Browsing by Author "R.P. Sinha"

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A cyanobacterial mutant resistant against a bleaching herbicide
(2000) A. Vaishampayan; R.P. Sinha; A.K. Gupta; D.-P. Häder
The nitrogen fixing cyanobacterium Nostoc muscorum has been found to be sensitive to the herbicide SAN 6706 [4-chloro-5 (dimethylamino)-2-(a,a,a,-trifluoro-m-tolyl)-3-(2H) pyridazinon] at 30-45 μM within 15 min. The toxicity was more severe in combined nitrogen-free N(comb)-free medium than in a combined nitrogen medium; this enhancement was reversible by supplementation of the medium with 3 mM glucose or 5 μM ATP, serving as carbon and/or energy source in this organism. A mutant of this cyanobacterium resistant to 3 mM SAN 6706 has been isolated and characterized to perform nitrogenase activity in exogenous ATP supplemented N(comb)-free medium. However, it exhibited a moderate growth in combined nitrogen media in the absence of external ATP. The resistance factor is higher than 100. Simultaneously, this strain possesses a cross-resistance to methylamine, a well-known inhibitor of photophosphorylation, irrespective of the exogenous ATP supply. The behavior of the mutant suggests a defective phosphorylation in its photosynthetic system.
A cyanobacterial recombination study, involving an efficient N2-fixing non-heterocystous partner
(2000) A. Vaishampayan; R.P. Sinha; A.K. Gupta; D.-P. Häder
Many filamentous cyanobacteria fix atmospheric nitrogen under natural conditions in specialized anaerobic compartments, heterocysts, interspersed between vegetative cells, which provide protection to the O2-sensitive nitrogenase. A few unicellular cyanobacterial strains are also known to fix nitrogen aerobically at a slower rate. Filamentous cyanobacteria lacking heterocysts are not known so far to fix nitrogen. We describe the isolation and purification of a non-heterocystous filamentous cyanobacterium from the fronds of the water-fern Azolla, fixing nitrogen at 18.7 ± 0.2 n moles ethylene μg Chl. a-1 h-1 when grown in nitrogen-free medium at a low level of oxygen between two layers of agar. This strain of Anabaena azollae has been designated as het- nif+ (non-heterocystous and nitrogen-fixing), and is found to be easily and effectively preserved in nitrogen-free medium in standard synthetic cyanobacterial nutrient medium (pH 8.5) at a continuous light intensity of 2800 lx at 25 ± 1°C. This het- nif+ strain is an effective donor of the nif+ marker to a het+ nif- strain of another cyanobacterium, Nostoc muscorum, when both are grown together in a recombination study.
Cyanobacterial biofertilizers in rice agriculture
(2001) A. Vaishampayan; R.P. Sinha; D.-P. Häder; T. Dey; A.K. Gupta; U. Bhan; A.L. Rao
Floodwater and the surface of soil provide the sites for aerobic phototrophic nitrogen (N) fixation by free-living cyanobacteria and the Azolla-Anabaena symbiotic N2-fixing complex. Free-living cyanobacteria, the majority of which are heterocystous and nitrogen fixing, contribute an average of 20-30 kg N ha-1, whereas the value is up to 600 kg ha-1 for the Azolla-Anabaena system (the most beneficial cyanobacterial symbiosis from an agronomic point of view). Synthesis and excretion of organic/growth-promoting substances by the cyanobacteria are also on record. During the last two or three decades a large number of studies have been published on the various important fundamental and applied aspects of both kinds of cyanobacterial biofertilizers (the free-living cyanobacteria and the cyanobacterium Anabaena azollae in symbiotic association with the water fern Azolla), which include strain identification, isolation, purification, and culture; laboratory analyses of their N2-fixing activity and related physiology, biochemistry, and energetics; and identification of the structure and regulation of nitrogen-fixing (nif) genes and nitrogenase enzyme. The symbiotic biology of the Azolla-Anabaena mutualistic N2-fixing complex has been clarified. In free-living cyanobacterial strains, improvement through mutagenesis with respect to constitutive N2 fixation and resistance to the noncongenial agronomic factors has been achieved. By preliminary meristem mutagenesis in Azolla, reduced phosphate dependence was achieved, as were temperature tolerance and significant sporulation/spore germination under controlled conditions. Mass-production biofertilizer technology of free-living and symbiotic (Azolla-Anabaena) cyanobacteria was studied, as were the interacting and agronomic effects of both kinds of cyanobacterial biofertilizer with rice, improving the economics of rice cultivation with the cyanobacterial biofertilizers. Recent results indicate a strong potential for cyanobacterial biofertilizer technology in rice-growing countries, which opens up a vast area of more concerted basic, applied, and extension work in the future to make these self-renewable natural nitrogen resources even more promising at the field level in order to help reduce the requirement for inorganic N to the bare minimum, if not to zero.
