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.

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.

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.

Bioaugmentation and bioaugmentation-assisted phytoremediation of heavy metal contaminated soil by a synergistic effect of cyanobacteria inoculation, biochar, and purslane (Portulaca oleracea L.).

In recent decades, soil contamination with heavy metals has become an environmental crisis due to their long-term stability and adverse biological effects. Therefore, bioremediation is an eco-friendly technology to remediate contaminated soil, which the efficiency requires further research. This study was designed to comparatively investigate two strategies: bioaugmentation by using a cyanobacterial species (Oscillatoria sp.) and bioaugmentation-assisted phytoremediation by using Oscillatoria sp. and purslane (Portulaca oleracea L.) for the bioremediation of soil contaminated by heavy metals (Cr (III), Cr (VI), Fe, Al, and Zn). Various quantities of biochar (0.5, 2, and 5% (w/w)) were used as an amendment in the experiments to facilitate the remediation process. The results of the bioaugmentation test showed that applying biochar and cyanobacteria into contaminated soil significantly increased the chlorophyll a, nitrogen, and organic carbon contents. In contrast, the extractable fractions of Cr (III), Cr (VI), Zn, Al, and Fe declined compared with those of the control treatment. The highest reduction content (up to 87 %) in the extractable portion was obtained for Cr (VI). The development of longer root and hypocotyl lengths and vigour index from lettuces and radish seeds grown in the remediated soil confirmed the success of remediation treatments. Moreover, the findings of the bioaugmentation-assisted phytoremediation test displayed a reduction in the bioavailable fraction of Cr (III), Cr (VI), Zn, Al, and Fe. Cr (III) presented the highest reduction (up to 90 %) in metal bioavailability. With cyanobacteria inoculation and biochar addition, the shoot and root lengths of purslane grew 4.6 and 3-fold while the heavy metal accumulation decreased significantly. Besides, these treatments enhanced the tolerance index (TI) quantities of purslane whereas diminished its bioaccumulation coefficient (BAC) and bioconcentration factor (BCF) values. For all heavy metals (except Zn), translocation factor (TF) and BAC values were found to be less than 1.0 at all treatments, indicating the successful phytoextraction by the purslane. These results suggest that the purslane can be considered an excellent phytoextracting agent for soils contaminated with heavy metals.

Effects of the interaction between nutrient concentration and DIN:SRP ratio on geosmin production by freshwater biofilms.

The global increase of cyanobacterial blooms occurrence has been associated with the presence of compounds that generate earthy and musty odor in freshwater systems, among which geosmin stands out. The lack of information on the factors associated to geosmin production by benthic organisms has driven the development of this study, whose main goal is to determine the effects of nutrient concentration and DIN:SRP ratio on geosmin formation and release. The experiment was performed in 18 microcosms under controlled conditions for 21 days, using a natural biofilm suspension from Ter river (NE, Spain) to promote biofilm settlement. Six treatments were set crossing three DIN:SRP ratios (A = 4:1, B = 16:1 and C = 64:1) with two nutrient concentrations (Low and High). After 7 days of experiment, geosmin was detected in biofilm, being higher under high nutrient concentration and low DIN:SRP ratio conditions. In this treatment, geosmin in biofilm reached its maximum concentration at day 16 (3.8 ± 0.9 ng/mg), decreasing at the end of the experiment (21d) due to cyanobacteria detachment and geosmin release into the water (136 ± 6 ng/L). Overall, this experimental study showed that high nutrient concentration and low DIN:SRP ratio favored the Oscillatoria genus development within biofilm communities, generating the optimal conditions for geosmin production. The interaction between these two factors was demonstrated to be a potential driver of benthic geosmin production and release, and should be monitored and controlled in rivers exploited for drinking water purposes.

Simultaneous bioelectricity generation and water desalination using Oscillatoria sp. as biocatalyst in photosynthetic microbial desalination cell.

