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The global population growth has led to a higher demand for food production, necessitating improvements in agricultural productivity. However, abiotic and biotic stresses pose significant challenges, reducing crop yields and impacting economic and social welfare. Drought, in particular, severely constrains agriculture, resulting in unproductive soil, reduced farmland, and jeopardized food security. Recently, the role of cyanobacteria from soil biocrusts in rehabilitating degraded land has gained attention due to their ability to enhance soil fertility and prevent erosion. The present study focused on Nostoc calcicola BOT1, an aquatic, diazotrophic cyanobacterial strain collected from an agricultural field at Banaras Hindu University, Varanasi, India. The aim was to investigate the effects of different dehydration treatments, specifically air drying (AD) and desiccator drying (DD) at various time intervals, on the physicochemical properties of N. calcicola BOT1. The impact of dehydration was assessed by analyzing the photosynthetic efficiency, pigments, biomolecules (carbohydrates, lipids, proteins, osmoprotectants), stress biomarkers, and non-enzymatic antioxidants. Furthermore, an analysis of the metabolic profiles of 96-hour DD and control mats was conducted using UHPLC-HRMS. Notably, there was a significant decrease in amino acid levels, while phenolic content, fatty acids, and lipids increased. These changes in metabolic activity during dehydration highlighted the presence of metabolite pools that contribute to the physiological and biochemical adjustments of N. calcicola BOT1, mitigating the impact of dehydration to some extent. Overall, present study demonstrated the accumulation of biochemical and nonenzymatic antioxidants in dehydrated mats, which could be utilized to stabilize unfavorable environmental conditions. Additionally, the strain N. calcicola BOT1 holds promise as a biofertilizer for semi-arid regions. [ABSTRACT FROM AUTHOR]

Specialization, contextualized in a resource axis of an organism niche, is a core concept in ecology. In biotic interactions, specialization can be determined by the range of interacting partners. Evolutionary and ecological factors, in combination with the surveyed scale (spatial, temporal, biological, and/or taxonomic), influence the conception of specialization. This study aimed to assess the specialization patterns and drivers in the lichen symbiosis, considering the interaction between the principal fungus (mycobiont) and the associated Nostoc (cyanobiont), from a community perspective considering different spatial scales. Thus, we determined Nostoc phylogroup richness and composition of lichen communities in 11 Nothofagus pumilio forests across a wide latitudinal gradient in Chile. To measure specialization, cyanobiont richness, Simpson's and d′ indices were estimated for 37 mycobiont species in these communities. Potential drivers that might shape Nostoc composition and specialization measures along the environmental gradient were analysed. Limitations in lichen distributional ranges due to the availability of their cyanobionts were studied. Turnover patterns of cyanobionts were identified at multiple spatial scales. The results showed that environmental factors shaped the Nostoc composition of these communities, thus limiting cyanobiont availability to establish the symbiotic association. Besides, specialization changed with the spatial scale and with the metric considered. Cyanolichens were more specialized than cephalolichens when considering partner richness and Simpson's index, whereas the d′ index was mostly explained by mycobiont identity. Little evidence of lichen distributional ranges due to the distribution of their cyanobionts was found. Thus, lichens with broad distributional ranges either associated with several cyanobionts or with widely distributed cyanobionts. Comparisons between local and regional scales showed a decreasing degree of specialization at larger scales due to an increase in cyanobiont richness. The results support the context dependency of specialization and how its consideration changes with the metric and the spatial scale considered. Subsequently, we suggest considering the entire community and widening the spatial scale studied as it is crucial to understand factors determining specialization. [ABSTRACT FROM AUTHOR]

Introduction: Today, the production of green silver nanoparticles by cyanobacteria as antimicrobial agents is widely used in medical and therapeutic industries. In this study, considering that so far no study has been conducted to investigate the potency of cyanobacteria Nostoc sp. as aquatic water belonging to the freshwater of Golestan province, we decided to evaluate the potential of this strain in the biosynthesis of silver nanoparticles by performing different techniques. Materials and Methods: After the growth and molecular identification of cyanobacteria Nostoc sp. in the BG-110 culture medium in the growth chamber, two wet biomass and boiling methods were used to produce silver nanoparticles. Then, by inoculating wet biomass at concentrations of 1, 2, and 3 mM silver nitrate and comparing color change, UV-Vis spectroscopy peaks, and measuring stability at 0, 12, 24, and 48 hours, the most efficient method of silver nanoparticle biosynthesis was selected. In addition, instrumental analysis of Raman and Fourier Transform Infrared (FTIR) spectroscopy, Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and antimicrobial disk antimicrobial properties for the best and most stable nanoparticle production method was done. Results: Among the two methods used in the production of silver nanoparticles, by examining the dark brown color and the strong 420 nm peak obtained from UV-Vis spectroscopy, the wet biomass method at a concentration of 1 mM at zero time had the highest adsorption compared to the boiling method. The results of FTIR showed successful production of silver nanoparticles using wet biomass of cyanobacterium Nostoc sp. at a concentration of 1 mM silver nitrate at time zero as a safe and biodegradable method, environmentally friendly, low cost, and in accordance with the principles of green chemistry. In addition, the results of FTIR showed that biosynthesized silver nanoparticles had a protein coating that plays a major role in the reduction and stability of silver nanoparticles. The DLS results showed that the nanoparticles produced were between 28 and 50 nanometers in size and the average size of silver nanoparticles was 16.1 nanometers. The results of SEM microscopy showed that the size of the produced nanoparticles was between 28 and 50 nm in terms of spherical morphology. Also, the results of the one-way analysis of variance and Tukey test showed significant inhibitory power of silver nanoparticles against Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa. Discussion and Conclusion: Cyanobacteria Nostoc sp. can be used as a potential factor in the production of silver nanoparticles with unique properties and performance for various applications in medicine, industry, etc. [ABSTRACT FROM AUTHOR]

The cyanobacteria Nostoc commune contains bioactive compounds with antimicrobial activity and high potential to control of phytopathogens. The objective of this work was to determine the in vitro effect of sonicated biomass of these cyanobacteria on the growth of Fusarium oxysporum. The biomass of N.commune was dissolved in sterile distilled water and subjected to centrifugation processes and ultrasound-assisted cell rupture. The antifungal effect was evaluated using the disk diffusion technique (Kirby-Bauer) in a PDA (Potato Dextrose Agar) medium. In the center of the Petri dish, an agar disk (0.7 cm) with pure mycelium of the fungus was placed in the center of the Petri dish and, around it, four filter paper disk impregnateed with the algae extract (0.7 cm) were placed. The radial growth of the pathogen was measured in the presence and absence of N. commune, until the control covered the entire Petri dish to assess the Percentage of Radial Inhibition of the pathogen (PICR %). The growth rate of the fungus was lower in the initial stages of measurement and the PICR fluctuated between 33 and 58%. However, there were no inhibition halos in the growth of the fungus, it is assumed that the antifungal effect of the cyanobacteria was not permanent over the time, but it could be potentiated by improving the extraction process of the extract. [ABSTRACT FROM AUTHOR]

The phycobilisome (PBS) is an antenna protein complex in cyanobacteria, Glaucocystophytes, and red algae. In the standard PBS, the rod-core PBS, the rods are connected to the core by the rod-core linker protein CpcG. The rod-core PBS transfers the light energy mainly to photosystem (PS) II and to a lesser extent to PSI. Cyanobacteria assemble another type of PBS, the CpcL-PBS, which consists of only one rod. This rod-type PBS is connected to the thylakoid membrane by the linker protein CpcL and is a PSI-specific antenna. In the filamentous heterocyst-forming cyanobacterium Anabaena (Nostoc) sp. PCC 7120, the CpcL-PBS forms a complex with the tetrameric PSI (PBS-PSI supercomplex). The CpcL-PBS and the rod part of the rod-core PBS are identical except for the linker proteins CpcL and CpcG. How cells control the accumulation of the two different types of PBS is unknown. Here, we analyzed two mutant strains which either lack the major rod-core linker CpcG4 or overexpress the rod-membrane linker CpcL. In both mutant strains, more and larger PBS-PSI supercomplexes accumulated compared to the wild type. Our results suggest that CpcL and CpcG4 compete for the same phycobiliprotein pool, and therefore the CpcL/CpcG4 ratio determines the levels of PBS-PSI supercomplexes. We propose that the CpcL-PBS and the rod-core PBS fulfill distinct functions in light harvesting. [ABSTRACT FROM AUTHOR]

