Scholarly Publications
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This community showcases the academic contributions of faculty and researchers at Banaras Hindu University (BHU) and provides a year-wise compilation of publications across disciplines. Institutional Repository BHU
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PublicationArticle Effect of UV-B on enzymes of nitrogen metabolism in the cyanobacterium Nostoc calcicola(Elsevier GmbH, 1996) Ashok Kumar; Rajeshwar P. Sinha; Donat-P. HäderThe effects of ultraviolet-B (UV-B; 280-315 nm) irradiation on nitrogenase and nitrate reductase (NR) activity have been studied in the filamentous and heterocystous N2-fixing cyanobacterium Nostoc calcicola. Exposure of cultures to UV-B (5W/m2) for as little as 30 min caused complete inactivation of nitrogenase activity whereas nitrate reductase activity was stimulated twofold in comparison to one exposed to fluorescent white light. GS activity was also inhibited by UV-B treatment, but there was no total loss of activity even after 4 h. NR activity showed a gradual stimulation up to 4 h and thereafter it became constant. Stimulation was also obtained in reductant deficient cultures (12 h incubation in the dark) suggesting independence of NR of PS-II under UV-B. NR activity was also unaffected in the presence of DCMU, a known inhibitor of PS-II. However, both O2 evolution and 14CO2 uptake were completely abolished following 30 min of UV-B treatment. Addition of the protein synthesis inhibitor chloramphenicol (25 μg/ mL) to cultures did not show any inhibitory effect on NR activity. SDS-PAGE analysis of UV-B treated cultures elicited gradual loss of protein bands with increasing duration of exposure. Our findings suggest that UV-B irradiance has differential effects on the enzymes of the nitrogen metabolism in the cyanobacterium Nostoc calcicola. Further studies are needed to reveal the exact mechanism involved in the stimulation of NR activity by UV-B. Whether UV-B has a direct effect on NO2- accumulation in the cells needs detailed investigation.PublicationBook Chapter Using systems biology to exploit the resources/natural reservoirs for biofuel production(Elsevier, 2024) Varsha K. Singh; Niharika Sahu; Sapana Jha; Amit Gupta; Ashish P. Singh; Palak Rana; Jyoti Jaiswal; Neha Kumari; Rajeshwar P. SinhaEnergy carriers such as lipids, starch, and hydrogen found in algae can be converted into biofuels, making them a promising sustainable substitute for fossil fuels. Systems biology, which comprises several types of omics techniques, might aid in the development of algal strains for biotechnological applications by providing important insights. A variety of natural products, including those used in pharmaceuticals, commodity chemicals, polymers, and fuels, have been produced by microorganisms. Increasing interest in producing transport fuels from renewable resources has sparked a number of research efforts that aim to modify microbial systems for the enhanced production of desired products. The development of resilient and productive production hosts depends on removing the limiting factors in microbial metabolic pathways and reducing stressors brought on by the production of these compounds. Research in systems biology provides a thorough understanding of the effects of pathway engineering on the host metabolism as a whole, the detection of stressors resulting from product synthesis, and the justification for designing industrial microbes that are both optimal and economical. The genes and metabolic networks involved can be identified through genomic and transcriptomic analyses, respectively. Proteomic estimations disclose protein quantities and posttranslational modifications (PTMs), which include glycosylation, phosphorylation, ubiquitination and acetylation, whereas metabolomics studies show metabolites, intermediates, and the products of the metabolism. This chapter details the applications of systems biology to better understand metabolic networks in algae and cyanobacteria, along with their role in bioenergy carrier accumulation. © 2025 Elsevier Ltd. All rights reserved.PublicationBook Chapter Peculiar Endosymbiosis in the Cyanobiont Nostoc azollae 0708: An In Silico Approach(Springer Nature, 2024) Minu Kesheri; Swarna Kanchan; Amit Kumar; Upasna Srivastava; Shivani Sharda; Bhagwan Malik; Tarun Mishra; Poonam Kaithal; Jitendra Narayan; Prashant Kumar; Prerna Priya; Rajeshwar P. SinhaNostoc azollae 0708 exhibits peculiar endosymbiosis owing to the unique commitment of cyanobiont’s association with fern throughout its life cycle. This chapter elaborates various in silico approaches adopted for intriguing proteomics aspects of Fe and Mn superoxide dismutase in the cyanobiont Nostoc azollae 0708. Prediction of physicochemical parameters elucidating molecular weight, isoelectric point (pI), instability index, aliphatic index, total no. of negatively charged residues (Asp + Glu), total no. of positively charged residues (Arg + Lys), extinction coefficient, and GRAVY are discussed in detail. Generating good quality 3D structural models for Fe-SOD and Mn-SOD by homology modeling and validation by Prosa-web, verify-3D, and PROCHECK is elaborately explained. Conservation of metal binding positions, domains, and motifs suggesting functional conservation, highly conserved exposed as well as buried amino acid residues advocating their structural and functional importance is also discussed. Generation of protein–protein interaction network using STRING illustrating the physical and functional interaction of superoxide dismutase with other proteins and biological cascade of these proteins in Nostoc azollae has been described. The NJ phylogenetic tree for Fe-SOD depicts Nostoc sp. PCC 7524 as the nearest evolutionary homolog, whereas Nostoc sp. PCC 7107 and Nostoc piscinale CENA 21 as evolutionary close homologs of Mn-SOD in Nostoc azollae. The present in silico methodologies discussed in this chapter may pave the way for further experimental validation aiding in exploring the biochemical, biotechnological, and biofertilizer potential of the cyanobiont recruited by the fern Azolla. