Browsing by Author "Lal Chand Rai"

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A comparative study of antioxidative defense system in the copper and temperature acclimated strains of Anabaena doliolum
(2008) Yogesh Mishra; Poonam Bhargava; Riti Thapar; Ashish Kumar Srivastava; Lal Chand Rai
This study provides first hand comparative account of growth and antioxidative defense system of the wild type, Cu2+ and temperature treated wild type and acclimated strains of Anabaena doliolum Bharadwaja against Cu2+ and high temperature. The acclimated strains showed perceptible growth at 250 μM Cu2+ and 47°C temperatures, respectively. In contrast to this the wild type strain on exposure to 50 μM Cu2+ and 47°C temperature depicted almost complete inhibition of growth. However, the peroxide content was significantly higher in the acclimated strains than the wild type. Superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) showed maximum activity at high temperature followed by Cu2+ acclimated and minimum in the wild type strains. The ascorbate (ASC) and glutathione (GSH) contents were increased by 2.3 and 43.3, and 15.5 and 36.5-fold in Cu2+ and 47°C acclimated strains, respectively. However, when the wild type strain was subjected to Cu2+ and temperature all antioxidative enzymes except SOD showed inhibition of their activity. In case of wild type the GSH content was inhibited by 0.39-fold at 50 μM Cu2+ but the ASC content registered increase by 2 and 2.7-fold on subjecting to Cu2+ and temperature, respectively. Thus increased activity of enzymatic antioxidants as well as accumulation of ascorbate and glutathione in both the acclimated strains suggests that enzymatic and non-enzymatic antioxidants help in the acclimation of A. doliolum Bharadwaja against Cu2+ and high temperature. However, inhibition of antioxidative defense system of wild type under Cu2+ and heat stress appears to be the reason for its non survival. In view of the appreciable increase in the level of antioxidants as well as greater inhibition of specific growth rate in temperature than Cu2+ acclimated strains, temperature (47°C) is proposed to be is more deleterious to the organism than copper (250 μM). © 2008 Springer Science+Business Media B.V.
A novel aldo-keto reductase (AKR17A1) of anabaena sp. PCC 7120 degrades the rice field herbicide butachlor and confers tolerance to abiotic stresses in E. coli
(Public Library of Science, 2015) Chhavi Agrawal; Sonia Sen; Shivam Yadav; Shweta Rai; Lal Chand Rai
Present study deals with the identification of a novel aldo/keto reductase, AKR17A1 from Anabaena sp. PCC7120 and adds on as 17th family of AKR superfamily drawn from a wide variety of organisms. AKR17A1 sharesmany characteristics of a typical AKR such as - (i) conferring tolerance to multiple stresses like heat, UV-B, and cadmium, (ii) excellent activity towards known AKR substrates (isatin and 2-nitrobenzaldehyde), and (iii) obligate dependence on NADPH as a cofactor for enzyme activity. Themost novel attribute of AKR17A1, first reported in this study, is its capability to metabolize butachlor, a persistent rice field herbicide that adversely affects agro-ecosystem and non-target organisms. The AKR17A1 catalyzed- degradation of butachlor resulted into formation of 1,2-benzene dicarboxylic acid and 2,6 bis (1,1, dimethylethyl) 4,-methyl phenol as the major products confirmed by GC-MS analysis. © 2015 Agrawal et al.
