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Cyanobacteria can form nitrogen-fixing symbioses with a broad range of plant species. Unlike other plant-bacteria symbioses, little is understood about the immunological responses induced by plant cyanobionts (symbiotic cyanobacteria). Here, we demonstrated that the model plant-symbiotic cyanobacteria, Nostoc punctiforme is capable of protecting against programmed cell death (PCD) when induced in Arabidopsis thaliana suspension cell cultures. We also profiled the early transcriptomic changes that were induced in response to conditioned medium (CM) from N. punctiforme cell cultures. Interestingly, the reduction in PCD was preceded by the induction of genes associated with defence and immunity, the most striking of which were a number of WRKY-family transcription factors. Down-regulated genes included those involved in the regulation of cell growth and differentiation. This work is the first to show that a cyanobiont can affect plant PCD and provides a useful transcriptome resource for studying early plant cell responses to symbiotic cyanobacteria.

The aim of this study was to isolate a filamentous nitrogen-fixing cyanobacterium Nostoc sphaeroides (NS) from brackish water of Chilika Lake, Odisha coast, and exploration of its use in the biosynthesis of silver-nanoparticles (AgNPs) against the urinary tract–infecting bacterial strains. The synthesized NS-AgNPs were structurally characterized by analytical techniques such as UV-visible-spectrophotometry, FTIR, XRD, SEM and SEM-EDX. The antibacterial efficacy of synthesized AgNPs had remarkable in vitro activities with the MIC value of 50 mg/ml. Moreover, Nostocine A, the inherent bioactive compound of Nostoc sp. was further investigated for molecular docking studies against the targeted bacterial DNA gyrase (Escherichia coli) and the obtained docking score was −7.9 kCal/mol as compared with the standard drug, Ciprofloxacin of a docking score −7.8 kCal/mol. The concordance between molecular docking and experimental results is excellent. Thus, the biogenic-synthesized “N. sphaeroides-AgNPs” would be used as an antibacterial agent in future.

The Nostoc sp. strain CCCryo 231-06 is a cyanobacterial strain capable of surviving under extreme conditions and thus is of great interest for the astrobiology community. The knowledge of its complete genome sequence would serve as a guide for further studies. However, a major concern has been placed on the effects of contamination on the quality of sequencing data without a reference genome. Here, we report the use of microfluidic technology combined with single cell sequencing and de novo assembly to minimize the contamination and recover the complete genome of the Nostoc strain CCCryo 231-06 with high quality. 100% of the whole genome was recovered with all contaminants removed and a strongly supported phylogenetic tree. The data reported can be useful for comparative genomics for phylogenetic and taxonomic studies. The method used in this work can be applied to studies that require high-quality assemblies of genomes of unknown microorganisms.

Iron is essential for growth of most organisms, including cyanobacteria, a ubiquitous and ecologically important group of microorganisms in nature. The present study was initiated to investigate the effects of iron starvation on the growth, frequency of heterocysts (the sites for nitrogen-fixation), photosynthetic pigments and photosynthesis in the filamentous, nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133. Iron starvation was achieved in cyanobacterial cultures by growing them in medium free of combined nitrogen containing 2,2’dipyridyl (a high affinity iron-chelator) without any addition of iron source. Compared to iron-sufficient control cultures, the iron-starved cultures showed decrease in growth determined for 15 days. The reduction in growth was coupled with a decreased heterocyst (N2-fixation sites) frequency and the number of cells per filament measured after 2 and 4 days of iron-starvation. Similarly, a considerable drop in the concentration of photosynthetic pigments such as, phycocyanin and chlorophyll a were also noticed in iron-starved cultures. Carotenoid level, however, was higher in iron-starved cultures compared to control. The maximum quantum efficiency of photosystem II photochemistry indicating the photosynthetic efficiency was severely affected in iron-starved Nostoc punctiforme ATCC 29133. Overall, the results presented in this study suggest that deficiency of iron negatively impacts growth, photosynthesis and perhaps nitrogen-fixation in the cyanobacterium N. punctiforme ATCC 29133. Given the role of cyanobacteria in biofertilizer technology, it is suggested that iron bio-availability in agricultural fields may strongly impact the biofertilizer potential of diazotrophic cyanobacteria. Therefore, efforts to improve biofertilizer potential of cyanobacteria may be directed towards identifying strains which can better adapt to iron deficiency.

Bacilli species are Gram-positive, aerobic, spore-forming bacteria that are widely spread in soil, dust, and water. One strain, Bacillus sp. strain WL1, was isolated from the surface of the cyanobacterium Nostoc flagelliforme in Yinchuan, Ningxia, China. The draft genome sequence of this strain was 5.62 Mbp.

