Scytonema Sp Research Articles

Pigments profile and antioxidant potential of extremophile cyanobacteria isolated from the Mexican Volcanic Lake Chichonal

Cyanobacteria are ancient and prolific microorganisms for which the current knowledge remains limited. The present work constitutes the first report on the presence of the cyanobacteria Tolypothrix sp. LEGE 221228, Nostoc sp. LEGE 221229, Scytonema sp. LEGE 221230 and Drouetiella sp. LEGE 221231 in the volcanic crater lake in Chichonal (Chiapas-Mexico), and in the characterization of their pigments profile and antioxidant potential, through the application of biorefinery approaches. The identification of cyanobacteria species was achieved through advanced morphology-based methods for cyanobacterial taxonomy. The HPLC-PDA analysis of the cyanobacteria acetone extracts revealed β-carotene, echinenone and chlorophyll-a as the main pigments. Drouetiella sp. LEGE 221231 presented the highest β-carotene concentration (63.67 μg/mL), total carotenoids (87.92 μg/mL) and chlorophylls (20.88 μg/mL), closely followed by Tolypothrix sp. LEGE 221228 (with 51.37, 75.14 and 14.88 μg/mL, respectively), this being the first report on the carotenoid and chlorophylls profile of these strains. Aqueous extracts revealed the highest content of phycoerythrin in Tolypothrix sp. LEGE 221228 (50.61 mg/g) and of phycocyanin in Nostoc sp. LEGE 221229 (57.66 mg/g), standing out in superoxide anion radical scavenging, while the acetonic ones were more effective in scavenging nitric oxide radical. For both, Tolypothrix sp. LEGE 221228 was the most effective, presenting the lowest IC50 (53.75 and 57.68 μg/mL, respectively). Overall, the present study enriches the knowledge on biodiversity of cyanobacteria from underexplored environments, enhancing their potential biotechnological applications as producers of added value secondary metabolites with interest in food, pharmaceutical and cosmetic industries.

An acidic exopolysaccharide α-D-galacturono-β-D-glucan produced by the cyanobacterium Scytonema sp.

Some cyanobacteria produce a wide range of secondary metabolites, some of which are of industrial interest. Exopolysaccharides, particularly interesting among them, represent relatively complex primary structures with interesting bioactivity, biodegradability and specific applications. Cultivation of the freshwater cyanobacterium Scytonema sp. provided a proteoglycan-type exopolysaccharide with a relatively low yield and a wide spectrum of molecular weights (Mw) ranging from 2.2 to 1313 × 103 g/mol. Chemical analyses detected the presence of carbohydrates (46 wt%), proteins (10 wt%) and uronic acids (8 wt%). Monosaccharide analysis revealed up to seven neutral sugars with a dominance of glucose (23.6 wt%), galactose (7.4 wt%) and fucose (5.0 wt%) residues, while the others had a much lower content (0.9–3.4 wt%). The presence of galacturonic acid (8.0 wt%) indicated the appearance of ionic type of exopolysaccharide. A preliminary structural study indicated that the α-D-galacturono-β-D-glucan forms a dominant part of Scytonema sp. exopolymer. Its backbone is composed of two 1,6-linked and one 1,2-linked β-D-Glcp residues, which is branched at O6 by side chains composed of α-D-GalAp(1 → 2)-β-D-Glcp(1→ dimer or monomeric β-D-Glcp(1→ residue.

Enhancing Biocrust Development and Plant Growth through Inoculation of Desiccation-Tolerant Cyanobacteria in Different Textured Soils.

In recent years, there has been a burgeoning interest in the utilization of cyanobacteria for the purpose of land rehabilitation via enhancements in soil fertility, prevent erosion, and counter desertification. This study evaluated the ability of Nostoc calcicola BOT1, Scytonema sp. BOT2, and their consortia to form biocrusts on the substrate of coarse sand, fine sand, and loamy soil. A nutrient- and water-deficient substrate was inoculated with cyanobacteria to facilitate biocrust formation and evaluate their impact on agriculture. Cyanobacteria inoculation resulted in significant improvements in soil fertility, especially in coarse and fine sand, which initially had the lowest fertility. The findings of this investigation underscore that the consortium of cyanobacteria exhibited greater efficacy than individual strains in enhancing soil fertility and stimulating plant growth. The loamy soil treated with the consortium had the highest plant growth across all soil types, in contrast to the individual strains. The consortium of cyanobacteria showed promising results in promoting biocrust formation and fostering rice seedling growth in fine sand. This study provides empirical evidence supporting the potential utility of cyanobacterial consortia as a valuable tool for the rehabilitation of degraded land. Furthermore, the results indicate that cyanobacterial species can persist in soil environments even following prolonged periods of desiccation.