Globally, the scarcity of drinking water has triggered the researchers towards the development of desalination techniques to turn up saline water into potable. Microbial Desalination Cell (MDC) is a novel green technology that shows potential approach for desalination along with electricity generation and wastewater treatment. However, the expensive catholyte/catalyst in the cathode side has limited the MDC for real time application. Hence, the main objective of this work was to investigate the electricity generation during dairy wastewater treatment and desalination efficiency using biocathode (Oscillatoria sp.) in the MDC. The results showed that the maximum open circuit voltage of 652 ± 10 mV, COD removal efficiency of 80.2 ± 0.5% and desalination efficiency of 65.8 ± 0.5%, were achieved respectively. The effect of saline water concentration was investigated and the performance of MDC was compared with real (sea) water. This study demonstrated that Oscillatoria sp. could be used as a potential biocatalyst in the cathode chamber for enhancing salinity removal along with electricity generation and wastewater treatment in the MDC.

Phycocyanin of marine Oscillatoria sp. inhibits lipoxygenase by protein-protein interaction-induced change of active site entry apace: A model for non-specific biofunctions of phycocyanins.

An overview of the biological properties of phycocyanin (PC) amply illustrates that it may not have any specific functional feature towards any system at which it may elicit a specific function, but for the molecular interactions. Nevertheless, based on existing evidences, it is hypothesized that PC has more than one functional target with the interacting systems; therefore, it has diversity of effects. The mechanism of PC action remains elusive of a comprehensive idea. The present investigation focuses on the pro inflammatory enzyme, lipoxygenase (LOX) inhibiting property of PC purified from Oscillatoria sp. Enzyme kinetics studies show that the molecular composite of PC is required for its inhibition shown on LOX. Isothermal titration calorimetric study proves that one molecule of PC interacts with two molecules of LOX. Molecular dynamics simulation study pertaining to PC-LOX interactions shows it to be appropriate as a model to give molecular mechanistic insight into the varied biological properties of PC, demonstrated elsewhere in experimental studies including animal model studies. It explains that the PC-LOX interaction is of a function-freezing, protein-protein interaction in nature. The wide spectrum of properties of PC might be due to its function as a powerful protein hub showing non-specific protein-protein interactions.

Evaluation of heavy metal pollution in the Zayandeh-Rud River as the only permanent river in the central plateau of Iran.

Zayandeh-Rud River is the only permanent river in the central plateau of Iran. This river has been subject to an extensive discharge of wastewater and effluents from several point and nonpoint pollution sources. Accordingly, sediment quality of Zayandeh-Rud River in Varzaneh region, were studied. Algae and the sediment were sampled through 3 replications at 6 stations in the downstream after crossing through the Isfahan city and reaching Gavkhuni international wetland. Chlorophyll content and As, Pb, and Cd concentrations were measured in each sample Cladophora sp. and Oscillatoria sp. were identified using standard identification keys. The mean concentrations of metals in all stations exceeded background levels. Mean concentration of arsenic (162.9 mg/kg) in the sediment is about 31 times more than the ISQG standard (5.9 mg/kg) and considerably higher than the similar studies in Iran and other regions of the world. The mean concentration of As in algae samples is higher than the most polluted areas of the world. The mean concentration of Pb in the sediment (19.69 mg/kg) is lower than the ISQGs standard (35 mg/kg) and most of the studied river in north of Iran such as Chalous, Baboul-Rud, Gorgan-Rud (North), Khiav (North West), and Anzali wetland. The mean concentration of Cd in the sediment (2.11 mg/kg) is significantly higher than ISQG standard (0.6 mg/kg and some north highly polluted wetlands of Iran such as Anzali. There is a significant positive correlation between the mean concentrations of As and Pb in the sediment and Cladophora sp. tissue, and a negative one between the mean concentration of Pb in the sediment and chlorophyll b/a. There are significant negative correlations between the mean concentration of As in the sediment and chlorophyll a, and the total chlorophyll concentration in Oscillatoria sp. The results of Muller index indicate that the concentrations of Pb, Cd, and As in all stations occur in the Unpolluted, Moderate/Heavy, and Heavy/Extreme groups, respectively. Degree of contamination and modified degree of contamination show very high degree of pollution in the studied area. RI in all the stations showed very high ecological risk. The bioaccumulation factor for all metals in both algae is less than one. So, these two species may not be described as heavy metal accumulators. This study is an alarm for the Zayandeh-Rud River as the most important freshwater source for the Iranian Plateau. Graphical abstract.