The chemical composition and influence of exometabolites of the soil cyanobacterium Nostoc paludosum 18 on the barley plants of Izumrud variety were studied. Exometabolites from the culture liquid were extracted with hexane and carbon tetrachloride. Organic substances in the studied substrates were determined by high-performance liquid chromatography on the Shimadzu LC-20 chromatograph, Prominence series with a diode-matrix detector and gas chromatography on the GС-2014 Shimadzu chromatograph with a TCD-2014 detector (Japan). The intensity of lipid peroxidation in barley cells was studied by the accumulation of malondialdehyde using SPEKOL 1300 spectrophotometer (Analytik Jena, Germany). Cyanobacterial suspension, culture liquid and extracts from it were similar in composition and quantity of organic substances and contained such compounds as phytoene, phytofluin, N-acetylglucosamine, peptidoglycan murein, lycopene, lutein, kauren (a precursor of gibberellin), vitamin A, provitamins, peptide borofitsin. The stimulating effect of N. paludosum exometabolites on linear growth of barley aboveground organs and roots mainly manifests itself in the first three days of their growth. Cyanobacterial exometabolites reduce the intensity of lipid peroxidation in plant cells, which indicates their antioxidant activity. Exometabolites of cyanobacterial suspension and hexane extract have a protective effect on plants, leveling the growth- inhibitory effect of copper (II) ions on the height of seedlings. The concentration of copper (II) ions was 3 mg / kg of the substrate for growing wheat. Cultivation of barley on cyanobacterial suspension and extraction of exometabolites with carbon tetrachloride results in the accumulation of peptide borofitsin in barley tissues in the amount of 0,0008–0,001 µg / g of dry weight.

The cyanobacterium Nostoc commune (Nostocales) is an isolate from the Schirmacher Oasis Antarctica. The cyanobacterium is psychrotropic in nature; and maintained in laboratory at 25 °C temperature,...

Volume 87, no. 2, e02499-20, 2021, [https://doi.org/10.1128/AEM.02499-20][1]. Supplemental material: Fig. S1 and S2 were missing from the originally published supplemental material file. Revised supplemental material is posted online. [1]: /lookup/doi/10.1128/AEM.02499-20

The influence of the cyanobacteriumNostoc muscorumon vital activity of barley seedlings of the species Novichok was researched. In the experiments different ways of cyanobacterial treatment were used: introducing microorganisms in the growth medium and pre-sowing inoculation of barley seeds with cyanobacteria. The influence of cyanobacterial treatment on biochemical indices and linear growth of barley plants was assessed. The share of plastid pigments and intensity of the processes of lipid peroxidation were assessed in a spectrophotometric way, standard methods were applied. It was stated thatNostoc muscorumhas a phytostimulating effect which consists in inhibiting oxidation processes in barley cells, accumulating substances with antioxidative activity, and activating growth processes. Pre-sowing inoculation of barley seeds with cyanobacteria is the most effective one.

The recently proposed concept of quaternary bioreceptivity applies to substrates treated with coating materials and it is considered in the present study with the alga Bracteacoccus minor and the cyanobacterium Nostoc sp. onto granite specimens treated with ethyl silicate and nano-sized silica doped with different amounts of TiO2 (0, 0.5, 1 and 3 wt%). The findings showed a lack of correlation between the amount of TiO2 and the level of colonization (main bioreceptivity estimator) to the presence of cracks on the surface, which annul the biocidal power of TiO2. Crack formation, which depends on the mechanical properties, greatly influences the bioreceptivity of the material. Thus, the cracks provided anchor points where water is retained, in turn strongly influencing the early stages of colonization kinetics, to a greater extent than the biocidal power of TiO2, which will probably increase as the biofilm develops over the entire surface. In addition, although the cracks were more abundant and wider in the ethyl silicate-based consolidant, the nano-sized silica provided better anchoring points, making the material treated with the corresponding consolidant more bioreceptive SI

