Browsing by Author "Manish Singh Kaushik"

Now showing 1 - 20 of 21

Agrochemicals influencing nitrogenase, biomass of N2-fixing cyanobacteria and yield of rice in wetland cultivation
(Elsevier Ltd, 2017) Nalinaxya Prasad Dash; Ajay Kumar; Manish Singh Kaushik; Gerard Abraham; Pawan Kumar Singh
Cyanobacteria maintain soil fertility by performing N2-fixation and act as a key biocatalyst in nitrogen cycle. Chemical N-fertilizers and pesticides as agrochemicals are intensively being used in rice farming to boost rice production, this work deals with the first hand information on their influence on native N2-fixing cyanobacteria, which play an important role in maintaining soil health. A field study was conducted for three consecutive seasons in water logged rice field to observe the influence of agrochemicals, urea, benthiocarb and carbofuran in isolation and in combinations on biomass, acetylene reduction activity (ARA) and N-yield of native cyanobacteria as well as, on growth and yield of rice. The ARA and N-yield followed almost same trend. It is discernible that both urea and benthiocarb had deleterious effects whereas, carbofuran was promoting effects on cyanobacterial growth, ARA and N-yield. The combination of all the three above agrochemicals was found inhibitory, but inhibition was comparatively less than that of urea or benthiocarb in isolation or urea plus benthiocarb treatments. It is concluded that the combination of agrochemicals was toxic, in comparison to the control, but was better than application of urea N or benthiocarb alone or with their combinations. It was recorded that along with rice straw and gain yields, panicle numbers were the maximum at the combination with treatments of benthiocarb+carbofuran. Adverse effects of used agrochemicals on cyanobacteria in wetland rice cultivation could be avoided by a prudent use of chemical N-fertilizers and pesticide(s) in combination. © 2016
Cyanobacterial (unicellular and heterocystous) biofertilization to wetland rice influenced by nitrogenous agrochemical
(Springer Netherlands, 2016) N.P. Dash; Ajay Kumar; Manish Singh Kaushik; Pawan Kumar Singh
Comparative growth and N2-fixation of cyanobacteria, namely Aphanothece sp. (unicellular) and Gloeotrichia sp. (heterocystous, filamentous), were studied after their inoculation to rice crop in the absence and presence of urea nitrogen fertilizer. In the absence of N-fertilizer application (control), inoculation of both cyanobacterial species showed significant increase in growth and acetylene reduction activity (ARA), but gradual reduction in these parameters was observed at 30 and 60 kg N ha−1 of urea application. In inoculation of Gloeotrichia sp. at control, 30 and 60 kg N ha−1 increased grain yield significantly over uninoculated control in both wet and dry seasons, but grain yield with Aphanothece sp. inoculation was statistically similar to the control at N levels during both seasons. The inoculation study showed that heterocystous cyanobacteria contributed better than unicellular ones, and application of N-fertilizer adversely affected both growth and N2-fixation of native as well of inoculated cyanobacteria. © 2016, Springer Science+Business Media Dordrecht.
Deciphering the evolutionary affiliations among bacterial strains (Pseudomonas and Frankia sp.) inhabiting same ecological niche using virtual RFLP and simulation-based approaches
(Springer Verlag, 2016) Meenakshi Srivastava; Manish Singh Kaushik; Amrita Srivastava; Anumeha Singh; Ekta Verma; Arun Kumar Mishra
To decipher an evolutionary lineage between two different but important bacterial groups, i.e., Pseudomonas strain (γ-Proteobacteria) and Frankia strain (actinobacteria) growing in the same ecological niche in and around of an actinorhizal plant Hippophae salicifolia D. Don, genetic diversity and comparative molecular phylogeny have been investigated using 16S rRNA gene sequences and computer-simulated and virtually directed restriction fragment length polymorphism (RFLP) through 10 restriction enzymes. Bayesian and coalescent analyses on the basis of 16S rRNA gene sequences suggested three major groups with close proximity between Pseudomonas and Frankia isolates. This result has been further validated based on the data observed through similarity coefficient value and computational RFLP. Principal component analysis and Mandel h and k statistical analysis also confirmed and strengthen the findings. Approximately 458 aligned sequence of all the taxa were used to decipher nucleotide diversity, polymorphism and gene flow between these taxa. Thus, our results suggest for a possible co-evolution or a heterologous gene transfer of distantly related microbial forms. Further, our study also advocate for the use of computer aided, virtual RFLP analysis as a cost effective and rapid identification tool. © 2016, The Author(s).
