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.

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.

Protochromic absorption changes in the two-cysteine photocycle of a blue/orange cyanobacteriochrome.

Cyanobacteriochromes (CBCRs) are phytochrome-related photosensors with diverse spectral sensitivities spanning the entire visible spectrum. They covalently bind bilin chromophores via conserved cysteine residues and undergo 15Z/15E bilin photoisomerization upon light illumination. CBCR subfamilies absorbing violet-blue light use an additional cysteine residue to form a second bilin-thiol adduct in a two-Cys photocycle. However, the process of second thiol adduct formation is incompletely understood, especially the involvement of the bilin protonation state. Here, we focused on the Oscil6304_2705 protein from the cyanobacterium Oscillatoria acuminata PCC 6304, which photoconverts between a blue-absorbing 15Z state ( 15Z Pb) and orange-absorbing 15E state ( 15E Po). pH titration analysis revealed that 15Z Pb was stable over a wide pH range, suggesting that bilin protonation is stabilized by a second thiol adduct. As revealed by resonance Raman spectroscopy, 15E Po harbored protonated bilin at both acidic and neutral pH, but readily converted to a deprotonated green-absorbing 15Z state ( 15Z Pg) at alkaline pH. Site-directed mutagenesis revealed that the conserved Asp-71 and His-102 residues are required for second thiol adduct formation in 15Z Pb and bilin protonation in 15E Po, respectively. An Oscil6304_2705 variant lacking the second cysteine residue, Cys-73, photoconverted between deprotonated 15Z Pg and protonated 15E Pr, similarly to the protochromic photocycle of the green/red CBCR subfamily. Time-resolved spectroscopy revealed 15Z Pg formation as an intermediate in the 15E Pr-to- 15Z Pg conversion with a significant solvent-isotope effect, suggesting the sequential occurrence of 15EP-to-15Z photoisomerization, deprotonation, and second thiol adduct formation. Our findings uncover the details of protochromic absorption changes underlying the two-Cys photocycle of violet-blue-absorbing CBCR subfamilies.

Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica.

Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30-17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

Application of high-mannose-type glycan-specific lectin from Oscillatoria Agardhii for affinity isolation of tumor-derived extracellular vesicles.

Tumor cells secrete membrane vesicles of various sizes, termed extracellular vesicles (EVs), which have gained increasing attention as potential tumor diagnostic markers. Tumor-derived EVs are enriched with high-mannose-type glycans. Here, we report the affinity isolation of EVs from human melanoma A375 cells by using high-mannose-type glycan-specific agglutinin from Oscillatoria Agardhii (OAA). Glycan analysis of melanoma EVs revealed the presence of high-mannose-type glycans with structural units preferred by OAA. We showed that in solution, OAA binds to melanoma EVs in a high-mannose-type glycan-dependent manner. Furthermore, OAA-immobilized beads were found to capture 60% of the particles and most proteinous components from melanoma EVs. Major EV glycoproteins that potentially interact with OAA were identified to be cluster of differentiation 109 (CD109), integrin α6 and a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10). In addition to melanoma EVs, OAA captured EVs from human lung cancer, glioblastoma and colon cancer cells, but not those from endothelial cells and fibroblasts. These results indicate that OAA-immobilized beads may serve as a novel platform for affinity-capture of tumor-derived EVs.

Study of capability of nanostructured zero-valent iron and graphene oxide for bioremoval of trinitrophenol from wastewater in a bubble column bioreactor

BACKGROUND: Bioremoval of phenolic compounds using fungi and bacteria has been studied extensively; nevertheless, trinitrophenol bioremediation using modified Oscillatoria cyanobacteria has been barely studied in the literature. RESULTS: Among the effective parameters of bioremediation, algal concentration (3.18 g·L−1 ), trinitrophenol concentration (1301 mg·L−1 ), and reaction time (3.75 d) were screened by statistical analysis. Oscillatoria cyanobacteria were modified by starch/nZVI and starch/graphene oxide in a bubble column bioreactor, and their bioremoval efficiency was investigated. Modifiers, namely, starch/zero-valent iron and starch/GO, increased trinitrophenol bioremoval efficiency by more than 10% and 12%, respectively, as compared to the use of Oscillatoria cyanobacteria alone. Conclusions: It was found that starch/nano zero-valent iron and starch/GO could be applied to improve the removal rate of phenolic compounds from the aqueous solution.

The C-terminal region affects the activity of photoactivated adenylyl cyclase from Oscillatoria acuminata.

