases were investigated using GC-MS to determine the growth stage of Microcystis aeruginosa at high risk for ß-cyclocitral production. Moreover, the synchronicity of the production of ß-cyclocitral and its precursor ß-carotene at both population and single-cell levels was assessed. The results indicated that ß-cyclocitral was the main odorous compound produced by M. aeruginosa cells. The intracellular concentration of ß-cyclocitral (Cß-cc) as well as its cellular quota (Qß-cc) increased synchronously in the log phase, along with the increase of cell density. However, they reached the maximum values of 415 µg/L and 10.7 fg/cell in the late stationary phase and early stationary phase, respectively. The early stage of the stationary phase is more important for ß-cyclocitral monitoring, and the sharp increase in Qß-cc is valuable for anticipating the subsequent increase in Cß-cc. The molar concentrations of ß-cyclocitral and ß-carotene showed a linear relationship, with an R2 value of 0.92, suggesting that the production of ß-cyclocitral was linearly dependent on that of ß-carotene, especially during the log phase. However, the increase in Qß-cc was slower than that in ß-carotene during the stationary phase, suggesting that ß-cyclocitral production turned to be carotene oxygenase-limited when the growth rate decreased. These results demonstrate that variations of ß-cyclocitral production on a single-cell level during different bacterial growth phases should be given serious consideration when monitoring and controlling the production of odorous compounds by M. aeruginosa blooms.


Assuntos
Microcystis , Aldeídos , Diterpenos , Ecossistema , beta Caroteno
11.
Toxins (Basel) ; 14(3)2022 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-35324711

RESUMO

The Vietnamese Mekong Delta is predicted to be one of the regions most impacted by climate change, causing increased temperature and salinity in inland waters. We hypothesized that the increase in temperature and salinity may impact the microcystin (MC) production of two Microcystis strains isolated in this region from a freshwater pond (strain MBC) and a brackish water pond (strain MTV). The Microcystis strains were grown at low (27 °C), medium (31 °C), high (35 °C) and extremely high (37 °C) temperature in flat photobioreactors (Algaemist). At each temperature, when cultures reached a stable state, sea salt was added to increase salinity to 4‱, 8‱, 12‱ and 16‱. MC concentrations and cell quota were reduced at high and extremely high temperatures. Salinity, in general, had comparable effects on MC concentrations and quota. At a salinity of 4‱ and 8‱, concentrations of MC per mL of culture and MC cell quota (based on chlorophyll, dry-weight and particle counts) were higher than at 0.5‱, while at the highest salinities (12‱ and 16‱) these were strongly reduced. Strain MBC produced five MC variants of which MC-RR and MC-LR were most abundant, followed by MC-YR and relatively low amounts of demethylated variants dmMC-RR and dmMC-LR. In strain MTV, MC-RR was most abundant, with traces of MC-YR and dmMC-RR only in cultures grown at 16‱ salinity. Overall, higher temperature led to lower MC concentrations and cell quota, low salinity seemed to promote MC production and high salinity reduced MC production. Hence, increased temperature and higher salinity could lead to less toxic Microcystis, but since these conditions might favour Microcystis over other competitors, the overall biomass gain could offset a lower toxicity.


Assuntos
Microcystis , Água Doce , Microcistinas , Lagoas , Salinidade
12.
Chemosphere ; 298: 134245, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35278451

RESUMO

The unique and efficient characteristics of allelopathy in submerged plants make it an environmentally friendly method to control harmful algal blooms. Increased research focus has been placed on the improved allelochemical extraction methods of submerged plants because of their cost-utility relationships. In this study, the growth inhibition effect of Vallisneria extract on Microcystis aeruginosa (M. aeruginosa) cells through the combination of enzyme and ultrasonic-assisted extraction method was analyzed. By establishing a co-cultivation experiment, the growth indicators, photosynthetic system, and oxidative stress system of M. aeruginosa were determined. The reactive oxygen species (ROS) and superoxide dismutase (SOD) activity, as well as the catalase (CAT) and Malondialdehyde (MDA) levels of algal cells were found to have increased significantly after co-cultivation, which indicated that the Vallisneria ultrasonic-cellulase extract could induce oxidative stress in Microcystis aeruginosa cells. The Vallisneria extract could promote at low concentrations and inhibit at high concentrations on the growth of Microcystis aeruginosa. The effective suppression of growth of algae cells with the extract was observed at 5 g/L (fresh weight). The results showed that the Vallisneria ultrasonic-cellulase extract had a significant inhibitory effect on M. aeruginosa, making the effective ingredients a useful reference for algae inhibitors.


