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γ-Glutamylcysteine (γ-EC) has antioxidant properties similar to those of glutathione (GSH) and acts as its precursor in mammals. There are a few procedures for the production of γ-EC, such as chemical synthesis or enzymatic synthesis from glutamate and cysteine; however, they are very costly and not suitable for industrial production. A phytochelatin synthase-like enzyme derived from Nostoc sp. Pasteur Culture Collection 7120 (NsPCS) catalyzes the hydrolysis of GSH to γ-EC and glycine in the absence of ATP or other additives. Our research aims to establish an alternative γ-EC production procedure with low cost and high productivity. To this end, we optimized the reaction conditions of NsPCS and characterized its properties in this study. We found that 200 mM potassium phosphate buffer, pH 8.0, at 37 °C, had the highest NsPCS activity among the conditions we tested. Under these conditions, NsPCS had a Km of 385 µM and a Vmax of 26 mol/min/mg-protein. In addition, NsPCS converted 100 mM GSH into γ-EC with high yields. These results suggest that the NsPCS reaction has great potential for the low-cost, industrial-scale production of γ-EC.

Interactions between Sphagnum (peat moss) and cyanobacteria play critical roles in terrestrial carbon and nitrogen cycling processes. Knowledge of the metabolites exchanged, the physiological processes involved, and the environmental conditions allowing the formation of symbiosis is important for a better understanding of the mechanisms underlying these interactions. In this study, we used a cross-feeding approach with spatially resolved metabolite profiling and metatranscriptomics to characterize the symbiosis between Sphagnum and Nostoc cyanobacteria. A pH gradient study revealed that the Sphagnum–Nostoc symbiosis was driven by pH, with mutualism occurring only at low pH. Metabolic cross-feeding studies along with spatially resolved matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) identified trehalose as the main carbohydrate source released by Sphagnum, which were depleted by Nostoc along with sulfur-containing choline-O-sulfate, taurine and sulfoacetate. In exchange, Nostoc increased exudation of purines and amino acids. Metatranscriptome analysis indicated that Sphagnum host defense was downregulated when in direct contact with the Nostoc symbiont, but not as a result of chemical contact alone. The observations in this study elucidated environmental, metabolic, and physiological underpinnings of the widespread plant–cyanobacterial symbioses with important implications for predicting carbon and nitrogen cycling in peatland ecosystems as well as the basis of general host-microbe interactions.

In aquatic ecosystems, allelopathic activity depends on the production and secretion of allelopathic compounds and their effective dispersal in the environment. In addition, macroalgae have been found to produce active metabolites that affect other organisms that compete with them for nutrients. However, the allelopathic activity of Baltic red and brown macroalgae on filamentous cyanobacteria is still insufficiently understood. Therefore, the main objective of this study was to demonstrate and compare the allelopathic effects of macroalgae Fucus vesiculosus L. and Coccotylus brodiei (Turner) Kütz. on the growth and photosynthetic activity of two Baltic cyanobacteria Aphanizomenon sp. and Nostoc sp. It was found a stimulating effect of different concentrations (5, 25, and 50 µL mL–1) of the aqueous extract obtained from C. brodiei on the number of cells of Nostoc sp. which constituted 108%, 140%, and 147%, respectively, relative to the control treatment. On the other hand, extracts obtained from F. vesiculosus had no statistically significant effect on the number of cells of the cyanobacteria Aphanizomenon sp. and Nostoc sp. Moreover, the C. brodiei extracts had no significant impact on the growth of Aphanizomenon sp. Furthermore, Baltic macroalgae F. vesiculosus and C. brodiei was able to exert allelopathic effects on photosynthesis performance of Nostoc sp. and Aphanizomenon sp. and compounds produced by them had inhibitory, stimulatory, or no significant effect on the maximum PSII quantum efficiency (Fv/Fm) and the effective quantum yield of PSII photochemistry (ΦPSII). The results obtained in this work constitute an important contribution to the knowledge on the allelopathic activity of Baltic red and brown algae on certain bloom-forming species of filamentous cyanobacteria.

Several studies have suggested the direct relationship between skin complications, air pollution, and UV irradiation. UVB radiations cause various skin complications such as skin aging, skin inflammation, and skin cancer. The current study is designed to develop an ultraviolet (UV) absorbing MAA-loaded topical gel and to evaluate its UVA and UVB screening potential. MAA was extracted from the Nostoc commune Vaucher ex Bornet et Flahault (N. commune) and characterized by HPLC-PDA (with a retention time 2.6 min), UV-Visible (absorption maximum 334 nm), and mass spectrometry (m/z 346.2) techniques. The methanolic (10%) solution of MAA (50–150 μl) was dissolved in propylene glycol and mixed with hydrated gel (1.5 % of carbopol 934) by using EDTA (0.3%). Eight (F1-F8) formulations were evaluated for their physico-chemical characters. F7 retained its physio-chemical characters for 90 days. Further selected formulation (F7) was evaluated for its gelling strength (GSg), gelling temperature (GT), melting temperature (MT), apparent viscosity (cp), molecular mass (MMS), pH, physical appearance, homogeneity, and spreading diameter (SD). The stability study of the fabricated gel formulation was done as per International Committee on Harmonization guidelines and sunscreen potential was determined by in vitro sunscreen UV method. Findings revealed that GSg (337 ± 1.7 g/cm2), GT (22.8 ± 0.2 °C), cp (71.1 ± 0.2), MMS (424.177 ± 0.7), pH (6.2 ± 0.04), and SD (56 ± 0.2). For in vitro sunscreen potential determination, different concentrations of F7 (50–150 μl) were prepared. Topical application of the F7 displayed UV-A/UV-B photoprotection with SPF 1.13 folds greater then marketed formulation (Lotus herbals UV screen gel). Based on these findings, it was concluded that methanolic extract derived from N. commune contains Porphyra-334 which can be potentially used as photo protective compound in several cosmetic preparations.

Fully understanding the environmental implications of engineered nanomaterials is crucial for their safe and sustainable use. Cyanobacteria, as the pioneers of the planet earth, play important roles in global carbon and nitrogen cycling. Here, we evaluated the biological effects of molybdenum disulfide (MoS2) nanosheets on a N2-fixation cyanobacteria (Nostoc sphaeroides) by monitoring growth and metabolome changes. MoS2 nanosheets did not exert overt toxicity to Nostoc at the tested doses (0.1 and 1 mg/L). On the contrary, the intrinsic enzyme-like activities and semiconducting properties of MoS2 nanosheets promoted the metabolic processes of Nostoc, including enhancing CO2-fixation-related Calvin cycle metabolic pathway. Meanwhile, MoS2 boosted the production of a range of biochemicals, including sugars, fatty acids, amino acids, and other valuable end products. The altered carbon metabolism subsequently drove proportional changes in nitrogen metabolism in Nostoc. These intracellular metabolic changes could potentially alter global C and N cycles. The findings of this study shed light on the nature and underlying mechanisms of bio-nanoparticle interactions, and offer the prospect of utilization bio-nanomaterials for efficient CO2 sequestration and sustainable biochemical production.

