Aphanizomenon Flos-aquae Research Articles

The Effect of a Combined Hydrogen Peroxide-MlrA Treatment on the Phytoplankton Community and Microcystin Concentrations in a Mesocosm Experiment in Lake Ludoš.

Harmful cyanobacteria and their toxic metabolites constitute a big challenge for the production of safe drinking water. Microcystins (MC), chemically stable hepatotoxic heptapeptides, have often been involved in cyanobacterial poisoning incidents. A desirable solution for cyanobacterial management in lakes and ponds would eliminate both excess cyanobacteria and the MC that they potentially produce and release upon lysis. Hydrogen peroxide (H2O2) has recently been advocated as an efficient means of lysing cyanobacteria in lakes and ponds, however H2O2 (at least when used at typical concentrations) cannot degrade MC in environmental waters. Therefore, mesocosm experiments combining the cyanobacteria-lysing effect of H2O2 and the MC-degrading capacity of the enzyme MlrA were set up in the highly eutrophic Lake Ludoš (Serbia). The H2O2 treatment decreased the abundance of the dominant cyanobacterial taxa Limnothrix sp., Aphanizomenon flos-aquae, and Planktothrix agardhii. The intracellular concentration of MC was reduced/eliminated by H2O2, yet the reduction of the extracellular MC could only be accomplished by supplementation with MlrA. However, as H2O2 was found to induce the expression of mcyB and mcyE genes, which are involved in MC biosynthesis, the use of H2O2 as a safe cyanobacteriocide still requires further investigation. In conclusion, the experiments showed that the combined use of H2O2 and MlrA is promising in the elimination of both excess cyanobacteria and their MC in environmental waters.

Natural Compounds as Beneficial Antioxidant Agents in Neurodegenerative Disorders: A Focus on Alzheimer's Disease.

The positive role of nutrition in chronic neurodegenerative diseases (NDs) suggests that dietary interventions represent helpful tools for preventing NDs. In particular, diets enriched with natural compounds have become an increasingly attractive, non-invasive, and inexpensive option to support a healthy brain and to potentially treat NDs. Bioactive compounds found in vegetables or microalgae possess special properties able to counteract oxidative stress, which is involved as a triggering factor in neurodegeneration. Here, we briefly review the relevant experimental data on curcuminoids, silymarin, chlorogenic acid, and compounds derived from the microalga Aphanizomenon flos aquae (AFA) which have been demonstrated to possess encouraging beneficial effects on neurodegeneration, in particular on Alzheimer’s disease models.

Heat-Resistant Aphanizomenon flos-aquae (AFA) Extract (Klamin®) as a Functional Ingredient in Food Strategy for Prevention of Oxidative Stress.

Microalgae are generally considered an excellent source of vitamins, minerals, and bioactive molecules that make them suitable to be introduced in cosmetics, pharmaceuticals, and food industries. Aphanizomenon flos-aquae (AFA), an edible microalga, contains numerous biomolecules potentially able to prevent some pathologies including age-related disorders. With the aim to include an AFA extract (Klamin®) as a functional ingredient in baked products, we investigated if its bioactive molecules are destroyed or inactivated after standard cooking temperature. The AFA extract was exposed to heat stress (AFA-HS), and no significant decrease in pigment, polyphenol, and carotenoid content was detected by spectroscopic analysis. Thermal stability of AFA-HS extract was demonstrated by thermogravimetric analysis (TGA), and no change in the morphology of the granules of the powder was noticed by SEM microscopic observation. By Folin-Ciocalteu, ORAC, and ABTS assays, no change in the antioxidant activity and polyphenol contents was found after high-temperature exposition. When added in cell culture, solubilized AFA-HS lost neither its scavenging ability against ROS generation nor its protective role against Abeta, the main peptide involved in Alzheimer's disease. Prebiotic and antioxidant activities of AFA extract that are not lost after thermal stress were verified on E. coli bacteria. Finally, AFA-HS cookies, containing the extract as one of their ingredients, showed increased polyphenols. Here, we evaluate the possibility to use the AFA extract to produce functional food and prevent metabolic and age-related diseases.

Nucleoside 2',3'-Cyclic Monophosphates in Aphanizomenon flos-aquae Detected through Nuclear Magnetic Resonance and Mass Spectrometry.