A single gene all3940 (Dps) overexpression in Anabaena sp. PCC 7120 confers multiple abiotic stress tolerance via proteomic alterations
(Springer Verlag, 2016) Om Prakash Narayan; Nidhi Kumari; Poonam Bhargava; Hema Rajaram; Lal Chand Rai
DNA-binding proteins (Dps) induced during starvation play an important role in gene regulation and maintaining homeostasis in bacteria. The nitrogen-fixing cyanobacterium, Anabaena PCC7120, has four genes annotated as coding for Dps; however, the information on their physiological roles is limiting. One of the genes coding for Dps, ‘all3940’ was found to be induced under different abiotic stresses in Anabaena and upon overexpression enhanced the tolerance of Anabaena to a multitude of stresses, which included salinity, heat, heavy metals, pesticide, and nutrient starvation. On the other hand, mutation in the gene resulted in decreased growth of Anabaena. The modulation in the levels of All3940 in Anabaena, achieved either by overexpression of the protein or mutation of the gene, resulted in changes in the proteome, which correlated well with the physiological changes observed. Proteins required for varied physiological activities, such as photosynthesis, carbon-metabolism, oxidative stress alleviation, exhibited change in protein profile upon modulation of All3940 levels in Anabaena. This suggested a direct or an indirect effect of All3940 on the expression of the above stress-responsive proteins, thereby enhancing tolerance in Anabaena PCC7120. Thus, All3940, though categorized as a Dps, is possibly a general stress protein having a global role in regulating tolerance to multitude of stresses in Anabaena. © 2015, Springer-Verlag Berlin Heidelberg.
Active-site plasticity revealed in the asymmetric dimer of AnPrx6 the 1-Cys peroxiredoxin and molecular chaperone from Anabaena sp. PCC 7210
(Nature Publishing Group, 2017) Yogesh Mishra; Michael Hall; Roland Locmelis; Kwangho Nam; Christopher A. G. Söderberg; Patrik Storm; Neha Chaurasia; Lal Chand Rai; Stefan Jansson; Wolfgang P. Schröder; Uwe H. Sauer
Peroxiredoxins (Prxs) are vital regulators of intracellular reactive oxygen species levels in all living organisms. Their activity depends on one or two catalytically active cysteine residues, the peroxidatic Cys (CP) and, if present, the resolving Cys (CR). A detailed catalytic cycle has been derived for typical 2-Cys Prxs, however, little is known about the catalytic cycle of 1-Cys Prxs. We have characterized Prx6 from the cyanobacterium Anabaena sp. strain PCC7120 (AnPrx6) and found that in addition to the expected peroxidase activity, AnPrx6 can act as a molecular chaperone in its dimeric state, contrary to other Prxs. The AnPrx6 crystal structure at 2.3 Å resolution reveals different active site conformations in each monomer of the asymmetric obligate homo-dimer. Molecular dynamic simulations support the observed structural plasticity. A FSH motif, conserved in 1-Cys Prxs, precedes the active site PxxxTxxCp signature and might contribute to the 1-Cys Prx reaction cycle. © 2017 The Author(s).
AhpC (alkyl hydroperoxide reductase) from Anabaena sp. PCC 7120 protects Escherichia coli from multiple abiotic stresses
(2009) Yogesh Mishra; Neha Chaurasia; Lal Chand Rai
Alkyl hydroperoxide reductase (AhpC) is known to detoxify peroxides and reactive sulfur species (RSS). However, the relationship between its expression and combating of abiotic stresses is still not clear. To investigate this relationship, the genes encoding the alkyl hydroperoxide reductase (ahpC) from Anabaena sp. PCC 7120 were introduced into E. coli using pGEX-5X-2 vector and their possible functions against heat, salt, carbofuron, cadmium, copper and UV-B were analyzed. The transformed E. coli cells registered significantly increase in growth than the control cells under temperature (47 °C), NaCl (6% w/v), carbofuron (0.025 mg ml-1), CdCl2 (4 mM), CuCl2 (1 mM), and UV-B (10 min) exposure. Enhanced expression of ahpC gene as measured by semi-quantitative RT-PCR under aforementioned stresses at different time points demonstrated its role in offering tolerance against multiple abiotic stresses. © 2009 Elsevier Inc. All rights reserved.