The identification and characterization of new β-galactosidases will provide diverse candidate enzymes for use in food processing industry. In this study, two β-galactosidases, Nf-LacZ and WspA1, from the terrestrial cyanobacterium Nostoc flagelliforme were heterologously expressed in Escherichia coli, followed by purification and biochemical characterization. Nf-LacZ was characterized to have an optimum activity at 40 °C and pH 6.5, different from that (45 °C and pH 8.0) of WspA1. Two enzymes had a similar Michaelis constant (Km = 0.5 mmol/liter) against the substrate o-nitrophenyl-β-D-galactopyranoside. Their activities could be inhibited by galactostatin bisulfite, with IC50 values of 0.59 µM for Nf-LacZ and 1.18 µM for WspA1, respectively. Gel filtration analysis suggested that the active form of WspA1 was a dimer, while Nf-LacZ was functional as a larger multimer. WspA1 was further characterized by the truncation test, and its minimum central region was found to be from residues 188 to 301, having both the glycosyl hydrolytic and transgalactosylation activities. Finally, transgenic analysis with the GFP reporter protein found that the N-terminus of WspA1 (35 aa) might play a special role in the export of WspA1 from cells. In summary, this study characterized two cyanobacterial β-galactosidases for potential applications in food industry.

Thymidylate kinase (TMK/TMPK) is an important enzyme in DNA biosynthesis and catalyses the conversion of dTMP to dTDP. Due to its therapeutic potential, the focus has been on characterizing the TMK proteins of pathogens and human origin, with very little information available on the TMK proteins of photosynthetic organisms and agriculturally important nitrogen-fixing organisms. In this work we report the characterisation of TMK in an evolutionarily ancient organism, cyanobacteria. The TMK protein of the photosynthetic, nitrogen-fixing cyanobacterium Nostoc PCC7120 (AnTMK) was found to have low conformational stability, which related to its low Tm of ~46 °C confirmed by D ifferential S canning F luorimetry (DSF) and D ifferential S canning C alorimetry (DSC) techniques. The AnTMK protein exhibited substrate specificity for dTMP and ATP with Km of 20.74 ± 1.47 μM and 20.17 ± 2.96 μM respectively. The enzyme kinetics data and the positive co-operativity observed between dTMP and ATP binding correlated well with the data obtained from I sothermal T itration C alorimetry (ITC). Homology model of the enzyme suggested that the binding mode of substrate nucleotides to the enzyme is conserved. When overexpressed constitutively in Nostoc PCC7120 (Antmk+), it supported faster growth measured in terms of chlorophyll a content under normal growth conditions, but exhibited lower photosynthetic efficiency. Compared to the vector control recombinant Nostoc AnpAM, the Antmk + cells exhibited higher photoinhibition at higher light irradiance with more open reaction centres and lower dissipation of heat, indicative of damage to photosynthetic machinery. This indicated that the TMK is likely to have a significant role in photosynthetic organisms.

The current investigation focuses on a systematic study of application of two dried algal biomass (i.e., Nostoc sp. and Turbinaria vulgaris) in removal of Cr(VI) from synthetic solution as well as tannery industrial wastewater. The optimized conditions for Cr(VI) removal are nearly same for the both the biosorbents (i.e., pH 2.8, initial Cr(VI) concentration 100 mg L−1, biomass dosage of 1.2g L−1, contact time 120 and 110 min). Nostoc sp. (qmax=23.94mg g−1) was observed to possess a superior removal capability when compared to Turbinaria vulgaris (qmax=21.8mg g−1). Desorption studies were performed with four different desorbing agents. Application study was conducted using tannery wastewater with Nostoc sp. and 94.20% removal of Cr(VI) was obtained. Hence, this study revealed that Nostoc sp. and T. vulgaris both have great potential to be an environment friendly and economic biosorbent for removal of Cr(VI) containing industrial effluent.

Nostoc flagelliforme is an endangered desiccation-tolerant cyanobacterium with dietary and herbal values. Enough availability of this biotic resource in food industry or for ecological management will come from the mass cultivation of its liquid suspension culture. Nostoc flagelliforme is sensitive to desiccation stress when cultivated as a cell suspension in liquid medium. In this study, we describe the desiccation tolerance acquisition of the liquid suspension culture on agar plates through slow drying treatment and investigate biochemical, proteomic, and ultrastructural changes of cells upon the drying induction. During the 16-day drying treatment, the cell suspension–derived solid cultures were maintained with 90 ~ 94% water content and the fresh weight increased nearly ninefold. Biochemical analysis showed that the biosynthesis of extracellular components, exopolysaccharide and scytonemin, was significantly increased in the solid cultures during the drying process. WspA protein, which can be secreted into the extracellular matrix, was also greatly induced. The contents of the compatible solutes trehalose and sucrose were not increased, but the content of trehalose maintained a high basal level. Proteomic analysis identified some highly upregulated proteins that are potentially crucial for desiccation tolerance, including WspA protein and Mn-containing catalase. Also, the biological processes regarding lipid or pigment metabolisms and the pathways regarding fructose and mannose metabolism and the biosynthesis of secondary metabolites were found among the most affected events during the drying process. Ultrastructural observation suggested that the structural modulation of the exopolysaccharide matrix occurred. In addition, the monosaccharide composition of exopolysaccharides was found to be specific for this liquid suspension culture or its derived solid culture. In general, this study provides insights into the mechanisms of desiccation tolerance acquisition in liquid suspension culture of N. flagelliforme and also proposes a new solution for developing desiccation-tolerant N. flagelliforme resource.

The main phycobiliprotein (PBP) found in cyanobacteria is phycocyanin (PC). The process of recovery is based on extraction followed by a purification stage. Among the methods of PBP extraction analyzed in this work, that is, freezing and thawing under sonication bath, vortex disruption with glass beads, maceration with pestle and mortar and ultrasonic homogenizer, the most efficient method was 5 freezing cycles (− 15 ± 1 °C) for 1.5 h and thawing (25 ± 1 °C) for 30 min in an ultrasonic bath, obtaining the highest PC concentrations of 32.87 μg mL−1 and 34.53 μg mL−1 and purities of 0.59 and 0.55, for Anabaena variabilis and Nostoc sp., respectively. In the purification by aqueous two-phase systems (ATPS), the systems of PEG (1500 and 4000) and two salts, potassium phosphate and sodium citrate, were evaluated using different volume ratios. The best system found was PEG 1500-potassium phosphate, in the proportion PEG, 10% (w/w) and salt, 15.9% (w/w), obtaining a recovery of 82.10%, partition coefficient of 5.73 and purity of 1.12 for the extract from Anabaena variabilis and recovery of 79.10%, partition coefficient of 6.36 and purity of 1.34 for the extract from Nostoc sp., both in adequate purity conditions for food grade.