Assuntos
Celulase , Hydrocharitaceae , Microcystis , Alelopatia , Extratos Vegetais/farmacologia , Ultrassom
13.
J Environ Manage ; 312: 114904, 2022 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-35344874

RESUMO

Allelochemicals are widely accepted as promising algaecide to mitigate Microcystis-dominated cyanobacterial blooms (MCBs). Allelopathic algicidal effect of single luteolin or kaempferol against Microcystis had been confirmed, but their joint effect against Microcystis was unclear. This study comprehensively explored time-dependent joint effect and mechanisms of luteolin and kaempferol on Microcystis growth during 14 day-test. The 50%-inhibitory threshold of their mixture (IC50 mix) was verified as 4.872 and 5.211 mg/L at equitoxic ratio, and 5.167 and 4.487 mg/L at equivalent ratio, respectively, on day 8 and 14. Using toxicity unit, isobologram and predictive models, results revealed that luteolin and kaempferol at equivalent ratio interacted additively at lower, median and higher dosages, while at equitoxic ratio interacted additively at lower dosage but synergistically at median and higher dosages in Microcystis on day 8 and 14, implying that their equitoxic mixture posed better algicidal effect against Microcystis. Various dosages of equitoxic mixture concurrently decreased aqueous and total microcystins (MCs) contents along test. Thus, luteolin and kaempferol could be jointly applied as high-efficacy and eco-safe algaecide with declined MCs pollution risks. As mixture dosage elevated, more strongly weakened cellular MCs retention and inhibited cellular photosynthetic pigments content during late stage, as well as decreased aqueous MCs content long test, jointly explained increasing growth inhibition ratio with rising mixture dosage. Yet, cell damage was gradually repaired due to early stimulated antioxidant defense at each mixture dosage, thus cell damage might not be a major reason for inhibited growth under mixture stress. This study provided novel insights and guidance to coupled application of luteolin and kamepferol for mitigating MCBs and decreasing MCs pollution risks.


Assuntos
Herbicidas , Microcystis , Quempferóis/farmacologia , Luteolina/farmacologia , Microcistinas
14.
Org Lett ; 24(11): 2226-2231, 2022 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-35293207

RESUMO

Class II lanthipeptide synthetases (LanMs) are relatively promiscuous to core peptide variations. Previous studies have shown that different LanMs catalyze identical reactions on the same core sequence fused to their respective cognate leaders. We characterized a new LanM enzyme from Microcystis aeruginosa NIES-88, MalM, and demonstrated that MalM and ProcM exhibited disparate dehydration and cyclization patterns on identical core peptides. Our study provided new insights into the regioselectivity of LanMs and showcased an appropriate strategy for lanthipeptide structural diversity engineering.


Assuntos
Ligases , Microcystis , Ciclização , Ligases/química , Microcystis/metabolismo , Peptídeos/química , Especificidade por Substrato
15.
Environ Pollut ; 302: 119079, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35245623

RESUMO

The excessive proliferation of Microcystis aeruginosa can lead to ecological damage, economic losses, and threaten animal and human health. For controlling Microcystis blooms, microorganism-based methods have attracted much attention from researchers because of their eco-friendliness and species-specificity. Herein, we first found that a Paucibacter strain exhibits algicidal activity against M. aeruginosa and microcystin degradation capability. The algicidal activity of DH15 (2.1 × 104 CFU/ml) against M. aeruginosa (2 × 106 cells/ml) was 94.9% within 36 h of exposure. DH15 also degraded microcystin (1.6 mg/L) up to 62.5% after 72 h. We demonstrated that the algicidal activity of DH15 against M. aeruginosa can be mediated by physical attachment and indirect attack: (1) Both washed cells and cell-free supernatant could kill M. aeruginosa efficiently; (2) Treatment with DH15 cell-free supernatants caused oxidative stress, altered the fatty acid profile, and damaged photosynthetic system, carbohydrate, and protein metabolism in M. aeruginosa. The combination of direct and indirect attacks supported that strain DH15 exerts high algicidal activity against M. aeruginosa. The expression of most key genes responsible for photosynthesis, antioxidant activity, microcystin synthesis, and other metabolic pathways in M. aeruginosa was downregulated. Strain DH15, with its microcystin degradation capacity, can overcome the trade-off between controlling Microcystis blooms and increasing microcystin concentration. Our findings suggest that strain DH15 possesses great potential to control outbreaks of Microcystis blooms.


