Cyanobacterium Nostoc Muscorum Research Articles

Externally supplied ascorbic acid moderates detrimental effects of UV-C exposure in cyanobacteria.

The defensive role performed by exogenously supplied ascorbic acid in the cyanobacterium Nostoc muscorum Meg1 against damages produced by UV-C radiation exposure was assessed in this study. Exposure to UV-C (24mJ/cm2) significantly enhanced reactive oxygen species (ROS) (50%) along with peroxidation of lipids (21%) and protein oxidation (22%) in the organism. But, addition of 0.5mM ascorbic acid prior to UV-C exposure showed reduction in ROS production (1.7%) and damages to lipids and proteins (1.5 and 2%, respectively). Light and transmission electron microscopic studies revealed that ascorbic acid not only protected filament breakage but also restricted severe ultrastructural changes and cellular damages in the organism. Although the growth of the organism was repressed up to 9% under UV-C treatment within 15days, a pre-treatment with ascorbic acid led to growth enhancement by 42% in the same period. Various growth parameters such as photo-absorbing pigments (phycoerythrin, phycocyanin, allophycocyanin, chlorophyll a, and carotenoids), water splitting complex (WSC), D1 protein, RuBisCO, glutamine synthetase and nitrogenase activities in the UV-C treated organism were seen to be relatively intact in the presence of ascorbic acid. Thus, a detailed analysis undertaken in the present study was able to demonstrate that ascorbic acid not only act as first responder against harmful UV-C radiation by down-regulating ROS production, it also accelerated the growth performance in the organism in the post UV-C incubation period as an immediate response to an adverse experience presented in the form of UV-C radiation exposure.

Nitric oxide and 5-aminolevulinic acid up-regulate growth, PS II photochemistry and antioxidant activity in UV-B stressed cyanobacterium Nostoc muscorum

The signaling molecules 5-aminolevulinic acid (ALA) and nitric oxide (NO) function as growth promoters in plants under abiotic stress. However, their roles in cyanobacteria remain unclear. This work has been attempted to examine the regulatory effects of ALA and NO (sodium nitroprusside; SNP as NO donor) against UV-B toxicity, and to investigate their interaction in regulating these effects in the cyanobacterium Nostoc muscorum ATCC 27,893. UV-B exposure (0.54 Wm−2) significantly reduced light-harvesting pigments, growth, and photosynthesis (PS-II photochemistry and oxygen evolution), while respiration rates increased considerably. Concurrently, oxidative stress biomarkers, including superoxide radical (O2•−), hydrogen peroxide (H2O2) and MDA equivalents (lipid peroxidation products), were substantially increased despite enhanced enzymatic antioxidant activity (glutathione -S- transferase, superoxide dismutase, peroxidase, and catalase). Exogenous ALA and NO mitigated the harmful UV-B impacts, leading to significant improvements in growth, pigment contents, photosynthesis, and normalization of respiration. The ALA and NO treatments further enhanced enzymatic antioxidant activity, resulting in significant reductions in O2•− and H2O2 contents, thereby minimizing UV-B induced damage to cells as evidenced by reduced lipid peroxidation rates. Moreover, supplementation of PTIO (NO scavenger) and L-NAME (NO inhibitor) reversed ALA's mitigating effect, indicating the dependency of ALA on the NO-mediated signaling process to counter UV-B stress in N. muscorum. The study suggests that SNP (NO), being cost-effective, could serve as a potent growth regulator to sustain the growth of N. muscorum, a biological nitrogen fixer and natural inhabitant of paddy fields, enabling sustainable agriculture even under unavoidable UV-B stress conditions.

Cyanobacterial degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D): Its response to the oxidative stress induced by the primary degradation product 2,4-dichlorophenol (2,4-DCP)