Local activation and long-range inhibition are mechanisms conserved in self-organizing systems leading to biological patterns. A number of them involve the production by the developing cell of an inhibitory morphogen, but how this cell becomes immune to self-inhibition is rather unknown. Under combined nitrogen starvation, the multicellular cyanobacterium Nostoc PCC 7120 develops nitrogen-fixing heterocysts with a pattern of one heterocyst every 10–12 vegetative cells. Cell differentiation is regulated by HetR which activates the synthesis of its own inhibitory morphogens, diffusion of which establishes the differentiation pattern. Here, we show that HetR interacts with HetL at the same interface as PatS, and that this interaction is necessary to suppress inhibition and to differentiate heterocysts. hetL expression is induced under nitrogen-starvation and is activated by HetR, suggesting that HetL provides immunity to the heterocyst. This protective mechanism might be conserved in other differentiating cyanobacteria as HetL homologues are spread across the phylum., eLife digest Cyanobacteria are the only bacteria on Earth able to draw their energy directly from the sun in the same way that plants do. In addition, some strains are able to ‘fix’ the nitrogen present in the atmosphere: they can extract this gas and transform it into nitrogen-based compounds necessary for life. However, both processes cannot happen in a given cell at the same time. A strain of cyanobacteria called Nostoc PCC 7120 can organise itself into long filaments of interconnected cells. Under certain conditions, one in every ten cells stops drawing its energy from the sun, and starts fixing atmospheric nitrogen instead. Exactly how the bacteria are able to ‘count to ten’ and organize themselves in such a precise pattern is still unclear. Cells can communicate and establish patterns by exchanging molecular signals that switch on and off certain cell programs. For instance, a protein called HetR turns on the genetic program that allows cyanobacteria to fix nitrogen; on the other hand, a signal known as PatS binds to HetR and turns it off. Cells starting to specialise in fixing nitrogen produce both HetR and PatS, with the latter diffusing in surrounding cells and preventing them from extracting nitrogen. However, it remained unclear how the nitrogen-fixing cell could ignore its own PatS signal and keep its HetR signal active. HetL – another protein produced by the future nitrogen-fixing cell – could potentially play this role, but how it acts was unknown. Here, Xu et al. show that HetL cannot diffuse from one cell to the other, and that it binds to HetR at the same place than PatS does. When both PatS and HetL are present, they compete to attach to HetR, which stops PatS from turning off HetR and deactivating the nitrogen-fixing program. Understanding how cyanobacteria fix nitrogen could help to develop new types of natural fertiliser. More generally, dissecting how these simple organisms can create patterns could help to grasp how patterning emerges in more complex creatures.

Microalgal biopolymers are studied mainly in terms of physico-chemical characterization, biological effects as well as possible biotechnological applications. Due to the significant antitussive, bronchodilator, anti-inflammatory and immunomodulatory effects of the previously isolated crude extracellular polysaccharide (EPS) produced by the cyanobacterium Nostoc sp., the purified biopolymer and its oligosaccharides, obtained after partial acid hydrolysis, were subjected to an in-depth NMR structural study. Analyses of the data obtained by chemical methods and NMR showed that the EPS backbone is composed of the repeating unit [→4)-β-D-Xylp-(1 → 4)-β-D-Glcp-(1 → 4)-α-L-Arap-(1 → 3)-β-D-Manp-(1→]n, in which about 60% of glucose units are substituted at C6 by uronic acids, in particular by the unusual unsaturated 3-O-lactyl-4-deoxy-α-erythro-hex-4-enopyranuronic acid, and to a lesser extent by β-D-glucuronic acid and 3-O-lactyl-β-D-glucuronic acid. These findings, structural features and identified biological effects, suggest the potential use of this biopolymer in the medical-pharmaceutical field.

Se realizó la caracterización de ficoeritrina de la cepa A5 de Nostoc sp., seguida de investigación de su actividad biológica para aplicaciones biotecnológicas. Para la extracción de ficoeritrina, el uso de tampón acetato (pH 5.1) produjo 65.04 µg mL-1, y se identificó como C-ficoeritrina. Los resultados de su actividad antioxidante sugirieron su acción como un potente eliminador de radicales libres. Además, la C-ficoeritrina de Nostoc mostró una capacidad notable como agente antibacteriano y antifúngico, con estabilidad significativa de hasta 10 días. La glucosa (4 mg mL-1) fue un buen conservante para la C-ficoeritrina a 25 y 4 ºC. Se obtuvo por primera vez una C-ficoeritrina estable de Nostoc sp. en condiciones de sequía en piedra caliza, lo que demuestra la necesidad de estudiar microorganismos de ambientes extremos. The phycoerythrin characterization from Nostoc sp. strain A5 was done, followed by investigation of its biological activity for biotechnological applications. For phycoerythrin extraction, the use of acetate buffer (pH 5.1) resulted in 65.04 µg mL-1, and C-phycoerythrin was identified. Results of its antioxidant activity suggested action as a potent free radical scavenger. In addition, Nostoc's C-phycoerythrin showed noteworthy ability for antibacterial and antifungal agents with significant stability up to 10 days. Glucose (4 mg mL-1) was a good preservative for C-phycoerythrin at 25 and 4 ºC. A stable C-phycoerythrin from Nostoc sp. was obtained for the first time from limestone drought conditions, showing the need of studying microorganisms from extreme environments.

Availability of water may influence activities of all living organisms, including cyanobacterial communities. Filamentous cyanobacterium Nostoc commune is well adapted to wide spectrum of ecosystems. For this reason, N. commune had to develop diverse protection strategies due to exposition to regular rewetting and drying processes. Few studies have been conducted on activities, by which cyanobacteria are trying to avoid water deficit. Therefore, the present study using physiological and morphological parameters is focused on comparison between European and Antarctic ecotypes of N. commune during rewetting. Gradual increase of F V /F M ratios, as the markers of active PS II, demonstrated the recovery processes of N. commune colonies from Europe as well as from Antarctica after time dependent rehydration. During the initial hours of rewetting, there was lower content of soluble proteins in colonies from Antarctica in comparison to those from Europe. Total content of nitrogen was higher in European ecotypes of N. commune. Significantly higher frequency of occurrence of heterocysts in Antarctic ecotypes was observed. The heterocyst cells were significantly longer in Antarctic ecotypes rather than European ecotypes of N. commune.

