Consumption of toxic benthic cyanobacteria by two common demersal fish: Growth, antioxidant and liver histopathology responses.

Benthic freshwater cyanobacteria have the potential to produce toxins. Compared with more extensively studied plankton species, little is known about the impact of harmful benthic cyanobacteria on aquatic organisms. As demersal fish are usually in direct contact with benthic cyanobacteria, it is important to understand their interactive effects. This study investigated the physio-chemical responses of two demersal fish (Xenocypris davidi and Crucian carp) after exposure to benthic Oscillatoria (producing cylindrospermopsin, 2 × 106 cells/mL) for 7 days. Interestingly, benthic Oscillatoria had less adverse effects on X. davidi than C. carp. The two demersal fish effectively ingested Oscillatoria, but Oscillatoria cell sheathes could not be fully digested in C. carp intestines and led to growth inhibition. Oscillatoria consumption induced oxidative stress and triggered alterations in detoxification enzyme activities in the X. davidi liver. Superoxide dismutase (SOD) and glutathione reductase (GR) activities significantly increased in the C. carp liver, but catalase (CAT) and detoxification enzymes glutathione S-transferase (GST) and glutathione (GSH) activities were insignificantly changed. This suggested that C. carp may have a relatively weak detoxification capacity for toxic Oscillatoria. Oscillatoria ingestion led to more pronounced liver pathological changes in C. carp, including swelling, deformation, and loss of cytoskeleton structure. Simultaneously, fish consumption of Oscillatoria increased extracellular cylindrospermopsin concentration. These results provide valuable insights into the ecological risks associated with benthic cyanobacteria in aquatic ecosystems.

Integrated approaches for heavy metal-contaminated soil remediation: harnessing the potential of Paulownia elongata S. Y. Hu, Oscillatoria sp., arbuscular mycorrhizal fungi (Glomus mosseae and Glomus intraradices), and iron nanoparticles.

In recent years, researchers have extensively investigated the remediation of heavy metal-contaminated soil using plants, microorganisms, and iron nanoparticles. The objective of this study was to investigate and compare the individual and simultaneous effects of Paulownia elongata S. Y. Hu, cyanobacteria (Oscillatoria sp.), arbuscular mycorrhizal fungi (AMF) including Glomus mosseae and Glomus intraradices, and zero-valent iron nanoparticles (nZVI) on the remediation of heavy metal-contaminated soil containing chromium (Cr VI and Cr III) and nickel (Ni). The study found significant variations in parameters such as pH (acidity), electrical conductivity (EC), nitrogen (N), phosphorus (P), potassium (K), and organic carbon (OC) among different treatments. The addition of cyanobacteria, AMF, and nZVI influenced these properties, resulting in both increases and decreases compared to the control treatment. The treatment involving a combination of cyanobacteria, AMF, and nZVI (CCAN25) exhibited the highest increase in growth parameters, such as total dry mass, root length, stem diameter, and leaf area, while other treatments showed varied effects on plant growth. Moreover, the CCAN25 treatment demonstrated the highest increase in chlorophyll a, chlorophyll b, and carotenoid levels, whereas other treatments displayed reductions in these pigments compared to the control. Moderate phytoaccumulation of Cr and Ni in P. elongata samples across all treatments was observed, as indicated by the bioconcentration factor and bioaccumulation coefficient values being less than 1.0 for both metals. The findings provide insights into the potential application of these treatments for soil remediation and plant growth enhancement in contaminated environments.

Light-induced Trpin/Metout Switching During BLUF Domain Activation in ATP-bound Photoactivatable Adenylate Cyclase OaPAC.