Excessive use of herbicides in agricultural fields has become a major environmental concern due to the negative effects on the ecosystem. Microbial degradation has been well-known as an effective approach for combating such non-natural substances in soil. In the present study, the degradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) as a result of metabolic activities of a cyanobacterium Nostoc muscorum Meg 1 was investigated using GC–MS analysis. After seven days of 2,4-D exposure, the main residue obtained was 2,4-dichlorophenol (2,4-DCP) at RT: 8.334 (confirmed using NIST library). The effects of 2,4-DCP were studied in a cyanobacterium Nostoc muscorum Meg 1 isolated from a rice field where 2,4-D is commonly used. Exposure to 2,4-DCP at 20, 40, and 80 ppm significantly increased ROS production in the cyanobacterium by 74, 107, and 211 % (p < 0.001). With rising 2,4-DCP concentrations in the surroundings, lipid peroxidation and protein oxidation in the organism correspondingly increased, indicating cellular injury. The mRNA and protein contents, and also the activities of different oxidant neutralizing enzymes such as CAT, SOD, GR, and GPx and the non-enzymatic antioxidants (proline, GSH, thiol and phytochelatin content) were found augmented in 20 ppm 2,4-DCP exposed cultures. However, in the presence of 40 and 80 ppm 2,4-DCP, most enzymatic and non-enzymatic antioxidants were severely compromised. At higher exposures, the organism's attempt to mitigate the oxidants was still visible, as both proline and TSH levels increased. SEM and TEM analysis aided in visualizing the effects of 2,4-DCP on the morphology and ultrastructures of the organism.

Physiology of Osmoregulation and Cell Composition in Salt Li+ and Na+Adaptation of Nostoc muscorum

Adaptation to salt in the cyanobacterium Nostoc muscorum, is composed of a few mechanisms which together lead to the generation of a salt-tolerant cell. The initial mechanism combines a stimulation of photosynthetic activity with the accumulation of sucrose as an osmoregulator. The secondary mechanism involves the adaptation of N2fixationactivity and protein biosynthesis. Under conditions for photoautotrophic growth, significant Na+ extrusion was observed 30 min after salt shock. Sucrose accumulation reached a maximum value after 16 hours and Li+ accumulation reached equilibrium after 40 hours. The final concentrations of Li+ and Na+and sucrose and glucose inside the 0.6 molar Na+ and Li+ grown cells indicate that the inorganic ions and organic ;compatible' solutes are the major osmotic species which account for the adaptation of Nostoc muscorum to Li+and Na+. Thus, in the present investigation microarray data identifies the genes that represent various functional categories needs more intensive research with genetics and physiology to determine gene functions, their chromosomal organization and their mode of regulation

Homeostatic influence of calcium and kinetin: Regulation of defense strategies against NaCl stress in cyanobacterium Nostoc muscorum ATCC 27893

• 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 (Ca 2+ , 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 Ca 2+ improved the growth, pigments contents and performance of PS II photochemistry by down-regulating the oxidative stress biomarkres. Application of Ca 2+ 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 Ca 2+ in NaCl-induced toxicity alleviation by KN. The overall results suggest that Ca 2+ 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.

Role of Iron Uptake Systems in Coordinating Iron Homeostasis in NaCl-resistant Mutant of the Cyanobacterium Nostoc muscorum

Aims: To investigate the effect of NaCl stress on parent Nostoc muscorum and its spontaneously occurring mutant clone showing resistance to growth inhibitory action of NaCl in terms of various physiological parameters. We have further analyzed the role of iron uptake systems in providing a resistant phenotype.&#x0D; Place and Duration of Study: Division of Microbiology, Department of Botany, Government Motilal Science College, Bhopal 462008 (M.P.) India. This work was carried out between August 2021 to May 2022.&#x0D; Methodology: We have examined the various physiological parameters viz. growth, specific growth rate, photosynthetic O2 evolution, and nitrogenase activity as per the prescribed protocol. Further, DNA microarray analysis was carried out using the Agilent platform.&#x0D; Results: NaCl stress adversely affected growth, photosynthetic O2 evolution, and nitrogenase activity of the wild-type Nostoc muscorum, while NaCl-resistant mutant remains unaffected under a given stress. Microarray data analysis identified 24 ORF related to the uptake of iron with fold regulation ≥2 in the mutant strain. These ORFs belonging to the ABC-type ferric iron transporter that plays a significant role in the iron acquisition were identified in the mutant strain.&#x0D; Conclusion: The mechanism of iron homeostasis in the NaCl-resistant mutant has been explained. The results presented are essential to explain the regulatory role of the iron uptake system in stressed conditions.