Although toxic effects of silver nanoparticles (AgNPs) on aquatic organisms have been extensively reported, responses of nitrogen-fixing cyanobacteria to AgNPs/Ag+ under environmentally relevant concentrations are largely unknown. Here, cyanobacteria were exposed to different concentrations of AgNPs (0.01, 0.1, and 1 mg/L) or Ag+ (0.1, 1, and 10 μg/L) for 96 h. The impacts of AgNPs and Ag+ on photosynthesis and N2 fixation in cyanobacteria (Nostoc sphaeroides) were evaluated. In addition, gas chromatography-mass spectrometry (GC-MS)-based metabolomics was employed to give an instantaneous snapshot of the physiological status of the cells under AgNP/Ag+ exposure. Exposure to high doses of AgNPs (1 mg/L) or Ag+ (10 μg/L) caused growth inhibition, reactive oxygen species overproduction, malondialdehyde accumulation, and decreased N2 fixation. In contrast, low doses of AgNPs (0.01 and 0.1 mg/L) and Ag+ (0.1 and 1 μg/L) did not induce observable responses. However, metabolomics revealed that metabolic reprogramming occurred even at low concentrations of AgNP and Ag+ exposure. Levels of a number of antioxidant defense-related metabolites, especially phenolic acid and polyphenols (gallic acid, resveratrol, isochlorogenic acid, chlorogenic acid, cinnamic acid, 3-hydroxybenzoic acid, epicatechin, catechin, and ferulic acid), significantly decreased in response to AgNPs or Ag+. This indicates that AgNPs and Ag+ can disrupt the antioxidant defense system and disturb nitrogen metabolism even at low-dose exposure. Metabolomics was shown to be a powerful tool to detect "invisible" changes, not observable by typical phenotypic-based endpoints.

Cyanobacteriochromes (CBCRs) are small, bistable linear tetrapyrrole (bilin)-binding light sensors which are typically found as modular components in multidomain cyanobacterial signaling proteins. The CBCR family has been categorized into many lineages that roughly correlate with their spectral diversity, but CBCRs possessing a conserved DXCF motif are found in multiple lineages. DXCF CBCRs typically possess two conserved Cys residues: a first Cys that remains ligated to the bilin chromophore and a second Cys found in the DXCF motif. The second Cys often forms a second thioether linkage, providing a mechanism to sense blue and violet light. DXCF CBCRs have been described with blue/green, blue/orange, blue/teal, and green/teal photocycles, and the molecular basis for some of this spectral diversity has been well established. We here characterize AM1_1499g1, an atypical DXCF CBCR that lacks the second cysteine residue and exhibits an orange/green photocycle. Based on prior studies of CBCR spectral tuning, we have successfully engineered seven AM1_1499g1 variants that exhibit robust yellow/teal, green/teal, blue/teal, orange/yellow, yellow/green, green/green, and blue/green photocycles. The remarkable spectral diversity generated by modification of a single CBCR provides a good template for multiplexing synthetic photobiology systems within the same cellular context, thereby bypassing the time-consuming empirical optimization process needed for multiple probes with different protein scaffolds.

The suomilide and the banyasides are highly modified and functionalized non-ribosomal peptides produced by cyanobacteria of the order Nostocales. These compound classes share several substructures, including a complex azabicyclononane core, which was previously assumed to be derived from the amino acid tyrosine. In our study we were able to isolate and determine the structures of four suomilides, named suomilide B - E (1-4). The compounds differ from the previously isolated suomilide A by the functionalization of the glycosyl group. Compounds 1-4 were assayed for anti-proliferative, antibiofilm and anti-bacterial activities, but no significant activity was detected. The sequenced genome of the producer organism Nostoc sp. KVJ20 enabled us to propose a biosynthetic gene cluster for suomilides. Our findings indicated that the azabicyclononane core of the suomilides is derived from prephenate and is most likely incorporated by a proline specific non-ribosomal peptide synthetaseunit. [ABSTRACT FROM AUTHOR]

The effects of plant inoculation with plant growth-promoting cyanobacteria on the activity of phenylalanine ammonialyase (PAL), peroxidase (POD) and cell wall POD enzymes in T. vulgaris L. were investigated. A greenhouse experiment with five replications was carried out using inoculation of five cyanobacteria suspensions (2.5%) including Anabaena torulosa ISB213, Nostoc calcicola ISB215, Nostoc ellipsosporum ISB217, Trichormus doliolum ISB214 and Oscillatoria sp. ISB2116 on T. vulgaris L. plants during four months. on T. vulgaris L. plants. After four months, the plants were harvested, and the enzyme levels were measured. The statistical analysis revealed that the treatment with Nostoc ellipsosporum ISB217 had the most significant impact on PAL enzyme activity in the treated plants. Compared to the control group (0.13 ± 0.002), the plants treated with T. doliolum ISB214 exhibited the highest activity of POD (0.69 ± 0.03) enzyme and cell wall POD (0.53 ± 0.05). Also, the amount of lignin in the treated plants had a significant increase compared to the control. Considering the valuable medicinal properties of the secondary metabolites found in thyme plants and the crucial role of nutritional management in enhancing the production and quality of this medicinal plant. The usage of appropriate growth stimulants has the potential to enhance the biosynthesis of these compounds. This study demonstrated the successful application of microalgae extract as a completely natural and eco-friendly substance for increasing the yield of T. vulgaris L. plants. [ABSTRACT FROM AUTHOR]

Filamentous cyanobacteria exhibit some of the greatest developmental complexity observed in the prokaryotic domain. This includes the ability to differentiate nitrogen-fixing cells known as heterocysts, spore-like akinetes, and hormogonia, which are specialized motile filaments capable of gliding on solid surfaces. Hormogonia and motility play critical roles in several aspects of the biology of filamentous cyanobacteria, including dispersal, phototaxis, the formation of supracellular structures, and the establishment of nitrogen-fixing symbioses with plants. While heterocyst development has been investigated extensively at the molecular level, much less is known about akinete or hormogonium development and motility. This is due, in part, to the loss of developmental complexity during prolonged laboratory culture in commonly employed model filamentous cyanobacteria. In this review, recent progress in understanding the molecular level regulation of hormogonium development and motility in filamentous cyanobacteria is discussed, with a focus on experiments performed using the genetically tractable model filamentous cyanobacterium Nostoc punctiforme, which retains the developmental complexity of field isolates. [ABSTRACT FROM AUTHOR]

Ricasolia virens is an epiphytic lichen-forming fungus mainly distributed in Western Europe and Macaronesia in well-structured forests with ecological continuity that lack eutrophication. It is considered to be threatened or extinct in many territories in Europe (IUCN). Despite its biological and ecological relevance, studies on this taxon are scarce. The thalli are tripartite, and the mycobiont has a simultaneous symbiotic relationship with cyanobacteria and green microalgae, which represent interesting models to analyse the strategies and adaptations resulting from the interactions of lichen symbionts. The present study was designed to contribute to a better understanding of this taxon, which has shown a clear decline over the last century. The symbionts were identified by molecular analysis. The phycobiont is Symbiochloris reticulata, and the cyanobionts (Nostoc) are embedded in internal cephalodia. Light, transmission electron and low-temperature scanning microscopy techniques were used to investigate the thallus anatomy, ultrastructure of microalgae and ontogeny of pycnidia and cephalodia. The thalli are very similar to its closest relative, Ricasolia quercizans. The cellular ultrastructure of S. reticulata by TEM is provided. Non-photosynthetic bacteria located outside the upper cortex are introduced through migratory channels into the subcortical zone by the splitting of fungal hyphae. Cephalodia were very abundant, but never as external photosymbiodemes. [ABSTRACT FROM AUTHOR]