The understanding of signal transduction mechanisms in photoreceptor proteins is essential for elucidating how living organisms respond to light as environmental stimuli. In this study, we investigated the ATP binding, photoactivation and signal transduction process in the photoactivatable adenylate cyclase from Oscillatoria acuminata (OaPAC) upon blue light excitation. Structural models with ATP bound in the active site of native OaPAC at cryogenic as well as room temperature are presented. ATP is found in one conformation at cryogenic- and in two conformations at ambient-temperature, and is bound in an energetically unfavorable conformation for the conversion to cAMP. However, FTIR spectroscopic experiments confirm that this conformation is the native binding mode in dark state OaPAC and that transition to a productive conformation for ATP turnover only occurs after light activation. A combination of time-resolved crystallography experiments at synchrotron and X-ray Free Electron Lasers sheds light on the early events around the Flavin Adenine Dinucleotide (FAD) chromophore in the light-sensitive BLUF domain of OaPAC. Early changes involve the highly conserved amino acids Tyr6, Gln48 and Met92. Crucially, the Gln48 side chain performs a 180° rotation during activation, leading to the stabilization of the FAD chromophore. Cryo-trapping experiments allowed us to investigate a late light-activated state of the reaction and revealed significant conformational changes in the BLUF domain around the FAD chromophore. In particular, a Trpin/Metout transition upon illumination is observed for the first time in the BLUF domain and its role in signal transmission via α-helix 3 and 4 in the linker region between sensor and effector domain is discussed.

Appraising the phycoremediation potential of cyanobacterial strains Phormidium and Oscillatoria for nutrient removal from textile wastewater (TWW) and synchronized biodiesel production from TWW-tolerant biomass.

In this study, phycoremediation of textile wastewater (TWW) by freshwater cyanobacterial strains such as sp., Oscillatoria sp. F01 and Oscillatoria sp. F02 was evaluated, and lipids were simultaneously extracted from biomass for biodiesel production. Onset of the study, Phormidium sp. and Oscillatoria sp. F01 has better growth rates, increased biomass production, high chlorophyll content, and efficient nutrient utilization in TWW compared to Oscillatoria sp. F02. Phormidium sp. showed 1.41 g/L dry weight, followed by Oscillatoria sp. F01 with 1.39 g/L and Oscillatoria sp. F02 with 1.02 g/L biomass. Both strains demonstrated their capability to elevate the pH level while reducing TDS and eliminating/reducing several nutrients such as nitrates, nitrites, phosphates, sulphates, sulphides, chlorides, calcium, sodium, and magnesium. Further, the total lipids extracted from the TWW-grown Phormidium sp., Oscillatoria sp. F01 and Oscillatoria sp. F02 was estimated to be 8.20, 13.70 and 11.20 %, respectively, on day 21, which was higher than the lipid content obtained from control cultures. Further, biodiesel produced from the lipids of all strains showed higher levels of C12:0, C16:0, C16:1, C18:1, C18:2, and C18:3 among all the fatty acids. Therefore, they can potentially offer a valuable source of lipids and diverse fatty acids for high-quality biodiesel production. This integrated system not only offers a solution for TWW treatment but also provides a feedstock for renewable fuel production simultaneously.

Nanosynthesis, phycochemical constituents, and pharmacological properties of cyanobacterium Oscillatoria sp.

The Oscillatoria sp., a blue-green alga or cyanobacterium, consists of about 305 species distributed globally. Cyanobacteria are prokaryotes possessing several secondary metabolites that have industrial and biomedical applications. Particularly, the published reviews on Oscillatoria sp. have not recorded any pharmacology, or possible details, while the detailed chemical structures of the alga are reported in the literature. Hence, this study considers pertinent pharmacological activities of the plethora of bioactive components of Oscillatoria sp. Furthermore, the metallic nanoparticles produced with Oscillatoria sp. were documented for plausible antibacterial, antifungal, antioxidant, anticancer, and cytotoxic effects against several cultured human cell lines. The antimicrobial activities of solvent extracts of Oscillatoria sp. and the biotic activities of its derivatives, pyridine, acridine, fatty acids, and triazine were structurally described in detail. To understand the connotations with research gaps and provide some pertinent prospective suggestions for further research on cyanobacteria as potent sources of pharmaceutical utilities, attempts were documented. The compounds of Oscillatoria sp. are a potent source of secondary metabolites that inhibit the cancer cell lines, in vitro. It could be expected that by holistic exploitation, the natural Oscillatoria products, as the source of chemical varieties and comparatively more potent inhibitors, would be explored against pharmacological activities with the integument of SARs.