Metabolic composition of the cyanobacterium Nostoc muscorum as a function of culture time: A 1H NMR metabolomics study

Cyanobacteria are considered a factory of added-value compounds. However, knowledge about the array of interesting compounds that could be extracted from these prokaryotic organisms is still very limited. Nuclear Magnetic Resonance (NMR) spectroscopy is a widely used technique for metabolic profiling that allows an overview of the main metabolites present in complex biological matrices. In this work, high resolution 1H NMR was employed to screen the metabolic composition of the freshwater cyanobacterium Nostoc muscorum. This species showed high longevity, being able to grow for more than one hundred days without any medium supplementation. During the period of study, several interesting metabolites were detected, such as several sugars and oligosaccharides, lipids (e.g., glycolipids, ω-3 and ω-6 fatty acids), amino acids, including mycosporin-like, peptides, and pigments (e.g., chlorophyll a and carotenoids). Owing to the long-term monitoring implemented in this study, the production of these compounds could be associated to specific moments of the growth of N. muscorum, providing new insights into the most appropriate harvesting time points for the biotechnological exploitation of specific molecules.

Unrestricted availability of α-ketoglutarate influences biomass production in the cyanobacterium Nostoc muscorum Meg 1 by impacting rates of photosynthesis, nitrogen fixation and lipid synthesis

Unrestricted availability of α-ketoglutarate influences biomass production in the cyanobacterium Nostoc muscorum Meg 1 by impacting rates of photosynthesis, nitrogen fixation and lipid synthesis

A biochemical, physiological and molecular evaluation of how the herbicide 2, 4-dichlorophenoxyacetic acid intercedes photosynthesis and diazotrophy in the cyanobacterium Nostoc muscorum Meg 1.

Among the non-target microorganisms residing in crop fields that are potentially vulnerable to herbicides are cyanobacteria. They contribute to the maintenance of soil quality and fertility and hence are considered to be an important component of soil microflora. Consequently, the present study was aimed to check the influence of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on some major parameters of carbon (CO2) and nitrogen (N2) fixations of a cyanobacterium Nostoc muscorum Meg 1 isolated from a rice field in Cherrapunji, Meghalaya, India. These include various photosynthetic pigments, the oxygen-evolving complex activity of the PSII, the protein contents of RuBisCO, D1 protein, isocitrate dehydrogenase (IDH), nitrogenase and glutamine synthetase (GS) enzymes, the heterocyst percentage, nitrogenase and GS enzyme activities, and production of total proteins and carbohydrates in the cyanobacterium in a varying range of 50 to 125 ppm doses of 2,4-D. The mRNA levels of several proteins were also analyzed. Besides carotenoid concentration that enhanced at 50 ppm, all other parameters were compromised by 2,4-D in a dose-dependent manner resulting in a reduction in photosynthetic and N2-fixing activities. The negative effect on N2-fixation was partly due to compromised IDH activity. RT-PCR analysis further showed that these negative effects were initiated at transcription levels as mRNA contents of all enzymes studied were found compromised under 2,4-D exposure. The scanning and transmission electron microscopy further revealed herbicide induced adverse changes in the morphology and ultrastructure of the organism. The significance of the work lies in its detailed analysis of the effect of 2,4-D at biochemical, physiological, and molecular levels.

Evaluation of the phycoremediation potential of microalgae for captan removal: Comprehensive analysis on toxicity, detoxification and antioxidants modulation

Captan is one of the most widely used organochlorine fungicides, its frequent application contaminates both terrestrial and aquatic ecosystems and negatively affects their key ecological processes. This study demonstrated the toxicity and efficient removal of captan by two different taxonomic species; the green microalga Scenedesmus obliquus and cyanobacterium Nostoc muscorum. After a week of exposure to mild (15 mg/L) and severe (30 mg/L) captan doses, the intracellular captan uptake, degradation and metabolic regulation of captan detoxification were studied. Compared to N. muscorum, S. obliquus accumulated more captan, but efficiently degraded it into two safe eco-friendly by-products; phthalic acid and 1,2,3,6-tetrahydro phthalimide. S. obliquus showed less decrease in cell growth, photosynthesis activity and related parameters including Chla content and activity of PEPC and RuBisCo enzymes. Captan at the severe dose induced oxidative damage particularly in N. muscorum, as expressed by the high levels of H2O2, MDA, NADPH oxidase and protein peroxidation. Both species invested glutathione-s-transferase enzyme in captan detoxification however, induction of antioxidant defence system e.g. ascorbate and glutathione cycle was more pronounced in S. obliquus which could explain its tolerance ability. This study provided a better understanding of the environmental risks of captan and introduced S. obliquus as a promising captan phycoremediator.