Physiological differences between free-floating and periphytic filamentous algae, and specific submerged macrophytes induce proliferation of filamentous algae: A novel implication for lake restoration.

Restoration of submerged macrophytes is widely applied to counteract eutrophication in shallow lakes. However, proliferation and accumulation of filamentous algae (possessing free-floating and periphytic life forms) hamper growth of submerged macrophytes. Here, we explored factors triggering the excessive proliferation of filamentous algae during lake restoration using field investigations and laboratory experiments. Results showed that, compared with free-floating Oscillatoria sp. (FO), periphytic Oscillatoria sp. (PO) showed faster growth rate, greater photosynthetic capacities and higher phosphorus (P) affinity. Therefore, PO was physiologically competitively superior to FO under low P concentration and improved light conditions. And proliferation of filamentous algae was mainly manifested in periphytic life form. Besides, field results showed that density of filamentous algae in water column might be related to substrate types. Some macrophyte (Ceratophyllum oryzetorum and Potamogeton crispus) might provide proper substrates for proliferation of filamentous algae. Further physiological experiments found that Oscillatoria showed specific eco-physiological responses to different macrophyte species. Hydrilla verticillata and C. oryzetorum promoted growth and photosynthetic activity of Oscillatoria, while Potamogeton malaianus inhibited growth and P uptake of PO. Myriophyllum spicatum exhibited no impact on growth of Oscillatoria. Our results revealed the intrinsic (physiological differences between free-floating and periphytic life forms of filamentous algae) and extrinsic (different macrophytes) factors affect the proliferation of filamentous algae, which are important for guidance on planting of submerged macrophytes during lake restoration.

Green synthesis of silver nanoparticle using Oscillatoria sp. extract, its antibacterial, antibiofilm potential and cytotoxicity activity.

Green route biosynthesis of silver nanoparticles (SNPs) using methanol extract of Oscillatoria sp. was investigated. The nanoparticles (OsSNPs) were characterized by UV-Vis spectrophotometry, FTIR, SEM, Thermogravimetry, EDX and DLS. The antibacterial, antibiofilm and in vitro cytotoxicity activity of the OsSNPs was determined. Surface Plasmon Resonance peak was at 500 nm. Functional groups such as hydroxyl; alcohol, phosphate, and amine among others were responsible for the capping and stabilization of proteins in the nanoparticles. The OsSNPs were spherical with size of 10 nm and are thermostable to an extent without totally losing its weight. EDX analysis revealed a strong signal of silver element. DLS shows the particle diameter average of 0.000 nm and 558.1 nm with a polydispersity index of 0.580. The OsSNPs had effective antibacterial activity against the test bacterial pathogens with zone of inhibition ranged from 1 - 21 mm. OsSNPs exhibited strong antibiofilm activity. However, the toxicity of the OsSNPs to Artemia salina (brine shrimp) was observed to be insignificant with the highest mortality at 4000 µg/mL and lethal dose (LC50) of 2630.3 µg/mL. Greenly synthesized OsSNPs had effective antibacterial potency and low cytotoxicity which suggests its use in biomedical and pharmacological applications.

Adaptation dynamics and evolutionary rescue under sulfide selection in cyanobacteria: a comparative study between Microcystis aeruginosa and Oscillatoria sp. (cyanobacteria).

Experimental evolution studies using cyanobacteria as model organisms are scarce despite the role of cyanobacteria in the evolution of photosynthesis. Three different experimental evolution approaches have been applied to shed light on the sulfide adaptation process, which played a key role in the evolution of this group. We used a Microcystis aeruginosa sulfide-sensitive strain, unable to grow above ~0.1 mM, and an Oscillatoria sp. strain, isolated from a sulfureous spa (~0.2 mM total sulfide). First, performing a fluctuation analysis design using the spa waters as selective agent, we proved that M. aeruginosa was able to adapt to this sulfide level by rare spontaneous mutations. Second, applying a ratchet protocol, we tested if the limit of adaptation to sulfide of the two taxa was dependent on their initial sulfide tolerance, finding that M. aeruginosa adapted to 0.4 mM sulfide, and Oscillatoria sp. to ~2 mM sulfide, twice it highest tolerance level. Third, using an evolutionary rescue approach, we observed that both speed of exposure to increasing sulfide concentrations (deterioration rate) and populations' genetic variation determined the survival of M. aeruginosa at lethal sulfide levels, with a higher dependence on genetic diversity. In conclusion, sulfide adaptation of sensitive cyanobacterial strains is possible by rare spontaneous mutations and the adaptation limits depend on the sulfide level present in strain's original habitat. The high genetic diversity of a sulfide-sensitive strain, even at fast environmental deterioration rates, could increase its possibility of survival even to a severe sulfide stress.