Aphanizomenon flos-aquae (AFA) cyanobacteria from Klamath Lake (Oregon) are considered a "superfood" due to their broad nutritional profile that has proved to have health-enhancing properties. The AFA metabolome is quite complex. Here, we present a study that, combining multinuclear 1H, 31P, and 13C Nuclear Magnetic Resonance (NMR) spectroscopy and high-resolution mass spectrometry, led to the detection of uncommon phosphorylated metabolites in AFA. We focused our attention on 31P NMR signals at 20 ppm, a chemical shift that usually points to the presence of phosphonates. The molecules contributing to 20 ppm 31P NMR signals revealed, instead, to be nucleoside 2',3'-cyclic monophosphates. These metabolites were fully characterized by multinuclear 1H, 31P, and 13C NMR spectroscopy and high-resolution mass spectrometry.

Ultrasound-Assisted Extraction and Assessment of Biological Activity of Phycobiliprotein-Rich Aqueous Extracts from Wild Cyanobacteria (Aphanizomenon flos-aquae).

Cyanobacteria are photosynthetic microorganisms that are considered as an important source of bioactive metabolites, among which phycobiliproteins (PBPs) are a class of water-soluble macromolecules of cyanobacteria with a wide range of applications. Massive proliferation of cyanobacteria can lead to excessive surface water blooms, of which removal, as a management measure, should be prioritized. In this study, the utilization of wild cyanobacteria biomass (Aphanizomenon flos-aquae) for extraction of phycobiliproteins is reported. Extraction of phycobiliproteins by conventional methods, such as homogenization, freeze-thaw cycles, and solid-liquid extraction, were optimized prior to ultrasound-assisted extraction. Standardization of ultrasonication for different parameters, such as ultrasonication amplitude (38, 114, and 190 μm) and ultrasonication time (1, 5.5, and 10 min), was carried out using a central composite design and response surface methodology for each of the primary techniques. A substantial increase on the individual and total phycobiliprotein yields was observed after ultrasonic treatment. The highest total PBP yield (115.37 mg/g of dry weight) was observed with samples treated with a homogenizer (30 min, 30 °C, and 1 cycle) combined with ultrasound treatment (8.7 min at 179 μm). Moreover, in vitro antioxidant capacity was observed for the obtained extracts in the Folin-Ciocalteu and ABTS* + assays. In addition, a cytotoxic effect against C6 glioma cells was observed for A. flos-aquae PBPs. Conclusively, wild cyanobacteria could be considered as an alternative feedstock for recovery of PBPs.

Study of The Effect of Bisphenol A and Anise Oil on Some Sexual Hormones in Male Albino Rats and Illustration of The Effects of Aphanizomenon Flos-Aquae on Their Actions

Background: Xenoestrogens are compounds like estrogens in effect but not in structure which are mimicking the action of endogenous estrogen and activate estrogen receptor. Phytoestrogens are naturally occurring non-steroidal plant chemicals that can act like the female hormone estrogen. Aphanizomenon Flos-aquae (AFA) is a blue-green microalgal species which has antioxidant properties. Objective: The aim of the study was to clarify the effects of both Bisphenol A (BPA) and anise oil (phytoestrogen) together on some sexual hormonal pattern in male albino rats and illustration of the adverse effects of AFA on their actions. Materials and methods: Thirty male albino rats were used. They were divided into three groups: Group I: control (untreated group), Group II: rats treated with BPA and Anise oil and Group III: rats treated with BPA and Anise oil in addition to AFA. Blood samples were collected for different biochemical investigations. Results: The biochemical results showed highly significant increase (p<0.01) in the activities of ALT, AST, urea, creatinine, FSH, prolactin and lipid profile (total cholesterol, triglycerides, HDL-C, VLDL, LDL/HDL & TC/HDL). While, there was a highly significant decrease (p < 0.01) in LDL-C, total protein, albumin, Globulin, testosterone and LH. These results returned back to the normal values after receiving the AFA as compared to normal group. Conclusion: It could be concluded that phytoestrogen and xenoestrogen have undesirable effects and it is recommended to minimize the utilization of these compounds to protect people from its hazardous effects.