Modulation in isocitrate dehydrogenase activity under citrate enrichment affects carbon and nitrogen fixations in the cyanobacterium Nostoc muscorum Meg 1

The enzyme isocitrate dehydrogenase (IDH) converts isocitrate synthesized from citrate to α-ketoglutarate in the TCA cycle. In cyanobacteria, α-KG has an additional role where it donates its carbon skeleton for ammonium assimilation in the GS-GOGAT pathway thereby linking carbon and nitrogen metabolisms. Looking at this crucial function of IDH that makes α-KG available for both carbon and nitrogen assimilation, changes brought about in its activity under excess availability of citrate in a cyanobacterium was evaluated. Further, how these changes are transmitted downstream affecting carbon and nitrogen metabolisms were also evaluated. A 100 μM citrate supplementation induced IDH activity. Consequently, there was an increase in concentrations of photosynthetic pigments, D1 protein and RuBisCO as well as in PSII activity. Heterocyst differentiation was initiated and an upsurge in the activities of nitrogenase and GS were recorded. An enhancement in the total protein and carbohydrate content reiterated the positive influence of citrate enrichment on carbon and nitrogen fixation. The increase in the mRNA contents of IDH, D1 protein, RuBisCO, nitrogenase and GS indicated their induction at the genetic level. Finally, there was augmentation in total biomass production by ∼28%. Interestingly as citrate concentration was increased to 500 μM, both C- and N- fixations were highly compromised suggesting that even though citrate is an essential metabolite in the cells, it became toxic beyond a certain concentration to the organism. SEM and TEM studies showed no changes in the organism's morphology and ultra-structure in presence of 100 μM citrate while adverse changes were noticed in presence of 500 μM citrate.

Calcium mediated nitric oxide responses: Acquisition of nickel stress tolerance in cyanobacterium Nostoc muscorum ATCC 27893

Calcium (Ca2+) and nitric oxide (NO) are potentially active and multitasking signaling molecules which are known to regulate abiotic stresses in plants, but their interactive role in the acquisition of metal stress tolerance in cyanobacteria remains elusive. In current study the signaling role of Ca2+ (800 μM) and NO (10 μM SNP) on key physiological and biochemical attributes of the agriculturally and economically important cyanobacterium Nostoc muscorum ATCC 27893 subjected to Ni stress (2 μM) was examined. Results revealed that Ni at elevated level caused severe damages to the test organism but exogenous supplementation of Ca2+ and NO efficiently mitigated its toxic effects and up-regulated the growth, pigment contents, rate of photosynthesis (whole cell oxygen evolution and Chl a fluorescence indices: Kinetic traits: ΦP0, Ψ0, ΦE0 and PIABS, along with Fv/F0), nitrogen metabolism (NO3‾ and NO2‾ uptake, nitrate:NR and NiR; and ammonia:GS and GOGAT; assimilating enzymes), and boosted the enzymatic (SOD, POD, CAT and GST) along with non-enzymatic (proline, cysteine and NP-SH) antioxidants. Whereas the increased values of energy flux traits: (ABS/RC, TR0/RC, DI0/RC and ET0/RC) along with F0/Fv, rate of respiration, oxidative stress biomarkers (SOR, H2O2 and MDA), and activity of GDH enzyme exhibited lowering trends with application of Ca2+ and NO. Further, addition of EGTA (Ca2+ scavenger) and PTIO (NO scavenger) reversed the positive impacts of Ca2+ and NO and worsened the toxicity of Ni on test cyanobacterium, but the damages were more pronounced under PTIO application that demonstrated Ca2+ mediated signaling role of NO in Ni toxicity alleviation.