Ubiquitous presence of cyanobacteria even under extreme conditions since millions of years is due to their ease in adaptability to these environments through various cellular and molecular modifications. Formation of biofilms has been found to be one of the effective modes of survival under harsh environmental conditions, with exopolysaccharides (EPS) contributing to the formation of these biofilms. Cyanobacterial EPS are unique heteropolysaccharides and being anionic in nature, they have the capabilities for excellent heavy metal adsorption and thus, play a vital role in conferring tolerance against heavy metal toxicity. EPS biosynthesis occurs through multiple pathways involving a multitude of genes. A comprehensive overview on these genes in cyanobacteria using Nostoc sp. strain PCC7120 as the model organism has been discussed in this review. The review also emphasizes on the contribution of EPS to heavy metal remediation and biofilm formation. In the age of developing eco-friendly approaches for environmental clean-up, this information would help engineer cyanobacteria as a potential green technology tool for bioremediation and waste water management.

Research on the UVA, UVB, and oxidative (as reactive oxygen species, ROS) stress response in cyanobacteria has typically focused on each individual stress condition, with limited studies addressing the intersection. Here we evaluated the transcriptomic responses of the model cyanobacterium Nostoc punctiforme after exposure to each of these conditions. Overall, response to UVA was characterized by more gene down-regulation than the UVB or ROS response, although UVB affected over four-fold more genes than UVA or ROS. Regarding expression patterns, responses to UVA and ROS were more similar and differentiated from those to UVB. For example, genes involved in ROS metabolism were up-regulated under both UVA and ROS. However, when it came to RNA and protein metabolism, there were more up-regulated genes under UVB and ROS compared to UVA. This suggests that the response to UVB and ROS is more active than the response to UVA, which stimulated more genes in secondary metabolism. Histidine kinases and response regulators were often differentially expressed, demonstrating that regulatory systems were at the base of the patterns. This study provides background for future studies targeting different genes, proteins, and systems sensitive to these conditions. It also highlights the significance of considering multiple stress conditions.

Terrestrial cyanobacteria, originated from aquatic cyanobacteria, exhibit a unique mechanism for drought adaptation during long-term evolution. To elucidate this diverse adaptive mechanism exhibited by terrestrial cyanobacteria from the post-translation modification aspect, we performed a global phosphoproteome analysis on the abundance of phosphoproteins in response to dehydration using Nostoc flagelliforme, a kind of terrestrial cyanobacteria having strong ecological adaptability to xeric environments. A total of 329 phosphopeptides from 271 phosphoproteins with 1168 phosphorylation sites were identified. Among these, 76 differentially expressed phosphorylated proteins (DEPPs) were identified for each dehydration treatment (30, 75, and 100% water loss), compared to control. The identified DEPPs were functionally categorized to be mainly involved in a two-component signaling pathway, photosynthesis, energy and carbohydrate metabolism, and an antioxidant system. We concluded that protein phosphorylation modifications related to the reactive oxygen species (ROS) signaling pathway might play an important role in coordinating enzyme activity involved in the antioxidant system in N. flagelliforme to adapt to dehydration stress. This study provides deep insights into the extensive modification of phosphorylation in terrestrial cyanobacteria using a phosphoproteomic approach, which may help to better understand the role of protein phosphorylation in key cellular mechanisms in terrestrial cyanobacteria in response to dehydration.

Phycoerythrobilin (PEB) is a special pigment in red algae and cyanobacteria that plays an important role in capturing light energy. As a natural non-toxic pigment with antioxidant properties, PEB is widely used in food and cosmetics industries. At present, the presence of other pigments in red algae and cyanobacteria, such as chlorophyll and phycocyanobilin, makes the preparation of PEB complicated and costly. In this study, the PEB synthesizing enzyme genes of hox1 from Synechocystis sp. PCC6803 and pebS from Nostoc sp. PCC 7120 were co-expressed in Escherichia coli to produce recombinant PEB. In addition, single-factor and response surface methods were used to enhance the yield of recombinant PEB. Under the conditions of lactose concentration at 4 mmol L−1, induction temperature at 27 °C, OD600 nm of 0.9, and induction time at 14 h, the concentration of PEB reached 20.37 mg L−1. In addition, a high-purity (purity > 70%) PEB was obtained through chloroform extraction, and the purified product was verified in UV spectrometry, high-performance liquid chromatography, and mass spectrometry.

Nostoc flagelliforme is a remarkable drought-resistant terrestrial cyanobacterium whose exopolysaccharides (EPS) have been found to exert important physiological and ecological functions, and the EPS are known to improve soil physicochemical properties. In this study, we used physiological and molecular methods to investigate the influences of three moisture loss levels on EPS production and the antioxidant system in N. flagelliforme. The aim was to reveal the EPS production mechanism involved in the gene differential expression and antioxidant system of N. flagelliforme in response to drought. Our results showed that EPS contents increased by 13% and 22% after 6-h and 48-h dehydration (6HAD and 48HAD) compared with 4-h rehydration (4HAR), respectively. The same trends were also detected for most EPS synthesis genes, especially glycosyltransferases. Furthermore, the intracellular reactive oxygen species (ROS) levels in N. flagelliforme were generally higher at 6HAD and 48HAD than at 4HAR. Superoxide dismutase (SOD) and peroxidase (POD) activities were restricted in N. flagelliforme under 6HAD and 48HAD compared with 4HAR, but the opposite result was found in catalase (CAT) activity. These results provide a new foundation for understanding the mechanism of EPS accumulation in N. flagelliforme in response to drought.

A living consortium of green algae (Ankistrodesmus) and cyanobacteria (Nostoc and Anabaena) was tested for the removal of heavy metal ions (Fe (II), Cu (II), Pb (II), Cr (VI) and Zn (II)) from dump...

Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors that exhibit photochromism between two states: a thermally stable dark-adapted state and a metastable light-adapted state with bound linear tetrapyrrole (bilin) chromophores possessing 15Z and 15E configurations, respectively. The photodynamics of canonical red/green CBCRs have been extensively studied; however, the time scales of their excited-state lifetimes and subsequent ground-state evolution rates widely differ and, at present, remain difficult to predict. Here, we compare the photodynamics of two closely related red/green CBCRs that have substantial sequence identity (∼68%) and similar chromophore environments: AnPixJg2 from Anabaena sp. PCC 7120 and NpR6012g4 from Nostoc punctiforme. Using broadband transient absorption spectroscopy on the primary (125 fs to 7 ns) and secondary (7 ns to 10 ms) time scales together with global analysis modeling, our studies revealed that AnPixJg2 and NpR6012g4 have comparable quantum yields for initiating the forward (15ZPr → 15EPg) and reverse (15EPg → 15ZPr) reactions, which proceed through monotonic and nonmonotonic mechanisms, respectively. In addition to small discrepancies in the kinetics, the secondary reverse dynamics resolved unique features for each domain: intermediate shunts in NpR6012g4 and a Meta-Gf intermediate red-shifted from the 15ZPr photoproduct in AnPixJg2. Overall, this study supports the conclusion that sequence similarity is a useful criterion for predicting pathways of the light-induced evolution and quantum yield of generating primary intermediate Φp within subfamilies of CBCRs, but more studies are still needed to develop a comprehensive molecular level understanding of these processes.