Single Amino Acid Mutation Decouples Photochemistry of the BLUF Domain from the Enzymatic Function of OaPAC and Drives the Enzyme to a Switched-on State.

Photoactivated adenylate cyclases (PACs) are light-activated enzymes that combine a BLUF (blue-light using flavin) domain and an adenylate cyclase domain that are able to increase the levels of the important second messenger cAMP (cyclic adenosine monophosphate) upon blue-light excitation. The light-induced changes in the BLUF domain are transduced to the adenylate cyclase domain via a mechanism that has not yet been established. One critical residue in the photoactivation mechanism of BLUF domains, present in the vicinity of the flavin is the glutamine amino acid close to the N5 of the flavin. The role of this residue has been investigated extensively both experimentally and theoretically. However, its role in the activity of the photoactivated adenylate cyclase, OaPAC has never been addressed. In this work, we applied ultrafast transient visible and infrared spectroscopies to study the photochemistry of the Q48E OaPAC mutant. This mutation altered the primary electron transfer process and switched the enzyme into a permanent 'on' state, able to increase the cAMP levels under dark conditions compared to the cAMP levels of the dark-adapted state of the wild-type OaPAC. Differential scanning calorimetry measurements point to a less compact structure for the Q48E OaPAC mutant. The ensemble of these findings provide insight into the important elements in PACs and how their fine tuning may help in the design of optogenetic devices.

The toxicological effects of life-cycle exposure to harmful benthic cyanobacteria Oscillatoria on zebrafish growth and reproduction: A comparative study with planktonic Microcystis.

The risks of planktonic cyanobacteria blooms have been the focus of much scientific research, but studies on the ecotoxicological effects of benthic cyanobacteria are lagging. The impacts of cyanobacteria cells on fish populations might be more complex in contrast to purified cyanotoxins or cyanobacteria extracts. This study systematically compared the chronic effects of benthic Oscillatoria sp. (producing cylindrospermopsins) and planktonic Microcystis aeruginosa (producing microcystins) on the growth and reproduction of zebrafish through life-cycle exposure (5- 90 days post fertilization). The results showed that both Oscillatoria sp. and M. aeruginosa exposure caused growth inhibition and fecundity reduction in F0 generation by disrupting sex hormone levels, delayed ovarian and sperm development, and induced pathological lesions in zebrafish gonads. Furthermore, exposure to Oscillatoria sp. or M. aeruginosa in adult zebrafish increased mortality and teratogenicity in F1 embryos (without exposure), indicating a parental transmission effect of developmental toxicity. The difference was that M. aeruginosa exposure led to significant alterations in pathways, such as tissue development, redox processes, and steroid hormone synthesis. In contrast, Oscillatoria sp. exposure primarily disrupted the PPAR signaling pathway, cell adhesion molecules, and lipid transport pathways. Interestingly, the differentially expressed genes revealed that male fish were more sensitive to harmful cyanobacteria than females, whether exposed to Oscillatoria sp. or M. aeruginosa. These findings contribute to a better mechanistic understanding of the chronic toxic effects of distinct types of harmful cyanobacteria, suggesting that the ecological risk of benthic cyanobacteria requires further attention.

Assessment of Antimicrobial and Antioxidant Potential of Oscillatoria sancta and Oscillatoria proteus Isolated from Chilika Lake.