Spectral and photochemical diversity of tandem cysteine cyanobacterial phytochromes

The atypical trichromatic cyanobacterial phytochrome NpTP1 from Nostoc punctiforme ATCC 29133 is a linear tetrapyrrole (bilin)-binding photoreceptor protein that possesses tandem-cysteine residues responsible for shifting its light-sensing maximum to the violet spectral region. Using bioinformatics and phylogenetic analyses, here we established that tandem-cysteine cyanobacterial phytochromes (TCCPs) compose a well-supported monophyletic phytochrome lineage distinct from prototypical red/far-red cyanobacterial phytochromes. To investigate the light-sensing diversity of this family, we compared the spectroscopic properties of NpTP1 (here renamed NpTCCP) with those of three phylogenetically diverged TCCPs identified in the draft genomes of Tolypothrix sp. PCC7910, Scytonema sp. PCC10023, and Gloeocapsa sp. PCC7513. Recombinant photosensory core modules of ToTCCP, ScTCCP, and GlTCCP exhibited violet-blue-absorbing dark-states consistent with dual thioether-linked phycocyanobilin (PCB) chromophores. Photoexcitation generated singly-linked photoproduct mixtures with variable ratios of yellow-orange and red-absorbing species. The photoproduct ratio was strongly influenced by pH and by mutagenesis of TCCP- and phytochrome-specific signature residues. Our experiments support the conclusion that both photoproduct species possess protonated 15E bilin chromophores, but differ in the ionization state of the noncanonical "second" cysteine sulfhydryl group. We found that the ionization state of this and other residues influences subsequent conformational change and downstream signal transmission. We also show that tandem-cysteine phytochromes present in eukaryotes possess similar amino acid substitutions within their chromophore-binding pocket, which tune their spectral properties in an analogous fashion. Taken together, our findings provide a roadmap for tailoring the wavelength specificity of plant phytochromes to optimize plant performance in diverse natural and artificial light environments.

In silico molecular docking analysis of cancer biomarkers with GC/MS identified compounds of Scytonema sp.

This study was aimed to perform pre-clinical evaluation of the gas chromatography–mass spectrometry (GC/MS) identified bioactive compounds of cyanobacterium Scytonema sp. MGL002 as an anticancer drug resource using in silico docking approaches. Among the twenty GC/MS identified cyanobacterial compounds, only four of them viz. tetradecanoic acid; palmitoleic acid; 9,12-octadeca dien-1-ol, (Z, Z)- and 6-octadecanoic acid (Z)- were found to be potent anticancer therapeutic agent through molecular docking study. These anticancerous compounds were also accepted as a potent drug-like compound through Lipinski drug likeliness test and ADME (Absorption, distribution, metabolism, excretion and toxicity) toxicity investigation. Studies on molecular docking of ligand {tetradecanoic acid, palmitoleic acid and 9,12-octadeca dien-1-ol, (Z, Z)-} with cancer targets revealed that these compounds interacted more efficiently with hsp90 protein (PDBID:3NMQ) with good binding affinity and best positive energy. Ligand–protein interaction was strengthened by electrostatic, van der Waals, covalent and hydrogen bonds. There might be possibility that these cyanocompounds bind with hsp90, modify their orientation and ultimately alter the functioning of hsp90 protein. In this respect, the present report provides useful insights to widen the knowledge on molecular interaction for new anticancer compound and opens new research area to work further on cancer cell lines followed by clinical trials to validate anticancerous property of these cyanocompounds.