Biogas-based production of glycogen by Nostoc muscorum: Assessing the potential of transforming CO2 into value added products

The potential of the filamentous N2-fixing cyanobacterium Nostoc muscorum for CO2 capture from high-loaded streams (i.e. flue gas or biogas) combined with the accumulation of glycogen (GL) and polyhydroxybutyrate (PHB), was evaluated under nutrient-sufficient and nutrient-limited conditions. N. muscorum was able to grow under CO2 contents from 0.03 up to 30% v/v, thus tolerating CO2 concentrations similar to those found in raw biogas or flue-gas, with maximum CO2-fixation rates of 191.9 ± 46 g m−3 d−1 at a biomass concentration of 733.3 ± 207.4 mg TSS L−1. Despite N. muscorum was inhibited by the presence of H2S, the co-inoculation with activated sludge resulted in both CO2 and H2S depletion. Moreover, N. muscorum accumulated GL up to ∼54% dcw under N and P-deprivation, almost 36 times higher than that recorded under nutrients sufficient condition. The addition of 10% extra carbon in the form of valeric acid not only did not hamper the growth of N. muscorum (336.0 ± 113.1 mg TSS L−1) but also increased the GL content to ∼58% dcw. On the contrary, a negligible PHB accumulation was found under the tested conditions, likely due to the high CO2 concentration of 30% v/v in the headspace and therefore the high availability of inorganic carbon for the cultures. N. muscorum cultures achieved VFAs degradations up to ∼78% under controlled pH. These results supported N. muscorum as a sustainable alternative for CO2-capture and greenhouse gas mitigation or for photosynthetic biogas upgrading coupled with value added biomass production.

Analyzing dose dependency of antioxidant defense system in the cyanobacterium Nostoc muscorum Meg 1 chronically exposed to Cd2+

The aim of the present study was to analyze the dose dependency of oxidant-antioxidant homeostasis in Cd2+ exposed Nostoc muscorum Meg 1 cells. Quantification of percent DNA loss, protein oxidation and lipid peroxidation was carried out to assess Cd2+ induced ROS mediated damages to the organism. The countermeasures adopted by the cyanobacterium were also evaluated by computing various components of both enzymatic and non-enzymatic antioxidants. Exposure to different Cd2+ (0.1, 0.2, 0.3, 0.5, 1, 1.5, 2, 2.5, 3 ppm) doses showed substantial increase in ROS content in the ranges of 20–181% and 116–323% at the end of first and seventh day. The DNA damage, protein oxidation and lipid peroxidation were increased by 11–62%, 7–143% and 13–183% with increasing Cd2+ concentrations at the end of seven days. TEM images clearly showed damages to the cell wall, cell membrane and thylakoid organization at higher Cd2+ (0.5–3 ppm) concentrations. Cd2+ exposure up to 0.5 ppm registered increase in contents of antioxidative enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)) and in non-enzymatic antioxidants (glutathione, total thiol, phytochelatin and proline) indicating stimulation of ROS mitigating machinery. However, toxicity of Cd2+ was evident as at higher concentrations the cellular morphology and ultra-structures were negatively affected and the capacities of the cells to generate various antioxidant measures were highly compromised. The organism registered 96–98% sorption ability from a solution supplemented with 0.3 ppm Cd2+ and thus show realistic potential as Cd2+ bioremediator in wastewater treatment.

Phytohormone up-regulates the biochemical constituent, exopolysaccharide and nitrogen metabolism in paddy-field cyanobacteria exposed to chromium stress

BackgroundCyanobacteria are well known for their inherent ability to serve as atmospheric nitrogen fixers and as bio-fertilizers; however, increased contaminants in aquatic ecosystem significantly decline the growth and function of these microbes in paddy fields. Plant growth regulators play beneficial role in combating the negative effects induced by heavy metals in photoautotroph. Current study evaluates the potential role of indole acetic acid (IAA; 290 nm) and kinetin (KN; 10 nm) on growth, nitrogen metabolism and biochemical constituents of two paddy field cyanobacteria Nostoc muscorum ATCC 27893 and Anabaena sp. PCC 7120 exposed to two concentrations of chromium (CrVI; 100 μM and 150 μM).ResultsBoth the tested doses of CrVI declined the growth, ratio of chlorophyll a to carotenoids (Chl a/Car), contents of phycobiliproteins; phycocyanin (PC), allophycocyanin (APC), and phycoerythrin (PE), protein and carbohydrate associated with decrease in the inorganic nitrogen (nitrate; NO3— and nitrite; NO2—) uptake rate that results in the decrease in nitrate and ammonia assimilating enzymes; nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT) except glutamate dehydrogenase (GDH). However, exogenous supplementation of IAA and KN exhibited alleviating effects on growth, nitrogen metabolism and exopolysaccharide (EPS) (first protective barrier against metal toxicity) contents in both the cyanobacteria, which probably occurred as a result of a substantial decrease in the Cr uptake that lowers the damaging effects.ConclusionOverall result of the present study signifies affirmative role of the phytohormone in minimizing the toxic effects induced by chromium by stimulating the growth of cyanobacteria thereby enhancing its ability as bio-fertilizer that improved fertility and productivity of soil even in metal contaminated condition.