Cyanobacterial secondary metabolites
(2011) Shweta Yadav; R.P. Sinha; M.B. Tyagi; Ashok Kumar
Cyanobacteria inhabit a range of diverse and extreme habitats and have potential to produce an elaborate array of secondary metabolites with unusual structures and potent bioactivity. This review summarizes several classes of cyanobacterial secondary metabolites some of which pose a threat to human or animal health in aquatic ecosystems because of their acute toxicity. This class includes hepatotoxins (microcystins and nodularins), neurotoxins (saxitoxin and anatoxins) and irritant toxins (lipopolysachharides). Another important class includes the phytohormones (IAAs, cytokinin and gibberillin-like compounds) and iron-chelators (schizokinen, anachelin and synechobactins) which besides exerting profound effect on the productivity of the ecosystem have also potential for use as medicine for treatment of persistent metal toxicity. Several cyclic peptides and depsipeptides such as cyanopeptolins, micropeptin and oscillaeptin which have been categorized as protease inhibitors make cyanobacteria unattractive as a food source to grazers and help in their survival. UV-screening compounds such as scytonemin and mycosporin-like amino acids (MAAs) produced by cyanobacteria inhabiting habitats exposed to intense solar radiation may find use in development of artificial sunscreens.
Effects of UV irradiation on certain physiological and biochemical processes in cyanobacteria
(Elsevier B.V., 1996) R.P. Sinha; N. Singh; A. Kumar; H.D. Kumar; M. Häder; D.-P. Häder
The effects of artificial UV (280-400 nm, 5 W m-2) radiation on heterocyst differentiation, nitrogenase activity, 14CO2 uptake and protein profile of whole cell and isolated heterocysts have been studied in four cyanobacterial strains isolated from Indian rice paddy fields. Exposure of cells to UV for 1 h significantly affected the differentiation of vegetative cells into heterocysts in four cyanobacterial strains studied (Anabaena sp., Nostoc sp., Nostoc carmium and Scytonema sp). Almost 50% fewer heterocysts were recorded in Anabaena sp. and Scytonema sp, and nearly 70% fewer in Nostoc sp. and Nostoc carinium after UV radiation in comparison with controls without UV. Nitrogenase activity in Anabaena sp. was completely inhibited within 45 min of UV exposure. 14CO2 uptake in Anabaena sp. was also severely affected by UV radiation. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) analyses of the total protein profile of Anabaena sp. showed a linear decrease in the protein content with increasing UV exposure time. Almost complete elimination of most of the protein bands occurred after 120 min of UV exposure. The SDS PAGE protein profile of isolated heterocysts of Anabaena sp. showed three prominent polypeptides of 26, 54 and 55 kDa, with a decrease in the first two and complete elimination of the last one after 1 h of UV radiation.
Effects of UV-B radiation on phytoplankton and macroalgae: Adaptation strategies
(2008) R.P. Sinha; S.P. Singh; D.-P. Häder
Recent results continue to indicate ozone depletion-related increases in solar ultraviolet-B radiation (UV-B; 280-315 nm) reaching the Earth's surface. Harmful doses of UV-B radiation can penetrate deep (up to several dozen meters) into the water column and may thus affect aquatic ecosystems. Aquatic ecosystems are key components of the Earth's biosp.here since they produce more than 50 % of the biomass on our planet. Phytoplankton and macroalgac are the major biomass producers and form the basis of the aquatic food webs. The highly energetic UV-B has the greatest potential for cell damage caused by both direct effects on DNA and proteins and indirect effects via the production of reactive oxygen sp.ecies. UV-B can cause wide ranging damage such as reduction in development and reproduction resulting in loss of productivity of phytoplankton and macroalgac. Consequences of loss of productivity are reduced sink capacity for atmosp.heric CO 2 and negative effects on sp.ecies diversity, ecosystem stability, trophic interactions and ultimately biogeochemical cycles. However, a number of sp.ecies have developed various adaptation strategies to counteract the damaging effects of UV-B. These strategics include vertical migration within the water column, repair of DNA damage and production of UV-absorbing/screcning mycosp.orine-like amino acids (MAAs). This article deals with the effects of UV-B radiation on phytoplankton and macroalgac and the adaptation strategies applied by them to reduce the negative effects of UV-B.