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The cyanobacterium Nostoc sp. contains considerable amounts of protein, iron, and calcium that could mitigate the problems of anemia and malnutrition in humans. However, the nutritional value of the edible species Nostoc sphaericum Vaucher ex Bornet & Flahault, which grows in the Moquegua region, is unknown. Descriptive research was developed, and samples were obtained from the community of Aruntaya, located in the region of Moquegua. Water samples were taken at two different points (spring and reservoir), and samples of the cyanobacteria were taken in the reservoir. The design used was completely randomized, with three repetitions. Sixteen characteristics associated with the water collected at two points were evaluated, and from the nutritional point of view, seven characteristics were evaluated in the collected algae. The physicochemical characteristics were determined using methods established in the Codex Alimentarius. For the morphological characterization at the macroscopic level, it was observed that the seaweed collected was spherical in shape, grayish-green in color, soft to the touch, and palatable. After carrying out the physicochemical and morphological characterization of the collected samples, it was verified that all were of N. sphaericum. When comparing the sixteen characteristics related to water at the two collection sites, highly significant differences (p < 0.01) were observed for most of the variables evaluated. The average data of the characteristics of the algae showed protein values of 28.18 ± 0.33%, carbohydrates of 62.07 ± 0.69%, fat of 0.71 ± 0.02%, fiber of 0.91 ± 0.02%, ash of 7.68 ± 0.10%, and moisture of 0.22 ± 0.01%. Likewise, calcium reported an average value of 377.80 ± 1.43 mg/100 g and iron of 4.76 ± 0.08 mg/100 g. High correlations (positive and negative) were obtained by evaluating seven characteristics associated with the reservoir water where the algae grew in relation to eight nutritional characteristics of the algae. In relation to the nutritional value, the amounts of protein, iron, and calcium exceed the main foods of daily intake. Therefore, it could be considered a nutritious food to combat anemia and malnutrition. [ABSTRACT FROM AUTHOR]

Currently, biotechnological advances demonstrate the potential of cyanobacteria in various areas, thus becoming a group of high economic value. The objective of this study was to obtain and develop, by biotechnological means, a consortium of cyanobacteria isolated from the rhizospheric soil of Carica papaya. The culture was carried out in BG110 culture medium, with aeration of 0,32 Lmin-1, at a light intensity of 48,83 μEm-2s-1, with a temperature of 22 °C ± 2. A consortium formed was isolated and developed. by the species Nostoc commune, Calothrix sp. and Aphanothece mitussima. The effective development of this consortium at the laboratory level is verified, with values of chlorophylls, carotenes, proteins and lipids at the end of the test of 0,18 ±0,02 µgmL-1, 0,12 ±0,004 µgmL-1, 31, 25±8,49% and 13,92±2,95 % respectively, and a decrease in nitrate concentrations of 4,03±0,12 mgL-1 in the medium. The highest values of phycocyanin were obtained 21 days after the start of the experiments (4,38±0,001 µgmL-1), which allows expanding the spectrum of microorganisms obtained from the rhizosphere with potential stimulators. [ABSTRACT FROM AUTHOR]

Lysine malonylation (Kmal) is an evolutionarily conserved post-translational modification (PTM) that has been demonstrated to be involved in cellular and organismal metabolism. However, the role that Kmal plays in response to drought stress of the terrestrial cyanobacteria N. flagelliforme is still unknown. In this study, we performed the first proteomic analysis of Kmal in N. flagelliforme under different drought stresses using LC-MS/MS. In total, 421 malonylated lysine residues were found in 236 different proteins. GO and KEGG enrichment analysis indicated that these malonylated proteins were highly enriched in several metabolic pathways, including carbon metabolism and photosynthesis. Decreased malonylation levels were found to hinder the reception and transmission of light energy and CO2 fixation, which led to a decrease in photosynthetic activity. Kmal was also shown to inhibit the flux of the TCA cycle and activate the gluconeogenesis pathway in response to drought stress. Furthermore, malonylated antioxidant enzymes and antioxidants were synergistically involved in reactive oxygen species (ROS) scavenging. Malonylation was involved in lipid degradation and amino acid biosynthesis as part of drought stress adaptation. This work represents the first comprehensive investigation of the role of malonylation in dehydrated N. flagelliforme, providing an important resource for understanding the drought tolerance mechanism of this organism. [ABSTRACT FROM AUTHOR]

Lipoxygenase (EC1.13.11.12, LOX) has been potentially used in the food industry for food quality improvement. However, the low activity, poor thermal stability, narrow range of pH stability, as well as undesirable isoenzymes and off-flavors, have hampered the application of current commercial LOX. In this study, a putative mini-lipoxygenase gene from cyanobacteria, Nostoc sphaeroides (NsLOX), was cloned and expressed in E. coli BL21. NsLOX displayed only 26.62% structural identity with the reported LOX from Cyanothece sp., indicating it as a novel LOX. The purified NsLOX showed the maximum activity at pH 8.0 and 15 °C, with superior stability at a pH range from 6.0 to 13.0, retaining about 40% activity at 40 °C for 90 min. Notably, NsLOX exhibited the highest specific activity of 78,080 U/mg towards linoleic acid (LA), and the kinetic parameters—Km, kcat, and kcat/Km—attain values of 19.46 μM, 9199.75 s−1, and 473.85 μM−1 s−1, respectively. Moreover, the activity of NsLOX was obviously activated by Ca2+, but it was completely inhibited by Zn2+ and Cu2+. Finally, NsLOX was supplied in steamed bread and contributed even better improved bread quality than the commercial LOX. These results suggest NsLOX as a promising substitute of current commercial LOX for application in the food industry. [ABSTRACT FROM AUTHOR]

Nocuolin A (1), an oxadiazine, was isolated from the cyanobacterium Nostoc sp. Its chemical structure was elucidated using NMR and mass spectroscopic data. From this compound, two new oxadiazines, 3-[(6R)-5,6-dihydro-4,6-dipentyl-2H-1,2,3-oxadiazin-2-yl]-3-oxopropyl acetate (2) and 4-{3-[(6R)-5,6-dihydro-4,6-dipentyl-2H-1,2,3-oxadiazin-2-yl]-3-oxopropoxy}-4-oxobutanoic acid (3), were synthesised. The chemical structures of these two compounds were elucidated by a combination of NMR and MS analysis. Compound 3 showed cytotoxicity against the ACHN (0.73 ± 0.10 μM) and Hepa-1c1c7 (0.91 ± 0.08 μM) tumour cell lines. Similarly, compound 3 significantly decreased cathepsin B activity in ACHN and Hepa-1c1c7 tumour cell lines at concentrations of 1.52 ± 0.13 nM and 1.76 ± 0.24 nM, respectively. In addition, compound 3 showed no in vivo toxicity in a murine model treated with a dose of 4 mg/kg body weight. [ABSTRACT FROM AUTHOR]

Blue-green algae, also known as cyanobacteria, play a significant role in soil habitats as they impact the growth and development of plants. They serve as Plant Growth Promoting Rhizobacteria (PGPR) by conducting photosynthesis, fixing nitrogen, and enhancing soil mass growth and nitrogen levels. This research aimed to isolate cyanobacteria from various Governorates including Kafr El-Sheikh, El-Gharbia, El-Dakahlia, Damietta, and El-Behiera, and identified 50 different cyanobacterial isolates through morphological characterizations such as thallus color, morphology and dimension, heterocyst size, vegetative and reproductive cells. The majority of isolates were identified as Nostoc sp., Anabaena sp., Calothrix sp., and Oscillatoria sp., while the lesser frequent ones included Calothrix sp., Oscillatoria sp., Phormidium sp., and Pseudanabaena sp. Those isolates that exhibited the most favorable properties in fixed nitrogen and mass production were identified using molecular 16S rRNA and were found to belong to Nostoc lichenoides, Nostoc indistinguendun and Nostoc favosum. [ABSTRACT FROM AUTHOR]