Summary Questions about in vivo substrates for proanthocyanidin (PA) biosynthesis and condensation have not been resolved and wide gaps in the understanding of transport and biogenesis in ‘tannosomes’ persist. Here we examined the evolution of PA biosynthesis in ferns not previously reported, asking what PAs are synthesised and how.Chemical and gene‐expression analyses were combined to characterise PA biosynthesis, leveraging genome annotation from the floating fern Azolla filiculoides. In vitro assay and phylogenomics of PIP‐dehydrogenases served to infer the evolution of leucoanthocyanidin reductase (LAR).Sporophyte‐synthesised (epi)catechin polymers, averaging only seven subunits, accumulated to 5.3% in A. filiculoides, and 8% in A. pinnata biomass dry weight. Consistently, a LAR active in vitro was highly expressed in A. filiculoides. LAR, and paralogous fern WLAR‐enzymes with differing substrate binding sites, represent an evolutionary innovation of the common ancestor of fern and seed plants.The specific ecological niche of Azolla ferns, a floating plant–microbe mat massively fixing CO2 and N2, shaped their metabolism in which PA biosynthesis predominates and employs novel fern LAR enzymes. Characterisation of in vivo substrates of these LAR, will help to shed light on the recently assigned and surprising dual catalysis of LAR from seed plants.

The terrestrial cyanobacterium Nostoc commune has a cosmopolitan distribution. It is edible, and dry thalli are sold as a food in China under the name of Di Pi Cai. The pigment composition and the genotypes were characterized to identify the cyanobacterium Di Pi Cai from China as N. commune. Myxol glycosides and ketocarotenoids were detected, as expected in Nostoc sp., but β-carotene and hydroxylated carotenoids were not detected. Nostoc-756, mycosporine-2-(4-deoxygadusoyl-ornitine), was found to be a main mycosporine-like amino acid, which indicates that Di Pi Cai belongs to the N. commune chemotype C. However, the 16S rRNA gene and the petH gene encoding ferredoxin-NADP+ oxidoreductase of Di Pi Cai did not exactly match those of genotype C found in Japan. These results suggest the unique molecular genetic features of Di Pi Cai and the global diversity of N. commune.

La alta tasa de perecibilidad en fresas (Fragaria x ananassa) complica su almacenamiento postcosecha, surgiendo la necesidad de desarrollar medios de conservación eficaces. En la investigación se estudiaron las cualidades físicoquímicas de fresas recubiertas con películas comestibles a base de Nostoc (Nostoc Sphaericum). Las películas se generaron al sumergir el fruto en soluciones de polisacáridos de Nostoc al 0,7 % (A), 1,0 % (B) y 1,3 % (C) de concentración (p/v). El producto se almacenó durante 8 días a temperatura ambiente (18 ± 2 °C), posteriormente se midieron los parámetros de calidad. Se aplicó el diseño DBCA con nivel de significancia 5%. Se determinó que la textura varía directamente con la concentración de polisacárido en la cobertura. La pérdida promedio de peso para los tratamientos A, B, C y el control fueron 66,92%, 60,92%, 49,06% y 41,72%, respectivamente. En todos los casos se observó una variación inferior a 0,3 en la escala de pH y superior al 0,3% para la acidez, sin diferencias significativas. La variación en SST para los tratamientos fue de 4,9 (C), 5,2 (A) y 7,4 (B) °brix. Se determinó una extensión de la vida útil del 16% de fresas hasta dos días. Se determinó que la aplicación de películas de Nostoc prolongan la vida útil de fresas, resaltando su desempeño en la pérdida de peso y textura frente a la muestra control, en la escala descendiente C > B > A.

Reham Samir Hamida,1 Mohamed Abdelaal Ali,2 Doaa A Goda,3 Mayasar Ibrahim Al-Zaban4 1Molecular Biology Unit, Department of Zoology, Faculty of Science, Alexandria University, Alexandria, Egypt; 2Biotechnology Unit, Department of Plant Production, College of Food and Agriculture Science, King Saud University, Riyadh, Saudi Arabia; 3Bioprocess Development Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City of Scientific Research and Technological Applications (SRTA-City), Alexandria, Egypt; 4Department of Biology, College of Science Princess Nourah bint Abdulrahman University, Riyadh, Saudi ArabiaCorrespondence: Mohamed Abdelaal Ali Email mali3@ksu.edu.saMayasar Ibrahim Al-Zaban Email Mialzaban@pnu.edu.saBackground: Increasing antibiotic resistance and the emergence of multidrug-resistant (MDR) pathogens have led to the need to develop new therapeutic agents to tackle microbial infections. Nano-antibiotics are a novel generation of nanomaterials with significant antimicrobial activities that target bacterial defense systems including biofilm formation, membrane permeability, and virulence activity.Purpose: In addition to AgNO3, the current study aimed to explore for first time the antibacterial potential of silver nanoparticles synthesized by Nostoc sp. Bahar_M (N-SNPs) and their killing mechanisms against Streptococcus mutans, methicillin-resistant Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium.Methods: Potential mechanisms of action of both silver species against bacteria were systematically explored using agar well diffusion, enzyme (lactate dehydrogenase (LDH) and ATPase) andantioxidant (glutathione peroxidase and catalase) assays, and morphological examinations. qRT-PCR and SDS-PAGE were employed to investigate the effect of both treatments on mfD, flu, and hly gene expression and protein patterns, respectively.Results: N-SNPs exhibited greater biocidal activity than AgNO3 against the four tested bacteria. E. coli treated with N-SNPs showed significant surges in LDH levels, imbalances in other antioxidant and enzyme activities, and marked morphological changes, including cell membrane disruption and cytoplasmic dissolution. N-SNPs caused more significant upregulation of mfD expression and downregulation of both flu and hly expression and increased protein denaturation compared with AgNO3.Conclusion: N-SNPs exhibited significant inhibitory potential against E. coli by direct interfering with bacterial cellular structures and/or enhancing oxidative stress, indicating their potential for use as an alternative antimicrobial agent. However, the potential of N-SNPs to be usable and biocompatible antibacterial drug will evaluate by their toxicity against normal cells.Keywords: biological synthesis, nanoparticles, pathogenic bacteria, Nostoc sp. Bahar_M, silver, antibacterial activity