Alr0882 encoding a hypothetical protein of Anabaena PCC7120 protects Escherichia coli from nutrient starvation and abiotic stresses
(2012) Alok Kumar Shrivastava; Sarita Pandey; Prashant Kumar Singh; Snigdha Rai; Lal Chand Rai
This study is the first to demonstrate cloning of alr0882, a hypothetical protein gene of Anabaena PCC7120, its heterologous expression in Escherichia coli strain LN29MG1655 (uspA::Kan) and functional complementation of abiotic stress tolerance of E. coli UspA. The recombinant vector pGEX-5X-2-alr0882 was used to transform uspA E. coli strain. The IPTG induced expression of a 56.6kDa GST fusion protein was visualized on SDS-PAGE and attested by immunoblotting. E. coli uspA strain harboring pGEX-5X-2-alr0882 when grown under carbon, nitrogen, phosphorus and sulphur limitation and abiotic stresses e.g. nalidixic acid, cycloserine, CdCl2, H2O2, UV-B, phenazine methosulphate (PMS), dinitrophenol (DNP), NaCl, heat, carbofuron and CuCl2 demonstrated about 22.6-51.6% increase in growth over the cells transformed with empty vector. Expression of alr0882 gene in mutant E. coli as measured by semi-quantitative RT-PCR at different time points under selected treatments reaffirmed its role in tolerance against stresses employed in this study. Thus the results of this study vividly demonstrated that the novel protein alr0882, although appreciably different from the known UspA of E. coli, offers tolerance to abiotic stresses hence holds potential for the development of transgenic cyanobacteria. © 2012 Elsevier B.V.
Author Correction: Active-site plasticity revealed in the asymmetric dimer of AnPrx6 the 1-Cys peroxiredoxin and molecular chaperone from Anabaena sp. PCC 7120 (Scientific Reports (2017) DOI: 10.1038/s41598-017-17044-3)
(Nature Publishing Group, 2018) Yogesh Mishra; Michael Hall; Roland Locmelis; Kwangho Nam; Christopher A. G. Söderberg; Patrik Storm; Neha Chaurasia; Lal Chand Rai; Stefan Jansson; Wolfgang P. Schröder; Uwe H. Sauer
The original version of this Article contained an error in the title of the paper, where "Anabaena sp. PCC 7120" was incorrectly given as "Anabaena sp. PCC 7210". This has now been corrected in the PDF and HTML versions of the Article, and in the accompanying Supplementary Information file. © 2018 The Author(s).
Biochemical and molecular basis of arsenic toxicity and tolerance in microbes and plants
(Elsevier, 2023) Sarita Pandey; Rashmi Rai; Lal Chand Rai
Arsenic is a ubiquitous toxic metalloid abundant in Earth's crust. It is of major concern with respect to its increased accumulation in soils, in the food chain, or in drinking water. This chapter will focus on recent progress on the mechanisms of its uptake, toxicity, and detoxification in microbes and in planta. Due to widespread occurrence in nature, both microbes and plants have evolved a wide range of tolerance and detoxification mechanisms such as reduced uptake, immobilization, chelation, reduction/oxidation, methylation, and efflux. Among microbes, the ars operon is a well-characterized genetic system for arsenic detoxification. The mechanisms proposed for metal detoxification and hyperaccumulation within the plant involve chelation of the metal cation by ligands and binding with thiol groups or sequestration of metals away from sites or metabolism in the cytoplasm, notably into the vacuole or cell wall. Finally, this chapter will also shed light on hyperaccumulators and mechanisms of hyperaccumulation. © 2023 Elsevier Inc. All rights reserved.
Biochemical and Molecular Basis of Arsenic Toxicity and Tolerance in Microbes and Plants
(Elsevier Inc., 2015) Sarita Pandey; Rashmi Rai; Lal Chand Rai
Arsenic is a ubiquitous toxic metalloid abundant in Earth's crust. It is of major concern with respect to its increased accumulation in soils, in the food chain, or in drinking water. This chapter will focus on recent progress on the mechanisms of its uptake, toxicity, and detoxification in microbes and in planta. Due to widespread occurrence in nature, both microbes and plants have evolved a wide range of tolerance and detoxification mechanisms such as reduced uptake, immobilization, chelation, reduction/oxidation, methylation, and efflux. Among microbes, the ars operon is a well-characterized genetic system for arsenic detoxification. The mechanisms proposed for metal detoxification and hyperaccumulation within the plant involve chelation of the metal cation by ligands and binding with thiol groups or sequestration of metals away from sites or metabolism in the cytoplasm, notably into the vacuole or cell wall. Finally, this chapter will also shed light on hyperaccumulators and mechanisms of hyperaccumulation. © 2015 Elsevier Inc. All rights reserved.