Toxicity of NSAID drug (paracetamol) to nontarget organism-Nostoc muscorum.

Due to many folds increase in application of human and veterinary medicines, pharmaceuticals, a new category of pollutants, have emerged in our environment. They exist as residues in rivers, sewage effluents, streams, surface, ground, and potable water. Paracetamol (acetaminophen) is one such drug that is used as an antipyretic and analgesic medicine. It is a non-steroidal antiinflammatory drug (NSAID) and is easily available in the market because no medical prescription is necessary for its purchase and use. Paracetamol remains physiologically active even after their expiry period. Their detection in the environment in bioactive form has resulted in adverse effects on nontarget species. To determine the effect of paracetamol on aquatic photosynthetic organic (Cyanobacteria-Nostoc muscorum), present study was performed. Paracetamol (25mg/L, 50mg/L, 75mg/L, 100, 125, and 150mg/L) exposure showed toxic responses on the test organism by generating oxidative stress (MDA, H2O2, O2.-). Paracetamol caused a significant decrease in growth of cyanobacteria and showed EC50 113.68mg/L after the 6th day of treatment. Photosynthetic pigments (chlorophyll, carotenoid, and phycobiliprotein) decreased with paracetamol increase. Antioxidant enzymatic (SOD, CAT, APX, GST, and GR) and osmolyte (Proline) also increased with increase in paracetamol to counteract the oxidative stress.

Characterization of Nostoc muscorum NCCU-442 Derived Poly-3- hydroxybutyrate (PHB) and Polyethylene Glycol (PEG) Blends

Background: Poly-3-hydroxybutyrate (PHB) has attracted much consideration as biodegradable biocompatible polymer. This thermoplastic polymer has comparable material properties to polypropylene. Materials with more valuable properties may result from blending, a common practice in polymer science. Objective: In this paper, blends of PHB (extracted from cyanobacterium Nostoc muscorum NCCU- 442 with polyethylene glycol (PEG) were investigated for their thermal, tensile, hydrophilic and biodegradation properties. Methods: Blends were prepared in different proportions of PHB/PEG viz. 100/0, 98/2, 95/5, 90/10, 80/20, and 70/30 (wt %) using solvent casting technique. Morphological properties were investigated by using Scanning Electron Microscopy (SEM). Differential scanning calorimetry and thermogravimetric analysis were done for thermal properties determination whereas the mechanical and hydrophilic properties of the blends were studied by means of an automated material testing system and contact angle analyser respectively. Biodegradability potential of the blended films was tested as percent weight loss by mixed microbial culture within 60 days. Results: The blends showed good misciblity between PEG and PHB, however increasing concentrations of plasticizer caused morphological alteration as evidenced by SEM micrographs. PEG addition (10 % and above) showed significant alternations in the thermal properties of the blends. Increase in the PEG content increased the elongation at break ratio i.e enhanced the required plasticity of PHB. Rate of microbial facilitated degradation of the blends was greater with increasing PEG concentrations. Conclusion: Blending with PEG increased the crucial polymeric properties of cyanobacterial PHB.