Filamentous cyanobacteria are a promising source of biologically active secondary metabolites with antioxidant, antimicrobial, antiviral and anticancer properties. Previously, cyanobacteria isolated from fresh and marine water were studied extensively, but those isolated from brackish water were less investigated. The purpose of this study was to examine the antimicrobial activities as well as the potential antioxidant capacity of two cyanobacterial strains (Oscillatoria proteus and Oscillatoria sancta) obtained from Chilika Lake. The pigment and antioxidant was assayed using a spectrophotometer; antimicrobial activity was studied by minimum inhibitory concentration (MIC); and the presence of phytoconstituents was detected using gas chromatography mass spectrometry (GC-MS). The solvents used for extraction were methanol, acetone and benzene. The experimental data indicates that the total phenolic and flavonoid content was highest in O. sancta (58.26 ± 0.72 µg/g, 38.45 ± 0.79 µg/g, respectively). Similarly, the methanol extract of O. sancta presented the maximum antioxidant potential in both DPPH (83.18 ± 0.57%) and ABTS (68.42 ± 1.40%) radicals. Besides, more reducing power was also recorded in methanol extract of O. sancta as compared to O. proteus. Further, higher enzymatic activity (superoxide dismutase and catalase) was observed in O. sancta. The antimicrobial potential against bacterial and fungal pathogens demonstrated better activity in O. sancta. In GC-MS analysis seven major chemical classes have been detected. Differential results was found in the two species of Oscillatoria; however, both have potential antimicrobial and antioxidant properties. The findings have pharmaceutical and nutraceutical importance.

Impact of anthropogenic accumulation on phytoplankton community and harmful algal bloom in temporarily open/closed estuary.

Spatio-temporal variation in phytoplankton community dynamics in a temporarily open/closed Swarnamukhi river estuary (SRE), located on the South East coast of India was investigated and correlated to that of the adjacent coastal waters. Understanding the seasonal variability of the phytoplankton community and influencing factors are essential to predicting their impact on fisheries as the river and coastal region serve as the main source of income for the local fishing communities. Downstream before the river meets the sea, an arm of the Buckingham Canal (BC), carrying anthropogenic inputs empties into the Swarnamukhi River (SR1). The impact of anthropogenic effects on the phytoplankton community at BC was compared to other estuarine stations SR2 (upstream), SR1 (downstream), SRM (river mouth) and coastal station (CS). In BC station, harmful algal blooms (HABs) of Chaetoceros decipiens (2940 × 103 cells L-1) and Oscillatoria sp. (1619 × 103 cells L-1) were found during the southwest monsoon and winter monsoon, respectively. These HABs can be linked to the anthropogenic input of increased nutrients and trace metals. The HABs of Oscillatoria sp. were shown to be induced by elevated concentrations of nitrate (10.18 µM) and Ni (3.0 ppm) compared to ambient, while the HABs of C. decipiens were caused by elevated concentrations of silicate (50.35 µM), nitrite (2.1 µM), and phosphate (4.37 µM). Elevated nutrients and metal concentration from the aquaculture farms, and other anthropogenic inputs could be one of the prime reasons for the recorded bloom events at BC station. During this period, observed bloom species density was found low at other estuarine stations and absent at CS. The formation of bloom events during the closure of the river mouth could be a major threat to the coastal ecosystem when it opens. During the Osillatoria sp. bloom, both the Cu and Ni levels were higher at BC. The elevated concentration of nutrients and metals could potentially affect the coastal ecosystem and in turn fisheries sector in the tropical coastal ecosystem.

Photocycle alteration and increased enzymatic activity in genetically modified photoactivated adenylate cyclase OaPAC.

Photoactivated adenylate cyclases (PACs) are light activated enzymes that combine blue light sensing capacity with the ability to convert ATP to cAMP and pyrophosphate (PPi) in a light-dependent manner. In most of the known PACs blue light regulation is provided by a blue light sensing domain using flavin which undergoes a structural reorganization after blue-light absorption. This minor structural change then is translated toward the C-terminal of the protein, inducing a larger conformational change that results in the ATP conversion to cAMP. As cAMP is a key second messenger in numerous signal transduction pathways regulating various cellular functions, PACs are of great interest in optogenetic studies. The optimal optogenetic device must be "silent" in the dark and highly responsive upon light illumination. PAC from Oscillatoria acuminata is a very good candidate as its basal activity is very small in the dark and the conversion rates increase 20-fold upon light illumination. We studied the effect of replacing D67 to N, in the blue light using flavin domain. This mutation was found to accelerate the primary electron transfer process in the photosensing domain of the protein, as has been predicted. Furthermore, it resulted in a longer lived signaling state, which was formed with a lower quantum yield. Our studies show that the overall effects of the D67N mutation lead to a slightly higher conversion of ATP to cAMP, which points in the direction that by fine tuning the kinetic properties more responsive PACs and optogenetic devices can be generated.