Biogenic synthesis and characterization of selenium nanoparticles and their applications with special reference to antibacterial, antioxidant, anticancer and photocatalytic activity
(Springer Science and Business Media Deutschland GmbH, 2021) Shraddha Pandey; Nikee Awasthee; Anusmita Shekher; Lal Chand Rai; Subash Chandra Gupta; Santosh Kumar Dubey
Oxyanions of selenium, selenite (SeO3)2− and selenate (SeO4)2− are toxic to terrestrial and aquatic biota but few microorganisms including cyanobacteria are resistant to high levels of selenite. Cyanobacteria evade selenite toxicity through bioreduction and synthesis of selenium nanoparticles (SeNPs). In this study, extracellular biosynthesis of SeNPs (Se0) using cyanobacterium, Anabaena sp. PCC 7120 on exposure to sodium selenite and characterization was done by using UV–visible spectroscopy, SEM–EDX, TEM and FTIR analyses which confirmed spherical shape with size range of 5–50 nm diameter. These biogenic SeNPs demonstrated significant antibacterial and anti-biofilm activity against bacterial pathogens. Furthermore, these SeNPs showed high antioxidant activity at minimum concentration of 50 µg/mL and significant anti-proliferative activity against HeLa cell line with IC50 value of 5.5 µg/mL. The SeNPs also induced accumulation of cancer cells in the sub-G1 phase which was clearly observed in cellular and nuclear morphology. These biofabricated SeNPs also reduced and decolorized toxic methylene blue dye significantly through photocatalytic degradation. Therefore Anabaena sp. PCC 7120 may be employed as a green bioresource to synthesize SeNPs with potential applications in medicine and environmental bioremediation. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Characterization of various functional groups present in the capsule of Microcystis and study of their role in biosorption of Fe, Ni and Cr
(2007) Subhashree Pradhan; Sarita Singh; Lal Chand Rai
This study demonstrates highest biosorption of Fe followed by Ni and Cr by Microcystis in single, bi and trimetallic combination. Fe was not only preferentially adsorbed from the metal mixtures but Ni and Cr failed to decrease its biosorption. The agreement of the data of Fe biosorption with the Langmuir model suggested monolayer sorption and existence of constant sorption energy during the experimental conditions. In contrast to Fe biosorption, Ni and Cr sorption followed the Freundlich isotherm; this demonstrates a multilayer biosorption of the two metals. IR analysis of Microcystis cells confirmed the presence of a large number of -COO- and some amino groups in the Microcystis cell wall. The oxygen and nitrogen donor atoms from carboxyl and amino groups were found to play a vital role in metal biosorption by Microcystis cell walls, and ion exchange mechanisms were involved in the biosorption of test metals. Extra peaks present in Ni and Cr treated cells implied that amino groups are more responsible for Ni and Cr biosorption. © 2006 Elsevier Ltd. All rights reserved.
Cloning expression and analysis of phytochelatin synthase (pcs) gene from Anabaena sp. PCC 7120 offering multiple stress tolerance in Escherichia coli
(2008) Neha Chaurasia; Yogesh Mishra; Lal Chand Rai
Phytochelatin synthase (PCS) is involved in the synthesis of phytochelatins (PCs), plays role in heavy metal detoxification. The present study describes for first time the functional expression and characterization of pcs gene of Anabaena sp. PCC 7120 in Escherichia coli in terms of offering protection against heat, salt, carbofuron (pesticide), cadmium, copper, and UV-B stress. The involvement of pcs gene in tolerance to above abiotic stresses was investigated by cloning of pcs gene in expression vector pGEX-5X-2 and its transformation in E. coli BL21 (DE3). The E. coli cells transformed with pGEX-5X-pcs showed better growth than control cells (pGEX-5X-2) under temperature (47 °C), NaCl (6% w/v), carbofuron (0.025 mg ml-1), CdCl2 (4 mM), CuCl2 (1 mM), and UV-B (10 min) exposure. The enhanced expression of pcs gene revealed by RT-PCR analysis under above stresses at different time intervals further advocates its role in tolerance against above abiotic stresses. © 2008 Elsevier Inc. All rights reserved.