Cytokinin alleviates cypermethrin toxicity in Nostoc muscorum by involving nitric oxide: Regulation of exopolysaccharides secretion, PS II photochemistry and reactive oxygen species homeostasis

Growth of the most important nitrogen fixing cyanobacterium Nostoc muscorum is reported to be badly affected by the application of insecticides. To overcome their damaging effects, several strategies are being used. Out of these, some works on kinetin (KN, a synthetic cytokinin) has been recognized that it can overcome toxicity of insecticides in cyanobacteria. Besides this, it is now known that every hormone needs certain second messengers such as nitric oxide (NO) for its action. But implication of NO in KN-mediated regulation of insecticide toxicity is yet to be investigated. Hence in the current study, we have investigated the possible involvement of NO in KN-mediated regulation of cypermethrin toxicity in the cyanobacterium Nostoc muscorum. Cypermethrin decreased growth of Nostoc muscorum which was accompanied by decreased pigment contents and altered photosystem II (PS II) photochemistry that resulted in inhibition of photosynthetic process but KN significantly ameliorated cypermethrin toxicity. Cypermethrin induced production of free radicals (in-vivo and in-vitro) and weakened defensive mechanism (enzymatic and non-enzymatic defense system) which was restored by KN. Further, the results revealed that NG-nitro-l-arginine methyl ester (l-NAME, an inhibitor of nitric oxide synthase) worsened the effect of cypermethrin toxicity even in the presence of KN while 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, a scavenger of NO) reversed KN-mediated amelioration even in the presence of sodium nitroprusside (SNP, an NO donor), suggesting that endogenous NO is required for mitigation of cypermethrin toxicity. Overall, our results first time show that endogenous NO is essential for KN-mediated mitigation of cypermethrin toxicity in the Nostoc muscorum.

Ozone enhanced production of potentially useful exopolymers from the cyanobacterium Nostoc muscorum

Extracellular polysaccharides (EPS) from Nostoc muscorum, a heterocystous, filamentous cyanobacterium isolated from a jhumland (shifting cultivation) soil of Assam, North-East India, was physico-chemically characterized to find out its potential applications and to improve its production with some stress source like ozone. Using Response Surface Methodology (RSM), EPS production was improved. Accordingly, with magnesium sulfate (MgSO4·7H2O) at 62 mg L−1, Sodium Chloride (NaCl) at 58 mg L−1 and 56 mg L−1 di-potassium hydrogen phosphate (K2HPO4), a yield of 126.73 μg mL−1 of EPS in 12 days was obtained which was four-fold higher than un-optimised control. An important finding of this study is that EPS production could be further enhanced by over 50% with a mild stress by a strong oxidizing agent ozone (O3). Physico-chemical properties of this Ozone induced EPS was evaluated and found identical to uninduced EPS. EPS was composed of the hexoses- Glucose (14.80%), Galactose (18.01%) and Mannose (12.64%), the pentoses- Arabinose (17.86%) and Xylose (11.66%), the deoxyhexose- Fucose (12.53%) and Rhamnose (12.50%). Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analysis revealed the presence of the functional groups uronic acid and traces of sulfate group. The Zeta potential analysis revealed that the emulsions were stabilized electrosterically rather than by pure electrostatic repulsion and steric stabilization. EPS at 1% in hydrocarbons and vegetable oils was observed to be an excellent emulsifier (99%), with reasonable stability. Rheological study revealed that the EPS (1%) was a non- Newtonian weak gel, useful for emulsification activity. Unlike petroleum-based emulsifiers now in use, bio-based EPS are renewable, economical and eco-friendly. The physico-chemical characteristics suggest their utility in a wide variety of other applications including bioremediation, manufacture of paints, shear reduction in oil drilling etc.

Influence of calcium on cadmium uptake and toxicity to the cyanobacterium Nostoc muscorum Meg 1

It is well known that Ca2+ interferes with uptake and expression of toxicity of Cd2+ in numerous organisms. This study demonstrated that the morphological alterations expressed in the cyanobacterium Nostoc muscorum Meg 1 cells exposed to 0.5mgL−1 Cd2+ for 7 days were prevented when 10mgL−1 Ca2+ was included in the experimental set-up. The spectroscopic analysis confirmed a severe reduction in contents of chlorophyll a, phycocyanin, allophycocyanin, phycoerythrin, carotenoids and total protein at the end of 168h (7 days) in presence of Cd2+; inclusion of Ca2+ significantly lessened these effects. Heterocyst frequency, nitrogenase and, glutamine synthetase activities were similarly improved in the presence of Ca2+. Uptake studies showed a reduction in 94% biosorption of supplied Cd2+ to 50% in the presence of Ca2+ indicating its competition with Cd2+ binding onto the cyanobacterial cell surfaces.