Search Results (426)

Reported incidences of cyanobacterial harmful algal blooms (CHABs) are increasing across the world due to climate change and nutrient loading, dominating freshwater ecosystems and producing dangerous cyanotoxins that cause ecological damage. Microcystis aeruginosa is one of the most common species of cyanobacteria; it produces hepatotoxic and neurotoxic microcystin-LR. The ecological and human impact of algal blooms is immense, and traditional CHAB remediation methods are not always adequate in eutrophic regions such as Lake Erie in North America. As a result, a proactive, targeted approach is needed to bioremediate cyanobacteria in their pre-colonial stages. Nematodes, such as the model organism Caenorhabditis elegans, are potential candidates for bioremediating cyanobacteria such as M. aeruginosa. C. elegans have metabolic pathways that could detoxify microcystin-LR and enable tolerance to cyanobacteria in nature. We analyzed C. elegans health and fat accumulation on a diet of toxic M. aeruginosa and found that C. elegans can ingest, digest, metabolize, and survive off of this diet. The mean lifespans of the worm populations were only slightly different at 20.68 ± 0.35 (mean ± S.E.M) and 17.89 ± 0.40 when fed E. coli and toxic M. aeruginosa, respectively. In addition, a diet of toxic M. aeruginosa compared to E. coli did not have any significant impact on C. elegans pharyngeal pumping (304.2 ± 9.3 versus 330.0 ± 10.4 pumps/min), dauer response (86.3 ± 1.0 versus 83.65 ± 1.0% in dauer), mobility (209.25 ± 7.0 versus 210.15 ± 4.4 thrashes/min), or SKN-1 expression based on SKN1::GFP fluorescence measurements. Overall, a diet of toxic M. aeruginosa was able to sustain C. elegans development, and C. elegans was tolerant of it. These results suggest that C. elegans and similar nematodes could be viable candidates for cyanobacterial bioremediation. Full article

Toxic algal-bloom-forming cyanobacteria are a persistent problem globally for many aquatic environments. Their occurrence is attributed to eutrophication and rising temperatures due to climate change. The result of these blooms is often the loss of biodiversity, economic impacts on tourism and fisheries, and risks to human and animal health. Of emerging interest is the poorly understood interplay between viruses and toxic species that form blooms. This is because recent studies have suggested that viruses may exacerbate the harmful effects of these blooms by contributing to the release of toxins into a dissolved phase upon cell lysis. However, to date, there is no experimental evidence that explicitly implicates viruses in microcystin release. Here, we show experimentally that a virus infection of the toxin-producing, harmful, algal-bloom-forming cyanobacterium Microcystis aeruginosa results in a 4-fold increase in the toxin microcystin-LR two days post-infection (dpi). We also show that the concentrations of microcystin remain high after culture discoloration and host cell lysis. Collectively, our results directly implicate viruses as major contributors to microcystin release from cyanobacteria and emphasize the importance of taking viruses into account in predictive models and in the assessment of water quality and safety. Full article

Microcystis aeruginosa is an important species causing cyanobacterial blooms, which can be effectively infected and lysed by cyanophages. Several strategies have been developed by M. aeruginosa to resist cyanophage infections, including the CRISPR-Cas systems. However, detailed information on the CRISPR-Cas systems in M. aeruginosa is rare. In the present study, the CRISPR-Cas systems of M. aeruginosa FACHB-524 were analyzed by genome re-sequencing, which showed that there are two type I (Cluster 1, I-B1; Cluster 2, I-D) and three type III-B (Cluster 3/4/5) CRISPR-Cas systems in the cyanobacteria. Further comparison revealed that spacer sequences of two type III-B systems targeted several genes of the cyanophage MaMV (M. aeruginosa myovirus) strains. One of the type III systems (Cluster 4) was then cloned and expressed in Escherichia coli BL21 (DE3). Protein purification and mass spectrometry identification revealed that a Cmr-crRNA effector complex formed in the E. coli. Subsequently, T4 phage (T4) was used to infect the E. coli, expressing the Cmr-crRNA complex with or without accessory proteins. The results showed that the Cmr-crRNA effector complex exhibited anti-phage activity and the accessory protein Csx1 enhanced the immune activity of the complex. Collectively, our results comprehensively demonstrate the CRISPR systems encoded by a strain of M. aeruginosa, and for the first time, one of the CRISPR systems was constructed into E. coli, providing a foundation for further in-depth analysis of cyanobacterial CRISPR systems. Full article