In this report, we compare the femtosecond to nanosecond primary reverse photodynamics (15EPg → 15ZPr) of eight tetrapyrrole binding photoswitching cyanobacteriochromes in the canonical red/green family from the cyanobacterium Nostoc punctiforme. Three characteristic classes were identified on the basis of the diversity of excited-state and ground-state properties, including the lifetime, photocycle initiation quantum yield, photointermediate stability, spectra, and temporal properties. We observed a correlation between the excited-state lifetime and peak wavelength of the electronic absorption spectrum with higher-energy-absorbing representatives exhibiting both faster excited-state decay times and higher photoisomerization quantum yields. The latter was attributed to both an increased number of structural restraints and differences in H-bonding networks that facilitate photoisomerization. All three classes exhibited primary Lumi-Go intermediates, with class II and III representatives evolving to a secondary Meta-G photointermediate. Class II Meta-GR intermediates were orange absorbing, whereas class III Meta-G had structurally relaxed, red-absorbing chromophores that resemble their dark-adapted 15ZPr states. Differences in the reverse and forward reaction mechanisms are discussed within the context of structural constraints.

Complex structure of cyanobacterium Nostoc sp. exopolysaccharide (EPS), with apparent molecular weight 214 × 103 g/mol, can be deduced from its composition. Chemical and NMR analyses found four dominant sugar monomers, namely (1 → 4)-linked α- l -arabinopyranose, β- d -glucopyranose, β- d -xylopyranose and (1 → 3)-linked β- d -mannopyranose, two different uronic acids and a lactyl group, with (1 → 4,6)-linked β- d -glucopyranose as the only branch point suggest a complex structure of this polymer. The dominant uronic acid is α-linked, but it remained unidentified. β- d -Glucuronic acid was present in lower amount. Their position as well as that of lactyl remained undetermined too. Different doses of orally administered EPS in guinea pigs evoked a significant decrease in cough effort and a decrease in airway reactivity. The antitussive efficacy and bronchodilator effect of higher doses of EPS were found to be similar to that of the antitussive drug codeine and the antiasthmatic salbutamol. Without significant cytotoxicity on the RAW 264.7 cells, EPS stimulated the macrophage cells to produce pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and prostaglandins (PGs) and nitric oxide (NO) via induction of COX-2 and iNOS expression, respectively, suggesting that this biopolymer potentiates an early innate immune response and can therefore be used as a new immune modulator.

Biological soil crusts (BSC) (Cyanobacteria) play an important role in the soil nitrogen fixation and soil stabilization. However, limited researches were carried out about the diversity and distribution of Bio crust in sacred forests. The study aims to identify the distribution of cyanobacteria in biological soil crusts from different sacred groves of Ariyalur and Pudukottai, Tamil Nadu. We identified following microbes of Microcoleus, Scytonema, Anabaena and Nostoc in biological soil crust. A surface experiment was conducted for the efficacy of biological soil crusts on crops seedling growths. The efficacy was assessed by measuring the root & shoot length, dry & fresh weight of the plant, total chlorophyll, protein & carbohydrate content, with reducing sugar. The plant growth was higher in biocrust inoculated pot than the control. In corresponding nitrogenase activity was determined by the acetylene reduction assay, and phytohormones documentation was executed by the high-performance liquid chromatography. The results indicating that the biological soil crusts are the promising factors influencing the plant growth by plant growth-stimulating auxins and nitrogenase activity.

In nitrogen-limited boreal forests, associations between feathermoss and diazotrophic cyanobacteria control nitrogen inputs and thus carbon cycling, but little is known about the molecular regulators required for initiation and maintenance of these associations. Specifically, a benefit to the cyanobacteria is not known, challenging whether the association is a nutritional mutualism. Targeted mutagenesis of the cyanobacterial alkane sulfonate monooxygenase results in an inability to colonize feathermosses by the cyanobacterium Nostoc punctiforme, suggesting a role for organic sulfur in communication or nutrition. Isotope probing paired with high-resolution imaging mass spectrometry (NanoSIMS) demonstrated bidirectional elemental transfer between partners, with carbon and sulfur both being transferred to the cyanobacteria, and nitrogen transferred to the moss. These results support the hypothesis that moss and cyanobacteria enter a mutualistic exosymbiosis with substantial bidirectional material exchange of carbon and nitrogen and potential signaling through sulfur compounds.

This study investigates the influence of immobilized bacterial anode on the performance of algal-assisted microbial fuel cell (AAMFC) that treats dairy wastewater with concurrent bioelectricity and bioactive compound production. Immobilized exoelectrogenic bacterium—Enterobacter aerogenes—was used in the anode region, and Nostoc sp. was used in the cathode region. The investigation on the influence of sodium alginate (SA) concentration indicated that E. aerogenes immobilized using 20 g/L SA produced highest power density of 168 ± 3.5 mW/m2, whereas free cells showed 75 ± 5.32 mW/m2. The coulombic efficiency, chemical oxygen demand (COD) removal, and volatile fatty acid (VFA) recovery obtained for cells immobilized using 20 g/L SA were 12.54, 83.15, and 92%, respectively. This system gave a CO2 supply of 4.2 mM, which increased the productivity of Nostoc sp. to 64.3 ± 3.8 mg/L d. Algal cathode produced a maximum dissolved oxygen content of 12.8 mg/L. The constituents of Nostoc sp. were extracted using ethanol, and the antimicrobial activity of the extract was tested against aquatic bacterial pathogens. The extract at a dosage of 500 μg showed highest zone of inhibition of 11 mm for the gram-negative bacteria Citrobacter freundii and least inhibition of 2 mm for Escherichia coli. FTIR analysis of the extract confirmed the presence of bioactive compounds. This study substantiated that the immobilized anodic exoelectrogens with microalgal biocathode in an AAMFC will find a promising application in energy harvesting from wastewater and bioactive compound synthesis.

Nostoc flagelliforme is a terrestrial cyanobacterium distributed in arid or semiarid steppes in western and northwestern China. Cyanophycin is synthesized by cyanophycin synthetase (CphA), which serves as a storage polymer for nitrogen, carbon, and energy in N. flagelliforme. In the present study, cphA (GenBank Accession No.: KX469292), an open reading frame (ORF) of 2706 bp encoding a protein of 901 amino acid residues, was cloned. We found that cyanophycin synthesis was promoted by the expression of cphA in E. coli. The function of the cphA gene in Arabidopsis thaliana under drought stress was investigated, and stable integration and expression of transgenes in transgenic lines were confirmed by PCR, Western blot, Southern blot, and real-time PCR analyses. The transcript abundance of cphA was markedly increased in transgenic A. thaliana compared with that in the untransformed plants. A subcellular localization assay confirmed that cphA protein was targeted to the cytoplasm. The survival rate was also significantly higher in cphA overexpression lines than that in untransformed plants under drought stress, which verified by drought tolerance assay of the transgenic plants. These findings highlight the potential importance of cphA in the drought tolerance of N. flagelliforme.