Assuntos
Agentes de Controle Biológico , Burkholderiales , Microcystis , Agentes de Controle Biológico/metabolismo , Agentes de Controle Biológico/farmacologia , Burkholderiales/metabolismo , Herbicidas/metabolismo , Microcistinas/metabolismo , Microcystis/metabolismo , Fotossíntese
16.
BMC Microbiol ; 22(1): 78, 2022 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-35321650

RESUMO

BACKGROUND: Cyanobacteria blooms have become a major environmental problem and concern because of secondary metabolites produced by cyanobacteria released into the water. Cyanobacteria produce volatile organic compounds (VOCs), such as the compounds ß-cyclocitral and ß-ionone, which comprise odors, off-flavors, defense compounds, as well as growth regulators. Therefore, the general objective of this work was to evaluate the VOCs produced by two strains of Microcystis aeruginosa, differing in their ability to produce microcystins (LTPNA 01-non-producing and LTPNA 08-toxin-producing). The analysis of VOC production was carried out in (1) normal culture conditions, (2) under different light intensities (LI), and (3) after the external application of ß-ionone in both cultures. RESULTS: The results showed that ß-cyclocitral and ß-ionone are produced in all growth phases of LTPNA 01 and LTPNA 08. Both strains were producers of ß-cyclocitral and ß-ionone in normal culture conditions. It was observed that the ß-cyclocitral concentration was higher than ß-ionone in all light intensities investigated in this study. Additionally, the strain LTPNA 01 produced more ß-cyclocitral than LTPNA 08 at almost all times and LIs analyzed. However, the strain LTPNA 08 produced more ß-ionone, mainly at the initial times. In addition, the experiment results with the external addition of ß-ionone in the cultures showed that the strain LTPNA 01 produced more ß-cyclocitral in control conditions than in treatment. Nonetheless, ß-ionone production was higher in treatment conditions in LTPNA 08, indicating that the addition of ß-ionone may favor the production of these compounds and inhibit the production of ß-cyclocitral. CONCLUSION: Our results showed that some abiotic factors, such as different light intensities and external application of ß-ionone, can be triggers that lead to the production of VOCs.


Assuntos
Cianobactérias , Microcystis , Compostos Orgânicos Voláteis , Aldeídos/metabolismo , Cianobactérias/metabolismo , Diterpenos , Norisoprenoides/metabolismo , Compostos Orgânicos Voláteis/análise
17.
Water Res ; 215: 118242, 2022 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-35259559

RESUMO

Harmful cyanobacterial blooms (HCBs), mainly caused by eutrophication, have deleterious impacts on water resources and pose a great threat to human health and natural ecosystems. Thus, an environmentally-friendly method to inhibit HCBs is urgently needed. Learning from nature, herein, natural product cercosporin, produced by the fungi Cercospora to damage plant cells under natural sunlight, was developed as a powerful photosensitive algicidal reagent to inhibit HCBs. Microcystis aeruginosa could be severely inactivated by 20 µM cercosporin in 36 h with 95% inhibition ratio under 23 W compact fluorescent light irradiation. Further mechanism investigation showed that algal cell walls and membranes along with the antioxidant and photosynthetic systems were damaged via two mechanisms, those being, reactive oxygen species generation and cell adsorption. More importantly, the practical applicability of cercosporin was demonstrated by its effectiveness in a 2 L-scale photoinactivation experiment using cyanobacterial blooms from Taihu Lake, China under natural sunlight with a lower dosage of cercosporin (7.5 µM). This study established the bifunctional mechanisms by which cercosporin inactivates HCBs, opening design possibilities for the development of novel photosensitive algicidal reagents to control HCBs.