Land degradation effects on composition of pioneering soil communities: An alternative successional sequence for dryland cyanobacterial biocrusts

Abstract In drylands, soil surfaces in interplant spaces are usually covered by biocrusts, which consist of communities of heterotrophic and chemoautotrophic bacteria, cyanobacteria, mosses, lichens, microalgae, fungi and other organisms. Cyanobacteria are of special interest because of their capacity to promote biocrust succession or increase soil fertility and stability. Therefore, some studies have analyzed their communities in different ecosystems, focusing on how different factors, such as temperature or altitude, influence their composition. Nevertheless, to our knowledge, the relationship between ecosystem degradation and cyanobacterial community composition has not yet been studied in depth. This could be determinant for the successful development of tools for restoring degraded biocrusts by cyanobacterial inoculation. Thus, the objective of this study was to analyze the effect of the ecosystem degradation level on cyanobacteria composition from topsoil communities, where they are keystone pioneering organisms. To do this, we analyzed the cyanobacterial diversity by molecular sequencing (16S rRNA gene) of the DNA extracted from biocrusts at different developmental stages, which were collected from three ecosystems in southeastern Spain. The selected ecosystems represent different “land-condition” states as a result of degradation processes. In one of them soil was removed by mining (the Gádor quarry), the second is a natural badland area (El Cautivo) where water erosion is intense, and the third ecosystem is a well-preserved area (Balsa Blanca). Our findings show that cyanobacterial richness decreases (up to 28 OTUs) as degradation increases and biocrust developmental stage decreases. Also, the relative abundances of most of the species were significantly correlated with the degradation state of the sampling site, either showing a positive or negative trend. Two of the species which increased in abundance with site degradation, and were especially abundant in incipient biocrusts, were Leptolyngbya frigida and Trichocoleus desertorum, while other species, also showing an increase in abundance with degradation, but having a higher relative abundance in most developed biocrusts, were Nostoc commune, Tolypothrix distorta and Scytonema sp. The significant correlation of these species with degradation at different biocrusts developmental stages, suggests an alternative developmental sequence for drylands, at least in more degraded ecosystems. In less degraded ones, the composition of the major cyanobacterial groups followed the common pattern of bundle-forming cyanobacteria (54.7%) pertaining to the Microcoleus genus followed by other non-heterocystous filamentous (17.4%), unicellular/colonial (7.5%) and heterocystous cyanobacteria (1.1%). In comparison, the cyanobacterial groups dominating the most incipient biocrusts, colonizing the most degraded soil, were the filamentous non-heterocystous (50.7%) and the bundle-forming cyanobacteria (48.9%). Therefore, our results show that some cyanobacterial species, which do not belong to traditional pioneer genera, are frequent colonizers of degraded soils, and then, they could be potentially used for producing a more efficient inoculum for inducing biocrust formation and restoring degraded soils. Finally, it is also remarkable that L. frigida appears as dominant in some biocrusts from drylands (up to 74.9% of abundance) being therefore demonstrated its wide distribution in nonpolar biomes and its capacity to also inhabit degraded arid soils.

Scytodecamide from the Cultured Scytonema sp. UIC 10036 Expands the Chemical and Genetic Diversity of Cyanobactins.

Cyanobactins are a large family of cyanobacterial ribosomally synthesized and post-translationally modified peptides (RiPPs) often associated with biological activities, such as cytotoxicity, antiviral, and antimalarial activities. They are traditionally described as cyclic molecules containing heterocyclized amino acids. However, this definition has been recently challenged by the discovery of short, linear cyanobactins containing three to five amino acids as well as cyanobactins containing no heterocyclized residues. Herein we report the discovery of scytodecamide (1) from the freshwater cyanobacterium Scytonema sp. UIC 10036. Structural elucidation based on mass spectrometry, 1D and 2D NMR spectroscopy, and Marfey's method revealed 1 to be a linear decapeptide with an N-terminal N-methylation and a C-terminal amidation. The genome of Scytonema sp. UIC 10036 was sequenced, and bioinformatic analysis revealed a cyanobactin-like biosynthetic gene cluster consistent with the structure of 1. The discovery of 1 as a novel linear peptide containing an N-terminal N-methylation and a C-terminal amidation expands the chemical and genetic diversity of the cyanobactin family of compounds.