Three cyanobacterial filamentous, heterocystous isolates (A, B, and C) were isolated from sandy soil collected from the Ismailia Agricultural Research Station (ARC), Ismailia Governorate, Egypt. A polygenic approach was used to characterize these isolates, which included morphology, ultrastructure, and molecular analyses. The morphological analyses for the three strains agree with the molecular data (16S, ITS, and 23S rRNA sequences and phylogeny); the order of our isolates is: Nostocales and family: Nostocaceae, they identified as the following: isolate A: Trichormus variabilis; isolate C: Trichormus sp.) which are filamentous and terminal heterocysts; and isolate B: Nostoc sp.) colonies formed of filamentous heterocysts enclosed in a membrane and gelatinous polysaccharide sheath. Dry weight, pigment content, phytohormones, total nitrogen, total protein, exopolysaccharides, and phosphate dissolving were determined for three strains. The results showed that Trichormus variabilis has the highest chlorophyll a content, Nostoc sp. has the highest carotenoid content, and three strains have almost similar phycocyanin content, while three strains can secrete phytohormones and nitrogen in their medium and dissolve phosphate, with near values in Trichormus variabilis and Trichormus sp. and a slight difference in Nostoc sp. According to the findings of this study, cyanobacterial strains isolated from Ismailia Agricultural Research Station can be used as biofertilizers and nitrogen-fixing fertilizers because of their ability to secrete phytohormones and bioactive compounds and fix air nitrogen in free nitrogen medium. [ABSTRACT FROM AUTHOR]

Under nitrogen‐limiting conditions, the filamentous cyanobacterium Nostoc PCC7120 differentiates nitrogen‐fixing heterocysts at semi‐regular intervals along filaments generating a periodic pattern of two distinct cell types. Heterocysts are micro‐oxic cells that host the oxygen‐sensitive nitrogenase allowing two antagonistic activities to take place simultaneously. Although several factors required to control the differentiation process are known, the molecular mechanisms engaged have only been elucidated for a few of them. The patB (cnfR) gene has been shown to be essential for heterocyst formation and nitrogen fixation in this cyanobacterium, but its function remains to be clarified. Here, we show that PatB acts as a direct transcriptional regulator of genes required for nitrogenase production and activity. The DNA‐binding activity of PatB does not depend on micro‐oxia as it interacts with its target promoters under aerobic conditions both in vitro and in vivo. The absence of the DNA‐binding domain of PatB can be rescued in the heterocyst but not in the vegetative cell. Furthermore, the putative ferredoxin domain of PatB is not essential to its interaction with DNA. The patB gene is widely conserved in cyanobacterial genomes and its function can be pleiotropic since it is not limited to nitrogen fixation control. [ABSTRACT FROM AUTHOR]

The biotechnological potential of Nostoc linckia as a biofertilizer and source of bioactive compounds makes it important to study its growth physiology and productivity. Since nitrogen is a fundamental component of N. linckia biomass, we compared the growth and biochemical composition of cultures grown in BG11 (i.e., in the presence of nitrate) and BG110 (in the absence of nitrate). Cultures grown in BG11 accumulated more cell biomass reaching a dry weight of 1.65 ± 0.06 g L–1, compared to 0.92 ± 0.01 g L–1 in BG110 after 240 h of culture. Biomass productivity was higher in culture grown in BG11 medium (average 317 ± 38 mg L–1 day–1) compared to that attained in BG110 (average 262 ± 37 mg L–1 day–1). The chlorophyll content of cells grown in BG11 increased continuously up to (39.0 ± 1.3 mg L–1), while in BG110 it increased much more slowly (13.6 ± 0.8 mg L–1). Biomass grown in BG11 had higher protein and phycobilin contents. However, despite the differences in biochemical composition and pigment concentration, between BG11 and BG110 cultures, both their net photosynthetic rates and maximum quantum yields of the photosystem II resulted in similar. [ABSTRACT FROM AUTHOR]

Thermophilic cyanobacteria thrive in sulphur-rich thermal springs. Mesophilic cyanobacteria thrive at temperatures between 28℃ and 37 ℃. This research was aimed at determining whether mesophilic cyanobacteria could thrive at high temperatures in the presence of sulphide and what could be the possible role of sulphide play in lessening thermal stress in mesophilic cyanobacterial organisms. The growth of the mesophilic cyanobacterium Nostoc ellipososporum was examined under thermal stress at its optimal growth temperature and in the presence and absence of sulphide. Under the same settings, the amount of enzymatic antioxidant was determined. Out of nine mesophilic cyanobacterial organisms tested, Nostoc ellipososporum was one thatgrew at 42°C, though at a slower rate than at 28°C. This organism's tolerance threshold for Sulphide was determined by growing it in a range of sodium sulphide concentrations (0.5 to 5 mM). The deleterious effect of thermal stress was eliminated by adding 2.5 mM sulphide to the cell cultures at 42℃. Enzymatic antioxidants (SOD, POD, and CAT) in the test organism were estimated under temperature stress and in the presence of sulphide. In the presence of sulphide, the levels of enzymatic antioxidants was evaluated. With an increase in antioxidants such as SOD, POD, and CAT the organism does exhibited growth with a slower rate at high temperature stress conditions. This is the first study to look into the role of sulphide in thermal stress relief by stimulating enzymatic reactions in the mesophilic cyanobacterium Nostoc ellipososporum. This revealed that reactive oxygen species were produced in response to heat stress but these antioxidants scavenged the free radicals that were generated. [ABSTRACT FROM AUTHOR]

Plant endosymbiosis with nitrogen-fixing cyanobacteria has independently evolved in diverse plant lineages, offering a unique window to study the evolution and genetics of plant-microbe interaction. However, very few complete genomes exist for plant cyanobionts, and therefore little is known about their genomic and functional diversity. Here, we present four complete genomes of cyanobacteria isolated from bryophytes. Nanopore long-read sequencing allowed us to obtain circular contigs for all the main chromosomes and most of the plasmids. We found that despite having a low 16S rRNA sequence divergence, the four isolates exhibit considerable genome reorganizations and variation in gene content. Furthermore, three of the four isolates possess genes encoding vanadium (V)-nitrogenase (vnf), which is uncommon among diazotrophs and has not been previously reported in plant cyanobionts. In two cases, the vnf genes were found on plasmids, implying possible plasmid-mediated horizontal gene transfers. Comparative genomic analysis of vnf-containing cyanobacteria further identified a conserved gene cluster. Many genes in this cluster have not been functionally characterized and would be promising candidates for future studies to elucidate V-nitrogenase function and regulation.

The suomilide and the banyasides are highly modified and functionalized non-ribosomal peptides produced by cyanobacteria of the order Nostocales. These compound classes share several substructures, including a complex azabicyclononane core, which was previously assumed to be derived from the amino acid tyrosine. In our study we were able to isolate and determine the structures of four suomilides, named suomilide B – E (1–4). The compounds differ from the previously isolated suomilide A by the functionalization of the glycosyl group. Compounds 1–4 were assayed for anti-proliferative, anti-biofilm and anti-bacterial activities, but no significant activity was detected. The sequenced genome of the producer organism Nostoc sp. KVJ20 enabled us to propose a biosynthetic gene cluster for suomilides. Our findings indicated that the azabicyclononane core of the suomilides is derived from prephenate and is most likely incorporated by a proline specific non-ribosomal peptide synthetase-unit.