Carbon source limitation is a critical factor restricting the treatment efficiency of domestic wastewater by algae–bacteria consortia. Using agricultural waste as an external carbon source to enhance purification performance holds significant potential. This study investigated the effects of peanut shell powder (PSP) on wastewater treatment in algae–bacteria consortia. The results demonstrated that the optimal PSP dosage (2 mg/L) improved the removal efficiencies of TN, TP, and COD by 29.6%, 40.9%, and 18.7%, respectively. In contrast, excessive PSP reduced the removal performance. The primary mechanism by which PSP influenced the algae–bacteria consortia involved changes in microbial biomass and community structure. An optimal PSP dosage promoted the proliferation of the dominant algal species, Chlorella, enhanced photosynthetic activity, and increased the relative abundance of Rhodanobacter, known for its effective degradation of benzene compounds. Conversely, excessive PSP caused microbial cell rupture, inhibited Chlorella growth and photosynthesis, and elevated the abundance of Microcystis and Brevundimonas, which pose significant health risks. In conclusion, PSP can improve effluent quality and safety in algae–bacteria consortia, which represents a green, economical pathway for optimizing wastewater treatment processes. Full article

Eutrophication and its resultant cyanobacterial blooms are a severe environmental issue in global water bodies, and phosphate is regarded as one of the primary triggers. In this study, the in situ-synthesized heated kaolinite lanthanum hydroxide composite (HKL-LH) was used to treat cyanobacterial blooms through phosphate removal. A typical cyanobacteria species—Microcystis aeruginosa—was selected as the target organism. HKL-LH efficiently removed phosphate in the solution with the inoculation of M. aeruginosa over the course of one day. A good performance of HKL-LH on control cyanobacterial blooms with initial cell densities ranging from 10⁴ cells mL⁻¹ to 10⁵ cells mL⁻¹ was observed. Although the genetic expression relating to photosynthesis and cell division was upregulated under the stress of phosphorus deficiency, M. aeruginosa growth was significantly inhibited, i.e., the inhibition rate of up to 98% was achieved by 0.1g L⁻¹ of HKL-LH. In addition to cell growth, the photosynthetic activity and viability of M. aeruginosa cells were decreased by HKL-LH. Furthermore, the production of associated toxins (microcystins) and algal organic matters were effectively inhibited, which can reduce the ecological risk and challenges that follow water treatment. In this study, it is shown that HKL-LH has excellent application potential in the mitigation of cyanobacterial blooms in eutrophic water. Full article

Algal blooms caused by Microcystis aeruginosa are a common occurrence and pose significant threats to freshwater ecosystems. This study investigates the antialgal effects and underlying mechanisms of two plant-derived fatty acids, nonanoic acid and palmitic acid, on Microcystis aeruginosa. The results show that the inhibitory effects of both fatty acids on M. aeruginosa increase with higher concentrations. Algal recovery occurs when nonanoic acid concentrations are below 0.5 mg/L and palmitic acid concentrations are below 50 mg/L. Acute toxicity tests indicate that the safe concentrations of nonanoic acid and palmitic acid are below 1.87 mg/L and 263.3 mg/L, respectively. The inhibitory effect of nonanoic acid is more pronounced under conditions of pH 5.5, 15 °C temperature, 0.75 mg/L nitrogen, and 2 mg/L phosphorus, with inhibition efficiency remaining unaffected by increased light intensity. Both fatty acids exert their strongest inhibitory effects in the early stages of addition (0–8 days), causing cell death and the release of extracellular organic matter primarily consisting of aromatic compounds and proteins. Oxidative stress analysis reveals that high concentrations of fatty acids can cause irreversible damage to the algae’s antioxidant defense system. These findings provide valuable insights for the prevention and control of cyanobacterial blooms, which can help promote the sustainable development of freshwater ecosystems. Full article

The improper disposal of hospital wastewater (HWW) is a primary source of pharmaceutical pollution in aquatic systems. The complexity of the HWW matrix presents significant challenges for analytical chemists, necessitating meticulous sample preparation as the initial step for the analysis, followed by instrumental analysis. In the present study, a combination of dispersive solid phase extraction and solid phase extraction was evaluated for the preparation of HWW samples from two hospitals in Porto Alegre, Brazil, both for screening and quantitative analysis. The experiments performed by UHPLC-QTOF MS allowed the identification of 27 compounds and 23 suspected compounds. Furthermore, the UHPLC-QqQ-MS analysis enabled the quantification of 21 compounds, with concentrations ranging from 1.17 µg L⁻¹ to 213.33 µg L⁻¹. Notably, the pharmaceutical ciprofloxacin was detected at a concentration that exceeded the reported risk level for Microcystis aeruginosa. The environmental risk assessment revealed that the risk quotient (RQ) for several of the compounds quantified in the two HWW matrices exceeded 1, with the risk quotient of the mixture of compounds (RQ_mix) being approximately 30 × 10⁶ for Hospital A and 20 × 10⁶ for Hospital B. According to these findings, the two HWW systems exhibited risk levels for aquatic species and small rodents, thereby contributing to the persistence of pharmaceuticals in the environment. Full article