Photoactivated adenylyl cyclase (PAC) is a unique protein that, upon blue light exposure, catalyzes cAMP production. The crystal structures of two PACs, from Oscillatoria acuminata (OaPAC) and Beggiatoa sp. (bPAC), have been solved, and they show a high degree of similarity. However, the photoactivity of OaPAC is much lower than that of bPAC, and the regulatory mechanism of PAC photoactivity, which induces the difference in activity between OaPAC and bPAC, has not yet been clarified. Here, we investigated the role of the C-terminal region in OaPAC, the length of which is the only notable difference from bPAC. We found that the photoactivity of OaPAC was inversely proportional to the C-terminal length. However, the deletion of more than nine amino acids did not further increase the activity, indicating that the nine amino acids at the C-terminal critically affect the photoactivity. Besides, absorption spectral features of light-sensing domains (BLUF domains) of the C-terminal deletion mutants showed similar light-dependent spectral shifts as in WT, indicating that the C-terminal region influences the activity without interacting with the BLUF domain. The study characterizes new PAC mutants with modified photoactivities, which could be useful as optogenetics tools.

Molecular mechanism of photoactivation of a light-regulated adenylate cyclase.

The photoactivated adenylate cyclase (PAC) from the photosynthetic cyanobacterium Oscillatoria acuminata (OaPAC) detects light through a flavin chromophore within the N-terminal BLUF domain. BLUF domains have been found in a number of different light-activated proteins, but with different relative orientations. The two BLUF domains of OaPAC are found in close contact with each other, forming a coiled coil at their interface. Crystallization does not impede the activity switching of the enzyme, but flash cooling the crystals to cryogenic temperatures prevents the signature spectral changes that occur on photoactivation/deactivation. High-resolution crystallographic analysis of OaPAC in the fully activated state has been achieved by cryocooling the crystals immediately after light exposure. Comparison of the isomorphous light- and dark-state structures shows that the active site undergoes minimal changes, yet enzyme activity may increase up to 50-fold, depending on conditions. The OaPAC models will assist the development of simple, direct means to raise the cyclic AMP levels of living cells by light, and other tools for optogenetics.

Sampling of Glycan-Bound Conformers by the Anti-HIV Lectin Oscillatoria agardhii agglutinin in the Absence of Sugar.

Lectins from different sources have been shown to interfere with HIV infection by binding to the sugars of viral-envelope glycoproteins. Three-dimensional atomic structures of a number of HIV-inactivating lectins have been determined, both as free proteins and in glycan-bound forms. However, details on the mechanism of recognition and binding to sugars are elusive. Herein we focus on the anti-HIV lectin OAA from Oscillatoria agardhii: We show that in the absence of sugars in solution, both the sugar-free and sugar-bound protein conformations that were observed in the X-ray crystal structures exist as conformational substates. Our results suggest that glycan recognition occurs by conformational selection within the ground state; this model differs from the popular "excited-state" model. Our findings provide further insight into molecular recognition of the major receptor on the HIV virus by OAA. These details can potentially be used for the optimization and/or development of preventive anti-HIV therapeutics.

Almiramide D, cytotoxic peptide from the marine cyanobacterium Oscillatoria nigroviridis.

Marine benthic cyanobacteria are widely known as a source of toxic and potentially useful compounds.These microorganisms have been studied from many Caribbean locations, which recently include locations in the Colombian Caribbean Sea. In the present study, six lipopeptides named almiramides D to H, together with the known almiramide B are identified from a mat characterized as Oscillatoria nigroviridis collected at the Island of Providence (Colombia, S.W. Caribbean Sea). The most abundant compounds, almiramides B and D were characterized by NMR and HRESIMS, while the structures of the minor compounds almiramides E to H were proposed by the analysis of their HRESIMS and MS2 spectra. Almiramides B and D were tested against six human cell lines including a gingival fibroblast cell line and five human tumor cell lines (A549, MDA-MB231, MCF-7, HeLa and PC3) showing a strong but not selective toxicity.

Broad anti-HIV activity of the Oscillatoria agardhii agglutinin homologue lectin family.