Ferric Uptake Regulator (FUR) protein: properties and implications in cyanobacteria
(Springer Verlag, 2016) Manish Singh Kaushik; Prashant Singh; Balkrishna Tiwari; Arun Kumar Mishra
The Ferric uptake regulator (Fur) protein is a global iron regulator found in most prokaryotes. Although the Fur protein is involved in a variety of metabolic pathways, it is specifically known for the regulation of several iron responsive genes. It binds to the highly conserved sequences located in the upstream promoter region known as iron boxes, using ferrous ion as a co-repressor. Apart from that, the Fur protein is also directly/indirectly involved in a variety of other crucial physiological pathways. Hence, understanding the mechanism of action and the mechanistic pathways of iron regulation by Fur is necessary and important. The basic understanding of the functioning and properties of Fur protein along with its role, interaction and regulation at various levels in cyanobacteria has been discussed in detail. © 2015, Springer-Verlag Berlin Heidelberg and the University of Milan.
Field evaluations of agrochemical toxicity to cyanobacteria in rice field ecosystem: a review
(Springer Netherlands, 2019) Manish Singh Kaushik; Ajay Kumar; Gerard Abraham; Nalinaxya Prasad Dash; Pawan Kumar Singh
The adverse effects of chemical nitrogen fertilizers affecting soil fertility, water pollution and native microorganisms, particularly cyanobacteria, in wetland rice cultivation have drawn global attention towards the use of alternative sources like N 2 -fixing cyanobacteria as a biofertilizer for sustainable rice farming. Although chemical nitrogen fertilizers are extensively used for obtaining higher rice yield, they are likely to have a deleterious effect on the growth and N 2 -fixation of diazotrophs, including cyanobacteria. In addition, biocides (herbicides and insecticides) are widely being used in rice cultivation for optimizing crop yield, but these chemicals also affects non-target organisms adversely. There are several reports indicating impacts of these agrochemicals on cyanobacteria, but most such studies were carried out under laboratory conditions. This article reviews information from different field evaluations on the impact of agrochemicals on cyanobacteria along with rice crop in wetland rice field ecosystem. © 2018, Springer Nature B.V.
Impairment of ntcA gene revealed its role in regulating iron homeostasis, ROS production and cellular phenotype under iron deficiency in cyanobacterium Anabaena sp. PCC 7120
(Springer Netherlands, 2017) Manish Singh Kaushik; Meenakshi Srivastava; Anumeha Singh; Arun Kumar Mishra
Iron deficiency ends up into several unavoidable consequences including damaging oxidative stress in cyanobacteria. NtcA is a global nitrogen regulator controls wide range of metabolisms in addition to regulation of nitrogen metabolism. In present communication, NtcA based regulation of iron homeostasis, ROS production and cellular phenotype under iron deficiency in Anabaena 7120 has been investigated. NtcA regulates the concentration dependent iron uptake by controlling the expression of furA gene. NtcA also regulated pigment synthesis and phenotypic alterations in Anabaena 7120. A significant increase in ROS production and corresponding reduction in the activities of antioxidative enzymes (SOD, CAT, APX and GR) in CSE2 mutant strain in contrast to wild type Anabaena 7120 also suggested the possible involvement of NtcA in protection against oxidative stress in iron deficiency. NtcA has no impact on the expression of furB and furC in spite of presence of consensus NtcA binding site (NBS) and −10 boxes in their promoter. NtcA also regulates the thylakoid arrangement as well as related photosynthetic and respiration rates under iron deficiency in Anabaena 7120. Overall results suggested that NtcA regulates iron acquisition and in turn protect Anabaena cells from the damaging effects of oxidative stress induced under iron deficiency. © 2017, Springer Science+Business Media B.V.