Annual net primary productivity of a cyanobacteria-dominated biological soil crust in the Gulf Savannah, Queensland, Australia

Abstract. Biological soil crusts (biocrusts) are a common element of the Queensland (Australia) dry savannah ecosystem and are composed of cyanobacteria, algae, lichens, bryophytes, fungi and heterotrophic bacteria. Here we report how the CO2 gas exchange of the cyanobacteria-dominated biocrust type from Boodjamulla National Park in the north Queensland Gulf Savannah responds to the pronounced climatic seasonality and on their quality as a carbon sink using a semi-automatic cuvette system. The dominant cyanobacteria are the filamentous species Symplocastrum purpurascens together with Scytonema sp. Metabolic activity was recorded between 1 July 2010 and 30 June 2011, during which CO2 exchange was only evident from November 2010 until mid-April 2011, representative of 23.6 % of the 1-year recording period. In November at the onset of the wet season, the first month (November) and the last month (April) of activity had pronounced respiratory loss of CO2. The metabolic active period accounted for 25 % of the wet season and of that period 48.6 % was net photosynthesis (NP) and 51.4 % dark respiration (DR). During the time of NP, net photosynthetic uptake of CO2 during daylight hours was reduced by 32.6 % due to water supersaturation. In total, the biocrust fixed 229.09 mmol CO2 m−2 yr−1, corresponding to an annual carbon gain of 2.75 g m−2 yr−1. Due to malfunction of the automatic cuvette system, data from September and October 2010 together with some days in November and December 2010 could not be analysed for NP and DR. Based on climatic and gas exchange data from November 2010, an estimated loss of 88 mmol CO2 m−2 was found for the 2 months, resulting in corrected annual rates of 143.1 mmol CO2 m−2 yr−1, equivalent to a carbon gain of 1.7 g m−2 yr−1. The bulk of the net photosynthetic activity occurred above a relative humidity of 42 %, indicating a suitable climatic combination of temperature, water availability and light intensity well above 200 µmol photons m−2 s−1 photosynthetic active radiation. The Boodjamulla biocrust exhibited high seasonal variability in CO2 gas exchange pattern, clearly divided into metabolically inactive winter months and active summer months. The metabolic active period commences with a period (of up to 3 months) of carbon loss, likely due to reestablishment of the crust structure and restoration of NP prior to about a 4-month period of net carbon gain. In the Gulf Savannah biocrust system, seasonality over the year investigated showed that only a minority of the year is actually suitable for biocrust growth and thus has a small window for potential contribution to soil organic matter.

Sequential role of biosorption and biodegradation in rapid removal degradation and utilization of methyl parathion as a phosphate source by a new cyanobacterial isolate Scytonema sp. BHUS-5

ABSTRACTA new isolate of genus Scytonema distinct from its closest relative cyanobacterium, Scytonema hofmanni was found efficient in the removal and degradation of organophosphorus (OP) pesticide, methyl parathion (MP). The cyanobacterial isolate was also capable of utilizing the phosphorus present in the MP following its degradation, which was evident from the increase in growth (chlorophyll content), biomass, protein content, and total phosphorus in comparison to cyanobacterium grown in phosphate-deficient cultures. The rapid removal of MP by the cyanobacterium during initial 6 hours of incubation was defined by the pseudo-second-order biosorption kinetics model, which indicated the involvement of chemosorption in initial removal of pesticide. Further, degradation of MP was also confirmed by the appearance of p-nitrophenol in the medium after 24 hours of incubation. Thus, the cyanobacterial isolate of Scytonema sp. BHUS-5 seems to be a potential bioremediation agent for the removal of OP pesticide, MP from the habitat.

The impact of culture conditions on growth and metabolomic profiles of freshwater cyanobacteria.

Cultured cyanobacteria produce secondary metabolites with a wide range of biological activities and are an important source of natural products. In the context of secondary metabolite discovery, microbial culture conditions are expected to support optimum growth, induce maximum chemical diversity, and be suitable for the majority of cyanobacterial strains. We investigated the effect of nitrate and phosphate on biomass production and metabolomic profiles of three filamentous freshwater cyanobacterial strains: cf. Oscillatoria sp. UIC 10045, Scytonema sp. UIC 10036, and Nostoc sp. UIC 10110. A standardized inoculation procedure allowed for the assessment of cell mass production. Dried cyanobacterial cell mass was extracted and analyzed by liquid chromatography coupled with high resolution mass spectrometry (UPLC-HRMS), followed by comparative metabolomics analysis using XCMS Online. Results showed that low nitrate media significantly reduced cell mass production for all three strains. Low nitrate also induced production of primary metabolites (heterocyst glycolipids) in strains UIC 10036 and UIC 10110. Changes in phosphate levels affected each strain differently. Strain UIC 10110 showed a significant increase in production of merocyclophane C when cultivated in low phosphate, while strain UIC 10036 displayed higher production of tolytoxin under high phosphate. Additionally, these experiments led to the identification of a potentially new peptide produced by strain UIC 10036.