In the boreal forests, feather mosses such as Hylocomium splendens and Pleurozium schreberi are colonized by cyanobacteria, which provide large amounts of nitrogen to forest ecosystems through nitrogen fixation. Although these feather mosses are also ubiquitous in subalpine forests of East Asia, little is known regarding their associated cyanobacteria and their ability to fix nitrogen. In this study, we investigated (1) whether cyanobacteria co-exist and fix nitrogen in the two species of feather mosses that cover the ground surface in a subalpine forest of Mt. Fuji, (2) whether cyanobacteria belonging to a common cluster with boreal forests are found in feather mosses in Mt. Fuji, and (3) whether moss-associated nitrogen fixation rates differed among moss growing substrates, canopy openness, and moss nitrogen concentrations in the same forest area. Our results showed that cyanobacteria colonized feather mosses in the subalpine forests of Mt. Fuji and acetylene reduction rates as an index of nitrogen fixation tended to be higher in H. splendens than in P. schreberi. Based on analysis of the nifH gene, 43 bacterial operational taxonomic units (OTUs) were identified, 28 of which represented cyanobacteria. Among the five clusters of cyanobacteria classified based on their nifH gene and identified in northern Europe, four (Nostoc cluster I, Nostoc cluster II, Stigonema cluster, and nifH2 cluster) were also found at Mt. Fuji. The acetylene reduction rate differed depending on the moss growing substrate and the total nitrogen concentration of moss shoots, and a strong negative correlation was observed with the total nitrogen concentration. [ABSTRACT FROM AUTHOR]

Peltigera lichens can colonize extreme habitats, such as high-elevation ecosystems, but their biodiversity is still largely unknown in these environments, especially in the southern hemi- sphere. We assessed the genetic diversity of mycobionts and cyanobionts of 60 Peltigera lichens collected in three high Andean steppes of southern Chile using LSU, b-tubulin, COR3 and ITS loci for mycobionts, and SSU and rbcLX loci for cyanobionts. We obtained 240 sequences for the different mycobiont markers and 118 for the cyanobiont markers, including the first report of b-tubulin sequences of P. patagonica through modifying a previously designed primer. Phylogenetic analyses, ITS scrutiny and variability of haplotypes were used to compare the sequences with those previously reported. We found seven mycobiont species and eleven cyanobiont haplotypes, including considerable novel symbionts. This was reflected by ~30% of mycobionts and ~20% of cyanobionts haplotypes that yielded less than 99% BLASTn sequence identity, 15 new sequences of the ITS1-HR, and a putative new Peltigera species associated with 3 Nostoc haplotypes not previously reported. Our results suggest that high Andean steppe ecosystems are habitats of unknown or little-explored lichen species and thus valuable environments to enhance our understanding of global Peltigera biodiversity. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and lead (Pb) are global environmental pollutants. In this study, Nostoc sp. MK-11 was used as an environmentally safe, economical, and efficient biosorbent for the removal of Cd and Pb ions from synthetic aqueous solutions. Nostoc sp. MK-11 was identified on a morphological and molecular basis using light microscopic, 16S rRNA sequences and phylogenetic analysis. Batch experiments were performed to determine the most significant factors for the removal of Cd and Pb ions from the synthetic aqueous solutions using dry Nostoc sp. MK1 biomass. The results indicated that the maximum biosorption of Pb and Cd ions was found under the conditions of 1 g of dry Nostoc sp. MK-11 biomass, 100 mg/L of initial metal concentrations, and 60 min contact time at pH 4 and 5 for Pb and Cd, respectively. Dry Nostoc sp. MK-11 biomass samples before and after biosorption were characterized using FTIR and SEM. A kinetic study showed that a pseudo second order kinetic model was well fitted rather than the pseudo first order. Three isotherm models Freundlich, Langmuir, and Temkin were used to explain the biosorption isotherms of metal ions by Nostoc sp. MK-11 dry biomass. Langmuir isotherm, which explains the existence of monolayer adsorption, fitted well to the biosorption process. Considering the Langmuir isotherm model, the maximum biosorption capacity (qmax) of Nostoc sp. MK-11 dry biomass was calculated as 75.757 and 83.963 mg g−1 for Cd and Pb, respectively, which showed agreement with the obtained experimental values. Desorption investigations were carried out to evaluate the reusability of the biomass and the recovery of the metal ions. It was found that the desorption of Cd and Pb was above 90%. The dry biomass of Nostoc sp. MK-11 was proven to be efficient and cost-effective for removing Cd and especially Pb metal ions from the aqueous solutions, and the process is eco-friendly, feasible, and reliable. [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (ZnONPs) are the top candidate in the field of biological applications because of their high surface area and excellent catalytic activities. In the present study, the cyanobacteria-mediated biosynthesis of zinc oxide NPs using Nostoc sp. extract as a stabilizing, chelating, and reducing agent is reported. ZnONPs were biologically synthesized using an eco-friendly and simple technique with a minimal reaction time and calcination temperature. Various methods, including X-ray diffraction (XRD), ultraviolet spectroscopy (UV), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the biosynthesized zinc oxide NPs. XRD analysis depicted the crystalline form of zinc oxide NPs, and the Scherrer equation determined a mean crystalline size of ~28.21 nm. The SEM results reveal the spherical shape of the biosynthesized nanoparticles. Various functional groups were involved in the capping and stabilization of the zinc oxide NPs, which were confirmed by FTIR analysis. The zinc oxide NPs showed strong UV-vis absorption at 340 nm. Multiple in vitro biological applications showed significant therapeutic potential for zinc oxide NPs. Potential antimicrobial assays were reported for zinc oxide NPs via the disc-diffusion method and food poisoning method, respectively. All other activities mentioned below are described with the concentration and IC50 values. Biocompatibility with human erythrocytes and macrophages (IC50: 433 µg/mL, IC50 > 323 µg/mL) and cytotoxic properties using brine shrimps (IC50: 11.15 µg/mL) and Leishmania tropics (Amastigotes IC50: 43.14 µg mL−1 and Promastigotes IC50: 14.02 µg mL−1) were determined. Enzyme inhibition assays (protein kinase and alpha amylase) were performed and showed strong potential. Free radical scavenging tests showed strong antioxidant capacities. These results indicate that zinc oxide NPs synthesized by Nostoc sp. have strong biological applications and are promising candidates for clinical development. [ABSTRACT FROM AUTHOR]

To significantly improve the polysaccharide production of Nostoc flagelliforme, a total of 12 chemicals were evaluated for their effects on polysaccharide accumulation. The results showed that salicylic acid and jasmonic acid increased the accumulation of the polysaccharides in N. flagelliforme significantly, by more than 20%. Three polysaccharides, namely control-capsule polysaccharide, salicylic acid-capsule polysaccharide, and jasmonic acid-capsule polysaccharide, were extracted and purified from N. flagelliforme under normal, salicylic acid, and jasmonic acid culture conditions, respectively. Their chemical compositions slightly differed regarding the total sugar and uronic acid contents, with average molecular weights of 2.06 × 103, 2.16 × 103 and 2.04 × 103 kDa, respectively. They presented similar Fourier transform infrared spectra and no significant difference in antioxidant activity. It was revealed that the salicylic acid and jasmonic acid significantly increased the level of nitric oxide. By investigating the effects of the exogenous nitric oxide scavenger and nitric oxide donor on the nitric oxide levels and polysaccharide yield of N. flagelliforme, the results showed that the increase in intracellular nitric oxide levels might be an important factor promoting the accumulation of polysaccharides. These findings provide a theoretical foundation for enhancing the yield of secondary metabolites by regulating the intracellular nitric oxide levels. [ABSTRACT FROM AUTHOR]

Cyanobacteria bioactive compounds are chemical treasure troves for product discovery and development. The wound healing effects and antioxidant capacities of water extracts from Nostoc NIES-2111_MUM004 were evaluated via in vitro wound scratch assay and three antioxidant assays respectively. Results showed that the water extracts were protein-rich and exhibited good antioxidant properties in ABTS radical scavenging (11.27 ± 0.205 mg TAE g−1 extract), Ferric reducing antioxidant power (1652.71 ± 110.71 mg TAE g−1 extract) and β-carotene bleaching assay (354.90 ± 31.80 mg TAE g−1 extract). Also, extracts were non-cytotoxic in concentrations up to 250 µg/mL as reflected in cytotoxicity assay. Importantly, water extracts showed considerable proliferation and migration activity at 125 µg/mL with wound closure rate as high as 42.67%. Statistical correlation revealed no significant relationship (p > 0.05) between protein fraction and the wound healing properties, confirming that phycobiliproteins were not solely responsible for wound healing activities. Subsequent Q-TOF-LCMS analysis identified six protein families involved in enhancing the proliferation and migration of epithelial cells. These findings are antecedent in the uncovering of continuous supplies of bioactive compounds from new and sustainable sources. Ultimately, enriching the microalgae menu for applications in pharmaceutical, nutraceutical and cosmeceuticals. [ABSTRACT FROM AUTHOR]