2,6-Dichloro-1,4-benzoquinone (2,6-DCBQ) is an emerging chlorinated disinfection byproduct (DBP) in bodies of water. However, this compound poses an unknown toxic effect on cyanobacteria. In this study, the toxicological mechanisms of 2,6-DCBQ in Microcystis aeruginosa (M. aeruginosa) were investigated through physiological and nontargeted metabolomic assessments. The results show that 2,6-DCBQ inhibited the growth of M. aeruginosa, reduced its photosynthetic pigment and protein contents, increased the levels of reactive oxygen species, damaged the antioxidant defense system, and aggravated the cytomembrane. Meanwhile, 2,6-DCBQ stimulated the production and release of microcystin-LR (MC-LR) and altered the transcripts of genes associated with its synthesis (mcyA, mcyD) and transport (mcyH). In addition, nontargeted metabolomics of M. aeruginosa cells exposed to 0.1 mg/L 2,6-DCBQ identified 208 differential metabolites belonging to 10 metabolic pathways and revealed the considerable interference caused by 2,6-DCBQ among ABC transporters, the two-component system, and folate biosynthesis. This study deepens the understanding of the physiological and nontargeted metabolomic responses of M. aeruginosa exposed to 2,6-DCBQ, offers insights into the toxic effect of 2,6-DCBQ on M. aeruginosa, and provides a theoretical basis for the ecological risk assessment of emerging DBPs in accordance with water quality criteria. Full article

Grazing by zooplankton can regulate bloom-forming cyanobacteria but can also transfer toxin-producing cells, as well as toxic metabolites, to the food web. While laboratory investigations have provided extensive knowledge on zooplankton and toxic cyanobacteria interactions, information on zooplankton feeding on toxin-producing cyanobacteria in natural water bodies remains scarce. In this study, we quantified Microcystis-specific mcyE synthase genes from the gut contents of various cladoceran and copepod taxa to assess the in situ crustacean community and taxon-specific ingestion of potentially toxic Microcystis in Lake Peipsi, a large eutrophic lake in Estonia, Northern Europe. Microcystis cells with mcyE genes were found in all crustaceans examined. However, some species, such as the cyclopoid copepod Mesocyclops leuckarti, were more efficient in ingesting potentially toxic Microcystis than other co-occurring cladocerans (Daphnia spp., Bosmina spp., Chydorus sphaericus) and copepods (Eudiaptomus gracilis). The amount of toxigenic Microcystis cells grazed by crustacean population changed temporarily, and copepods were the predominant consumers of toxigenic Microcystis during several months of the 5-month study period. Crustacean ingestion of toxigenic Microcystis was not related to Microcystis biomass or mcyE gene copy numbers in the environment but was instead related to the abundance of major crustacean grazers. Our findings emphasize the close interaction between crustacean zooplankton and toxigenic Microcystis, indicating that some species may play a more significant role in linking toxic cells within the food web than others. Full article

Due to the high altitude, unique geographical location, difficult accessibility and low temperature, the environmental factors influencing phytoplankton composition have rarely been investigated in the Selin Co Lake, which is the largest lake in the Tibetan Plateau. Phytoplankton composition can indicate aquatic ecosystem conditions, which may be sensitive to environmental factors in the Tibetan Plateau. In this study, we investigated the main environmental factors that influence phytoplankton species in the Selin Co Lake by analyzing the spatial distribution and applying statistical analyses. We also compared the influential environmental factors in this lake with other lakes around the world. The results suggest that the eleven environmental variables can explain about 46.78% of the phytoplankton’s composition. DO and fluoride were the most significant environmental variables, followed by arsenic and COD, and the other variables had comparatively smaller and more insignificant influences on phytoplankton composition. There were five dominant phytoplankton species in the Selin Co Lake, namely, Microcystis sp., Navicula spp., Chlorella vulgaris, Ankistrodesmus falcatus, and Westella sp. Some of these dominant species were also found in other tropical lakes, suggesting that the phytoplankton community could adapt to environmental changes. A clear understanding of the influential environmental variables affecting phytoplankton composition could help us to make proper water quality protection strategies in future climate change scenarios. Full article