Facile technique of protein precipitation by application of electric current
(Kluwer Academic Publishers, 1993) Anita Sharma; R.P. Sinha; Minni Srivastava; Ashok Kumar
Precipitation of proteins has been achieved following passage of direct electric current in various protein solutions. Application of as low as 3 V of electric current showed precipitation but the rate increased with increase in electric current. With 9 V there was more than 85% precipitation of protein within 15 min. Precipitation occurred at a wide range of pH and temperature. Electrophoretic analysis of precipitated proteins show that they are not denatured by application of electric current. Proteins thus precipitated can be easily recovered by centrifugation. © 1993 Science & Technology Letters.
Life of wetland cyanobacteria under enhancing solar UV-B radiation
(2008) R.P. Sinha; R.P. Rastogi; N.K. Ambasht; D.-P. Häder
The continuing depletion of stratosp.heric ozone layer mainly due to anthropogenically released pollutants such as chlorofluorocarbons (CFCs) has resulted in an increase in solar ultraviolet-B (UV-B; 280-315 nm) radiation reaching to the Earth's surface. UV-B is a small (less than 1% of total energy) but highly active component of solar radiation that can penetrate deep into biologically significant depths in lakes, ponds, rivers and oceans. Photosynthctic prokaryotes such as cyanobacteria are dependent on solar energy and thereby always sense and face the stress of UV-B radiation. UV-B can cause wide ranging effects including mutagenesis, destruction of proteins/enzymes, inhibition of a number of vital metabolic processes and formation of thymine dimers in DNA leading to death of microbes. The degree of damaging effects brought about by UV-B varies in different sp.ecies suggesting the existence of certain protective mechanisms operative in cyanobacteria. A number of sp.ecies counteract the damaging effects of UV-B by synthesizing UV protective compounds such as mycosp.orine-like amino acids (MAAs) and the sheath pigment, scytonemin. These compounds are known to act as natural sunscreens and their synthesis is induced by UV-B radiation. In this article an attempt has been made to highlight some of the notable effects of UV-B radiation on wetland cyanobacteria and the role of photoprotective mechanisms in mitigating the damage.
Novel method for the detection of HIV using rp24 recombinant protein from E. Coli BL-21
(2010) S.C. Singh; M. Vasudevan; Richa; R.P. Sinha
A novel method for the purification of recombinant protein 24 (rp24) of human immunodeficiency virus type 1 (HIV- 1) from Escherichia coli is described. The protein was over-expressed in E. coli (BL21 lDE3) cells to the levels of ~ 30 % total cell protein in the soluble fraction. The recombinant protein was extracted and purified to near homogeneity by ion-exchange steps followed by ultrafiltration. The recombinant protein in combination with synthetic peptides from immuno-dominant stretches derived from the 'envelope' proteins of HIV-1 and HIV-2 was used for the development of an ELISA kit, for detection of antibodies against the virus in human serum and/or plasma.