Interaction of turmeric (Curcuma longa L.) with beneficial microbes: a review
(Springer Verlag, 2017) Ajay Kumar; Amit Kishore Singh; Manish Singh Kaushik; Surabhi Kirti Mishra; Pratima Raj; P.K. Singh; K.D. Pandey
Curcuma longa L., commonly known as turmeric, is a rhizomatous herb of the family Zingiberaceae. It is mostly used as a spice, a coloring agent and broadly used in traditional medicine such as Ayurveda, Unani, etc., Turmeric rhizomes interact with a large numbers of rhizosphere-associated microbial species, and some enter the plant tissue and act as endophytes. Both rhizospheric and endophytic species are directly or indirectly involved in growth promotion and disease management in plants and also play an important role in the modulation of morphological growth, secondary metabolite production, curcumin content, antioxidant properties, etc. The present review focuses on the rhizobacterial and endophytic bacterial and fungal populations associated with the turmeric. © 2017, Springer-Verlag GmbH Germany.
Iron Homeostasis in Cyanobacteria
(Elsevier, 2018) Manish Singh Kaushik; Meenakshi Srivastava; Arun Kumar Mishra
Cyanobacteria are a diverse group of Gram-negative oxygenic photoautotrophs and many of them have ability to perform nitrogen fixation in addition to carbon fixation. The demand of iron in cyanobacteria is exceptionally high due to its involvement in the function of a variety of crucial enzymes. Hence, iron acquisition process and its regulation is essential. The Fe2+/Fe3+ imbalance in the cells causes severe abnormal changes and it needs to be regulated for proper growth and survival of cyanobacteria. Therefore, cyanobacteria have evolved complex metabolic pathways with different mechanisms to regulate intracellular levels of iron for their survival in a changing environment, by tightly regulating iron uptake. In cyanobacteria, iron uptake is regulated by TonB system which includes a barrel-shaped TonB-dependent transporter (TBDT), integral membrane protein ExbB, and the membrane-anchored periplasmic protein ExbD. At the center to this regulatory network of iron homeostasis is the ferric uptake regulator (Fur), which is a global iron regulator in prokaryotes including cyanobacteria. Considering the importance of availability of iron, understanding the complex iron homeostasis and associated regulatory mechanisms involving Fur is necessary and important. The complex regulatory mechanisms of iron homeostasis along with the basic understanding of the functioning of Fur protein and its interaction with other transcriptional regulator in cyanobacteria have been discussed in this chapter. © 2019 Elsevier Inc. All rights reserved.
Iron induced modifications in physiological attributes and SDS-PAGE of whole cell proteins pattern of Anabaena PCC 7120 and its derivative ntcA mutant
(National Institute of Science Communication and Information Resources (NISCAIR), 2015) Manish Singh Kaushik; Arun Kumar Mishra
The influence of the various levels of iron (0-500 μM) on Anabaena sp. PCC 7120 and its derivative CSE2 mutant impaired in ntcA gene have been investigated to determine the requirement of specific concentration of iron for the regulation of photosynthetic pigments, cellular constituents, heterocyst spacing pattern, enzyme activities and SDS-PAGE of whole cell protein profiling. Iron at lower concentrations (≤50 μM) causes increase in chlorophyll a, carotenoid, phycocyanin, carbohydrate, protein, nitrogenase, nitrate reductase and glutamine synthetase activities in wild type as well as in mutant strain (except nitrogenase and nitrate reductase activities), while higher concentrations (>50 μM) were toxic and cause significant reductions in these physiological attributes. Nitrogenase and nitrate reductase activity were found absent in ntcA mutant. Further, 50 μM iron concentration also supported the maximum heterocyst frequency with changed heterocyst spacing pattern in wild type, whereas no visible sign of heterocyst development was observed in mutant strain. SDS-PAGE of whole cell protein revealed the occurrence of maximum number of bands at 50 μM iron concentration in both wild type and mutant strain. Results suggested that 50 μM of iron concentration was the specific concentration (critical concentration) that supported optimal physiological and biochemical activities in Anabaena 7120 and its mutant strain CSE2 (ntcA).