Towards enhancement of fungal hydrolytic enzyme cocktail using waste algal biomass of Oscillatoria obscura and enzyme stability investigation under the influence of iron oxide nanoparticles.

Development of low-cost and economic cellulase production is among the key challenges due to its broad industrial applications. One of the main topics of research pertaining to sustainable biomass waste based biorefinaries is the development of economic cellulase production strategies. The main cause of the increase in cellulase production costs is the use of commercial substrates; as a result, the cost of any cellulase-based bioprocess can be decreased by employing a productive, low-cost substrate. The goal of the current study is to develop low-cost cellulase using the carbohydrate-rich, renewable, and widely accessible cyanobacteria algae Oscillatoria obscura as the production substrate. Maximum cellulase was produced utilising the fungus Rhizopus oryzae at substrate concentration of 7.0 g among various tested concentrations of algal biomass. Maximum production rates of 22 IU/gds FP, 105 IU/gds BGL, and 116 IU/gds EG in 72 h were possible under optimal conditions and substrate concentration. Further investigations on the crude enzyme's stability in the presence of iron oxide nanoparticles (IONPs) revealed that it was thermally stable at 60 °C for up to 8 h. Additionally, the crude enzyme demonstrated pH stability by maintaining its complete activity at pH 6.0 for 8 h in the presence of the optimal dose of 15 mg IONPs. The outcomes of this research may be used to investigate the possibility of producing such enzymes in large quantities at low cost for industrial use.

Photoautotrophic black-colored cyanobacterial soil crust biosynthesizes photoprotective compounds and is capable of using blue, green, and red wavelengths of light for its growth.

Several cyanobacteria can adjust their light-harvesting machinery in response to existing light signals in a process called chromatic acclimation (CA) which permits the utilization of available light resources for photosynthesis. CA involves alteration in the pigment composition of a major light-harvesting complex called phycobilisome (PBS) and allows some cyanobacteria to utilize green light (GL) to drive photosynthesis. However, cyanobacteria, in contrast with eukaryotic algae and higher plants, can not utilize blue light (BL) for photosynthesis due to their dependency on PBS. Here, we studied a black-colored soil crust that was composed of a single cyanobacterium identified and named Oscillatoria sp. Malviya-1 after phenotypic and phylogenetic analyses. The black-colored crust can absorb light from almost all parts of photosynthetically active radiation (400-700 nm) and ultraviolet radiation (280-400 nm) due to the presence of photosynthetic pigments and microbial sunscreens such as chlorophyll ɑ, carotenoids, phycoerythrin, phycocyanin, allophycocyanin, mycosporine-like amino acids, and scytonemin. Unlike other cyanobacteria, Oscillatoria sp. Malviya-1 can grow using GL, BL, and red light (RL) in addition to white light (WL) which was accompanied by the different colors of the mat under different light conditions. The presence of CA and sunscreens compounds can maximize the fitness of soil crust under a dynamic light environment, UVR, and desiccation. Detailed study of Oscillatoria sp. Malviya-1 will provide information on the mechanism of CA in cyanobacterial soil crust and its unique ability to use both GL and BL.

Phycotoxicity and catalytic reduction activity of green synthesized Oscillatoria gelatin-capped silver nanoparticles.