Photosynthetic performance of Anabaena variabilis PCC 7937 under simulated solar radiation
(Kluwer Academic Publishers, 2013) S.P. Singh; R.P. Rastogi; R.P. Sinha; D.-P. Häder
In vivo chlorophyll fluorescence analysis reflecting the photosystem II functionality was investigated in the cyanobacterium Anabaena variabilis PCC 7937 under simulated solar radiation in a combination with various cut-off filters (WG 280, WG 295, WG 305, WG 320, WG 335, WG 345, and GG 400) to assess the effects of photosynthetically active radiation (PAR), ultraviolet-A (UV-A), and ultraviolet-B (UV-B) radiations on photosynthesis. The photosynthetic activity (PA) was severely inhibited immediately after 10 min of exposure to high PAR, UV-A, and UV-B radiations compared with low PAR grown control samples. After 1 h of exposure, PA of 17.5 ± 2.9% was detected in the high PAR exposed samples compared with the control, while only a trace or no PA was observed in the presence of ultraviolet radiation (UVR). A recovery of PA was recorded after 2 h of the exposure, which continued for next 4, 8, 12, and 24 h. After 24 h of the exposure, PA of 57.5 ± 1.9%, 36.1 ± 11.7%, 23.5 ± 3.3%, 22.3 ± 5.2%, 20.8 ± 6.7%, 13.2 ± 6.6%, and 21.6 ± 9.5% was observed compared with the control sample in 400, 345, 335, 320, 305, 295, and 280 nm cut-off filters-covered samples, respectively. The relative electron transport rate, measured after 24 h exposure, showed also a disturbance in electron transfer between the two photosystems under the high PAR and UVR treatments relative to the control samples, suggesting the inhibition of photosynthesis. This study suggests that both high PAR and UVR inhibited the photosynthetic performance of A. variabilis PCC 7937 by damaging the photosynthetic apparatus, however, photoprotective mechanisms evolved by the organism allowed an immediate repair of ecologically important machinery, and enabled its survival. © 2013 Springer Science+Business Media Dordrecht.
Phytoplankton assemblage and UV-protective compounds in the river Ganges
(National Institute of Science Communication and Policy Research, 2021) H. Ahmed; J. Pathak; D.K. Singh; A. Pandey; Rajneesh; V. Singh; D. Kumar; P.R. Singh; R.P. Sinha
Interactions between physico-chemical parameters such as pH, temperature, nitrate, phosphate, alkalinity, acidity, biological oxygen demand (BOD), chemical oxygen demand (COD) and solar ultraviolet radiation (UVR) strongly affect aquatic ecosystems. Due to fluctuations in several environmental factors including river water pollution and UVR, organisms are under constant threat. However, phytoplankton protects themselves from environmental extremes by adopting several defense strategies including synthesis of photoprotective compounds such as scytonemin and mycosporine-like amino acids (MAAs). We investigated the presence of scytonemin and MAAs in phytoplankton of some polluted sites of one of the holy rivers of the world, the Ganges at Varanasi, India. We observed phytoplankton assemblages and studied certain environmental parameters which could possibly affect phytoplankton diversity in the river. Phytoplankton consisted mainly of 49 taxa of 34 genera belonging to Bacillariophyceae, Chlorophyceae, Cyanophyceae, and Chrysophyceae. The members belonging to Bacillariophyceae and Chlorophyceae were the two dominant classes, which comprised up to 75% of the total phytoplankton. Photoprotective compounds were isolated and characterized from phytoplankton. Electrospray ionization-mass spectrometry (ESI-MS) analysis of MAAs showed the presence of shinorine, palythinol, mycosporine-glycine and palythine. A high concentration of scytonemin was also observed with an absorption maximum at 386 nm in the studied phytoplankton. © 2021, National Institute of Science Communication and Policy Research. All rights reserved.
Plant-cyanobacterial symbiotic somaclones as a potential bionitrogen-fertilizer for paddy agriculture: Biotechnological approaches
(Elsevier GmbH, 1999) R.P. Sinha; A. Vaishampayan; D.-P. Häder
The role of N2-fixing cyanobacteria in improving the fertility of rice paddy fields is well known. Among all symbiotic associations, involving cyanobacteria, the Azolla-Anabaena complex is very efficient in water-logged rice paddy fields, contributing significant levels of nitrogen and organic matter thereby improving the physico-chemical properties of soils. This review focuses on some of the recent advances made in the areas of developing genetically improved somaclones of Azolla-Anabaena associative complex, and artificial plant-cyanobacterial symbiotic associations.