The feasibility and efficiency of carbon nanomaterials (CNMs) in algal biotechnology are less known. In this study, the influences of four CNMs, graphene (G), graphene oxide (GO), multiwalled carbon nanotube (MWCNT), and aminated multiwalled carbon nanotube (MWCNT-NH 2), on cell growth and exopolysaccharide (EPS) production, as well as the physiochemical properties of EPS, were investigated in cell culture of Nostoc flagelliforme. A proper concentration (15 mg L−1) of four CNMs was chosen for use after a preliminary test. Upon GO treatment, the biomass was improved by 11.1 % and the EPS production was increased by 36.1 % on day 16 compared to the nontreated control. Four CNM treatments significantly improved cellular O 2 ·− and H 2 O 2 levels as well as superoxide dismutase and catalase activities. The monosaccharide compositions and functional groups of the EPSs were obviously altered by the CNM treatments. Particularly, the GO treatment-resulting EPS showed obviously improved flocculating ability, water absorption ability, and reactive oxygen species scavenging ability. In general, four CNMs exerted distinct influences on the production and physio-chemical property alteration of the EPS in N. flagelliforme culture. This work expands our understanding of the application of CNMs in the induced production and functional modification of polysaccharides during algal cultivation. [ABSTRACT FROM AUTHOR]

A novel polysaccharide (NCVP-F) from Lactobacillus -fermented Nostoc commune Vauch. was obtained to investigate its underlying mechanism in cadmium-induced kidney injury. Results indicated that in comparison with NCVP, NCVP-F with lower molecular weight of 365.369 kDa, exhibited higher mole percentage of Man and Glc-UA, whereas slightly lower mole percentage of other monosaccharides. NCVP-F is a α-pyran polysaccharide similar to NCVP. Meanwhile, NCVP-F can more effectively alleviate hepatorenal injury (ALT, AST, TG, BUN and SCr) and kidney tissue lesions in Cd-injured mice model by increasing antioxidant enzyme activity (SOD, GSH and GSH-Px), inhibiting cytokines levels (IL-6, IL-1β, TNF-α and IL-18). In addition, NCVP-F effectively inhibited apoptosis proteins (Bax, cytochrome c , a-caspase-9 and a-caspase-3) and enhanced anti-apoptotic protein (Bcl-2) probably via activating PI3K/AKT/mTOR pathway in the Cd-injury kidney. Furthermore, 16S rRNA sequencing results indicated that NCVP-F better enriched Lachnospiraceae , reduced Muribaculaceae , Alloprevotella and Blautia to regulate Cd-induced gut microbiota disorders, which was probably down-regulated 7 pathways including apoptosis and lipopolysaccharide biosynthesis, and up-regulated 63 pathways, such as carbohydrate metabolism and lipid metabolism. This study suggested that applying functional NCVP-F prepared by biotransformation with low molecular weight might be more beneficial. [Display omitted] • A novel polysaccharide (NCVP-F) from Lactobacillus -fermentated N. commune has low M W. • NCVP-F exhibits better effect than NCVP on attenuating Cd-induced kidney injury. • NCVP-F may inhibit apoptosis by PI3K/AKT/mTOR pathway in Cd-injury kidney. • NCVPs enriched different gut microbiota involved in different metabolic pathways. [ABSTRACT FROM AUTHOR]

Owing to their crucial role in genome maintenance, RecQ helicases are ubiquitous and present across organisms. Though the multiplicity of RecQ helicases is well known in higher organisms, it is rare among bacteria. The ancient cyanobacterium Nostoc sp. strain PCC7120 was found to have three annotated RecQ helicases. This study aims at understanding its structural differences and evolution through bioinformatics approach and functionality through expression analysis studies. Nostoc RecQ helicases were found to be transcriptionally regulated by LexA and DNA damage inducing stresses. Bioinformatic analysis revealed that all three RecQ helicases of Nostoc possess helicases_C and Zn+2-binding domains. Two of the helicases (AnRecQ and AnRecQ2) lacked the complete RQC and HRDC domains, and AnRecQ2 had an additional Phosphoribosyl transferase domain (Pribosyltran), also seen in RecQ-like helicase (RqlH) protein of Mycobacterium smegmatis. AnRecQ1, which was similar to most bacterial RecQ helicases, differed in having a long C-terminal tail. STRING analysis revealed that the proteins also differed in their predicted protein interactome. Phylogenetic analysis suggested that the multiple recQ genes may have been acquired through duplication and acquisition of additional domains from the smallest of the RecQ helicases (AnRecQ) to cater multiple functions required to deal with the harsh environmental conditions. In course of evolution, however, the multiplicity was lost with the modern-day bacteria and lower eukaryotes which retained fewer RecQ helicases, while further duplication of the acquired RECQ occurred in higher animals and plants to deal with cellular complexity. [ABSTRACT FROM AUTHOR]

This research was carried out during 2019/2020 and 2020/2021 seasons, at the Experimental Station of the Central Laboratory for Agricultural climate CLAC, A.R.C, Dokki, Giza. This experiment was done under a plastic greenhouse to investigate the growth, fruit quality parameters and yield of sweet pepper plants grown under two different plastic mulch color and three different treatments of Nostoc clacicola fertilizations. The plastic mulch treatments were transparent polyethylene and white polyethylene with 100 microns thickness. Bare soil (uncovered soil) was used as a control. Transparent and white polyethylene was laid after the establishment of the double rows (0.80 m width). Beds were manually installed to correspond to treatments and Nostoc clacicola fertilization treatments: Nostoc clacicola foliar fertilization, Nostoc clacicola soil fertilization and Nostoc clacicola foliar with soil fertilization (spray+ Soil). Vegetative growth (plant height, stem diameter, number of leaves/plants, number of branches/plants, leaves fresh weight and leaf area), as well as fruit yield and quality (total yield, fruit length and fruit diameter), chemical contents (Nitrogen, Phosphorus, Potassium, Leaves dry matter% and Vitamin C) of sweet pepper (Capsicum species) Gedeon F1 Hybrid. Obtained results revealed that using transparent plastic mulch with a combination of Nostoc clacicola foliar and soil fertilization enhanced all vegetative growth measurements and increased all assayed chemical constituents of plant leaves, as well as increasing total fruit yield and components. [ABSTRACT FROM AUTHOR]

A new biosorbent based on Nostoc commune (NC) cyanobacteria, chemically modified with NaOH (NCM), has been prepared, characterized and tested as an effective biomass to remove Pb(II) in aqueous media. The adsorption capacity of NCM was determined to be qe = 384.6 mg g−1. It is higher than several other biosorbents reported in the literature. Structural and morphological characterization were performed by FTIR, SEM/EDX and point zero of charge pH (pHPZC) measurements. NCM biosorbent showed more porous surfaces than those NC with heterogeneous plates including functional adsorption groups such as OH, C = O, COO−, COH or NH. Optimal Pb(II) adsorption occurred at pH 4.5 and 5.5 with a biomass dose of 0.5 g L−1. The experimental data of the adsorption process were well fitted with the Freundlich-isotherm model and pseudo-2nd order kinetics, which indicated that Pb(II) adsorption was a chemisorption process on heterogeneous surfaces of NCM. According to the thermodynamic parameters, this process was exothermic (∆H0 < 0), feasible and spontaneous (∆G0 < 0). NCM can be regenerated and efficiently reused up to 4 times (%D > 92%). NCM was also tested to remove Pb (%R~98%) and Ca (%R~64%) from real wastewater. [ABSTRACT FROM AUTHOR]