MS/MS-Based Molecular Networking Approach for the Detection of Aplysiatoxin-Related Compounds in Environmental Marine Cyanobacteria.

Certain strains of cyanobacteria produce a wide array of cyanotoxins, such as microcystins, lyngbyatoxins and aplysiatoxins, that are associated with public health issues. In this pilot study, an approach combining LC-MS/MS and molecular networking was employed as a rapid analytical method to detect aplysiatoxins present in four environmental marine cyanobacterial samples collected from intertidal areas in Singapore. Based on 16S-ITS rRNA gene sequences, these filamentous cyanobacterial samples collected from Pulau Hantu were determined as Trichodesmium erythraeum, Oscillatoria sp. PAB-2 and Okeania sp. PNG05-4. Organic extracts were prepared and analyzed on LC-HRMS/MS and Global Natural Product Social Molecular Networking (GNPS) for the presence of aplysiatoxin-related molecules. From the molecular networking, six known compounds, debromoaplysiatoxin (1), anhydrodebromoaplysiatoxin (2), 3-methoxydebromoaplysiatoxin (3), aplysiatoxin (4), oscillatoxin A (5) and 31-noroscillatoxin B (6), as well as potential new analogues, were detected in these samples. In addition, differences and similarities in molecular networking clusters related to the aplysiatoxin molecular family were observed in extracts of Trichodesmium erythraeum collected from two different locations and from different cyanobacterial species found at Pulau Hantu, respectively.

Worse than cell lysis: The resilience of Oscillatoria sp. during sludge storage in drinking water treatment.

Benthic Oscillatoria sp. may form dense surface blooms especially under eutrophic and calm conditions, which poses a threat to drinking water safety because it can produce toxic and odorous metabolites. This is the first study to investigate the effect of the conventional coagulant polyaluminium ferric chloride (PAFC) on removal of Oscillatoria sp., and the behavior of Oscillatoria sp. cells in sludges formed from different dosages of PAFC (control, optimum, and overdose system) during storage was also studied. Oscillatoria sp. cells can be removed efficiently by coagulation of PAFC. The adverse environmental stresses of sludge, such as lack of light and anoxic environment, decrease cell viability and induce the increase of superoxide dismutase activity (SOD) and malondialdehyde content (MDA) in Oscillatoria sp. cells during the first 4 days. Because Oscillatoria sp. can adapt to the low-light and hypoxic circumstances in sludge gradually, the cells regrow with prolonged storage time. Compared to planktonic Microcystis aeruginosa and Cylindrospermopsis raciborskii, regrowth of Oscillatoria sp. during storage may present a bigger threat, even though Microcystis aeruginosa and Cylindrospermopsis raciborskii cells will be damaged and release toxic compounds. Growth rates of algae in coagulated systems were lower than that in control system because of the restriction of flocs. It is worth noting that the chlorophyll a level was increased by a factor of 3.5 in the optimal-dose system, and worse, the overdose system increased by a factor of 6 in chlorophyll a after 8 d storage due to the benefit of higher Fe levels. Concentrations of extracellular geosmin and cylindrospermopsin also increased during storage, especially after 4 d, and varied in the following sequence for a given storage duration: control system > overdose system > optimum system. Overall, due to decrease of SOD and MDA in Oscillatoria sp. cells after 4 d storage, algae cells regrew rapidly, especially in overdose system. Hence, sludge should be treated within 4 d and excess PAFC dosing should be avoided.

Cyanobacteria growing on tree barks possess high amount of sunscreen compound mycosporine-like amino acids (MAAs).