Study of The Effect of Bisphenol A and Anise Oil on Some Sexual Hormones in Male Albino Rats and Illustration of The Effects of Aphanizomenon Flos-Aquae on Their Actions

Background: Xenoestrogens are compounds like estrogens in effect but not in structure which are mimicking the action of endogenous estrogen and activate estrogen receptor. Phytoestrogens are naturally occurring non-steroidal plant chemicals that can act like the female hormone estrogen. Aphanizomenon Flos-aquae (AFA) is a blue-green microalgal species which has antioxidant properties. Objective: The aim of the study was to clarify the effects of both Bisphenol A (BPA) and anise oil (phytoestrogen) together on some sexual hormonal pattern in male albino rats and illustration of the adverse effects of AFA on their actions. Materials and methods: Thirty male albino rats were used. They were divided into three groups: Group I: control (untreated group), Group II: rats treated with BPA and Anise oil and Group III: rats treated with BPA and Anise oil in addition to AFA. Blood samples were collected for different biochemical investigations. Results: The biochemical results showed highly significant increase (p<0.01) in the activities of ALT, AST, urea, creatinine, FSH, prolactin and lipid profile (total cholesterol, triglycerides, HDL-C, VLDL, LDL/HDL & TC/HDL). While, there was a highly significant decrease (p < 0.01) in LDL-C, total protein, albumin, Globulin, testosterone and LH. These results returned back to the normal values after receiving the AFA as compared to normal group. Conclusion: It could be concluded that phytoestrogen and xenoestrogen have undesirable effects and it is recommended to minimize the utilization of these compounds to protect people from its hazardous effects.

Hypolipidemic Effects of Aphanizomenon flos-aquae and Slimquick on Cardiac Muscle Fibers of the Adult Male Albino Rats

Background: hyperlipidemia is a group of heterogeneous disorders characterized by an elevation of lipids in the blood stream. It accounts for the high danger of coronary heart disease and atherosclerosis which is known as a silent killer. Objectives: The aim of work was to evaluate the possible protective effects of Aphanizomenon flos-aquae (AFA) as a natural hypolipidemic product on the cardiac muscle of adult male albino rats, in comparison with Slimquick as a synthetic hypolipidemic drug and their ability to treat hyperlipidemia or to prevent it. Material and methods: fifty six male albino rats (Rattus albinus) were used and categorized into eight groups (7rats/group) .The 1st group (C) rats were used as a control, the 2nd group (H) rats were treated with high fat diet (HFD) (2% cholesterol) to induce hyperlipidemia for 4 weeks only then scarified, the 3rd group (A) rats were orally administrated with AFA only for 4 weeks(94.5 mg/kg body weight /day), the 4th group (H+A1) rats were treated with HFD enriched with 2% cholesterol for 2 weeks to induce hyperlipidemia and the other 2 weeks were fed on the same HFD plus AFA extract administration, the 5th group (H+A2) rats were treated with HFD diet enriched with 2% cholesterol for 4 weeks to induce hyperlipidemia and then they were fed on normal basal diet (BD) plus AFA extract administration for another 2 weeks, the 6th group (S) rats were orally administrated with Slimquick only for 4 weeks (5 mg orlistat/rat/day), the 7th group (H+S1) rats were treated with HFD diet enriched with 2% cholesterol for 2 weeks to induce hyperlipidemia and the other 2 weeks rats were fed on the same HFD plus Slimquick extract administration, the 8 th group (H+S2) rats were treated with HFD diet enriched with 2% cholesterol for 4 weeks to induce hyperlipidemia and then they were fed on normal basal diet (BD) plus Slimquick extract administration for another 2 weeks. Results: the biochemical parameters showed a highly significant increase in the mean value of LDH and CK in the cardiac muscle fibers of the high fat diet group. Many histopathological and histochemical changes were detected in the cardiac muscles of the high fat diet group. Meanwhile, treatment with AFA or Slimquick ameliorated the biochemical parameters, histological and histochemical results; but using AFA extract arrived to decrease the strong changes which were observed in the cardiac muscle fibers of the high fat diet group more than that observed with Slimquick. Conclusion: Aphanizomenon flos-aquae extract as a natural product and Slimquick as a synthetic drug ameliorated the biochemical, histopathological and histochemical changes in the cardiac muscle of the hyperlipidemic rats. Aphanizomenon flos-aquae extract proved to be a better hypolipidemic agent than Slimquick.