Screening of cyanobacterial strains for toxicity assay Of silver and silver nanoparticles

The growing incorporation of nanomaterials and excessive heavy metal discharge into the environment calls for the better understanding of their toxicological effects on the ecosystem. For analyzing their toxic effects we have chosen cyanobacteria as our model system. Cyanobacteria is known to accumulate heavy metals and act as a sink for many aquatic contaminants. The present study aims towards screening of four cyanobacterial strains namely Synechococcus sp., Scytonema sp., Nostoc muscorum and Plectonema boryanum, against silver stress. Our results indicated that out of four strains, two strains namely Nostoc muscorum and Plectonema boryanum were found to be less sensitive while Scytonema sp. exhibited highest sensitivity towards Ag stress. Our results state that the growth inhibition of cyanobacterial strains is in the order of Scytonema sp> Synechococcus sp >Nostoc muscorum> Plectonema boryanum which was estimated in terms of photosynthetic pigment (Chl a). Effect of Ag stress on carotenoids (Car) and total protein was also studied. Based on the above results, the less sensitive strains namely Nostoc muscorum and Plectonema boryanum were further studied against silver nanoparticles stress. All experiments were repeated three times to ascertain the reproducibility of the results. Values are represented as mean ± SE. Thus, the understanding of the responses incurred in cyanobacteria during heavy metal and metal nanoparticle stress can be very well used to evaluate their toxic responses in the environment.

A new species of Scytonema isolated from Bilaspur, Chhattisgarh, India

AbstractFilamentous cyanobacterium (strain 10C‐PS) isolated from a fresh water body of Bilaspur, Chhattisgarh, India is being described as new species of the polyphyletic genus Scytonema. Phenotypic, molecular and phylogenetic characterization was performed and the combined results validated the strain as a new species. Careful observations of the filaments, presence of a distinctly textured sheath throughout the length of the trichome, differences in the shape and dimensions of the vegetative cells, and heterocytes provided reliable morphological signals that the strain differed from rest of the closely related species. Sequencing of the 16S rRNA gene showed 96.89% sequence similarity with Scytonema hofmanni PCC 7110 while rbcl and psbA sequencing showed 95% and 92% similarities with Scytonema hofmanni PCC 7110 and Nostoc sp. PCC 7524 respectively while the nifD gene sequence similarity was found to be 96% with Scytonema hofmanni PCC 7110. The PC‐IGS region was sequenced and concatenated cpcB, IGS and cpcA regions indicated 97% closest similarity with Scytonema sp. PCC 7110 and Scytonema bohnerii Ind24. Subsequent phylogenetic analyses gave a strong pattern of distinct clustering in case of all the molecular markers. The phenotypic, genetic and phylogenetic observations prove conclusively that the strain 10C‐PS is a new species in the genus Scytonema with the name proposed being Scytonema bilaspurensis.

Antifungal compounds from cyanobacteria.

Cyanobacteria are photosynthetic prokaryotes found in a range of environments. They are infamous for the production of toxins, as well as bioactive compounds, which exhibit anticancer, antimicrobial and protease inhibition activities. Cyanobacteria produce a broad range of antifungals belonging to structural classes, such as peptides, polyketides and alkaloids. Here, we tested cyanobacteria from a wide variety of environments for antifungal activity. The potent antifungal macrolide scytophycin was detected in Anabaena sp. HAN21/1, Anabaena cf. cylindrica PH133, Nostoc sp. HAN11/1 and Scytonema sp. HAN3/2. To our knowledge, this is the first description of Anabaena strains that produce scytophycins. We detected antifungal glycolipopeptide hassallidin production in Anabaena spp. BIR JV1 and HAN7/1 and in Nostoc spp. 6sf Calc and CENA 219. These strains were isolated from brackish and freshwater samples collected in Brazil, the Czech Republic and Finland. In addition, three cyanobacterial strains, Fischerella sp. CENA 298, Scytonema hofmanni PCC 7110 and Nostoc sp. N107.3, produced unidentified antifungal compounds that warrant further characterization. Interestingly, all of the strains shown to produce antifungal compounds in this study belong to Nostocales or Stigonematales cyanobacterial orders.