The present study describes cyanobacterial species composition and their dominance in biological crusts from barks of different trees, roof top of building and soil of agricultural field. An attempt was also made to explore the presence of photoprotective compounds such as mycosporine-like amino acids (MAAs) in the crust samples. Microscopic examination and growth studies revealed the presence of Oscillatoria species in all the crust samples excluding the crust of roof top of a building. Study on the abundance of dominant genera showed marked differences among various crust samples but Hapalosiphon, Lyngbya, Oscillatoria and Scytonema sp. were the most dominant genera, Oscillatoria being dominant in three crust samples. Screening for the presence of photoprotective compounds showed the presence of major peaks in the range of 308-334 nm thereby pointing to the presence of MAAs in all the crust samples. The highest amount of MAAs was found in the crust of Borassus flabellifer (15,729 nmol g dry wt-1 of bark) followed by crust of roof top (14,543 nmol g dry wt-1 of crust). MAAs were separated and partially purified employing HPLC, the most common MAA present in all the crusts was identified as mycosporine-glycine. Presence of mycosporine-glycine (M-Gly) was further confirmed by FTIR and NMR. Test of in vitro colonization on the bark of Mangifera indica and Azadirachta indica by three isolates namely Hapalosiphon, Oscillatoria and Scytonema sp. showed sign of active colonization. It is felt that identification of all the MAAs other than M-Gly may prove useful in future studies especially for assessing their significance in the protection mechanism of cyanobacteria/algae against various types of abiotic stresses.

Effects of cyanobacteria Oscillatoria sp. lipopolysaccharide on B cell activation and Toll-like receptor 4 signaling.

Cyanobacteria ("blue-green algae"), such as Oscillatoria sp., are a ubiquitous group of bacteria found in freshwater systems worldwide that are linked to illness and in some cases, death among humans and animals. Exposure to cyanobacteria occurs via ingestion of contaminated water or food-products. Exposure of the gut to these bacteria also exposes their toxins, such as lipopolysaccharide (LPS), to B cells in the gut associated lymphoid tissue. However, the effect of Oscillatoria sp. LPS on B cell activation is unknown. To test the hypothesis that Oscillatoria sp. LPS exposure to murine B cells would result in B cell activation, murine B cells were incubated in the absence or presence of Oscillatoria sp. LPS or E. coli LPS as a positive control. The data indicate that Oscillatoria sp. LPS induces B cells to proliferate, upregulate MHC II and CD86, enhance antigen uptake and induce IgM production at low levels. Additional studies demonstrate that this low level of stimulation may be due to incomplete TLR4 signaling induced by Oscillatoria sp. LPS, since IRF-3 is not induced in B cells after stimulation with Oscillatoria sp. LPS. These findings have important implications for the mechanisms of toxicity of cyanobacteria in both humans and animals.

Crystal structures of aldehyde deformylating oxygenase from Limnothrix sp. KNUA012 and Oscillatoria sp. KNUA011.

The cyanobacterial aldehyde deformylating oxygenase (cADO) is a key enzyme that catalyzes the unusual deformylation of aliphatic aldehydes for alkane biosynthesis and can be applied to the production of biofuel in vitro and in vivo. In this study, we determined crystal structures of two ADOs from Limnothrix sp. KNUA012 (LiADO) and Oscillatoria sp. KNUA011 (OsADO). The structures of LiADO and OsADO resembled those of typical cADOs, consisting of eight α-helices found in ferritin-like di-iron proteins. However, structural comparisons revealed that while the LiADO active site was vacant of iron and substrates, the OsADO active site was fully occupied, containing both a coordinated metal ion and substrate. Previous reports indicated that helix 5 is capable of adopting two distinct conformations depending upon the existence of bound iron. We observed that helix 5 of OsADO with an iron bound in the active site presented as a long helix, whereas helix 5 of LiADO, which lacked iron in the active site, presented two conformations (one long and two short helices), indicating that an equilibrium exists between the two states in solution. Furthermore, acquisition of a structure having a fully occupied active site is unique in the absence of higher iron concentrations as compared with other cADO structures, wherein low affinity for iron complicates the acquisition of crystal structures with bound iron. An in-depth analysis of the ADO apo-enzyme, the enzyme with substrate bound, and the enzyme with both iron and substrate bound provided novel insight into substrate-binding modes in the absence of a coordinated metal ion and suggested a separate two-step binding mechanism for substrate and iron co-factors. Moreover, our results provided a comprehensive structural basis for conformational changes induced by binding of the substrate and co-factor.