Cyanobacteria are oxygen-evolving photosynthetic prokaryotes possessing a wide range of enzymatic antioxidants to tackle oxidative stress if and when it arises in cells. Glutathione peroxidase is an important enzyme in the antioxidative machinery of cells and may confer protection to various stress conditions. In the diazotrophic cyanobacterium Nostoc punctiforme ATCC 29133 (hereafter N.punctiforme), an open reading frame (ORF) encoding for a putative glutathione peroxidase was identified as NpunR_4660 by bioinformatics approach. This 486 bp ORF was amplified from the genomic DNA of N.punctiforme by polymerase chain reaction. The forward and reverse primers used for cloning the ORF contained NdeI and XhoI at their 5’ and 3’ end, respectively. The PCR amplified product was sub-cloned into pJET cloning vector. Further the ORF was introduced into pET-20B vector for overexpression of the corresponding protein in Escherichia coli BL21 DE3 strain. After induction of E.coli cultures by Isopropylthiogalactoside (IPTG) and, Sodium dodecyl sulphate–polyacrylamide gel electrophoresis of cell-free extracts, an approximately 18 kDa protein was detected in the cytoplasm, which matched with the theoretical molecular weight of the protein. This protein was not present in control cultures transformed with pET-20B without the cyanobacterial ORF. These results suggest that foreign enzymes such as glutathione peroxidase can be produced in large amounts for biotechnological purposes successfully even in cells of a different origin like E.coli.

The terrestrial cyanobacterium Nostoc flagelliforme, which contributes to carbon and nitrogen supplies in arid and semi-arid regions, adopts a filamentous colony form. Owing to its herbal and dietary values, this species has been overexploited. Largely due to the lack of understanding on its morphogenesis, artificial cultivation has not been achieved. Additionally, it may serve as a useful model for recognizing the morphological adaptation of colonial cyanobacteria in terrestrial niches. However, it shows very slow growth in native habitats and is easily disintegrated under laboratory conditions. Thus, a novel experimental system is necessary to explore its morphogenetic mechanism. Liquid-cultured N. flagelliforme has been well developed for exopolysaccharide (EPS) production, in which microscopic colonies (micro-colonies) are generally formed. In this study, we sought to gain some insight into the morphogenesis of N. flagelliforme by examining the effects of two external factors, the EPS and environmental stress-related growth rate, on the morphological shaping of micro-colonies. Our findings indicate that the EPS matrix could act as a basal barrier, leading to the bending of trichomes during their elongation, while very slow growth is conducive to their straight elongation. These findings will guide future cultivation and application of this cyanobacterium for ecological improvement.

Merocyclophanes C and D (1 and 2) were isolated from the cell extract of a cultured cyanobacterium, UIC 10110. The structures were determined by 1D NMR and HRESIMS and confirmed by 2D NMR techniques. The absolute configurations were determined using ECD spectroscopy. Merocyclophanes C and D represent the first known analogs of the merocyclophane core structure, a recently discovered scaffold of [7,7] paracyclophanes, characterized by an α-branched methyl at C-1 / C-14. 1 and 2 showed antiproliferative activity against the MDA-MB-435 cell line with IC50 values of 1.6 µM and 0.9 µM, respectively. Partial 16S analysis determined UIC 10110 to be a Nostoc sp. and it was found to clade with UIC 10062 Nostoc sp., the only other strain known to produce merocyclophanes. The genome of UIC 10110 was sequenced and a biosynthetic gene cluster was identified that is proposed to encode type I and type III polyketide synthases that are potentially responsible for production of the merocyclophanes, yet further experiments will be required to verify the true function of the gene cluster. The gene cluster provides a genetic basis for the observed structural differences of the [7,7] paracyclophane core structures.

Nostoc sp. strain KVJ20 was isolated from the symbiotic organs of the liverwort Blasia pusilla. This cyanobacterium has been shown to have broad symbiotic competence, and bacterial extracts have inhibitory effects on cancer cell lines and microbes. An array of genes for the production of secondary metabolites is present.

International audience; Ferritin-like proteins Dps (DNA-binding protein from starved cells) store iron and play a key role in the iron homeostasis in bacteria, yet their iron releasing machinery remains largely unexplored. The electron donor proteins that may interact with Dps and promote the mobilization of the stored iron have hitherto not been identified. Here, we investigate the binding capacity of the two atypical Dps proteins NpDps4 and NpDps5 from Nostoc punctiforme to isolated ferredoxins. We report NpDps-ferredoxin interactions by fluorescence correlation spectroscopy (FCS) and fluorescence resonance energy transfer (FRET) methods. Dynamic light scattering, size exclusion chromatography and native gel electrophoresis results show that NpDps4 forms a dodecamer at both pH 6.0 and pH 8.0, while NpDps5 forms a dodecamer only at pH 6.0. In addition, FCS data clearly reveal that the non-canonical NpDps5 interacts with DNA at pH 6.0. Our spectroscopic analysis shows that [Fe-S] centers of the three recombinantly expressed and isolated ferredoxins are properly incorporated and are consistent with their respective native states. The results support our hypothesis that ferredoxins could be involved in cellular iron homeostasis by interacting with Dps and assisting the release of stored iron.