Copper pretreatment augments ultraviolet B toxicity in the cyanobacterium Anabaena doliolum: A proteomic analysis of cell death
(2008) Poonam Bhargava; Arvind Kumar; Yogesh Mishra; Lal Chand Rai
This study provides first-hand proteomic characterisation of Cu-pretreatment-induced augmentation of ultraviolet B toxicity in the cyanobacterium Anabaena doliolum Bharadwaja. Of the three treatments (i.e. Cu, UV-B and Cu:+:UV-B) tested, the UV-B treatment of Cu-pretreated Anabaena produced a greater inhibition of oxygen evolution, 14C fixation, ATP and NADPH contents than UV-B alone. Proteomic analysis using two-dimensional gel electrophoresis (2DE), MALDI-TOF MS/MS and reverse transcription polymerase chain reaction (RT-PCR) of Cu, UV-B, and Cu:+:UV-B treated Anabaena exhibited significant and reproducible alterations in 12 proteins. Of these, manganese superoxide dismutase (Mn-SOD), iron superoxide dismutase (Fe-SOD) and peroxiredoxin (PER) are antioxidative enzymes; ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo), phosphoribulokinase (PRK), flavodoxin (Flv), plastocyanin (PLC), phosphoglycerate kinase (PGK), phycocyanin (PC) and phycoerythrocyanin α-chain (PC α-chain) are linked with photosynthesis and respiration; and DnaK and nucleoside diphosphate kinase (NDPK) are associated with cellular processes and light signalling, respectively. However, when subjected to a high dose of UV-B, Cu-pretreated Anabaena depicted a severe down-regulation of DnaK, NDPK and Flv, probably because of inevitable oxidative stress. Thus, the augmentation of UV-B toxicity by Cu can be attributed to the down-regulation of DnaK, NDPK and Flv. © CSIRO 2008.
Cyanobacteria: miniature factories for green synthesis of metallic nanomaterials: a review
(Springer Science and Business Media B.V., 2022) Shraddha Pandey; Lal Chand Rai; Santosh Kumar Dubey
Nanotechnology is one of the most promising and advanced disciplines of science that deals with synthesis, characterization and applications of different types of Nanomaterials (NMs) viz. nanospheres, nanoparticles, nanotubes, nanorods, nanowires, nanocomposites, nanoalloys, carbon dots and quantum dots. These nanosized materials exhibit different physicochemical characteristics and act as a whole unit during its transport. The unique characteristics and vast applications of NMs in diverse fields viz. electronics, agriculture, biology and medicine have created huge demand of different type of NMs. Conventionally physical and chemical methods were adopted to manufacture NMs which are expensive and end up with hazardous by-products. Therefore, green synthesis exploiting biological resources viz. algae, bacteria, fungi and plants emerged as a better and promising alternative due to its cost effective and ecofriendly approach and referred as nanobiotechnology. Among various living organisms, cyanobacteria have proved one of the most favourable bioresources for NMs biosynthesis due to their survival in diverse econiches including metal and metalloid contaminated sites and capability to withstand high levels of metals. Biosynthesis of metallic NMs is accomplished through bioreduction of respective metal salts by various capping agents viz. alkaloids, pigments, polysaccharides, steroids, enzymes and peptides present in the biological systems. Advancement in the field of Nanobiotechnology has produced large number of diverse NMs from cyanobacteria which have been used as antimicrobial agents against Gram positive and negative human pathogens, anticancer agents, luminescent nanoprobes for imaging of cells, antifungal agents against plant pathogens, nanocatalyst and semiconductor quantum dots in industries and in bioremediation in toxic pollutant dyes. In the present communication, we have reviewed cyanobacteria mediated biosynthesis of NMs and their applications in various fields. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Cyanobacterial diversity shifts induced by butachlor in selected Indian rice fields in Eastern Uttar Pradesh and Western Bihar analyzed with PCR and DGGE