Protective role of certain chemicals against UV-B-induced damage in the nitrogen-fixing cyanobacterium, Nostoc muscorum
(2003) R. Tyagi; A. Kumar; M.B. Tyagi; P.N. Jha; H.D. Kumar; R.P. Sinha; D.-P. Häder
The protective effects of L-cysteine, ascorbic acid, reduced glutathione, L-tryptophan, and sodium pyruvate against UV-B-induced damages were studied in the nitrogen-fixing cyanobacterium, Nostoc muscorum. When added to the culture suspension during UV-B treatment, these chemicals caused a significant protective effect on survival and growth of the organism. Sodium pyruvate conferred the strongest protection whereas the weakest effect was elicited by tryptophan. A 20 min exposure of a culture suspension to UV-B completely inactivated nitrogenase activity but the inactivation was strongly prevented by exogenous addition of ascorbic acid or reduced glutathione during UV-B exposure, and weakly prevented by pyruvate, cysteine and tryptophan. In vivo nitrate reductase activity was not completely lost even after 80 min of UV-B exposure, and addition of the test chemicals did not confer any significant protection to this enzyme. Whereas 14CO2 uptake was drastically inhibited (78% inhibition) by 30 min exposure to UV-B in the absence of any test chemical, about 76% activity remained when the UV-B exposure was given to cultures in the presence of ascorbic acid. These results suggest that the damaging effects of UV-B are substantially minimized by certain reducing agents, the protective effect being particularly strong on the O2 sensitive enzyme, nitrogenase. Presence of these chemicals in their natural habitat or inside the cells of living organisms may partially protect/repair the damaging effects of UV-B radiation.
Spectroscopic and Biochemical Analyses of UV Effects on Phycobiliproteins of Anabaena sp. and Nostoc carmium
(1995) R.P. Sinha; M. Lebert; A. Kumar; H.D. Kumar; D.‐P. Häder
The effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in two N2‐fixing cyanobacteria, Anabaena sp. and Nostoc carmium, isolated from rice paddy fields in India. Phycobiliproteins were isolated and separated by sucrose density gradient centrifugation. After UV exposure the top fraction mainly contained carotenoids (absorption maximum at 485 nm), which first showed an increase in intensity and absorption and then a gradual decrease with increasing UV exposure in Anabaena sp., whereas, in Nostoc carmium this fraction showed a steady increase over the whole exposure time. The bottom fraction of both organisms mainly contained phycocyanin (absorption peak at 620 nm) which showed a steady decline in intensity, as well as absorption. Fluorescence excitation at 620 nm resulted in an emission at 650 nm which underwent a shift towards shorter wave‐lengths with increasing UV‐exposure time, indicating a disassembly of the phycobilisomal complex and of impaired energy transfer from accessory pigments to the reaction centers. SDS PAGE analysis of the fractions revealed a loss of high molecular mass linker proteins and low molecular mass (αβ monomers indicating that the phycobiliproteins, which function as accessory pigments for the operation of photosystem II, disassemble during UV irradiation. 1995 Deutsche Botanische Gesellschaft/German Botanical Society
Ultraviolet radiation-induced generation of reactive oxygen species, DNA damage and induction of UV-absorbing compounds in the cyanobacterium Rivularia sp. HKAR-4
(Elsevier, 2014) R.P. Rastogi; S.P. Singh; A. Incharoensakdi; D.-P. Häder; R.P. Sinha
The effects of ultraviolet radiation (UVR) on certain biochemical processes were studied in the cyanobacterium Rivularia sp. HKAR-4. The generation of reactive oxygen species (ROS) was investigated under 295, 320 and 395nm cut-off filters using the ROS sensing probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). Contrary to photosynthetically active radiation (PAR) and PAR+UV-A (PA) radiation, ROS signals were more prominent under PAR+UV-A+UV-B (PAB) radiation. The low levels of ROS were also detected in the cells growing under dark as well as normal light conditions. The integrity of genomic DNA, the amplification of 16S rDNA and random amplified polymorphic DNA (RAPD) profile were considerably affected by PAB radiation. The formation of cyclobutane thymine dimers (T<>T) was observed under PAR as well as PA and PAB radiations but the intensity was found to be the highest under UV-B radiation. The formation of T<>T under PAR as well as PA radiation has not previously been reported in cyanobacterial systems. Furthermore, the synthesis of UVR-absorbing/screening compounds such as mycosporine-like amino acids (MAAs) was investigated under PAR and PAB. Dose-dependent induction of MAAs, mycosporine-glycine (MG; λmax310nm) as well as an unknown UV-absorbing compound (λmax 335nm) was observed under both PAR as well as UVR. The concentration of unknown MAA (hereafter, M-335) was higher than MG. Overall, in response to harmful effects of solar UVR, cyanobacteria have developed some photoprotective machinery to overcome its impact to grow in the adverse natural environments. © 2013 South African Association of Botanists.