Cyanobacteria are photosynthetic prokaryotes that are considered biotechnologically prominent organisms for production of high-value compounds. Cyanobacteria are subject to high-light intensities, ...

Mycosporine-like amino acids (MAAs) are considered efficient photoprotectants against high energy UV-photon flux. The present study is intended to probe the occurrence and synthesis of UV-absorbing MAAs and characterization of their induction, stability and free radical scavenging capacity in the cyanobacterium Nostoc sp. R76DM. HPLC-PDA detection, and LC–MS analysis revealed the occurrence of four different MAAs, palythine (λmax 320 nm, m/z 245), Asterina (λmax 331 nm, m/z 289), Porphyra (λmax 333 nm, m/z 347) and palythene (λmax 359 nm, m/z 285) with retention times 2.9, 4.71, 6.29 and 7.05 min, respectively. Induction of the synthesis of all MAAs was highly noticeable under UV-B radiation. These MAAs were exceedingly resistant to some physico-chemical factors such as UV-B, temperature, pH and a strong oxidizing agent. Total MAAs were extensively evaluated for their antioxidant properties by 2,2-diphenyl-1-picryl-hydrazyl, ferric reducing antioxidant power, superoxide radical scavenging and reducing power assay. MAAs exhibited significant and dose-dependent in vitro antioxidant and in vivo ROS scavenging potentials. Moreover, the results indicate the vital role of MAAs in life-saving mechanisms of cyanobacteria by virtue of their UV-absorbing/screening and antioxidant function. The results also added up evidence in favor of MAAs for possible use as active ingredients in cosmeceuticals.

Ecophysiological characterizations of photoautotrophic communities are not only necessary to identify the response of carbon fixation related to different climatic factors, but also to evaluate risks connected to changing environments. In biological soil crusts (BSCs), the description of ecophysiological features is difficult, due to the high variability in taxonomic composition and variable methodologies applied. Especially for BSCs in early successional stages, the available datasets are rare or focused on individual constituents, although these crusts may represent the only photoautotrophic component in many heavily disturbed ruderal areas, such as parking lots or building areas with increasing surface area worldwide. We analyzed the response of photosynthesis and respiration to changing BSC water contents (WCs), temperature and light in two early successional BSCs. We investigated whether the response of these parameters was different between intact BSC and the isolated dominating components. BSCs dominated by the cyanobacterium Nostoc commune and dominated by the green alga Zygogonium ericetorum were examined. A major divergence between the two BSCs was their absolute carbon fixation rate on a chlorophyll basis, which was significantly higher for the cyanobacterial crust. Nevertheless, independent of species composition, both crust types and their isolated organisms had convergent features such as high light acclimatization and a minor and very late-occurring depression in carbon uptake at water suprasaturation. This particular setup of ecophysiological features may enable these communities to cope with a high variety of climatic stresses and may therefore be a reason for their success in heavily disturbed areas with ongoing human impact. However, the shape of the response was different for intact BSC compared to separated organisms, especially in absolute net photosynthesis (NP) rates. This emphasizes the importance of measuring intact BSCs under natural conditions for collecting reliable data for meaningful analysis of BSC ecosystem services.

We report here the whole-genome sequence of Nostoc cycadae strain WK-1, which was isolated from cyanobacterial colonies growing in the coralloid roots of the gymnosperm Cycas revoluta . It can provide valuable resources to study the mutualistic relationships and the syntrophic metabolisms between the cyanobacterial symbiont and the host plant, C. revoluta .

To assess the effects of light intensity and quality on the growth and phycobiliproteins (PBP) accumulation in Nostoc sphaeroides Kützing (N. sphaeroides).Dry weights, dry matter, protein, chlorophyll and PBP contents were higher under 90 μmol m(-2) s(-1) than under other intensities (both higher and lower). Phycocyanin and allophycocyanin increased with light intensity while phycoerythrin decreased. Fresh weights, protein and PBP contents increased at the highest rates under blue light. Red light resulted in higher values of dry matter, phycocyanin and chlorophyll a.White light at 90 μmol m(-2) s(-1) or blue light 30 μmol m(-2) s(-1) were optimal for the growth and phycobiliprotein accumulation in N. sphaeroides.