Hypolipidemic Effects of Aphanizomenon flos-aquae and Slimquick on Cardiac Muscle Fibers of the Adult Male Albino Rats

Background: hyperlipidemia is a group of heterogeneous disorders characterized by an elevation of lipids in the blood stream. It accounts for the high danger of coronary heart disease and atherosclerosis which is known as a silent killer. Objectives: The aim of work was to evaluate the possible protective effects of Aphanizomenon flos-aquae (AFA) as a natural hypolipidemic product on the cardiac muscle of adult male albino rats, in comparison with Slimquick as a synthetic hypolipidemic drug and their ability to treat hyperlipidemia or to prevent it. Material and methods: fifty six male albino rats (Rattus albinus) were used and categorized into eight groups (7rats/group) .The 1st group (C) rats were used as a control, the 2nd group (H) rats were treated with high fat diet (HFD) (2% cholesterol) to induce hyperlipidemia for 4 weeks only then scarified, the 3rd group (A) rats were orally administrated with AFA only for 4 weeks(94.5 mg/kg body weight /day), the 4th group (H+A1) rats were treated with HFD enriched with 2% cholesterol for 2 weeks to induce hyperlipidemia and the other 2 weeks were fed on the same HFD plus AFA extract administration, the 5th group (H+A2) rats were treated with HFD diet enriched with 2% cholesterol for 4 weeks to induce hyperlipidemia and then they were fed on normal basal diet (BD) plus AFA extract administration for another 2 weeks, the 6th group (S) rats were orally administrated with Slimquick only for 4 weeks (5 mg orlistat/rat/day), the 7th group (H+S1) rats were treated with HFD diet enriched with 2% cholesterol for 2 weeks to induce hyperlipidemia and the other 2 weeks rats were fed on the same HFD plus Slimquick extract administration, the 8 th group (H+S2) rats were treated with HFD diet enriched with 2% cholesterol for 4 weeks to induce hyperlipidemia and then they were fed on normal basal diet (BD) plus Slimquick extract administration for another 2 weeks. Results: the biochemical parameters showed a highly significant increase in the mean value of LDH and CK in the cardiac muscle fibers of the high fat diet group. Many histopathological and histochemical changes were detected in the cardiac muscles of the high fat diet group. Meanwhile, treatment with AFA or Slimquick ameliorated the biochemical parameters, histological and histochemical results; but using AFA extract arrived to decrease the strong changes which were observed in the cardiac muscle fibers of the high fat diet group more than that observed with Slimquick. Conclusion: Aphanizomenon flos-aquae extract as a natural product and Slimquick as a synthetic drug ameliorated the biochemical, histopathological and histochemical changes in the cardiac muscle of the hyperlipidemic rats. Aphanizomenon flos-aquae extract proved to be a better hypolipidemic agent than Slimquick.

Responses of Aquatic Organisms to Cyanobacteria and Elodea in Microcosms.

The aim of the present study is investigation of the impact of mass development of cyanobacteria and Elodea on population characteristics (abundance, biomass, fecundity) and "health" parameters (the state of embryos, heart rate, and thermal resistance) of aquatic invertebrates in experiments with controlled conditions. In July-August 2018, in four variants of microcosms, the conditions were modeled characteristic of the coastal zone of the Rybinsk Reservoir in the period of mass development of cyanobacteria. Mass species were placed in microcosms of planktonic (with domination (80%) Daphnia longispina) and bottom animals (Unio pictorum, Gmelinoides fasciatus, Asellus aquaticus), as well as Elodea canadensis. In the variants with cyanobacteria, the toxic microcystins LR were revealed (24-53% of the sum of toxins, or from 6.6-66.5 μg/L). The presence of cyanobacteria (Aphanizomenon flos-aquae, Microcystis aeruginosa, and Gloeoitrichia spp.) influenced structural parameters of plankton: the quantity to green algae decreased, small-sized crustaceans increased. Influence of cyanobacteria caused reliable changes in parameters of aquatic animal from those of the control: thermal resitance of mollusks and amphipods decreased, time of restoration of heart rate after loads (salinity test) in mollusks increased; in amphipods, individual fecundity decreased, frequency of abnormalities and of mortality of embryos increased. The presence of Elodea intensified these effects. Thus, mass development of cyanobacteria and Elodea influences ecological-physiological parameters of aquatic animals, decreasing their adaptivity to natural stresses and deteriorating the quality of the progeny.