The high-energy radiation protectant extracellular sheath pigment scytonemin and its reduced counterpart in the cyanobacterium Scytonema sp. R77DM

A cyanobacterial extracellular sheath pigment from Scytonema sp. R77DM was partially characterized and investigated for its increased production under abiotic factors, and UV-screening function. HPLC with PDA detection, and ion trap liquid chromatography/mass spectrometry analysis revealed the presence of a pigment scytonemin and its reduced counterpart. Ultraviolet radiation showed more stimulative effects on scytonemin production. A significant synergistic enhancement of scytonemin synthesis was observed under combined stress of heat and UV radiation. Scytonemin also exhibited efficient UV-screening function by reducing the in vivo production of reactive oxygen species (ROS) and cyclobutane thymine dimer. UV-induced formation of ROS and thymine dimer was also reduced upon exposure of cyanobacterial cells to exogenous antioxidant, ascorbic acid; however, the effect was more significant when both scytonemin and ascorbic acid were applied in combination. Moreover, the results indicate the potential role of scytonemin pigment as natural photoprotectant against high energy solar insolation.

Thermostablility of phycobiliproteins and antioxidant activity from four thermotolerant cyanobacteria

SUMMARYFour cyanobacterial strains including Cyanosarcina sp. SK40, Phormidium sp. PD40‐1, Scytonema sp. TP40 and Leptolyngbya sp. KC45 were selected and investigated for the phycobiliprotein (PBP) content and thermostable antioxidant activity of their cell‐free extracts. The highest content of 181.63 mg/g dry weight phycobiliprotein was found in Leptolyngbya sp. KC45 with phycoerythrin (PE) as the main phycobiliprotein. Among the PBPs of four thermotolerant cyanobacteria, PE from Leptolyngbya sp. KC45 exhibited the highest thermal stability as 80% of the original level remained after being heated at 60°C for 30 min. Antioxidant activities were detected in the cell‐free extracts of all cyanobacteria and that of Leptolyngbya sp. KC45 was also found in the highest value of 7.44 ± 0.14 and 3.89 ± 0.08 mg gallic acid equivalent (GAE) g−1 dry weights determined by 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) and reducing power assay, respectively. This also corresponded to the phenolic compound content. Based on DPPH and reducing power assay, antioxidant activities of all cyanobacterial extracts showed the high thermostability as approximately 80% remained after being heated at 80°C for 30 min. However, it clearly indicated that the thermostability of antioxidant activity from the hot spring cyanobacterial cell‐free extract was not contributed only by the PE, but also came from phenolic compounds and other oxidative substances.

Mycosporine-like amino acids profile and their activity under PAR and UVR in a hot-spring cyanobacterium Scytonema sp. HKAR-3

The cyanobacterium Scytonema sp. HKAR-3 isolated from a hot spring in India was investigated for the presence of mycosporine-like amino acids (MAAs) and their induction under PAR and PAR+UVR. High-performance liquid-chromatograph (HPLC) analysis revealed the presence of two MAAs, mycosporine–glycine (λmax = 310 nm) and an unknown MAA-334 (λmax = 334 nm), with retention times of 4.1 and 8.7 min, respectively. This is the first report for the presence of two MAAs and, in particular, the synthesis of mycosporine–glycine in any strain of Scytonema. There was no effect of radiation type (PAR or PAR+UVR) on the synthesis of mycosporine–glycine; however, the synthesis of MAA-334 was found to be higher in samples receiving PAR+UVR than in those receiving PAR only. There was a circadian induction in the synthesis of MAAs under alternate 12-h light (PAR or PAR+UVR) and dark periods. MAAs were found to be induced mostly during the light period and their production dropped again during the dark period. This suggests that the synthesis of MAAs is an energy-dependent process and depends on solar energy for its maintenance in natural habitats.

Extracellular phycoerythrin-like protein released by freshwater cyanobacteria Oscillatoria and Scytonema sp.

During growth of the freshwater cyanobacteria, Oscillatoria sp. BTCC/A0004, and Scytonema sp. TISTR 8208, a pink pigment is released into the growth medium. The pigment from each source had a molecular weight of approximately 250 kDa and had adsorption maxima at 560 and 620 nm. These results suggest that pink pigment is a phycoerythrin-like protein. It inhibited the growth of green algae, Chlorella fusca and Chlamydomonas reinhardtii, but not other cyanobacteria or true bacteria. The concentration at which growth inhibition 50% occurred was 0.5, 6 and more than 10 mg ml(-1), respectively.