In this study, Nostoc muscorum, a native cyanobacterial species isolated from a coal mining site, was employed to remove Cu(II), Zn(II), Pb(II) and Cd(II) from aqueous solution containing these metals in the mixture. In this multicomponent study, carried out as per the statistically valid Plackett-Burman design of experiments, the results revealed a maximum removal of both Pb(II) (96.3 %) and Cu(II) (96.42 %) followed by Cd(II) (80.04 %) and Zn(II) (71.3 %) at the end of the 60-h culture period. Further, the removal of these metals was attributed to both passive biosorption and accumulation by the actively growing N. muscorum biomass. Besides, the specific removal rate of these metals by N. muscorum was negatively correlated to its specific growth rate. For a better understanding of the effect of these metals on each other’s removal by the cyanobacteria, the results were statistically analyzed in the form of analysis of variance (ANOVA) and Student’s t test. ANOVA of the metal bioremoval revealed that the main (individual) effect due to the metals was highly significant (P value

Anabaenopeptins are a diverse group of cyclic peptides, which contain an unusual ureido linkage. Namalides are shorter structural homologues of anabaenopeptins, which also contain an ureido linkage. The biosynthetic origins of namalides are unknown despite a strong resemblance to anabaenopeptins. Here, we show the cyanobacterium Nostoc sp. CENA543 strain producing new (nostamide B-E (2, 4, 5, and 6)) and known variants of anabaenopeptins (schizopeptin 791 (1) and anabaenopeptin 807 (3)). Surprisingly, Nostoc sp. CENA543 also produced namalide B (8) and the new namalides D (7), E (9), and F (10) in similar amounts to anabaenopeptins. Analysis of the complete Nostoc sp. CENA543 genome sequence indicates that both anabaenopeptins and namalides are produced by the same biosynthetic pathway through module skipping during biosynthesis. This unique process involves the skipping of two modules present in different nonribosomal peptide synthetases during the namalide biosynthesis. This skipping is an efficient mechanism since both anabaenopeptins and namalides are synthesized in similar amounts by Nostoc sp. CENA543. Consequently, gene skipping may be used to increase and possibly broaden the chemical diversity of related peptides produced by a single biosynthetic gene cluster. Genome mining demonstrated that the anabaenopeptin gene clusters are widespread in cyanobacteria and can also be found in tectomicrobia bacteria.

Eco-physiological characterization of photoautotrophic communities is not only necessary to identify the response of carbon fixation related to different climatic factors, but also to evaluate risks connected to changing environments. In biological soil crusts (BSCs), the description of eco-physiological features is difficult, due to the high variability in taxonomic composition and variable methodologies applied. Especially for BSCs in early successional stages, the available datasets are rare or focused on individual constituents, although these crusts may represent the only photoautotrophic component in many heavily disturbed ruderal areas, like parking lots or building areas with increasing surface area worldwide. We analyzed the response of photosynthesis and respiration to changing BSC water contents, temperature and light in two early successional BSCs. One BSC was dominated by the cyanobacterium Nostoc commune, the other by the green alga Zygogonium ericetorum. Independent of species composition, both crust types had convergent features like high light acclimatization and low or no depression in carbon uptake at water suprasaturation. This particular setup of eco-physiological features may enable these communities to cope with a high variety of climatic stresses, and may therefore be a reason for their success in heavily disturbed areas with ongoing human impact. Nevertheless, a major divergence between the two BSCs was their absolute carbon fixation rate on a chlorophyll basis, which was significantly higher for the cyanobacterial crust. This study emphasizes the importance of measuring intact BSCs under natural conditions for collecting reliable data.

A dense exopolysaccharide (EPS) matrix is crucial for cyanobacterial survival in terrestrial xeric environments, in which cyanobacteria undergo frequent expansion and shrinkage processes during environmental desiccation-rehydration cycles. However, it is unclear how terrestrial cyanobacteria coordinate the structural dynamics of the EPS matrix upon expansion and shrinkage to avoid potential mechanical stress while benefiting from the matrix. In the present study, we sought to answer this question by investigating the gene expression, protein dynamics, enzymatic characteristics, and biological roles of WspA, an abundantly secreted protein, in the representative terrestrial cyanobacterium Nostoc flagelliforme . The results demonstrated that WspA is a novel β-galactosidase that facilitates softening of the EPS matrix by breaking the polysaccharide backbone under substantial moisture or facilitates the thickening and relinkage of the broken matrix during the drying process, and thus these regulations are well correlated with moisture availability or desiccation-rehydration cycles. This coordination of flexibility and rigidity of the cyanobacterial extracellular matrix may contribute to a favorable balance of cell growth and stress resistance in xeric environments. IMPORTANCE How the exopolysaccharide matrix is dynamically coordinated by exoproteins to cope with frequent expansion and shrinkage processes in terrestrial colonial cyanobacteria remains unclear. Here we elucidated the biochemical identity and biological roles of a dominant exoprotein in these regulation processes. Our study thus gained insight into this regulative mechanism in cyanobacteria to combat periodic desiccation. In addition, the filamentous drought-adapted cyanobacterium Nostoc flagelliforme serves as an ideal model for us to explore this issue in this study.