Effects of edible algae on caecal microbiomes of ICR mice fed a high-sucrose and low–dietary fibre diet

To clarify the presence of algal-susceptible indigenous bacteria (SIB) in the gut, ICR mice were fed high-sucrose (50% w/w) diets containing either no fibre (NF), 5% brown alga “arame”, Eisenia bicyclis; 5% red alga “tsunomata”, Chondrus ocellatus; 5% (w/w) green alga “hitoegusa”, Monostroma nitidum; or 5% (w/w) cyanobacterium “blue-green alga”, Aphanizomenon flos-aquae for 14 days. Faecal frequency and weight were the highest in mice fed M. nitidum. Plasma cholesterol was the lowest in the mice fed C. ocellatus. The caecal microbiome was examined by 16S rDNA (V4) amplicon sequencing. Principal component analysis of operational taxonomical units (OTUs) revealed that the edible algae altered the microbiome. An increase in abundance levels of OTUs by E. bicyclis (Bacteroides acidifaciens-, Bacteroides intestinalis-, Bifidobacterium pseudolongum-like), C. ocellatus (Bacteroides vulgatus- and Escherichia coli-like), M. nitidum (Faecalibaculum rodentium- and Muribaculum sp.-like), and A. flos-aquae (Muribaculum sp.) was detected. Abundance of Lactobacillus johnsonii was the lowest in mice fed the algal diets. Bacteria that increased in numbers were identified as algal SIBs. SIBs might have different effects on host health depending on the food material consumed. From the algal SIBs, B. pseudolongum, B. vulgatus, F. rodentium, and L. johnsonii were isolated using blood-liver agar and identified with the 16S rDNA BLAST search. Future studies should be focused on isolation of other SIBs.

Responses of pro- and anti-inflammatory cytokines in zebrafish liver exposed to sublethal doses of Aphanizomenon flosaquae DC-1 aphantoxins

Blooms of the dominant cyanobacterium Aphanizomenon flosaquae are frequently encountered in natural waters, and their secretion of neurotoxic paralytic shellfish toxins called aphantoxins threatens environmental safety and human health worldwide. The liver is the primary detoxification organ in animals, and its pro- and anti-inflammatory responses are important functions in the detoxification of toxins. Therefore, we investigated the response of these inflammatory factors to aphantoxins in the liver of zebrafish (Danio rerio). A. flosaquae DC-1 was sampled during blooms in Dianchi Lake, China and cultured, and the toxin was extracted and analyzed using high performance liquid chromatography. The primary constituents were gonyautoxins 1 (34.04%) and 5 (21.28%) and neosaxitoxin (12.77%). Zebrafish were injected intraperitoneally with 5.3 μg (low dose) or 7.61 μg (high dose) of saxitoxin equivalents [equivalents (eq.)]/kg body weight of A. flosaquae DC-1 aphantoxins. Hyperemia, the hepatosomatic index (HSI), and physiological and molecular responses of pro- and anti-inflammatory cytokines in the zebrafish liver were investigated at different time points 1–24 h post-exposure. Aphantoxins significantly enhanced hepatic hyperemia and altered the HSI 3–24 h post-exposure, suggesting that inflammation caused morphological changes. Subsequent investigations using the enzyme-linked immunosorbent assay showed that the pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β (IL-1β), IL-6, and IL-8 and anti-inflammatory cytokines IL-10 and transforming growth factor β were higher in the liver of zebrafish exposed to aphantoxins, which indicated physiological inflammatory responses. Further analysis by real-time fluorescence quantitative polymerase chain reaction demonstrated upregulated mRNA expression of these cytokines, suggesting molecular inflammatory responses in the zebrafish liver. These changes showed dose- and time-dependent patterns. These results indicated that aphantoxins induced hyperemia and altered the HSI, and subsequently increased the levels of proinflammatory cytokines TNF-α, IL-1β, IL-6 and IL-8 to induce physiological inflammatory responses. These changes activated the anti-inflammatory cytokines IL-10 and TGF-β to suppress inflammatory damage. The induced changes were the result of upregulated mRNA expression of these inflammatory cytokines caused by aphantoxins. Aphantoxins resulted in hepatic immunotoxicity and response by inducing pro-inflammatory cytokines. Zebrafish liver in turn suppressed the inflammatory damage by upregulating the activities of anti-inflammatory cytokines. In the future, these pro- and anti-inflammatory cytokines in the zebrafish liver may be prove to be useful biomarkers of aphantoxins and blooms in nature.