Assuntos
Cianobactérias , Microcystis , Ecossistema , Eutrofização , Proliferação Nociva de Algas , Humanos , Lagos , Perileno/análogos & derivados , Luz Solar
18.
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
19.
Environ Pollut ; 301: 118971, 2022 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-35167928

RESUMO

The development of saline-alkali lands has contributed to the increasing discharge of alkaline salt-laden wastewater, which poses a threat to aquatic organisms. However, the comprehensive effect of alkaline salt on Microcystis aeruginosa, a harmful cyanobacterium, remains unclear. In this study, the growth, physiology, cell ultrastructure and production of microcystin-LR (MC-LR) in Microcystis aeruginosa exposed to four levels of alkaline salt stress were evaluated. The growth of Microcystis aeruginosa was stimulated at an electrical conductivity (EC) of 2.5 mS/cm compared to the control, as supported by the increased cell density, photosynthetic pigment and protein contents. Microcystis aeruginosa could tolerate a certain level of alkaline salt (i.e., EC of 5 mS/cm) via increasing photosynthetic pigment contents to protect cells from alkaline salt stress, but the antioxidant defence system and cell ultrastructure were not affected. When EC increased to 7.5 mS/cm, alkaline salt caused oxidative stress and toxicity in Microcystis aeruginosa, as evidenced by analysis of the integrated biomarker response (IBR). Furthermore, the photosynthetic pigment and protein contents decreased, and cell apoptosis associated with ultrastructural changes was observed. Therefore, we propose that EC of 7.5 mS/cm is a threshold for growth of Microcystis aeruginosa. Additionally, the intracellular MC-LR content was stimulated by alkaline salt, and the highest value was observed at EC of 2.5 mS/cm. The extracellular MC-LR content increased with the increasing alkaline salt concentration. When EC was 7.5 mS/cm, the extracellular MC-LR content was significantly higher than in the control and was associated with the upregulated mcyH gene. This study recommends that more attention should be paid to the risk of Microcystis aeruginosa bloom and microcystin-LR pollution in lakes located in salinization regions.


Assuntos
Cianobactérias , Microcystis , Cianobactérias/metabolismo , Toxinas Marinhas/metabolismo , Microcistinas/metabolismo , Microcystis/metabolismo
20.
Toxicon ; 210: 49-57, 2022 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-35217023

RESUMO

With the continued influx and accumulation of polycyclic aromatic hydrocarbons (PAHs) in eutrophic waters, the effects of PAHs on cyanobacteria bloom need to be clarified. PAHs usually existed as mixtures in aquatic environments, but the combined toxicity of PAH mixtures to toxigenic cyanobacteria remained unknown. This study investigated the effects of phenanthrene (Phe) and benzo [a]pyrene (BaP), alone or in combination, on the growth and physiology of Microcystis aeruginosa. The results showed that a hormesis effect on growth at low doses of the single Phe (≤1 mg/L) or PAH mixtures (≤0.279 mg/L) was observed, whereas the single BaP induced significant growth inhibitions at all concentrations (≥0.2 mg/L). The median effective concentrations (96 h) for Phe, BaP and their mixtures were 4.29, 1.29 and 1.07 mg/L, respectively. Mixture toxicity models showed that Phe and BaP elicited a synergistic interaction on M. aeruginosa. The synergy may be ascribed to the excessive oxidative stress induced by PAH mixtures, which further led to membrane structure damages, photosynthesis inhibitions and decreased metabolic activity. Moreover, the microcystins (MCs) release significantly increased by 25.3% and 31.9% upon exposure to 0.558 and 1.116 mg/L of PAH mixtures. In all, this study suggested that the enhanced release of MCs by PAH mixtures might exacerbate potential risks to the aquatic environment.


Assuntos
Microcystis , Hidrocarbonetos Policíclicos Aromáticos , Microcistinas/metabolismo , Microcistinas/toxicidade , Estresse Oxidativo , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/toxicidade
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