(Korean Society for Microbiolog and Biotechnology, 2012) Kumari; Nidhi; Om Prakash Narayan; Lal Chand Rai
The present study examines the effects of 30 mg/kg butachlor on the cyanobacterial diversity of rice fields in Eastern Uttar Pradesh and Western Bihar in India. A total of 40 samples were grouped into three classes [(i) acidic, (ii) neutral, and (iii) alkaline soils], based on physicochemical and principle component analyses. Acidic soils mainly harbored Westillopsis, Trichormus, Anabaenopsis, and unicellular cyanobacteria; whereas Nostoc, Anabaena, Calothrix, Tolypothrix, and Aulosira were found in neutral and alkaline soils. Molecular characterization using 16S rRNA PCR and DGGE revealed the presence of 13 different phylotypes of cyanobacteria in these samples. Butachlor treatment of the soil samples led to the disappearance of 5 and the emergence of 2 additional phylotypes. A total of 40 DGGE bands showed significant reproducible changes upon treatment with butachlor. Phylogenetic analyses divided the phylotypes into five major clusters exhibiting interesting links with soil pH. Aulosira, Anabaena, Trichormus, and Anabaenopsis were sensitive to butachlor treatment, whereas uncultured cyanobacteria, a chroococcalean member, Westillopsis, Nostoc, Calothrix, Tolypothrix, Rivularia, Gloeotrichia, Fischerella, Leptolyngbya, and Cylindrospermum, appeared to be tolerant against butachlor at their native soil pH. Butachlor-induced inhibition of nitrogen fixation was found to be 65% (maximum) and 33% (minimum) in the soil samples of pH 9.23 and 5.20, respectively. In conclusion, low butachlor doses may prove beneficial in paddy fields having a neutral to alkaline soil pH.
Cyanobacterial diversity: molecular insights under multifarious environmental conditions
(Elsevier, 2020) Nidhi Kumari; Lal Chand Rai
Cyanobacteria are the first oxygenic photoautotrophs, which are widely distributed in aquatic and terrestrial environments, including extreme habitats such as deserts, hot springs, and polar regions. This chapter presents an overview of recent advancements in cyanobacterial diversity using molecular techniques under various environmental conditions, for example, stromatolites, marine, and freshwater, dry valleys, rice fields, natural and artificial microbial mats, and hot and cold springs. The molecular techniques applied for cyanobacterial diversity assessment range from specific gene (16S ribosomal RNA, nif, rpo, its, etc.)-based PCR, sequencing, and phylogeny, denaturing gradient gel electrophoresis, microarray to metagenomics. It is pertinent to mention here that, nowadays, the polyphasic approach is considered as an indispensable method to register the overall existence of cyanobacteria that a single method is not sufficient to highlight. Microarray and metagenomics may positively contribute in deciphering and amplifying the horizon of cyanobacterial diversity in various natural milieus. © 2020 Elsevier Inc. All rights reserved.
Differential induction of enzymes and antioxidants of the antioxidative defense system in Anabaena doliolum exposed to heat stress
(2005) Yogesh Mishra; Poonam Bhargava; Lal Chand Rai
Anabaena doliolum subjected to 43, 48, 53 and 58°C temperature for 1, 2, 3 and 4 h, showed temperature and time-dependent increase in H 2O2 production and MDA contents. All the measured enzymes of the antioxidative defense system (SOD, CAT, APX and GR) showed increase in their activities at 43°C after 1 h of treatment, but at higher temperature their activity declined. The content of antioxidants (ASC, GSH, and α-TOC) increased significantly with rise in temperature as well as duration of treatment. This study clearly demonstrates that when enzymatic defense system becomes inactive, the antioxidants (GSH, and α-TOC) are induced to protect the cyanobacterium from heat stress. One of the major roles of these antioxidants appears to be the protection of PSII as reflected by an effect on O2 evolution up to 53°C. © 2005 Elsevier Ltd. All rights reserved.