In this study, the decolorization efficiency of seven microalgae isolates; Nostoc muscorum, Nostoc humifusum, Spirulina platensis, Anabaena oryzae, Wollea saccata, Oscillatoria sp. and Chlorella vu...

In the last decades, biotechnological applications have led to the optimization of the cultural conditions for the production of exopolysaccharides (EPSs) by cyanobacteria. Nostoc is a genus of cyanobacteria found in various environments that forms colonies composed of filaments of moniliform cells in a gelatinous sheath. The effect of some important nutritional and growth beside iron nanoparticles on production by Nostoc sp. was studied. Optimization of the cultural conditions was carried out using Central Composite Design (CCD), and it was achieved at pH 8.39, 1% of NaCl and 0.8 g.l-1 nitrate based in modified BG0 medium and more than 12 g.l-1 of EPS was obtained by phenol-sulphuric acid method. The present research investigated the possibility of inducing EPS production in the presence of Fe3O4 nanoparticles from optimized microalga cultures. This study revealed that Nostoc sp. treatment with 10 mg.l-1 Fe3O4 NPs induced maximal EPS production (4 µg.ml-1).

The feasibility of the semi-continuous cultivation of Arthrospira (Spirulina) sp. and Nostoc sp. PCC 7413, using the centrate from the anaerobic digestion of wastewater from a seafood canning industry as a nutrient source, was assessed. Semi-continuous cultures were carried out in aerated tubular culture units of 250 mL by replacing a 10–20% of the volume with the centrate every 2 days. Growth, ammonium, and nitrate removal were monitored, as well as phycobiliprotein and protein production by Arthrospira sp. and released exopolysaccharides production by Nostoc sp. PCC 7413. The ammonium removal efficiency by Arthrospira sp. was 84.9 ± 1.9% in a culture maintained with an ammonium concentration of 11.3 mM. Lower ammonium concentrations (4.9 mM) could be applied to Nostoc sp. PCC 7413, reaching similar relative removal efficiency (84.1%). Taking into account the high ammonium stripping that occurs at the high pH required in Arthrospira sp. cultures, results indicate a better nutrient removal by Nostoc sp., although Arthrospira sp. is more suitable for working at high ammonium concentrations. Since all the ammonium was removed during the first 24 h for both species, much lower residence time could be supported by the cultures. High concentrations of protein (2.5 ± 0.2 mg mL−1), phycobiliprotein (allophycocyanin, 84.3 ± 10.2 mg g−1; phycocyanin, 73.7 ± 7.7 mg g−1) were obtained by Arthrospira sp. cultures. A high concentration of released exopolysaccharides (962.7 ± 26.7 mg L−1) was also obtained for Nostoc sp. PCC 7413 when cultured in the anaerobic centrate. The results indicate the possibility of the use of filamentous cyanobacteria for the treatment of industrial effluents rich in ammonium, with different possibilities of valorization of the biomass produced.

The bio-sorption is the using of biological biomasses, live or dead form, for heavy metals removal from polluted wastewater. In the current work, live planktonic Nostoc sp. cells were used for hexa...

Phytochromes regulate central responses of plants and microorganisms such as shade avoidance and photosystem synthesis. Canonical phytochromes comprise a photosensory module of three domains. The C-terminal phytochrome-specific (PHY) domain interacts via a tongue element with the bilin chromophore in the central GAF (cGMP phosphodiesterase/adenylate cyclase/FhlA) domain. The bilin isomerizes upon illumination with red light, transforming the receptor from the Pr state to the Pfr state. The "knotless" phytochrome All2699 from the cyanobacterium Nostoc sp. PCC7120 comprises three GAF domains as a sensory module and a histidine kinase as an effector. GAF1 and GAF3 both bind a bilin, and GAF2 contains a tongue-like element. We studied the response of All2699, GAF1-GAF2, and GAF1 to red light by Fourier transform infrared difference spectroscopy, including a 13C-labeled protein moiety for assignment. In GAF1-GAF2, a refolding of the tongue from β-sheet to α-helix and an upshift of the ring D carbonyl stretch from 1700 to 1712 cm-1 were observed. Therefore, GAF1-GAF2 is regarded as the smallest model system available to study the tongue response and interaction with the chromophore. Replacement of an arginine in the tongue with proline (R387P) did not affect the unfolding of the β-sheet to Pfr but strongly impaired α-helix formation. In contrast, the Y55H mutation close to bilin ring D did not interfere with conversion to Pfr. Strikingly, the presence of GAF3 in the full-length All2699 diminished the response of the tongue and generated the signal pattern found for GAF1 alone. These results point to a regulatory or integrative role of GAF3 in All2699 that is absent in canonical phytochromes.

Applying enzymatic reactions to produce useful molecules is a central focus of chemical biology. Iron and 2-oxoglutarate (Fe/2OG) enzymes are found in all kingdoms of life and catalyze a broad array of oxidative transformations. Herein, we demonstrate that the activity of an Fe/2OG enzyme can be redirected when changing the targeted carbon hybridization from sp3 to sp2. During leucine 5-hydroxylase catalysis, installation of an olefin group onto the substrate redirects the Fe(IV)-oxo species reactivity from hydroxylation to asymmetric epoxidation. The resulting epoxide subsequently undergoes intramolecular cyclization to form the substituted piperidine, 2S,5S-hydroxypipecolic acid.

Flavin‐dependent ‘ene’‐reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic paradigms.

Single-chain Fv (scFv) is a recombinant antibody in which the variable regions of the heavy chain (VH) and light chain (VL) are connected by a short flexible polypeptide linker. Compared with monoclonal antibodies, scFvs have the advantages of low-cost production using Escherichia coli and easy genetic manipulation. ScFvs are, therefore, regarded as useful modules for producing next-generation medical antibodies. The practical use of scFvs has been limited due to their aggregation propensity mediated by interchain VH–VL interactions. To overcome this problem, we recently reported a cyclic scFv whose N-terminus and C-terminus were connected by sortase A-mediated ligation. Preparation of cyclic scFv is, however, a time-consuming process. To accelerate the application study of cyclic scFv, we developed a method to produce cyclic scFv by the combined use of a protein ligation technique based on protein trans-splicing reaction (PTS) by split intein and a chaperone co-expression system. This method allows for the preparation of active cyclic scFv from the cytoplasm of E. coli. The present method was applied to the production of cyclic 73MuL9-scFv, a GA-pyridine antibody, as a kind of advanced glycation end-product. These findings are expected to evoke further application study of cyclic scFv.