Linking the Physicochemical Properties with the Abundance and Diversity of Rhizospheric Bacterial Population Inhabiting Paddy Soil Based on a Concerted Multivariate Analysis of PCR-DGGE and RISA
(Taylor and Francis Inc., 2016) Meenakshi Srivastava; Manish Singh Kaushik; Arun Kumar Mishra
To unravel the existence of dominant bacterial population in the paddy fields of Eastern Uttar Pradesh, India and their relation to the prevailing soil physicochemistry using multivariate statistical analyses, a cumulative culture-independent 16S rRNA based Polymerase chain reaction-Denaturing gradient gel electrophoresis (PCR-DGGE) and a 16S-23S ribosomal intergenic spacer analysis (RISA) have been performed. Detrended correspondence analysis (DCA) and principal component analysis (PCA) biplot analyses were used to assess the relation between soil bacterial population and its physicochemistry. DCA analysis exhibited a strong dependence of bacterial existence on the soil physicochemical variables, such as organic matter, total nitrogen, inorganic nutrients, temperatures, and moisture status. Soil dehydrogenase activity (DHA) was assessed to check the metabolic activity of all soil samples which showed a range of 0.012–0.050 nmol TPF g−1min−1 with significant variation (p < 0.01). Out of 96 bands excised, 45 different phylotypes were obtained using both techniques which elucidated the abundance of Cyanobacteria over other soil bacterial population. Scytonema sp., Leptolyngbya sp. and different uncultured cyanobacterial species were the major genera found. Profiling data obtained through PCR-DGGE and RISA were used in alpha diversity and rarefaction curve analysis suggested site 6 (Chandauli) as the most diversity rich site. Thus extensive dataset of weighted and unweighted variables generated through DGGE and RISA coupled with metabolic functioning of soil and multivariate analyses provided an excellent opportunity to map the soil microbial structure in paddy fields and their regulation with existing soil environment. © 2016 Taylor & Francis Group, LLC.
Molecular phylogeny of heterotrophic nitrifiers and aerobic denitrifiers and their potential role in ammonium removal
(Wiley-VCH Verlag, 2016) Meenakshi Srivastava; Manish Singh Kaushik; Anumeha Singh; Deepti Singh; Arun Kumar Mishra
To investigate the physiology and taxonomic composition of the key players of nitrification and denitrification processes in paddy fields, culture dependent and independent studies have been carried out. A total of 28 bacterial strains have been screened in which six were capable of reducing nitrate and nitrite as well as having significant ammonium removal potential. 16S rRNA-PCR-DGGE-based molecular typing of enriched batch culture was done with time duration to explore and identify dominant and stable soil denitrifiers. Notably, three isolates namely PDN3, PDN19, PDN14 were found to be efficiently involved in the removal of 70.32, 71.46, and 81.50% of NH4 (+) and showed closest similarity (>98%) with Bacillus cereus, Bacillus subtilis, and Pseudomonas aeruginosa strains, respectively. The bacterial strain PDN14 showed maximum growth with highest ammonium removal rate (2.78 gN/(m(3) ·h) has also been characterized based on nosZ gene which showed similarity to uncultured γ- Proteobacteria, P. aeruginosa sp. B3. Median joining (MJ) network and rRNA secondary structure have been analyzed for their detailed taxonomic diversity and derived haplotype-based co-occurrence. Results demonstrated that such strains can serve as good candidate for in situ nitrogen transformation in paddy soils and improvingly characterized by physiological and detailed phylogenetic approaches. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Nitric oxide ameliorates the damaging effects of oxidative stress induced by iron deficiency in cyanobacterium Anabaena 7120
(Springer Verlag, 2016) Manish Singh Kaushik; Meenakshi Srivastava; Alka Srivastava; Anumeha Singh; Arun Kumar Mishra
In cyanobacterium Anabaena 7120, iron deficiency leads to oxidative stress with unavoidable consequences. Nitric oxide reduces pigment damage and supported the growth of Anabaena 7120 in iron-deficient conditions. Elevation in nitric oxide accumulation and reduced superoxide radical production justified the role of nitric oxide in alleviating oxidative stress in iron deficiency. Increased activities of antioxidative enzymes and higher levels of ROS scavengers (ascorbate, glutathione and thiol) in iron deficiency were also observed in the presence of nitric oxide. Nitric oxide also supported the membrane integrity of Anabaena cells and reduces protein and DNA damage caused by oxidative stress induced by iron deficiency. Results suggested that nitric oxide alleviates the damaging effects of oxidative stress induced by iron deficiency in cyanobacterium Anabaena 7120. © 2016, Springer-Verlag Berlin Heidelberg.