Trichormamides C and D, antiproliferative cyclic lipopeptides from the cultured freshwater cyanobacterium cf. Oscillatoria sp. UIC 10045.

Extract from the cultured freshwater cf. Oscillatoria sp. UIC 10045 showed antiproliferative activity against HT-29 cell line. Bioassay-guided fractionation led to the isolation of two new cyclic lipopeptides, named trichormamides C (1) and D (2). The planar structures were determined by combined analyses of HRESIMS, Q-TOF ESIMS/MS, and 1D and 2D NMR spectra. The absolute configurations of the amino acid residues were assigned by advanced Marfey's analysis after partial and complete acid hydrolysis. Trichormamides C (1) is a cyclic undecapeptide and D (2) is a cyclic dodecapeptide, both containing a lipophilic ß-aminodecanoic acid residue. Trichormamide C (1) displayed antiproliferative activities against HT-29 and MDA-MB-435 cancer cell lines with IC50 values of 1.7 and 1.0µM, respectively, as well as anti-Mycobacterium tuberculosis activity with MIC value of 23.8µg/mL (17.3µM). Trichormamide D (2) was found to be less potent against both HT-29 and MDA-MB-435 cancer cell lines with IC50 values of 11.5 and 11.7µM, respectively.

Crecimiento de la cianobacteria marina Oscillatoria sp. MOF-06 en relación al pH en cultivos discontinuos / Growth of the marine cyanobacteria Oscillatoria sp MOF-06 in relation to pH in discontinuous cultures

Se evaluó el crecimiento, contenido de pigmentos, carbohidratos, exopolisacáridos y proteínas en la cianobacteria marina Oscillatoria sp. a pH 6,7,8 y 9 en cultivos discontinuos. Todos los cultivos se realizaron por triplicado en medio de cultivo ALGAL, a 3,5% de salinidad, aireación constante, a 28 ± 2°C, iluminación a 156 μmol quanta m-2 s-1 y fotoperiodo 12:12h. Los cultivos a pH 9 y controles (pH 9-11), alcanzaron los valores más elevados de turbidez y masa seca. El contenido de clorofila a fue superior en fase exponencial, a pH 9 y control, con los valores más bajos a pH 6. La concentración de ficocianina también fue superior a pH 9 y en el control; mientras que a pH 6 y 7 se detectaron los valores más bajos. La concentración de proteínas y de carbohidratos también aumentó con el pH, en el siguiente orden control>9>8>7>6. En cambio, Oscillatoria produjo más exopolisacáridos a pH entre 6 y 8. Estos resultados demuestran que la cianobacteria marina Oscillatoria sp. MOF-06 incrementa la producción de biomasa, contenido de clorofila, proteínas y carbohidratos en condiciones alcalinas; mientras que, se induce una disminución en la producción de exopolisacáridos; pero sin afectar el contenido de carotenoides.

Growth, pigment content, carbohydrates, exopolysacharides and proteins were evaluated in the marine cyanobacteria Oscillatoria sp. in discontinuous cultures at pH 6, 7, 8 and 9. All cultures were done in triplicate in ALGAL culture medium, at 3.5% salinity, constant airing, 28 ± 2ºC, 156 µmol m-2 s-1 illumination, and 12:12h photoperiod. Cultures at pH 9 and controls (pH 9-11), reached the highest turbidity and dry mass values. The α chlorophyll content was higher in the exponential phase, at pH 9 and control, while the  lowest values were detected at pH 6 and 7. Protein and carbohydrate content also increased with pH in the following order: control>9>8>7>6. On the other hand, Oscillatoria produced more exopolysacharides at pHs between 6 and 8. These results show that the marine cyanobacteria Oscillatoria sp. MOF-06 increases its biomass production, and chlorophyll, protein and carbohydrate content under alkaline conditions, while this pH induces a decrease of exopolysacharide production, but without affecting the carotenoid content.