Genetic analysis of polyketide synthase and peptide synthetase genes in cyanobacteria as a mining tool for secondary metabolites

Molecular screening using degenerate PCR to determine the presence of secondary metabolite genes in cyanobacteria was performed. This revealed 18 NRPS and 19 PKS genes in the 21 new cyanobacterial strains examined, representing three families of cyanobacteria (Nostocales, Chroococales and Oscillatoriales). A BLAST analysis shows that these genes have similarities to known cyanobacterial natural products. Analysis of the NRPS adenylation domain indicates the presence of novel features previously ascribed to both proteobacteria and cyanobacteria. Furthermore, binding-pocket predictions reveal diversity in the amino acids used during the biosynthesis of compounds. A similar analysis of the PKS ketosynthase domain shows significant structural diversity and their presence in both mixed modules with NRPS domains and individually as part of a PKS module. We have been able to classify the NRPS genes on the basis of their binding-pockets. Further, we show how this data can be used to begin to link structure to function by an analysis of the compounds Scyptolin A and Hofmannolin from Scytonema sp. PCC 7110.

Photoprotective Compounds in Rice‐Field Cyanobacteria

AbstractCyanobacteria are cosmopolitan in distribution, forming a prominent component of microbial populations in both aquatic as well as terrestrial ecosystems. They are the dominant microflora in rice‐fields, where they significantly contribute to fertility as a natural biofertilizer. The fluence rates of UV‐B radiation impinging on the natural habitats is of major concern since being photoautotrophic organisms, cyanobacteria depend on solar radiation as the primary source of energy. UV‐B radiation causes reduction in growth, survival, pigment and protein content, heterocyst frequency and fixation of carbon and nitrogen in cyanobacteria. However, a number of cyanobacteria synthesize water soluble colorless mycosporine‐like amino acids (MAAs) and the lipid soluble yellow‐brown colored sheath pigment, scytonemin to counteract the damaging effects of UV‐B. Anabaena sp., Nostoc commune, Scytonema sp. and Lyngbya sp. were isolated from rice‐fields in India and screened for the presence of photoprotective compounds. Spectroscopic and biochemical analyses revealed the presence of shinorine, a bisubstituted MAA containing both glycine and serine group with an absorption maximum at 334 nm in all cyanobacteria except Lyngbya sp. There was a circadian induction in the synthesis of this compound by UV‐B. Polychromatic action spectra for the induction of MAAs in Anabaena sp. and N. commune show the induction to be UV‐B dependent peaking at 290 nm. Another photoprotective compound, scytonemin, with an absorption maximum at 386 nm (also absorbs significantly at 300, 278, 252 and 212 nm) was detected in all cyanobacteria except Anabaena sp. In addition, two unidentified, water‐soluble, yellowish and brownish compounds with an absorption maximum at 315 nm were recorded only in Scytonema sp. The spectral characteristics of these compounds neither matches with MAAs nor with scytonemin and seems to be a novel compound acting as an effective UV screens. In conclusion, a particular cyanobacterium having photoprotective compounds may be a potent candidate as biofertilizers for crop plants.

A lectin from the lichenized Basidiomycete Dictyonema glabratum

A lectin with hemagglutinating activity has been isolated from an aqueous extract of the symbiotic phenotype of Dictyonema glabratum and its cyanobacterial photobiont Scytonema sp. The purified lectin had a pI of 6.8 and its molecular mass was investigated by electrospray ionization mass spectrometry, gel filtration and SDS‐PAGE, which indicated its native conformation as a dimer formed by two identical subunits of 16540 Da. The lectin is a glycoprotein with a low degree of glycosylation, containing galactose, xylose, glucose and mannose as neutral monosaccharides, in addition to glucosamine, which could indicate both N‐ and O‐linkages. Amino acid analysis showed the predominance of nonpolar residues such as phenylalanine. Agglutination of human erythrocytes required divalent cations, which is affected by addition of EDTA. The lectin was more stable at 30 °C or less for at least 1 h and between pH 5.0 and 7.0. Among the various compounds tested for hemagglutination inhibition, N‐acetylgalactosamine was the most active. The potential role of this lectin in recognition of the compatible cyanobacterial photobiont is discussed.