Using allelochemicals produced by submerged plants to inhibit algal growth is an environmentally friendly approach to controlling harmful algal blooms in eutrophic lakes. This study aimed to evaluate the inhibition of cyanobacterial growth by allelochemicals accumulated by the aquatic plant Vallisneria natans, with enhancement through blue and red light-emitting diode (LED) supplementation. We conducted a laboratory experiment to assess the fluorescence parameters, enzyme activities, and phycocyanin contents of cyanobacteria Microcystis aeruginosa grown in different V. natans cultivation media. The fluorescence parameters in the BG-11 medium remained stable, but sharply decreased in both LED treatments, with nearly 100% inhibition observed after 12 h of incubation. Superoxide dismutase (SOD) and peroxidase activities were stable in the BG-11 treatment, but enhanced in both LED treatments, reaching maximum values within 48 h. Higher SOD activities were observed with blue LED compared with red LED, suggesting better performance with blue light. A constant high phycocyanin fluorescence intensity was observed in the BG-11 treatment, while both LED treatments showed lower intensities. These results provided strong evidence that LED supplementation enhances the inhibitory effects of V. natans on M. aeruginosa growth. The combination of aquatic plant growth with underwater LED light supplementation offers a promising approach to controlling cyanobacterial blooms. Full article

Increasingly frequent weather extremes induce changes in the quantity and quality of surface waters, complicating their use and resource management. These challenges are particularly relevant to dam reservoirs, designed to provide high-quality water for various recipients. The impact of extreme drought on lowland eutrophic reservoir–river systems remains poorly understood. Our research showed that the effects of extreme droughts, resulting in a decrease in the water level in a lowland reservoir and its outflow, are more severe than those of floods. During extreme droughts, reservoir pressure increases because the large load of cyanobacteria released from the reservoir, in conditions of low river discharge, is not diluted. unlike during floods. The increase in the total biomass of potamoplankton and, especially, cyanobacteria responsible for the production of toxic microcystins was positively correlated with reservoir outflow. Additionally, a shift in the dominant cyanobacteria species was observed, from Planktothrix agardhii to Microcystis spp., leading to changes in the oligopeptide profile, including microcystins. Full article

The organic material from cyanobacteria is a significant precursor to the generation of disinfection byproducts. This study’s aim was to evaluate the formation of assimilable organic carbon (AOC) in water contaminated with cyanobacteria. Furthermore, the formation of AOC was related to the generation of trihalomethanes (THMs) and dissolved organic carbon (DOC). The advanced oxidation process was caISOrried out by exposing Microcystis aeruginosa cells (250,000 cells mL⁻¹) to different peroxide dosages (10 to 100 mg L⁻¹) under ultraviolet radiation. Pseudomonas fluorescens (P-17), Spirillum sp. (NOX), and flow cytometry were used to determine the AOC concentration. The formation of AOC and THMs during the UV/H₂O₂ process was not directly related. The AOC concentration increased with low H₂O₂ doses and decreased at higher concentrations, while the levels of THMs decreased regardless of the AOC formed. After oxidation, the DOC concentration decreased, along with the concentration of THMs. Additionally, it was observed that the behavior of DOC and AOC is inversely proportional. These results suggest that the oxidation process has a complex effect on organic matter, influencing byproduct formation and AOC availability. Moreover, these findings highlight the importance of carefully monitoring and controlling the oxidation processes to better understand their impact on water treatment and byproduct formation. Full article

In order to promote the development of biodiversity, the present study conducted three sampling surveys at 26 representative sampling sites selected from the Chishui River, a freshwater river in China, in July (rainy season), November (flat water period), and April 2024 (dry season), respectively, focusing on the relationship between benthic algae and the response of water environmental factors. The results revealed that a total of 140 species from 48 genera and 7 phyla of benthic algae were identified, with the highest number of species belonging to the diatom phylum (85 species). The average density of benthic algae was highest during the flat water period, followed by the dry season and the flood season. Microcystis sp. was the dominant species during the flood season, while Gomphonema sp., Achnanthes tumescens, and Oscillatoria sp. were common dominant species during the dry and flat water periods. Achnanthes tumescens was the absolute dominant species in the upstream during the dry and flat water periods; Leptolyngbya sp. was the absolute dominant species in the midstream during the flat water period, and Oscillatoria sp. was the absolute dominant species in the middle reaches during the dry season. The Shannon-Wiener index, Margalef index, and species richness of benthic algae during the dry and flat water periods decreased from upstream to downstream. Non-metric multidimensional scaling analysis revealed significant differences in the community structures of benthic algae in the upper, middle, and downstream areas of the Chishui River during different periods, while cluster analysis indicated high similarity among benthic algae communities in locally adjacent areas. The differences in the benthic algae community structure increased with environmental and geographical distance, with environmental distance playing a greater role than geographical distance. RDA (Redundancy Analysis) identified TN (Total Nitrogen), TP (Total Phosphorus), DO (Dissolved Oxygen), EC (Electrical Conductivity), and NH₃-N (Ammonia Nitrogen) as key water environmental factors influencing the structure of benthic algal communities in the Chishui River. Full article