OBJECTIVES: Oscillatoria agardhii agglutinin homologue (OAAH) proteins belong to a recently discovered lectin family. The founding member OAA and a designed hybrid OAAH (OPA) recognize similar but unique carbohydrate structures of Man-9, compared with other antiviral carbohydrate-binding agents (CBAs). These two newly described CBAs were evaluated for their inactivating properties on HIV replication and transmission and for their potential as microbicides. METHODS: Various cellular assays were used to determine antiviral activity against wild-type and certain CBA-resistant HIV-1 strains: (i) free HIV virion infection in human T lymphoma cell lines and PBMCs; (ii) syncytium formation assay using persistently HIV-infected T cells and non-infected CD4+ T cells; (iii) DC-SIGN-mediated viral capture; and (iv) transmission to uninfected CD4+ T cells. OAA and OPA were also evaluated for their mitogenic properties and potential synergistic effects using other CBAs. RESULTS: OAA and OPA inhibit HIV replication, syncytium formation between HIV-1-infected and uninfected T cells, DC-SIGN-mediated HIV-1 capture and transmission to CD4+ target T cells, thereby rendering a variety of HIV-1 and HIV-2 clinical isolates non-infectious, independent of their coreceptor use. Both CBAs competitively inhibit the binding of the Manα(1-2)Man-specific 2G12 monoclonal antibody (mAb) as shown by flow cytometry and surface plasmon resonance analysis. The HIV-1 NL4.3(2G12res), NL4.3(MVNres) and IIIB(GRFTres) strains were equally inhibited as the wild-type HIV-1 strains by these CBAs. Combination studies indicate that OAA and OPA act synergistically with Hippeastrum hybrid agglutinin, 2G12 mAb and griffithsin (GRFT), with the exception of OPA/GRFT. CONCLUSIONS: OAA and OPA are unique CBAs with broad-spectrum anti-HIV activity; however, further optimization will be necessary for microbicidal application.

Structural insights into the anti-HIV activity of the Oscillatoria agardhii agglutinin homolog lectin family.

Oscillatoria agardhii agglutinin homolog (OAAH) proteins belong to a recently discovered lectin family. All members contain a sequence repeat of ~66 amino acids, with the number of repeats varying among different family members. Apart from data for the founding member OAA, neither three-dimensional structures, information about carbohydrate binding specificities, nor antiviral activity data have been available up to now for any other members of the OAAH family. To elucidate the structural basis for the antiviral mechanism of OAAHs, we determined the crystal structures of Pseudomonas fluorescens and Myxococcus xanthus lectins. Both proteins exhibit the same fold, resembling the founding family member, OAA, with minor differences in loop conformations. Carbohydrate binding studies by NMR and x-ray structures of glycan-lectin complexes reveal that the number of sugar binding sites corresponds to the number of sequence repeats in each protein. As for OAA, tight and specific binding to α3,α6-mannopentaose was observed. All the OAAH proteins described here exhibit potent anti-HIV activity at comparable levels. Altogether, our results provide structural details of the protein-carbohydrate interaction for this novel lectin family and insights into the molecular basis of their HIV inactivation properties.

Ability to use the diazo dye, C.I. Acid Black 1 as a nitrogen source by the marine cyanobacterium Oscillatoria curviceps BDU92191.

Ten different strains of marine cyanobacteria were tested for their ability to decolourise and degrade a recalcitrant diazo dye, C.I. Acid Black 1. Of them, Oscillatoria curvicepsBDU92191 was able to grow up to a tested concentration of 500 mG L(-1). The organism degraded 84% of the dye at 100 mG L(-1) in 8 days in a medium free of combined nitrogen. The dye degrading ability is attributed to the activities of the enzymes: laccase, polyphenol oxidase and azoreductase. The absence of the doublet amine peak in addition to the overall reduction of absorption in the IR spectra confirmed the mineralisation of the tested azo dye. The nitrogen assimilating enzyme studies along with nitrogenase assay strongly suggested the ability of the non-heterocystous, filamentous marine cyanobacterium, O. curvicepsBDU92191 to use C.I. Acid Black 1 as a nitrogen source in an oligotrophic environment.

Removal of cadmium(II) ion from aqueous system by dry biomass, immobilized live and heat-inactivated Oscillatoria sp. H1 isolated from freshwater (Mogan Lake).

Oscillatoria sp. H1 (Cyanobacteria, microalgae) isolated from Mogan Lake was used for the removal of cadmium ions from aqueous solutions as its dry biomass, alive and heat-inactivated immobilized form on Ca-alginate. Particularly, the effect of physicochemical parameters like pH, initial concentration and contact time were investigated. The sorption of Cd(II) ions on the sorbent used was examined for the cadmium concentrations within the range of 25-250 mg/L. The biosorption of Cd(II) increased as the initial concentration of Cd(II) ions increased in the medium up to 100 mg/L. Maximum biosorption capacities for plain alginate beads, dry biomass, immobilized live Oscillatoria sp. H1 and immobilized heat-inactivated Oscillatoria sp. H1 were 21.2, 30.1, 32.2 and 27.5 mg/g, respectively. Biosorption equilibrium was established in about 1 h for the biosorption processes. The biosorption was well described by Langmuir and Freundlich adsorption isotherms. Maximum adsorption was observed at pH 6.0. The alginate-algae beads could be regenerated using 50 mL of 0.1 mol/L HCl solution with about 85% recovery.