The present study was carried out to investigate cyanobacteria as a potential source for biodiesel production isolated from fresh water bodies of Sri Lanka. Semi mass culturing and mass culturing were carried out to obtain biomass for extracting total lipids. Fatty acid methyl ester (FAME) or biodiesel was produced from extracted lipid by trans-esterification reaction. FAME component was identified using gas chromatography (GC). Atotal of 74 uni-algal cultures were obtained from Biofuel and Bioenergy laboratory of the National Institute of Fundamental Studies (NIFS), Kandy, Sri Lanka. The total lipid content was recorded highest in Oscillatoria sp. (31.9 ± 2.01% of dry biomass) followed by Synechococcus sp. (30.6 ± 2.87%), Croococcidiopsis sp. (22.7 ± 1.36%), Leptolyngbya sp. (21.15 ± 1.99%), Limnothrixsp. (20.73 ± 3.26%), Calothrix sp. (18.15 ± 4.11%) and Nostoc sp. (15.43 ± 3.89%), Cephalothrixsp. (13.95 ± 4.27%), Cephalothrix Komarekiana (13.8 ± 3.56%) and Westiellopsisprolifica (12.80 ± 1.97%). FAME analysis showed cyanobacteria contain Methyl palmitoleate, Linolelaidic acid methyl ester, Cis-8,11,14-eicosatrienoic acid methyl ester, Cis-10-heptadecanoic acid methyl ester, Methyl myristate, Methyl pentadecanoate, Methyl octanoate, Methyl decanoate, Methyl laurate, Methyl tridecanoate, Methyl palmitoleate, Methyl pentadeconoate, Methyl heptadeconoate, Linolaidic acid methyl ester, Methyl erucate, Methyl myristate, Myristoloeic acid, Methyl palmitate, Cis-9-oleic acid methyl ester, Methyl arachidate and Cis-8,11,14-ecosatrieconoic acid methyl ester. The present study revealed that cyanobacteria isolated from Sri Lanka are potential source for biodiesel industry because of their high fatty acid content. Further studies are required to optimize the mass culture conditions to increase thelipid content from cyanobacterial biomass along with the research in the value addition to the remaining biomass.

Nostoc sp. PCC 7120 are filamentous cyanobacteria capable of both oxygenic photosynthesis and nitrogen fixation, with the latter taking place in specialized cells known as heterocysts that terminally differentiate from vegetative cells under conditions of nitrogen starvation. Cyanobacteria have existed on earth for more than 2 billion years and are thought to be responsible for oxygenation of the earth's atmosphere. Filamentous cyanobacteria such as Nostoc sp. PCC 7120 may also represent the oldest multicellular organisms on earth that undergo cell differentiation. Pentapeptide repeat proteins (PRPs), which occur most abundantly in cyanobacteria, adopt a right-handed quadrilateral β-helical structure, also referred to as a repeat five residue (Rfr) fold, with four-consecutive pentapeptide repeats constituting a single coil in the β-helical structure. PRPs are predicted to exist in all compartments within cyanobacteria including the thylakoid and cell-wall membranes as well as the cytoplasm and thylakoid periplasmic space. Despite their intriguing structure and importance to understanding ancient cyanobacteria, the biochemical function of PRPs in cyanobacteria remains largely unknown. Here we report the crystal structure of Alr1298, a PRP from Nostoc sp. PCC 7120 predicted to reside in the cytoplasm. The structure displays the typical right-handed quadrilateral β-helical structure and includes a four-α-helix cluster capping the N-terminus and a single α-helix capping the C-terminus. A gene cluster analysis indicated that Alr1298 may belong to an operon linked to cell proliferation and/or thylakoid biogenesis. Elevated alr1298 gene expression following nitrogen starvation indicates that Alr1298 may play a role in response to nitrogen starvation and/or heterocyst differentiation.

As genome mining becomes a more widely used approach to identify bacterial natural products, the challenge of matching biosynthetic gene clusters to their cognate secondary metabolites has become more apparent. Bioinformatic platforms such as AntiSMASH have made great progress in predicting chemical structures from genetic information, however the predicted structures are often incomplete. This complicates identifying the predicted compounds by mass spectrometry. Secondary metabolites produced by cyanobacteria represent a unique opportunity for bridging this gap. Cultured cyanobacteria incorporate inorganic nitrogen provided in chemically defined media into all nitrogen-containing secondary metabolites. Thus, stable isotope labeling with (15)N labeled nitrate and subsequent comparative metabolomics can be used to match biosynthetic gene clusters to their cognate compounds in cell extracts. Analysis of the sequenced genome of Nostoc sp. UIC 10630 identified six biosynthetic gene clusters predicted to encode the production of a secondary metabolite with at least one nitrogen atom. Comparative metabolomic analysis of the (15)N labeled and unlabeled cell extracts revealed four nitrogen containing compounds that contained the same number of nitrogen atoms as were predicted in the biosynthetic gene clusters. Two of the four compounds were new secondary metabolites, and their structures were elucidated by NMR, HRESIMS, and MS/MS.

Maintaining the structural integrity of the photosynthetic apparatus during dehydration is critical for effective recovery of photosynthetic activity upon rehydration in a variety of desiccation-tolerant plants, but the underlying molecular mechanism is largely unclear. The subaerial cyanobacterium Nostoc flagelliforme can survive extreme dehydration conditions and quickly recovers its photosynthetic activity upon rehydration. In this study, we found that the expression of the molecular chaperone NfDnaK2 was substantially induced by dehydration, and NfDnaK2 proteins were primarily localized in the thylakoid membrane. NfDnaJ9 was identified to be the cochaperone partner of NfDnaK2, and their encoding genes shared similar transcriptional responses to dehydration. NfDnaJ9 interacted with the NfFtsH2 protease involved in the degradation of damaged D1 protein. Heterologous expression of NfdnaK2 enhanced PSII repair and drought tolerance in transgenic Nostoc sp. PCC 7120. Furthermore, the nitrate reduction (NarL)/nitrogen fixation (FixJ) family transcription factors response regulator (NfRre1) and photosynthetic electron transport-dependent regulator (NfPedR) were identified as putative positive regulators capable of binding to the promoter region of NfdnaK2 and they may mediate dehydration-induced expression of NfdnaK2 in N. flagelliforme Our findings provide novel insights into the molecular mechanism of desiccation tolerance in some xerotolerant microorganisms, which could facilitate future synthetic approaches to the creation of extremophiles in microorganisms and plants.