A UV-absorbing compound was purified and identified as a novel glycosylated mycosporine-like amino acid (MAA), 13-O-β-galactosyl-porphyra-334 (β-Gal-P334) from the edible cyanobacterium Nostoc sphaericum, known as "ge xian mi" in China and "cushuro" in Peru. Occurrence of the hexosylated derivative of shinorine (hexosyl-shinorine) was also supported by LC-MS/MS analysis. β-Gal-P334 accounted for about 86.5% of total MAA in N. sphaericum, followed by hexosyl-shinorine (13.2%) and porphyra-334 (0.2%). β-Gal-P334 had an absorption maximum at 334nm and molecular absorption coefficient was 46,700 at 334nm. Protection activity of β-Gal-P334 from UVB and UVA+8-methoxypsoralen induced cell damage on human keratinocytes (HaCaT) was assayed in comparison with other MAA (porphyra-334, shinorine, palythine and mycosporine-glycine). The UVB protection activity was highest in mycosporine-glycine, followed by palythine, β-Gal-P334, porphyra-334 and shinorine in order. β-Gal-P334 had highest protection activity from UVA+8-methoxypsoralen induced cell damage followed by porphyra-334, shinorine, mycosporine-glycine and palythine. We also found an antioxidant (radical-scavenging) activity of β-Gal-P334 by colorimetric and ESR methods. From these findings, β-Gal-P334 was suggested to play important roles in stress tolerant mechanisms such as UV and oxidative stress in N. sphaericum as a major MAA. We also consider that the newly identified MAA, β-Gal-P334 has a potential for use as an ingredient of cosmetics and toiletries.

In diesem Jahr wurde das Cyanobakterium Nostoc durch die VAAM zur “Mikrobe des Jahres” gekurt. Nostoc ist ein vielzelliges Bakterium, das sich an verschiedene Umweltbedingungen anpassen und dementsprechend vielfaltige Habitate besiedeln kann. Das von Licht und Luft lebende Bakterium kann sporenahnliche Zellen bilden, sich mithilfe von Pili fortbewegen und der N2-Fixierung dienende Heterozysten bilden. Diese Eigenschaften machen es zu einem beliebten Partner in verschiedenen Symbiosen mit Pflanzen als auch heterotrophen Organismen. Seine autotrophe Lebensweise als photosynthetischer Organismus und die Fahigkeit zur Differenzierung von drei verschiedenen Zelltypen mit unterschiedlicher Funktion bedeuten fur Nostoc einen deutlichen Selektionsvorteil innerhalb aquatischer und terrestrischer Habitate. Seine Vielzelligkeit beweist es durch eine echte zellulare Arbeitsteilung und das Auftreten von Zellwandstrukturen, die eine Kommunikation zwischen den Zellen der Filamente erlauben. The multicellular bacterium Nostoc In 2014 the VAAM selected for the first time a ”microbe of the year“ and the winner was the cyanobacterium Nostoc. This multicellular filamentous prokaryote will be described in this article in more detail, focusing on its adaptations to various environmental conditions and sophisticated cell differentiation processes. The photoautotrophic bacterium can live solely on air and light. Under certain conditions it is able to form spore like cells, mobile short filaments, and N2-fixing heterocysts. Hence, Nostoc is a popular partner in several symbiotic interactions with plants and heterotrophic organisms. Its autotrophic lifestyle and the presence of differentiated cells, which show true division of labor, give Nostoc a clear selective advantage in many aquatic and terrestrial habitats. Nostoc is a true multicellular organism having special cell wall structures, which connect the cells and allow the communication between the cells of the filament.

Two new trypsin inhibitors, nostosin A (1) and B (2), were isolated from a hydrophilic extract of Nostoc sp. strain FSN, which was collected from a paddy field in the Golestan Province of Iran. Nostosins A (1) and B (2) are composed of three subunits, 2-hydroxy-4-(4-hydroxyphenyl)butanoic acid (Hhpba), L-Ile, and L-argininal (1) or argininol (2). Nostosins A (1) and B (2) exhibited IC50 values of 0.35 and 55 μM against porcine trypsin, respectively, suggesting that the argininal aldehyde group plays a crucial role in the efficient inhibition of trypsin. Molecular docking of nostosin A (1) (449 Da), leupeptin (426 Da, IC50 0.5 μM), and spumigin E (610 Da, IC500.1 μM) with trypsin suggested prominent binding similarity between nostosin A (1) and leupeptin but only partial binding similarity with spumigin E. The number of hydrogen bonds between ligands and trypsin increased according to the length and size of the ligand molecule, and the docking affinity values followed the measured IC50 values. Nostosin A (1) is the first highly potent three-subunit trypsin inhibitor with potency comparable to the known commercial trypsin inhibitor leupeptin. These findings expand the known diversity of short-chain linear peptide protease inhibitors produced by cyanobacteria.