Over the last decade, an extensive range of consumer products containing manufactured silver nanoparticles (AgNPs) have been progressively used. The unfitting usage and discharge of these materials can enable passage of AgNPs into the aquatic ecosystem causing prospective toxicological consequence. The present study shed new lights on the phycotoxicity of small (8.47-17.66 nm) and stable Oscillatoria reduced gelatin-capped silver nanoparticles (OG-AgNPs) fabricated using a completely green synthetic technique. In this work, estimating of the possible toxic effects of OG-AgNPs on two freshwater microalgae Chlorella vulgaris and Chlorella minutissima was carried. This study found that, the growth of cells and photosynthetic pigment inhibitory effects of OG-AgNPs exhibit a significant increase with increasing time and concentration compared to control. Based on the IC50 value C. vulgaris (3.705 µg/mL) was found to be more sensitive to OG-AgNPs than C. minutissima (5.8 µg/mL). This study revealed that OG-AgNPs exhibit potent phycotoxic effect against Chlorella species. Finally, the negative effect of OG-AgNPs on aquatic algae and these modifications might have severe effects on structure and function of aquatic ecosystems. Besides, the biosynthesized OG-AgNPs showed a catalytic activity in the reduction of hydrogen peroxide, one of the reactive oxygen species that represent a major threat to biological systems. This method pretends an auspicious non-skill dependent technique with a good sensitivity for determination of H2O2 concentration, particularly at trace ppm level for applying in numerous domains such as medical and industrial processes.

Antimicrobial, antibiofilm potential, and anti-quorum sensing activity of silver nanoparticles synthesized from Cyanobacteria Oscillatoria princeps.

Cyanobacteria are among the beneficial and environmentally friendly natural candidates used in the biosynthesis of nanoparticles, with their ability to accumulate heavy metals from their environment, thanks to their biologically active compounds. In the current study, an aqueous extract of Oscillatoria princeps fresh biomass was used for the green synthesis of AgNPs. UV-vis spectrum, Fourier transforms infrared, scanning electron microscopy, and energy-dispersive spectroscopy were used to validate and characterize biosynthesized of OSC-AgNPs. The biosynthesis of AgNPs was visually verified in terms of the change in the color of the AgNO3 solution from yellowish brown to brown colors from 72 h onwards. An absorption peak of approximately 420 nm was detected in the UV-vis spectrum, corresponding to the plasmon resonance of AgNPs. FT-IR analysis showed the presence of free amino groups in addition to sulfur-containing amino acid derivatives that act as stabilizing agents. SEM images detected the roughly spherical shape of OSC-AgNPs with an average size of 38 nm. The pathogens tested were all susceptible to OSC-AgNPs showing varying antimicrobial effects on pathogenic microorganisms. E. coli and C. albicans displayed the maximum susceptibility, with zones of inhibition of 14.6 and 13.8 mm at 3-mM concentration, respectively, while B. cereus had the lowest zone of inhibition (10.6 mm) at 3-mM OSC-AgN03 concentration. In conclusion, AgNPs synthesized from Oscillatoria princeps inhibit biofilm formation, suggesting that AgNPs may be a promising candidate for the prevention and treatment of biofilm-associated infections caused by bacteria and yeasts.

Targeted Discovery of Amantamide B, an Ion Channel Modulating Nonapeptide from a South China Sea Oscillatoria Cyanobacterium.

Amantamide B (1) is a new linear nonapeptide analogue of the cyanobacterial natural product amantamide A (2), and both have methyl ester and butanamide termini. These compounds were discovered in this study from the organic extract of a tropical marine filamentous cyanobacterium, Oscillatoria sp., collected around the Paracel Islands in the South China Sea. The use of LC-MS/MS molecular networking for sample prioritization and as an analytical dereplication tool facilitated the targeted isolation of 1 and 2. These molecules were characterized by spectroscopy and spectrometry, and configurational assignments were determined using chemical degradation and chiral-phase HPLC analysis. Compounds 1 and 2 modulated spontaneous calcium oscillations without notable cytotoxicity at 10 µM in short duration in vitro testing on primary cultured neocortical neurons, a model system that evaluates neuronal excitability and/or the potential activity on Ca2+ signaling. Both molecules were also found to be moderately cytotoxic in longer duration bioassays, with in vitro IC50 values of 1-10 µM against CCRF-CEM human T lymphoblastoid cells and U937 human histiocytic lymphoma cells. These formerly undiscovered bioactivities of known compound 2 expand upon its previously reported function as a selective CXCR7 agonist among 168 GPCR targets.