Phytoplankton functional groups in a monomictic reservoir: seasonal succession, ecological preferences, and relationships with environmental variables.

The seasonal succession of phytoplankton functional groups (PFGs), their ecological preferences, relationships between environmental variables and PFGs, and ecological status were investigated in the Batman Dam Reservoir, a warm monomictic reservoir, located in the Tigris River basin of Turkey. Altogether 60 species, 19 functional groups, and 10 prevailing functional groups were identified, and prevailing functional groups showed strong seasonal changes. Centric diatoms Cyclotella ocellata (group B) and Aulacoseira granulata (group P) were dominant in the spring, with water mixing and low temperature. Groups F (Elakatothrix gelatinosa, Elakatothrix gelatinosa, and Sphaerocystis schroeteri), J (Pediastrum simplex and Coelastrum reticulatum), G (Eudorina elegans and Volvox aureus), LM (Ceratium and Microcystis), and H1 (Aphanizomenon flos-aquae and Anabaena spiroides) dominated the phytoplankton community from summer to mid-autumn, with thermal stratification. Groups H1 and P became dominant in the late autumn, with the breakdown of stratification. With the deepening of the mixing zone, groups P and T (Mougeotia sp.) were dominant in the winter. The reservoir was meso-eutrophic according to trophic state index values based on total phosphorus (TP), chlorophyll a, Secchi depth and total nitrogen, habitat preferences of PFGs, and diversity indices of phytoplankton. Redundancy analysis (RDA) revealed that NO3-N, SiO2, TP, pH, and water temperature (WT) were the most important environmental factors controlling PFGs in the BDR. Weighted averaging regression results indicated that among PFGs, groups F and T had a narrower tolerance range for WT, pH, and SiO2, while groups G and T had a narrower tolerance range for TP and NO3-N.

Spatial and seasonal variation in N2-fixing cyanobacteria in Poyang Lake from 2012 to 2016: roles of nutrient ratios and hydrology

Large river floodplain systems provide a variety of societal, economic and biological benefits and are undergoing extensive and intensive environmental deterioration. Eutrophication coupled with undesired harmful cyanobacterial blooms is one of the most widespread and severe problems in floodplain ecosystems. However, our knowledge about cyanobacteria, particularly the biogeography of N2-fixing (Nfix) cyanobacteria in shallow floodplain lakes, is very limited, and the relationships of cyanobacterial blooms with nutrient ratios and hydrological alterations remain unclear. We used a comprehensive database of field data compiled over several years (2012 to 2016) to compare the biomass and distribution of Nfix cyanobacteria between the northern (high water velocity) and southern (low water velocity) parts of Poyang Lake and to investigate the roles of hydrology and the critical nutrient mass ratios of total nitrogen:total phosphorus (TN:TP) and dissolved inorganic nitrogen:orthophosphate (DIN:PO4-P) as significant predictors of Nfix cyanobacterial biomass and distribution in eutrophic floodplain ecosystems. Dolichospermum spp. (Dolichospermum flos-aquae, D. azotica, D. circinalis, and D. spiroides) were the most widely distributed and frequent diazotrophic cyanobacteria in the regions considered in this study, followed by Aphanizomenon flos-aquae. The Nfix cyanobacterial biomass was generally low (mean = 0.32 mg/l) across Poyang Lake and was lower in the north than in the south. Using Spearman’s rank correlations, we found that this pattern may be attributed to the high turbidity and washout from the high velocity of water flow in the north. The filament length and heterocyst frequency of Dolichospermum spp. in the lake were also strongly linked to variations in hydrological characteristics and water temperature. Our results imply that the nutrient mass ratios are more important determinants of Nfix cyanobacterial biomass than hydrology in the south part of the lake. The critical TN:TP mass ratio for the Nfix cyanobacterial communities in Poyang Lake is approximately 20, and the critical DIN:PO4-P mass ratio in the lake is approximately 40. Our analysis provides new information regarding the occurrence of bloom-forming Nfix cyanobacteria in Yangtze River floodplain lakes and thus fills an important knowledge gap in subtropical freshwater ecosystems.