Vitamin B12 contents in the edible cyanobacterium Nostoc flagelliforme, also known as hair vegetable, were assayed using a microbiological method. We detected high vitamin B12 contents in samples of naturally grown cells (109.2 ± 18.5 μg/100g dry weight) and cultured cells (120.2 ± 53.6 μg/100g dry weight). However, commercially available hair vegetable samples, which comprised fake substitutes and Nostoc, had variable contents (4.8 - 101.6 μg/100g dry weight) because concomitant fake items contain very low vitamin B12 contents. To evaluate whether natural and cultured N. flagelliforme samples contained vitamin B12 or pseudovitamin B12, corrinoid compounds were purified and identified as pseudovitamin B12 (approximately 72%) and vitamin B12 (approximately 28%) using silica gel 60 TLC bioautography and LC/MS. The results suggested that N. flagelliforme contains substantial amounts of pseudovitamin B12, which is inactive in humans.

The Macroscopic Cyanobacterium Nostoc Parmelioides in Swift Current Creek, SK, Canada

The present study relates to the use of cyanobacterium Nostoc muscorum as a model system for removal of heavy metals such as Pb and Cd from aquatic systems. The effects of various physicochemical factors on the surface binding and intracellular uptake of Pb and Cd were studied to optimize the metal removal efficiency of the living cells of N. muscorum. Results demonstrated that a significant proportion of Pb and Cd removal was mediated by surface binding of metals (85 % Pb and 79 % Cd), rather than by intracellular accumulation (5 % Pb and 4 % Cd) at the optimum level of cyanobacterial biomass (2.8 g L−1), metal concentration (80 μg mL−1), pH (pH 5.0–6.0), time (15–30 min), and temperature (30–40 °C). N. muscorum has maximum amounts of metal removal (q max) capacity of 833 and 666.7 mg g−1 protein for Pb and Cd, respectively. The kinetic parameters of metal binding revealed that adsorption of Pb and Cd by N. muscorum followed pseudo-second-order kinetics, and the adsorption behavior was better explained by both Langmuir and Freundlich isotherm models. The surface binding of both the metals was apparently facilitated by the carboxylic, hydroxyl, and amino groups as evident from Fourier transform infrared spectra.

Effects of two intensities (1 and 5 W m−2) of UV-B radiation on the synthesis of UV-absorbing compounds in a terrestrial cyanobacterium Nostoc flagelliforme were investigated. UV-B radiation resulted in lower biomass. Short period (less than 12 h) of UV-B radiation caused an increase of chlorophyll a content, but subsequent duration of treatment (more than 24 h) resulted in a rapid decrease. N. flagelliforme synthesized UV-absorbing compounds such as scytonemin and mycosporine-like amino acids (MAAs) in response to UV-B radiation. Upon 48 h of exposure to UV-B radiation, scytonemin content in cells increased by 103.8 and 164.0 % at 1 and 5 W m−2, respectively. Oligosaccharide-linked mycosporine-like amino acids increased by 145.5 % after 12 h at 5 W m−2 and 114.5 % after 48 h at 1 W m−2 UV-B radiation. HPLC analysis showed that nine MAAs existed in N. flagelliforme cells both from liquid suspension culture and field colony. But the concentration and kinds of them were different. At the two distinct levels of UV-B radiation, the content of particular MAAs increased, declined, or remained unchanged. Moreover, the appearance of two new MAAs was observed.

The article discusses the diversity, distribution and ecology of Nostoc genus in Lithuania. Nine Nostoc species including N. caeruleum, N. carneum, N. commune, N. ellipsosporum, N. linckia, N. pruniforme, N. punctiforme, N. spongiaeforme and N. verrucosum are recorded the most widespread of which are N. commune and N. caeruleum species. Five species were found in NATURA 2000 territories. The widest diversity of species is recorded in aquatic habitats and only two species (N. commune and N. ellipsosporum) are terrestrial. Nostoc species grew in natural and artificial water bodies when water’s pH is 6,0–8,7, temperature - 13,0–27,0 °C and conductivity - 150–390 μS/cm. Article in Lithuanian

Cyanobacteria are capable of tolerating environmental extremes. To survive in extreme environments, cyanobacteria have developed the capability to adapt to a variety of stresses. For example, cyanobacteria have adopted a number of strategies with which to survive UV stress, including expression of UV-screening pigments and antioxidant systems. We have previously shown that several antioxidants are significantly expressed in Nostoc sp. by UVB irradiation. We report here that the content of UV-responsive biomarkers such as beta-carotene and scytonemin can be easily detected by Fourier transform Raman spectroscopy with use of a small sample size and that the content of beta-carotene is dependant on the UVB intensity and exposure time. Our results indicate that Raman spectroscopy may be a helpful tool to analyze UV-protective molecules of cyanobacterium in astrobiological studies without access to large sample sizes and complicated extractions, which are needed by other analytical techniques such as high-performance liquid chromatography and mass spectrometry.