Luquilloamides, Cytotoxic Lipopeptides from a Puerto Rican Collection of the Filamentous Marine Cyanobacterium Oscillatoria sp.

Luquilloamides A-G (1-7) were isolated from a small environmental collection of a marine cyanobacterium found growing on eelgrass (Zostera sp.) near Luquillo, Puerto Rico. Structure elucidation of the luquilloamides was accomplished via detailed NMR and MS analyses, and absolute configurations were determined using a combination of advanced Mosher's method, J-based configuration analysis, semisynthetic fragment analysis derived from ozonolysis, methylation, Baeyer-Villiger oxidation, Mosher's esterification, specific rotations, and ECD data. Except for 2, the luquilloamides share a characteristic tert-butyl-containing polyketide fragment, ß-alanine, and a proposed highly modified polyketide extension. While compound 1 is a linear lipopeptide with two α-methyl branches and a vinyl chloride functionality in the polyketide portion, compounds 4, 6, and 7 possess a cyclohexanone structure with methylation on the α- or ß-positions of the polyketide as well as an acetyl group. Interestingly, the absolute configuration at C-5 and C-6 on the cyclohexanone unit in 7 is opposite to that of 4-6. Compound 3 was revealed to have a tert-butyl-containing polyketide, ß-alanine, and a PKS/NRPS-derived γ-isopropyl pyrrolinone. Compound 2 may be a hydrolysis product of 3. Of the seven new compounds, 1 showed the most potent cytotoxicity to human H-460 lung cancer cells.

In vitro assessment of dual (antiviral and antitumor) activity of a novel lectin produced by the newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1.

A novel lectin was purified from newly cyanobacterium isolate, Oscillatoria acuminate MHM-632 MK014210.1 using affinity chromatography with a molecular weight of 120 kDa under native-PAGE and 30 kDa on reducing-PAGE, represented tetramer nature of this lectin. Oscillatorial lectin showed stability at 60 °C for 30 min, pH-dependent, with the highest activities over the pH range of 6-8, and required zinc ions to express its full activity. Oscillatorial lectin is a glycan-binding protein with a neutral carbohydrate content of 7.0% as evaluated by the phenol-sulfuric acid method. Polyols and α- glycosides polymer of mannose sugar or sugars alcohol were completely inhibited oscillatorial lectin with MIC of 0.195 mM, while ß-glycosides sugars did not show any inhibition effect. The oscillatorial lectin has anti-proliferative activity against Huh-7 and MCF-7 cancer cells and inhibited their proliferation with EC50 values of 106.75 µg/ml and 254.14 µg/ml, respectively. Besides the anticancer effect, oscillatorial lectin also has potent antiviral activity against HSV-1 in a dose-dependent manner via virions neutralization and inhibition of viral replication with IC50 values of 90.95 ng/ml and 131.3 ng/ml, respectively. The unique carbohydrate affinity of oscillatorial lectin provides insight into its use as a promising candidate in many biotechnological applications, like fighting viral infection and combating cancer disease.Communicated by Ramaswamy H. Sarma.

Removal of malachite green and mixed dyes from aqueous and textile effluents using acclimatized and sonicated microalgal (Oscillatoria sp.) biosorbents and process optimization using the response surface methodology.

Synthetic dyes are toxic and their release into the environment harms the ecosystem. Phycoremediation of synthetic dyes with acclimatized and native species has advantages over other methods. In this study, textile effluent-acclimatized microalgae species of Oscillatoria were grown in Bold's Basal Medium (BBM), dried, powdered using sonication, and optimized the removal malachite green (MG), using the response surface methodology (RSM). The effects of algal biosorbent concentration (AC), pH, and contact time (CT) were studied with 1 g L-1 MG in an aqueous solution, and the interaction model exerted significance (p < 0.001). The removal of MG was higher at alkaline pH (90% at pH 8.5) than at acidic pH (70% at pH 4). Under the optimized conditions of 1.2 g L-1 AC, 8.5 pH, and 30 min CT, the MG removal was documented at 90.8% with the biosorption capacity of 757 mg g-1. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis revealed the occurrence of different electronegative functional groups, aromatic vibrations, and the crystalline nature of the biosorbent. The algal sorbent exhibited a good performance of 80.9% for the removal of the crude color in real textile effluents. This microalgal sorbent is an attractive option for promoting large-scale applications.