: Species of Peltigera (lichen-forming Ascomycota) establish obligate symbioses with several monophyletic groups (phylogroups) of Nostoc cyanobacteria. Some of these fungi are strict specialists and only associate with one Nostoc phylogroup throughout their range, while others are generalists and associate with many different Nostoc phylogroups. We sampled 20 Peltigera taxa, mostly representing the Peltigera section Peltigera, from grassland and forest habitats across Europe. Mycobionts' identities were confirmed using fungal ITS sequences. The Nostoc cyanobionts were identified and grouped based on single nucleotide differences in the trnL region and on the phylogenetic analysis of the rbcLX region. Our data confirmed that some Peltigera species clearly prefer open habitats, while others are largely confined to shady forest habitats. The two habitat preferences are consistently paired with association with different Nostoc groups. As a specific example, two ecologically versatile species, Peltigera canina and P. didactyla, both growing in open and shady habitats, consistently associated with different groups of Nostoc when growing in different habitats. As associations between specific mycobionts and cyanobionts are influenced by habitat conditions, the diversity of both taxon groups should be considered in the context of habitat management and conservation planning. [ABSTRACT FROM AUTHOR]

Phycobiliprotein (PB), which is produced by cyanobacteria, has potential applications as a valuable pharmaceutical product. In this study, PB was separated by using a nonwoven-fabric membrane (Rx-1) that contained quaternary amino groups. PB was extracted from a Nostoc commune, which is a type of microalga, by disrupting the cell walls by a freeze–thaw method. Two types of biomolecules, namely PB and other biomolecules X, were identified by gel permeation chromatography. Permeation of the PB-containing solution through Rx-1 increased the purity of the PB in the filtrate from 0.25 to 0.45. The adsorption constant (Kp) and maximum adsorbed amount of each protein on Rx-1 (qmax) were determined by fitting the experimental data to a mathematical model. The obtained values for Kp and qmax were used to simulate scaled-up treatment of a PB-containing solution. Permeation of a PB-containing solution (3.0 L at 1.2 × 10−3 m³/h) through Rx-1 (volume of scale-up membrane, 8.0 × 10−4 m³) enabled PB separation for 26 h. Further PB purification could be achieved by using the Rx-1 membrane in combination with precipitation with ammonium sulfate solution and an ultrafiltration membrane. [ABSTRACT FROM AUTHOR]

Two diazotrophic cyanobacteria (Anabaena cylindrica PCC 7122 and Nostoc sp. PCC 7120) were cultivated to produce cyanophycin, a nitrogen reserve compound, under nitrogen fixing conditions. In preliminary continuous experiments, Nostoc sp. was shown to be more efficient, accumulating a higher amount of cyanophycin and showing a greater capability to fix atmospheric nitrogen in the biomass (67 mgN d−1 of fixed nitrogen per liter of culture). The operating conditions were then optimized to maximize the cyanophycin productivity: the effect of incident light intensity, residence time and nitrogen availability were investigated. Nitrogen availability and/or pH played a major role with respect to biomass production, whereas phosphorus limitation was the main variable to maximize cyanophycin accumulation. In this way, it was possible to achieve a stable and continuous production of cyanophycin (CGP) under diazotrophic conditions, obtaining a maximum cyanophycin productivity of 15 mgCGP L−1 d−1. Key points: • Diazotrophic cyanobacteria produce stable amount of cyanophycin in continuous PBR. • Nostoc sp. proved to be more efficient in producing cyanophycin than Anabaena sp. • P deprivation is the major variable to increase cyanophycin productivity in continuous. [ABSTRACT FROM AUTHOR]

Platinum nanoparticles (PtNPs) are one of the widely used NPs, which contribute to potential risks to the aquatic ecosystem. However, PtNPs toxicity in phytoplankton remains inadequately understood, with significant gaps in knowledge regarding their biochemical bases and species-specific responses. Herein, we investigated the impact of PtNPs on two cyanobacterial species (Anabaena laxa and Nostoc muscorum) to explore the harmful pathways triggered by PtNPs in cyanobacteria, which may help in selecting appropriate biomarkers for PtNPs pollution in aquatic environments. We studied the effect of PtNPs on growth, oxidative stress markers, and antioxidant defense systems of the two species. The obtained results showed that PtNPs reduced the level of chlorophyll. Furthermore, they induced dose-dependent oxidative stress to the two species, expressed by significant increases in H 2 O 2 , malondialdehyde (MDA), and protein oxidation (p < 0.05). Stress-induced oxidative damages were more pronounced in N. muscorum , yet the two cyanobacterial species showed higher levels (p < 0.05) of antioxidant metabolites and antioxidant enzymes to combat oxidative stress. Compared to N. muscorum , A. laxa invested more in the induction of antioxidant metabolites including FRAP, polyphenols, flavonoids, and glutathione (GSH), as well as in antioxidant enzymes such as POX, CAT, GR, and GPX. Overall, A. laxa species could be exploited as efficient biomarkers for monitoring PtNPs-induced ecotoxicology. Further investigation of bio-absorption and uptake of PtNPs by microalgae is recommended for developing algae-based bioremediation technologies. [Display omitted] • Impact of PtNPs on two cyanobacterial species was investigated. • PtNPs reduced the levels of chlorophylls in cyanobacterial species. • PtNPs induced dose-dependent oxidative stress to the two cyanobacterial species. • Stress-induced oxidative damages were more pronounced in N. muscorum. • A. laxa can be used as a biomarker for monitoring PtNPs-induced toxicology. [ABSTRACT FROM AUTHOR]

Highlight Mixotrophic conditions can be used to optimize the biosorption controllable factors for the maximum metal removal efficiency. Different habitats (lime stones of Khuzestan province and fresh water of of Golestan province) can effect the uptake of heavy metal by two Nostoc species (Nostoc sp. N27P72 and Nostoc sp. FB71). Modification of culture media can maximize the uptake capacity of the heavy metal ions by two Nostoc species.

Cyanobacteria belonging to the genus Nostoc comprise free-living strains and also facultative plant symbionts. Symbiotic strains can enter into symbiosis with taxonomically diverse range of host plants. Little is known about genomic changes associated with evolutionary transition of Nostoc from free-living to plant symbiont. Here, we compared the genomes derived from 11 symbiotic Nostoc strains isolated from different host plants and infer phylogenetic relationships between strains. Phylogenetic reconstructions of 89 Nostocales showed that symbiotic Nostoc strains with a broad host range, entering epiphytic and intracellular or extracellular endophytic interactions, form a monophyletic clade indicating a common evolutionary history. A polyphyletic origin was found for Nostoc strains which enter only extracellular symbioses, and inference of transfer events implied that this trait was likely acquired several times in the evolution of the Nostocales. Symbiotic Nostoc strains showed enriched functions in transport and metabolism of organic sulfur, chemotaxis and motility, as well as the uptake of phosphate, branched-chain amino acids, and ammonium. The genomes of the intracellular clade differ from that of other Nostoc strains, with a gain/enrichment of genes encoding proteins to generate l-methionine from sulfite and pathways for the degradation of the plant metabolites vanillin and vanillate, and of the macromolecule xylan present in plant cell walls. These compounds could function as C-sources for members of the intracellular clade. Molecular clock analysis indicated that the intracellular clade emerged ca. 600 Ma, suggesting that intracellular Nostoc symbioses predate the origin of land plants and the emergence of their extant hosts.

Phytochrome photoreceptors control plant growth, development, and the shade avoidance response that limits crop yield in high-density agricultural plantings. Cyanobacteriochromes (CBCRs) are distantly related photosensory proteins that control cyanobacterial metabolism and behavior in response to light. Photoreceptors in both families reversibly photoconvert between two photostates via photoisomerization of linear tetrapyrrole (bilin) chromophores. Spectroscopic and biochemical studies have demonstrated heterogeneity in both photostates, but the structural basis for such heterogeneity remains unclear. We report solution NMR structures for both photostates of the red/green CBCR NpR6012g4 from Nostoc punctiforme In addition to identifying structural changes accompanying photoconversion, these structures reveal structural heterogeneity for residues Trp655 and Asp657 in the red-absorbing NpR6012g4 dark state, yielding two distinct environments for the phycocyanobilin chromophore. We use site-directed mutagenesis and fluorescence and absorbance spectroscopy to assign an orange-absorbing population in the NpR6012g4 dark state to the minority configuration for Asp657. This population does not undergo full, productive photoconversion, as shown by time-resolved spectroscopy and absorption spectroscopy at cryogenic temperature. Our studies thus elucidate the spectral and photochemical consequences of structural heterogeneity in a member of the phytochrome superfamily, insights that should inform efforts to improve photochemical or fluorescence quantum yields in the phytochrome superfamily.