Desmonostoc salinum CCM-UFV059 (Desmonostoc) is a novel cyanobacterial strain of the order Nostocales isolated from a saline-alkaline lake. The acclimation towards salt and desiccation stress of Desmonostoc was compared to the related and well-characterized model strain Nostoc sp. PCC7120 (Nostoc). Salt-stressed cells of Desmonostoc maintained low cellular Na+ concentrations and accumulated high amounts of compatible solutes, mainly sucrose and to a lower extent trehalose. These features permitted Desmonostoc to grow and maintain photosynthesis at 2-fold higher salinities than Nostoc. Moreover, Desmonostoc also induced sucrose over-accumulation under desiccation, which allowed this strain to recover from this stress in contrast to Nostoc. Additional mechanisms such as the presence of highly unsaturated lipids in the membrane and an efficient ion transport system could also explain, at least partially, how Desmonostoc is able to acclimate to high salinities and to resist longer desiccation periods. Collectively, our results provide first insights into the physiological and metabolic adaptations explaining the remarkable high salt and desiccation tolerance, which qualify Desmonostoc as an attractive model for further analysis of stress acclimation among heterocystous N2 -fixing cyanobacteria.

A metabolite screening of cyanobacteria was performed by nuclear magnetic resonance (NMR) analysis of the soluble material obtained through sequential extraction of the biomass with three different extractive ability solvents (hexane, ethyl acetate, and methanol). Twenty-five strains from the Coimbra Collection of Algae (ACOI) belonging to different orders in the botanical code that represent three subsections of the Stainer-Rippka classification were used. The 1 H NMR spectra of hexane extracts showed that only two strains of Nostoc genus accumulated triacylglycerols. Monogalactosyldiacylglycerols and digalactosyldiacylglycerols were the major components of the ethyl acetate extracts in a mono- to digalactosyldiacylglycerols ratio of 4.5 estimated by integration of the signals at δ 3.99 and 3.94 ppm (sn3 glycerol methylene). Oligosaccharides of sucrose and mycosporine-like amino acids, among other polar metabolites, were detected in the methanolic extracts. Strains of Nostocales order contained heterocyst glycolipids, whereas sulphoquinovosyldiacylglycerols were absent in one of the studied strains (Microchaete tenera ACOI 1451). Phosphathidylglycerol was identified as the major phospholipid in the methanolic extracts together with minor amounts of phosphatidylcholine based on 1 H, 31 P 2D correlation experiments. Chemotaxonomic information could be easily obtained through the analysis of the δ 3.0-0.5 ppm (fatty acid distribution) and δ 1.2-1.1 ppm (terminal methyl groups of the aglycons in heterocyst glycolipids) regions of the 1 H NMR spectra of the ethyl acetate and methanol extracts, respectively.

Cyanobacteria are an interesting source of biologically active natural products, especially chemically diverse and potent protease inhibitors. On our search for inhibitors of the trypanosomal cysteine protease rhodesain, we identified the homodimeric cyclopentenedione (CPD) nostotrebin 6 (1) and new related monomeric, dimeric, and higher oligomeric compounds as the active substances in the medium extract of Nostoc sp. CBT1153. The oligomeric compounds are composed of two core monomeric structures, a trisubstituted CPD or a trisubstituted unsaturated δ-lactone. Nostotrebin 6 thus far has been the only known cyanobacterial CPD. It has been found to be active in a broad variety of assays, indicating that it might be a pan-assay interference compound (PAIN). Thus, we compared the antibacterial and cytotoxic activities as well as the rhodesain inhibition of selected compounds. Because a compound with a δ-lactone instead of a CPD core structure was equally active as nostotrebin 6, the bioactivities of these compounds seem to be based on the phenolic substructures rather than the CPD moiety. While the dimers were roughly equally potent, the monomer displayed slightly weaker activity, suggesting that the compounds show unspecific activity depending upon the number of free phenolic hydroxy groups per molecule.

A large number of microalgae isolated from Thailand were screened for their hydrogen production capacity. The selected highly efficient microalga, identified as Nostoc sp. CU2561, was investigated for the conditions under which the cells had maximal hydrogen production rate. Nostoc sp. CU2561 showed highest hydrogen production rate when grown in BG11 medium deprived of nitrogen and sulfur (BG11-N-S). To further improve hydrogen production, newly invented agar beads were used as matrix for cell immobilization. The highest hydrogen production rate by 1.5% (w/v) agar bead immobilized cells was obtained using cell concentration of 0.125 mg dry wt mL−1. Agar bead–immobilized cells showed superior hydrogen production rate, 1.5-fold higher when compared with agar cube–immobilized cells, and 5- and 10-fold higher when compared with those in alginate bead–immobilized and alginate bead–suspended cells, respectively. Supplementation of 0.5% (w/v) fructose increased hydrogen production rate of agar bead–immobilized cells approximately 1.7-fold, whereas the reducing agent β-mercaptoethanol increased hydrogen production rate by about 8.2-fold. Overall, Nostoc sp. CU2561 immobilized in agar bead showed the highest hydrogen production rate when incubated in BG11-N-S containing 5 mM β-mercaptoethanol with the highest hydrogen production rate of 18.78 ± 1.44 μmol H2 mg−1 chl a h−1. In addition, agar bead–immobilized cells could continuously produce hydrogen for 3 cycles. The hydrogen production by immobilized cells could be prolonged up to 120 h during the first cycle. This study provides a potential of new immobilization strategy using cyanobacteria immobilized in agar bead for hydrogen production which can be applied to scale up at industrial level in the future.

This study includes isolation of oil producing algae (Anabaena, Nostoc. Spirulina, Diatom, Volvox, Spirogyra) and subjecting the mixture of algae to the sun dried pulp extract of Tamarindusindica to observe inhibitory effect of secondary metabolites on algal growth. The comparative analysis of inhibiting efficiency was done between the extracts of Tamarindusindica and Azadirachtaindica which proved that the secondary metabolites of Azadirachtaindica are more efficient than the secondary metabolites of Tamarindusindicain inhibiting the growth of algae. 100% and 75% concentration of the crude extracts were used to evaluate the inhibitory effect. Contamination from bacteria and fungi was prevented by maintaining the pH at 8.5. The extract of the sun dried pulp of Tamarindusindica showed inhibitory activity against the above mentioned species of algae.

Cyanobacteria are photosynthesizing prokaryotic microorganisms that stand out by the production of phycobiliproteins, which can be used as therapeutic agents, tools for medical diagnosis and as natural compounds for food coloring and cosmetics. Therefore, in order to purify the most relevant phycobiliproteins [phycocyanin (PC), allophycocyanin (APC) and phycoerythrin (PE)] from Anabaena variabilis and Nostoc sp., an aqueous two-phase system (ATPS) with different proportions of PEG/salt was used. The system was composed by PEG1500 and different salts, including potassium phosphate, sodium citrate and ammonium sulfate. Notably, both strains revealed high concentrations of phycobiliproteins when compared to other studies, highlighting the efficacy of the method. The highest values of the partition coefficient (K) observed in A. variabilis were obtained by 13% (w/w) PEG 14% (w/w) potassium phosphate proportion (KPC = 8.63 KAPC = 5.11 and KPE = 4,94) and for Nostoc sp., 13%PEG/14% sodium citrate proportion (KPC = 17.18, KAPC = 32,65 and KPE = 7.15).