This study used an algal (Oscillatoria sp.,) biosorbent isolated from textile effluents, and it was acclimatized to a particular effluent (synthetic dye). This biosorbent was prepared using the sonication method and sieved using a 50-µm mesh. With this novel approach of biosorbent preparation (acclimatization and sonication), this study demonstrated the maximum adsorption capacity of malachite green at 757 mg g⁻¹ biosorbent under optimized conditions (1.2 g of biosorbent, pH 8.5, and a contact time of 30 min). This algal biosorbent and preparation methods will have a huge impact on the wastewater treatment technology and possible applications at a large scale.HIGHLIGHTSBiosorbent was prepared using sonication of Oscillatoria sp., acclimatized to textile effluent.RSM revealed the optimized conditions of 1.2 g L⁻¹ biosordent, 8.5 pH and 30 min contact time with 90% removal of malachite green (MG)Maximum biosorption capacity of 757 mg g⁻¹ biosorbent was observed significantlyElectronegative functional groups and the crystalline nature were liable for the biosorption.Under optimized conditions, 81% of crude color was removed from real textile effluent.

Microalgal competence in urban wastewater management: phycoremediation and lipid production.

The present study was conducted to assess the strain aptness, phycoremediation potential and lipid yield in microalgae Chloroccocum humicola and Oscillatoria sp. Results revealed that microalgae treated with different concentration of wastewater (25%, 50%, 75% and 100%) recovered nutrients (Nitrogen: 50.55-85.90%, Phosphorus: 69.98-93.72%) and removed heavy metals (24.17-88.10%) from wastewater. Microalgae C. humicola showed significant reduction in physico-chemical parameters of wastewater at 25% and 50% respectively with considerable increase in lipid production (1.61 folds) at 50% wastewater concentration. In order to counterbalance the wastewater induced toxicity, both microalgae exhibited stimulated antioxidants viz., proline (1.26-4.04 folds), ascorbic acid (1.01-9.21 folds), cysteine (1.44-4.92 folds), catalase (0.99-3.63 folds), superoxide dismutase (1.15-1.43 folds) and glutathione reductase (1.43-6.67 folds) at different wastewater concentrations. Further, Fourier transforms infrared spectroscopy spectral elucidation of Chloroccocum humicola at 50% reflected high lipid peak in the regions 3000-2800 cm-1 as compared to Oscillatoria sp. Thus, growth characteristics, biochemical responses and lipid yield presented the suitability of the Chloroccocum humicola to be used in phycoremedation, resource recovery as well as lipid production, which may be further utilized as potent feedstock for third generation energy demand.

Direct Observation of Ultrafast Proton Rocking in the BLUF Domain.

We present direct observation of ultrafast proton rocking in the central motif of a BLUF domain protein scaffold. The mutant design has taken consideration of modulating the proton-coupled electron transfer (PCET) driving forces by replacing Tyr in the original motif with Trp, in order to remove the interference of a competing electron transfer pathway. Using femtosecond pump-probe spectroscopy and detailed kinetics analysis, we resolved an electron-transfer-coupled Grotthuss-type forward and reverse proton rocking along the FMN-Gln-Trp proton relay chain. The rates of forward and reverse proton transfer are determined to be very close, namely 51 ps vs. 52 ps. The kinetic isotope effect (KIE) constants associated with the forward and reverse proton transfer are 3.9 and 5.3, respectively. The observation of ultrafast proton rocking is not only a crucial step towards revealing the nature of proton relay in the BLUF domain, but also provides a new paradigm of proton transfer in proteins for theoretical investigations.