Differential response of antioxidative defense system of Anabaena doliolum under arsenite and arsenate stress
(2009) Ashish Kumar Srivastava; Poonam Bhargava; Riti Thapar; Lal Chand Rai
This study offers first hand information on the arsenite (As(III)) and arsenate (As(V))-induced oxidative tress and changes in antioxidative defense system of Anabaena doliolum. A requirement of 58 mM As(V) as compared to only 11 mM As(III) to cause 50% reduction in growth rate suggests that As(III) is more toxic than As(V) in the test cyanobacterium. In contrast to above, oxidative damage measured in terms of lipid peroxidation, electrolyte leakage and peroxide content were significantly higher after As(V) than As(III) treatment as compared to control. Similarly all the studied enzymatic parameters of antioxidative defense system except glutathione reductase (GR) and non-enzymatic parameters except glutathione reduced (GSH) showed greater induction against As(V) than As(III). Interestingly, higher increase in non-enzymatic counterpart than enzymatic in both the stresses suggests that detoxification is mainly managed by former than the later. This confirms the belief of pronounced stimulation of the antioxidative defense system by As(V) than As(III). In conclusion, the cyanobacterium may survive better in As(V) than As(III) contaminated fields because of its low toxicity and pronounced induction of antioxidative defense system. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Differential responses of three cyanobacteria to UV-B and Cd
(2003) Neelam Atri; Lal Chand Rai
Interactive effects of UV-B and Cd on growth, pigment, photosynthesis, and lipid peroxidation have been studied in Anabaena, Microcystis, and Nostoc; all the tested cyanobacteria showed differential sensitivity to different dosage of UV-B and Cd alone as well as in combination. Phycocyanin was severely affected by UV-B and Cd by all the strains; the degree of pigment bleaching was most pronounced in Anabaena followed by Microcystis and Nostoc. UV-B2+Cd2 produced nearly 83, 78, and 65% inhibition of phycocyanin in Anabaena, Microcystis, and Nostoc, respectively. The above treatment also significantly decreased the contents of Chl a and carotenoid. Presence of capsule in Microcystis protected the phycocyanin bleaching as compared to decapsulated cells. Laboratory-grown Microcystis revealed about 75 and 80% inhibition, following UV-B2+Cd2 treatment, respectively, in capsulated and decapsulated cells. Damage caused by Cd was more pronounced than UV-B. Inhibition of photosynthesis did occur in all the test strains, being maximum in Anabaena. PS II was the most sensitive component of the electron transport chain, showing 84, 80, and 70% inhibition in Anabaena, Microcystis, and Nostoc, respectively. As compared to control, significant lipid peroxidation (6.5-fold higher) was observed in Anabaena with UV-B2+Cd2. 14C-uptake was more susceptible to Cd and UV-B than oxygen-evolution. Approximately 84, 80, and 76% inhibition of 14C-uptake was observed in Anabaena, Microcystis, and Nostoc, respectively. Similarly, UV-B2+Cd2 inhibited ATP content of Anabaena by 87%. This study suggests that inhibition of carbon fixation was due to decreased ATP content of the test cyanobacteria by UV-B+Cd, where Anabaena was the most sensitive and Nostoc the most tolerant.
Effect of nickel and cadmium on ammonium uptake kinetics of free and immobilized cells of Anacystis nidulans; [Wirkung von nickel und cadmium auf die kinetik der ammonium-aufnahme freier und immobilisierter zellen von Anacystis nidulans]
(2004) Mamta Awasthi; Lal Chand Rai
The stress effect of Ni and Cd on the ammonium uptake varied significantly (ANOVA test) in free and immobilized state of the test organism. The effect due to the interaction between different variables (cell state type, metal type and metal dose) was studied to depict the significant or non-significant variation in the ammonium uptake by free and immobilized cells in the presence of metal ions. Ammonium uptake exhibited a competitive mode of inhibition in the presence of Ni in both free and immobilized state of the organism. However, Cd exhibited non-competitive and competitive inhibition in free and immobilized cells, respectively. The study demonstrates that there is a considerable influence of metal ions on the ammonium uptake. Cd was found to be more toxic compared to Ni in both free and immobilized state. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.