Nitrogenase and Hydrogenase: Enzymes for Nitrogen Fixation and Hydrogen Production in Cyanobacteria
(Elsevier, 2018) Arun Kumar Mishra; Manish Singh Kaushik; D.N. Tiwari
Cyanobacteria, one of the most ancient groups of oxygenic photoautotrophs are ubiquitously found in almost all habitats on earth. Under nitrogen limitation, some of the cyanobacteria have the ability to differentiate a specialized cell called heterocyst which provides the microoxic environment favorable for proper functioning of oxygen-sensitive enzyme nitrogenase. In heterocystous cyanobacteria, nitrogenase complex is involved in N2 fixation which is also accompanied by hydrogen production. Today, the limited sources of fossil fuel prompt us to exploit various unconventional methods including hydrogen gas as an alternate source of energy. H2 gas is an environmentally clean and efficient alternative for energy. Several microorganisms including cyanobacteria can produce hydrogen. Therefore, this chapter first of all, highlights the basics of nitrogen assimilation and its regulation in cyanobacteria. It also deals and discusses in detail the nitrogenase and its involvement in H2 production. Further, the cyanobacterial hydrogenases and their role in hydrogen production and regulation have also been discussed. Various approaches used to enhance hydrogen production, like genetic and metabolic engineering, have been emphasized along with information on the different types of photobioreactor which are being used for a large-scale industrial production of hydrogen gas. Overall, this chapter summarizes the information about the nitrogenases and hydrogenases involved in H2 production in cyanobacteria and the technologies being utilized for increasing hydrogen production at industrial level. Understanding the underlying mechanisms of hydrogen production in cyanobacteria and improving production methods enable commercialization of molecular hydrogen as an efficient and environment-friendly energy source. © 2019 Elsevier Inc. All rights reserved.
Nitrogenous agrochemicals inhibiting native diazotrophic cyanobacterial contribution in wetland rice ecosystem
(Springer Netherlands, 2017) Nalinaxya Prasad Dash; Ajay Kumar; Manish Singh Kaushik; Gerard Abraham; Pawan Kumar Singh
The diazotrophic cyanobacteria are known to play an important role in nitrogen economy of wetland rice ecosystem. Due to intensive use of nitrogenous fertilizers in rice cultivation, maintenance of soil health has become a challenging task. In this context, a systematic study was conducted in flooded rice field to determine the effects of different doses of commonly used urea and ammonium sulphate nitrogenous fertilizers on native cyanobacterial biomass, N2-fixation and N-yield at various stages of rice plants. The results clearly demonstrated that both urea and ammonium sulphate inhibited cyanobacterial growth and N2-fixation at different stages of rice crop. Maximum growth and N2-fixation were observed at heading stage of rice plant at 60 days after transplantation when compared with early and late stages of rice crop. Of the two fertilizers, urea was found more inhibitory to cyanobacteria and among the two seasons, these fertilizers were more inhibitory in the dry than in the wet season. This study suggests that N fertilizers need to be used judiciously in rice cultivation so that both cyanobacterial contribution and high rice yield are ensured. © 2016, Springer Science+Business Media Dordrecht.