Effects of typical algae species (Aphanizomenon flosaquae and Microcystis aeruginosa) on photoreduction of Hg2+ in water body

Photoreduction characteristics of divalent inorganic mercury (Hg2+) in the presence of specific algae species are still not well known. Laboratory experiments were conducted in the present study to identify the effects of different concentrations of living/dead algae species, including Aphanizomenon flosaquae (AF) and Microcystis aeruginosa (MA), on the photoreduction rate of Hg2+ under various light conditions. The experimental results showed that percentage reduction of Hg2+ was significantly influenced by radiation wavelengths, and dramatically decreased with the presence of algae. The highest percentage reduction of Hg2+ was induced by UV-A, followed by UV-B, visible light and dark for both living and dead AF, and the order was dark > UV-A > UV-B > visible light for both living and dead MA. There were two aspects, i.e., energy and attenuation rate of light radiation and excrementitious generated from algae metabolisms, were involved in the processes of Hg2+ photoreduction with the presence of algae under different light conditions. The percentage reduction of Hg2+ decreased from 15% to 11% when living and dead AF concentrations increased by 10 times (from 106 to 105 cells/mL), and decreased from11% to ~9% in the case of living and dead MA increased. Algae can adsorb Hg2+ and decrease the concentration of free Hg2+, thus inhibiting Hg2+ photoreduction, especially under the conditions with high concentrations of algae. No significant differences were found in percentage reduction of Hg2+ between living and dead treatments of algae species. The results are of great importance for understanding the role of algae in Hg2+ photoreduction.

In vitro antioxidant, anti-glycation and immunomodulation activities of fermented blue-green algae Aphanizomenon flos-aquae.

To clarify the antioxidant, anti-glycation and immunomodulatory capacities of fermented blue-green algae Aphanizomenon flos-aquae (AFA), hot aqueous extract suspensions made from 10% AFA were fermented by Lactobacillus plantarum AN7 and Lactococcus lactis subsp. lactis Kushiro-L2 strains isolated from a coastal region of Japan. The DPPH and O2- radical scavenging capacities and Fe-reducing power were increased in the fermented AFA. The increased DPPH radical scavenging capacity of the fermented AFA was fractionated to mainly < 3kDa and 30-100kDa. The increased O2- radical scavenging capacities were fractionated to mainly < 3kDa. Anti-glycation activity in BSA-fructose model rather than BSA-methylglyoxal model was increased by the fermentation. The increased anti-glycation activity was fractionated to mainly 30-100kDa. The NO concentration in the murine macrophage RAW264.7 culture media was high with the fermented AFA. The increased immunomodulation capacity was also fractionated to mainly 30-100kDa. These results suggest that the fermented AFA is a more useful material for health foods and supplements.

Enhanced In Situ Availability of Aphanizomenon Flos-Aquae Constituents Entrapped in Buccal Films for the Treatment of Oxidative Stress-Related Oral Diseases: Biomechanical Characterization and In Vitro/Ex Vivo Evaluation

In recent years, the key role of oxidative stress in pathogenesis of oral diseases has been emphasized and the use of antioxidant agents has been encouraged. Aphanizomenon flos-aquae (AFA) is a unicellular blue-green alga with antioxidant and anti-inflammatory properties. The aim of this study was the formulation and characterization of mucoadhesive thin layer films loaded with AFA, finalized to the treatment of oxidative stress (OS)-related oral diseases. First, to enhance the bioavailability of AFA constituents, the raw food grade material was appropriately treated by a high frequency homogenization able to disrupt cell walls. Thus, Eudragit® E100-based buccal films were produced by the solvent casting method, containing 7% and 18% of AFA. The films, characterized by uniformity in thickness, weight, and drug content, showed low swelling degree, good muco-adhesiveness and controlled drug release. The mechanical tests showed elastic moduli of films of almost 5 MPa that is well-suitable for human buccal applications without discomfort, besides biaxial tests highlighted a marked material isotropy. Permeation studies through porcine mucosae demonstrated the ability of films to promote AFA penetration in the tissues, and when sublingually administered, they produced a drug flux up to six-fold higher than an AFA solution. The new formulations represent an interesting alternative for the development of cosmetics and nutraceuticals with a functional appeal containing plant extracts.

Cyanobacteria reduce motility of quagga mussel (Dreissena rostriformis bugensis) sperm.