In this paper, Nostoc commune crude polysaccharide was extracted by heating and Ultrasonic-assisted methods separately, homogeneous polysaccharide HNCP3 and UNCP4 were obtained after purified by DEAE-52 cellulose column chromatography and Sephacryl G-100 gel column chromatography. The structures of HNCP3 and UNCP4 were characterized by molecular weight determination, infrared spectroscopy, DSC detection, sodium periodate oxidation, smith degradation reaction and methylation analysis. The conformation of the solution was studied by SEM and AFM. The results showed that the Ultrasonic-assisted extraction had effects on the molecular weight, monosaccharide composition, molar ratio and configuration of Nostoc commune. The main chain of HNCP3 and UNCP4 was → 6)-D-Glcp(1→ and → 2, 6)-D-Glcp, but UNCP4 contained 1, 2, 6-galactose and 2, 3-Me2-D-Ara branches, while HNCP3 did not. The results of the monosaccharides composition of indicated that mannose was presented in both HNCP3 and UNCP4. SEM and AFM showed that the structure of UNCP4 was helical, and the solution conformations of HNCP3 and UNCP4 were different in different solution environments. Studies on DPPH radicals, superoxide anions, and hydroxyl radicals scavenging abilities showed that UNCP4 had higher antioxidant activity, while studies on the antidiabetic activities showed that the hypoglycemic effect of UNCP4 was stronger than that of HNCP3. Therefore, Ultrasonic-assisted extraction (UAE) increases the bioactivity of Nostoc commune polysaccharide (NCP) as well as the extraction rate. [ABSTRACT FROM AUTHOR]

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 hexavalent Chromium [Cr(VI)] elimination from Cr-contaminated wastewater. Optimisation process was achieved in order to obtain the optimum conditions that help achieving the highest Cr(VI) removal efficiency. For instance, One Factor At a Time 'OFAT' experiments were performed for the determination of the coded factors levels (low/high levels) that can be included in the Full factorial design experiment 'many interacted factors at a time'. Afterwards, a small reactor design was implemented to develop Nostoc sp. algal biofilm. After that, the algal biofilm was applied in the Cr(VI) removal process to facilitate harvesting and dewatering of the biomass after the treatment process. Results showed that, live planktonic Nostoc sp. achieved the highest Cr(VI) removal efficiency of 98.16%at 100 ppm after 7 days contact time. Furthermore, Nostoc sp. stated its great ability to form a biofilm on polystyrene substrate which achieved the highest Cr(VI) removal of '86.498%' at a concentration of 100 ppm after 7 days contact time. Some characterisation techniques such as Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analyses were applied on the developed biofilm of Nostoc sp. Isotherm and kinetics were investigated for the Cr(VI) removal process using Nostoc sp. biofilm. [ABSTRACT FROM AUTHOR]

Multicellular organisms require controlled intercellular communication for their survival. Strains of the filamentous cyanobacterium Nostoc regulate cell–cell communication between sister cells via a conformational change in septal junctions. These multi-protein cell junctions consist of a septum spanning tube with a membrane-embedded plug at both ends, and a cap covering the plug on the cytoplasmic side. The identities of septal junction components are unknown, with exception of the protein FraD. Here, we identify and characterize a FraD-interacting protein, SepN, as the second component of septal junctions in Nostoc. We use cryo-electron tomography of cryo-focused ion beam-thinned cyanobacterial filaments to show that septal junctions in a sepN mutant lack a plug module and display an aberrant cap. The sepN mutant exhibits highly reduced cell–cell communication rates, as shown by fluorescence recovery after photobleaching experiments. Furthermore, the mutant is unable to gate molecule exchange through septal junctions and displays reduced filament survival after stress. Our data demonstrate the importance of controlling molecular diffusion between cells to ensure the survival of a multicellular organism. The filamentous cyanobacterium Nostoc regulates communication between sister cells via a conformational change in septal junctions. Here, the authors identify and characterize protein SepN as a component of septal junctions, and highlight the importance of controlling molecular diffusion between cells to ensure the survival of a multicellular organism. [ABSTRACT FROM AUTHOR]

Different activities related to uranium mining and nuclear industry may have a negative impact on the environment. Bioremediation of nuclear pollutants using microorganisms is an effective, safe, and economic method. The present study compared the uranium biosorption efficiency of two immobilized algae: Nostoc sp. (cyanophyte) and Scenedesmus sp. (chlorophyte). Effects of metal concentration, contact time, pH, and biosorbent dosage were also studied. The maximum biosorption capacity (60%) by Nostoc sp. was obtained at 300 mg/l uranium solution, 60 min, pH 4.5, and 4.2 g/l algal dosage, whereas Scenedesmus sp. maximally absorbed uranium (65 %) at 150 mg/l uranium solution, 40 min, pH 4.5, and 5.6 g/l of algal dosage. The interaction of metal ions as Na2SO4, FeCl3, CuCl2, NiCl2, CoCl2, CdCl2, and AlCl3 did not support the uranium biosorption by algae. The obtained data was adapted to the linearized form of the Langmuir isotherm model. The experimental qmax values were 130 and 75 mg/g for Nostoc sp. and Scenedesmus sp., respectively. Moreover, the pseudo-second-order kinetic model was more applicable, as the calculated parameters were close to the experimental data. The biosorbents were also characterized by Fourier-transform infrared spectroscopy (ATR-FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) analyses. The results suggest the applicability of algae, in their immobilized form, for recovery and biosorption of uranium from aqueous solution. [ABSTRACT FROM AUTHOR]

• NaCl negatively affected the growth and growth related parameters i.e. proteins and exopolysaccharides contents, light harvesting pigments and photosynthesis as well as PS II photochemistry by increasing the oxidative stress. • Calcium and kinetin alleviated the toxicity induced by NaCl on cyanobacterial physiology. • Calcium is essentially needed for kinetin mediated regulation of NaCl toxicity. In the present study, the possible roles of kinetin (KN, 20 nM) and calcium (Ca2+, 0.8 mM) in the alleviation of the salinity stress (50 mM NaCl) induced damage on the growth, and metabolism of cyanobacterium Nostoc muscorum ATCC 27893 was explored. The results revealed that salinity stress decreased the growth, light-harvesting pigments (chlorophyll a , carotenoids and phycobiliproteins) and exopolysaccharides (EPS) contents, photosynthesis (whole-cell oxygen evolution), and the performance of PS II photochemistry [Chl a fluorescence kinetics: maximum photosynthetic quantum yield (Fv/Fm or Phi_Po), quantum yield of electron transport flux (Phi_Eo), yield of electron transport per trapped exciton (Psi_o), size and number of active photosynthetic reaction centers (Fv/Fo) and performance index (PI ABS)]. Reverse to this, enhancement of respiratory rate and values of PS II related energy flux parameters [absorption flux per reaction center (ABS/RC), trapping flux per reaction center (TRo/ RC), dissipation flux per reaction center (DIo/RC), and electron transport flux per reaction center (ETo/RC)], and rise in levels of oxidative biomarkers (superoxide radical; O 2 • , hydrogen peroxide; H 2 O 2, and malonaldehyde; MDA equivalents) even under accelerated activity of enzymatic antioxidants (superoxide dismutase; SOD, peroxidase; POD, catalase; CAT and glutathione-s-transferase; GST) were observed. Kinetin in presence of Ca2+ improved the growth, pigments contents and performance of PS II photochemistry by down-regulating the oxidative stress biomarkres. Application of Ca2+ scavenger (EGTA) in KN treated samples increased the damaging effect on growth and photosynthesis by aggravating oxidative stress under NaCl stress, thereby indicating the positive role of Ca2+ in NaCl-induced toxicity alleviation by KN. The overall results suggest that Ca2+ together with KN could be applied in paddy fields to up-regulate the growth of N 2 –fixing cyanobacterium Nostoc muscorum ATCC 27893, an inhabitant of paddy field under NaCl stress, hence they may be considered for sustainable agriculture. [ABSTRACT FROM AUTHOR]