NtcA transcriptional factor: A global nitrogen regulator and connecting link between nitrogen metabolism and other crucial metabolisms
(Nova Science Publishers, Inc., 2017) Manish Singh Kaushik; Meenakshi Srivastava; Anumeha Singh; Arun Kumar Mishra
Nitrogen fixing cyanobacteria play a crucial role in extracting and supplying biologically useful nitrogen to the biosphere. Nitrogen is the essential building block for the synthesis of proteins and amino acids. Nitrogen deficiency leads to several unavoidable consequences. In cyanobacteria, heterocyst is the site for nitrogen fixation under nitrogen starved condition. Heterocyst provides microoxic environment required for the nitrogenase enzyme activity. Nitrogen fixation is the highly regulated phenomenon in cyanobacteria. NtcA is the transcriptional factor regulating wide range of genes involved in the nitrogen metabolism. NtcA is a protein dimer which binds to the upstream promoter region of target genes (such as those involved in heterocyst differentiation and nitrogen fixation) at a specific site known as NtcA box having consensus sequence “GTAN8TAC.” NtcA act both as activator and repressor of variety of genes in cyanobacteria. Apart from regulating nitrogen fixation, NtcA also coordinates genes involved several other metabolisms such as photosynthesis, iron metabolism, oxidative stress etc., hence considered as a global transcriptional regulator. Considering the utmost importance of this particular protein for cyanobacteria, this article is devoted to discuss about the ntcA, its expression and the mechanisms of its regulation. Further, NtcA dependent regulations of different metabolisms are also discussed to understand the connections between nitrogen metabolism and other crucial metabolisms. © 2017 by Nova Science Publishers, Inc. All rights reserved.
Phylogenetic analysis of heterocystous cyanobacteria (Subsections IV and V) using highly iterated palindromes as molecular markers
(Springer India, 2014) Prashant Singh; Manish Singh Kaushik; Meenakshi Srivastava; Arun Kumar Mishra
Highly iterated palindromes (HIP) have been used as high resolution molecular markers for assessing the genetic variability and phylogenetic relatedness of heterocystous cyanobacteria (subsections IV and V) representing 12 genera of heterocystous cyanobacteria, collected from different geographical areas of India. DNA fingerprints generated using four HIP markers viz. HIP-AT, HIP-CA, HIP-GC, and HIP-TG showed 100 % polymorphism in all the heterocystous cyanobacteria studied and each marker produced unique and strain-specific banding pattern. Furthermore, phylogenetic affinities based on the dendrogram constructed using HIP DNA profiles of heterocystous cyanobacteria suggest the monophyletic origin of this entire heterocystous clade along with a clear illustration of the polyphyletic origin of the branched Stigonematalean order (Subsection V). In addition, phylogenetic affinities were validated by principal component analysis of the HIP fingerprints. The overall data obtained by both the phylogeny and principal component assessments proved that the entire heterocystous clade was intermixed, and there are immediate needs for classificatory reforms that satisfy morphological plasticity and environmental concerns. © 2014 Prof. H.S. Srivastava Foundation for Science and Society.
Regulation of organophosphate metabolism in cyanobacteria. A review
(Maik Nauka Publishing / Springer SBM, 2015) Balkrishna Tiwari; Savita Singh; Manish Singh Kaushik; Arun Kumar Mishra
Cyanobacteria sense the environmental phosphate level and respond accordingly with the help of a two component regulatory system SphS-SphR orthologous to PhoR-PhoB of E. coli, where SphS act as a sensor kinase and SphR as a response regulator. Under phosphate limiting condition SphS-SphR regulates the expression of many genes including genes which do not have the direct role in metabolism and transport of phosphate. Thus there is some crosstalk mechanism which connects this regulatory system to the other metabolic processes. Different types of enzymes and transporters are expressed by cyanobacteria under phosphate limitation to release and transport the phosphate from different organic compounds present in the environment. Genes encoding these enzymes and transporters contain Pho boxes in their promoter region where SphR binds and regulate their expression under phosphate limitation. The machinery and mechanism of regulation is not uniform in cyanobacteria as it varies in different groups according to their evolutionary adaptations. This review article is summarizing the reports on machinery and mechanism of organophosphate metabolism in cyanobacteria. © 2015, Pleiades Publishing, Ltd.