Ultraviolet-B-induced destruction of phycobiliproteins in cyanobacteria
(2005) R.P. Sinha; A. Kumar; M.B. Tyagi; D.-P. Häder
Cyanobacteria, structurally Gram-negative photosynthetic prokaryotes, are the most abundant nitrogen-fixing microorganisms in both aquatic as well as terrestrial habitats particularly in rice-fields where they significantly contribute to fertility as a natural biofertilizer. In cyanobacteria light harvesting is carried out primarily by phycobiliproteins that are organized in macromolecular complexes called phycobilisomes (PBSs). There are three major classes of coloured phycobiliproteins present in the PBSs, e.g., phycoerythrin (red; λmax 540-570), phycocyanin (blue; λmax 610-620) and allophycocyanin (blue with a hint of green; λmax 650 -655). They are soluble in aqueous media and may constitute about 50 % of the soluble proteins of the cell. The building block of each of these complexes is a monomer (αβ) having a molecular mass of 15-20 kDa for α and 17-22 kDa for β subunit, each bearing covalently attached tetrapyrrole prosthetic groups. The stable in vitro assembly forms of these proteins are disc-shaped trimers (αβ)3 or hexamers (αβ)6. In addition phycobilisomes also contain mostly non-pigmented linker polypeptides with molecular weight between 30 -100 kDa that stabilizes the PBSs assembly. Ultraviolet-B (UV-B; 280-315 nm) radiation reaching the Earth's surface due to the depletion of the stratospheric ozone layer have been shown to cause destruction of phycobiliproteins, loss in linker polypeptides and finally disassembly of PBSs in cyanobacteria. This review deals with UV-B-induced destruction of phycobiliproteins in cyanobacteria.
Use of genetically improved nitrogen-fixing cyanobacteria in rice paddy fields: Prospects as a source material for engineering herbicide sensitivity and resistance in plants
(Georg Thieme Verlag, 1998) A. Vaishampayan; R.P. Sinha; D.-P. Häder
Cyanobacteria are the largest and most widely distributed group of photosynthetic prokaryotes on Earth, forming a prominent component of microbial populations in wetland soils, especially in rice paddy fields, and significantly contributing to fertility as a natural biofertilizer. Modern agricultural fields are generally treated with high doses of synthetic nitrogenous fertilizers and pesticides having adverse effects on the soil microflora of naturally occurring N2-fixing cyanobacteria. This review deals with some of the advances made during the last few decades in the areas of developing ammonia derepressible pesticide-resistant cyanobacterial mutants for algalization of the wet agricultural fields as a viable and efficient N-photobiofertilizer.
World Agriculture and Impact of Biotechnology
(Elsevier Inc., 2017) J. Pathak; Rajneesh; Ashok Pandey; Shailendra P. Singh; R.P. Sinha
Global agriculture is facing a serious threat from climate change, which may result in reduced productivity. Increasing food prices and greater global food insecurity are the outcomes of decreased productivity, and the persistence of such conditions may lead to a further increase in food prices, which could lead to social unrest and famine in certain instances. To ensure continued food security for an increasing global population, we must focus on improving crop productivity by exploiting new genetic sequencing and advanced "genomic breeding" and proteomics technologies. These technologies hold promise for crop improvement by developing crop species for particular environmental conditions. These technologies also allow plant breeders to target new crop species and traits effectively and simultaneously, such as resilience, quality, and yield, which are crucial to food security. Molecular breeding has a crucial role in improving crops. Although genetically modified (GM) crops hold good promise in enhancing crop productivity, GM crops face several challenges in agricultural growth, development, and sustainability. In this chapter, we discuss advances in the field of agriculture using advanced tools of biotechnology. © 2017 Elsevier B.V. All rights reserved.