The temporal expansion of harmful algal blooms, primarily associated with cyanobacteria, may impact aquatic organisms at vulnerable life-history stages. Broadcast spawning species release gametes into the water column for external fertilization, directly exposing sperm to potential aquatic stressors. To determine if cyanobacteria can disrupt reproduction in freshwater broadcast spawners, we evaluated sublethal effects of cyanobacteria exposure on quagga mussel (Dreissena rostriformis bugensis) sperm. In laboratory studies, sperm were collected after inducing mussels to spawn using serotonin and exposed to 11 cultures of cyanobacteria including Anabaena flos-aquae, Aphanizomenon flos-aquae, Dolichospermum lemmermannii, Gloeotrichia echinulata, 5 cultures of Microcystis aeruginosa, M. wesenbergii, and Planktothrix suspensa. Sperm motility, using endpoints of cumulative distance traveled and mean velocity, was calculated for a minimum of 10 individual sperm using a novel optical biotracking assay method. The distance and velocity at which sperm traveled decreased when exposed to Aphanizomenon flos-aquae and 2 M. aeruginosa cultures. Our findings indicate that cyanobacteria impede the motility of quagga mussel sperm, which can potentially result in reproductive impairments to mussels and potentially other broadcast spawning species. Environ Toxicol Chem 2019;38:368-374. © 2018 SETAC.

The effect of potentially toxic cyanobacteria on ciliates (Ciliophora)

The most frequently observed cyanotoxins are microcystins. They trigger a cascade of events leading to cellular responses. The hypothesis of the study was that cyanobacteria affect ciliates as solitary species and as assemblages. The aim of our study was to determine whether ciliates respond to cyanobacteria because of the presence of cyanotoxins (microcystins—MC). We set up experiments with toxic (Planktothrix agardhii and Microcystis aeruginosa) and non-toxic (Aphanizomenon flos-aquae) cyanobacteria, solitary Spirostomum sp. (Ciliophora), and a simple ciliate assemblage. Predicted values showed statistically significant increase during the solitary Spirostomum sp. abundance in the presence of toxic P. agardhii (MC total concentration in cells 323.9 µg/l) and M. aeruginosa (MC total concentration in cells 31.9 µg/l) but a decrease in the presence of non-toxic A. flos-aquae. The abundance of Spirostomum sp., being a component of ciliate assemblage, decreased significantly in the presence of all the three species of cyanobacteria due to competition from small-sized ciliate species that graze bacteria more effectively compared to large-cell-sized Spirostomum. We conclude that toxic cyanobacteria may affect ciliates in various ways, not necessarily because of production of toxins. As a consequence of the presence cyanotoxins, a cascading effect of passing carbon in the food web might be induced.

Reducing surface accumulation of Aphanizomenon flos-aquae using wetland water to increase cellular turgor pressure and interfere with buoyancy regulation

Rouhe AC, Rueter JG. Reducing surface accumulation of Aphanizomenon flos-aquae using wetland water to increase cellular turgor pressure and interfere with buoyancy regulation. Lake Reserve Manage. 34:426–446.The ability to regulate buoyancy (sinking and floating) using cellular gas vesicles is a unique characteristic that allows many common bloom-forming cyanobacteria to accumulate at water surfaces and dominate systems. Typical control and management strategies of cyanobacterial blooms include nutrient manipulation and phosphorus reduction, which are effective but do not reduce the advantage of buoyancy control. Since buoyancy control is based upon a mechanism driven by photosynthesis, along with environmental conditions that trigger vesicle formation and ion exchange, buoyancy regulation can be influenced by manipulating extracellular conditions. In this study, we manipulated extracellular conditions using wetland water and additions of potassium, sodium, and calcium in small-scale lab experiments containing Aphanizomenon flos-aquae from Upper Klamath Lake, Oregon. The results indicate a target mixture of 10% wetland water reduces surface accumulation, increases cellular turgor pressure (a measure of the ability of gas vesicle–forming cells to control buoyancy), and leads to fewer cyanobacterial filament rafts near the surface of the water column. By adding ions at the same concentration as the target wetland mixture, similar results were found. This research represents the basis of a possible strategy for mitigating surface blooms of buoyant cyanobacteria in lakes using wetland water and/or ion additions that could be used in tandem with nutrient manipulation and phosphorus reduction.