Role of manganese in protection against oxidative stress under iron starvation in cyanobacterium Anabaena 7120
(Wiley-VCH Verlag, 2015) Manish Singh Kaushik; Meenakshi Srivastava; Ekta Verma; Arun Kumar Mishra
The cyanobacterium Anabaena sp. PCC 7120 was grown in presence and absence of iron to decipher the role of manganese in protection against the oxidative stress under iron starvation and growth, manganese uptake kinetics, antioxidative enzymes, lipid peroxidation, electrolyte leakage, thiol content, total peroxide, proline and NADH content was investigated. Manganese supported the growth of cyanobacterium Anabaena 7120 under iron deprived conditions where maximum uptake rate of manganese was observed with lower Km and higher Vmax values. Antioxidative enzymes were also found to be elevated in iron-starved conditions. Estimation of lipid peroxidation and electrolyte leakage depicted the role of manganese in stabilizing the integrity of the membrane which was considered as the prime target of oxygen free radicals in oxidative stress. The levels of total peroxide, thiol, proline and NADH content, which are the representative of oxidative stress response in Anabaena 7120, were also showed increasing trends in iron starvation. Hence, the results discerned, clearly suggested the role of manganese in protection against the oxidative stress in cyanobacterium Anabaena 7120 under iron starvation either due to its antioxidative properties or involvement as cofactor in a number of antioxidative enzymes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Siderophore mediated attenuation of cadmium toxicity by paddy field cyanobacterium Anabaena oryzae
(Elsevier, 2016) Anumeha Singh; Manish Singh Kaushik; Meenakshi Srivastava; Devendra Nath Tiwari; Arun Kumar Mishra
The efficacy of dihydroxamate siderophore in attenuation/mitigation of cadmium toxicity, an optimum level of cadmium under which cyanobacterium can grow and produce siderophore, complexation behaviour of cadmium and siderophore and kinetics of complexation along with in silico analysis have been investigated in paddy field cyanobacterium Anabaena oryzae under iron replete and deplete conditions. Results showed that cadmium concentration as 1.0 μM is optimum for growth as well as siderophore production in iron replete and deplete culture conditions. The complexation between cadmium-siderophore was evident in spectral scan. Kinetic studies as well as in silico docking analysis indicate that like iron, cadmium also forms a thermodynamically stable complex with siderophore. Thus our results suggest that the siderophore produced by Anabaena oryzae can act as a biological sequestering agent for the mitigation of cadmium metal ions from the paddy fields to improve crop productivity. © 2016 Elsevier B.V.
Tolerance of wetland rice field's cyanobacteria to agrochemicals in cultural condition
(Elsevier Ltd, 2018) Manish Singh Kaushik; Nalinaxya Prasad Dash; Ajay Kumar; Gerard Abraham; Pawan Kumar Singh
The wetland rice fields are favorable for cyanobacterial growth, which play an important role in building soil fertility. Since agrochemicals are intensively being applied in rice fields to boost crop productivity, this study was undertaken to observe their effects on dominant N2-fixing cyanobacteria i.e. filamentous, heterocystous Nostoc linckia and unicellular Aphanothece pallida. These cyanobacteria were isolated from flooded rice fields and used to find out the effects of urea N-fertilizer, herbicide benthiocarb and insecticide metacid (in isolation and combinations) on their growth and N2-fixation ability. It was observed that N. linckia and A. pallida grew up to 25 days after inoculation (DAI) whereas acetylene reduction activity (ARA) increased up to 15 DAI in N-free medium without supplementation of agrochemicals in both cyanobacteria where N. linckia exhibited higher growth and ARA than A. pallida. Urea-N (30 ppm) was inhibitory for the growth of N. linckia whereas it stimulated the growth of A. pallida. Addition of benthiocarb (0.5 ppm) was found to have no significant impact on the growth of N. linckia but showed initial enhancement in the growth of A. pallida up to 10 DAI. Metacid supplementation at 0.25 ppm supported growth and ARA of both the cyanobacteria. It was also revealed that the use of urea-N, benthiocarb and metacid in combination reduced the growth and N2-fixation of N. linckia, however, these chemicals together were promotary for A. pallida. Overall, it was observed that combinations of these agrochemicals caused additive toxicity to heterocystous cyanobacterium whereas these were promotary to unicellular ones. © 2018 Elsevier Ltd