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.PublicationArticle Effects of ultraviolet radiation on cellular functions of the cyanobacterium Synechocystis sp. PCC 6803 and its recovery under photosynthetically active radiation(Elsevier B.V., 2024) Prashant R. Singh; Amit Gupta; Ashish P. Singh; Jyoti Jaiswal; Rajeshwar P. SinhaCyanobacteria are photosynthetic organisms and challenged by large number of stresses, especially by ultraviolet radiation (UVR). UVR primarily impacts lipids, proteins, DNA, photosynthetic performance, which lowers the fitness and production of cyanobacteria. UVR has a catastrophic effect on cyanobacterial cells and eventually leads to cell death. UVR tolerance in the Synechocystis was poorly studied. Therefore, we irradiated Synechocystis sp. PCC 6803 to varying hours of photosynthetically active radiations (PAR), PAR + UV-A (PA), and PAR + UV-A + UV-B (PAB) for 48 h. To study the tolerance of Synechocystis sp. PCC 6803 against different UVR. The study shows that Chl a and total carotenoids content increased up to 36 h in PAR and PA, after 36 h a decrease was observed. PC increased up to 4-fold in 48 h of PA irradiation compared to 12 h. Maximum increase in ROS was observed under 48 h PAB i.e., 5.8-fold. Flowcytometry (FCM) based analysis shows that 25% of cells do not give fluorescence of Chl a and H2DCFH. In case of cell viability 10% cells were found to be non-viable in 48 h of PAB irradiance compared to 12 h. From the above study it was found that FCM-based approaches would provide a better understanding of the variations that occurred within the Synechocystis cells compared to fluorescence microscopy-based methods. © 2023PublicationArticle Effects of ultraviolet and photosynthetically active radiation on morphogenesis, antioxidants and photoprotective defense mechanism in a hot-spring cyanobacterium Nostoc sp. strain VKB02(Elsevier Masson s.r.l., 2024) Nasreen Amin; Rajeshwar P. Sinha; Vinod K. KannaujiyaThe continuous increase in global temperature and ultraviolet radiation (UVR) causes profound impacts on the growth and physiology of photosynthetic microorganisms. The hot-spring cyanobacteria have a wide range of mitigation mechanisms to cope up against current unsustainable environmental conditions. In the present investigation, we have explored the indispensable mitigation strategies of an isolated hot-spring cyanobacterium Nostoc sp. strain VKB02 under simulated ultraviolet (UV-A, UV-B) and photosynthetically active radiation (PAR). The adaptive morphological changes were more significantly observed under PAB (PAR, UV-A, and UV-B) exposure as compared to P and PA (PAR and UV-A) irradiations. PAB exposure also exhibited a marked decline in pigment composition and photosynthetic efficiency by multi-fold increment of free radicals. To counteract the oxidative stress, enzymatic and non-enzymatic antioxidants defense were significantly enhanced many folds under PAB exposure as compared to the control. In addition, the cyanobacterium has also produced shinorine as a strong free radicals scavenger and excellent UV absorber for effective photoprotection against UV radiation. Therefore, the hot-spring cyanobacterium Nostoc sp. strain VKB02 has unique defense strategies for survival under prolonged lethal UVR conditions. This study will help in the understanding of environment-induced defense strategies and production of highly value-added green photo-protectants for commercial applications. © 2024 Institut PasteurPublicationArticle Extraction, characterization and antioxidative potentials of UV-screening compound, mycosporine-like amino acids from epilithic cyanobacterium Lyngbya sp. HKAR − 15(Springer Science and Business Media B.V., 2024) Abha Pandey; Nasreen Amin; Vinod K. Kannaujiya; Rajeshwar P. SinhaMycosporine-like amino acids (MAAs) are a unique class of UV-screening bioactive molecules with potent antioxidants and photoprotective properties, synthesized by various species of cyanobacteria in different habitats. The cyanobacterial biofilms play a crucial driver in the development of ecological communities. The current study examined the existence of the photoprotective MAAs in a novel epilithic cyanobacterium Lyngbya sp. strain HKAR-15 isolated from cyanobacterial biofilms on the rock surface. The isolated MAAs were identified, purified and characterized using UV-Vis spectroscopy, HPLC (High-Performance Liquid Chromatography), ESI-MS (Electrospray Ionization-Mass Spectrometry), FTIR (Fourier Transform Infrared Spectroscopy) and NMR (Nuclear Magnetic Resonance). The compounds were recognized as palythine (retention time (RT): 2.7 min; UV λmax: 320 nm; m/z: 245.02) and porphyra-334 (RT: 3.6 min; UV λmax: 334 nm; m/z: 347.1). FTIR spectroscopy analyses also revealed the presence of functional groups of both compounds. NMR spectroscopy analyses confirmed the presence of both palythine and porphyra-334. The UV-induced production of both MAAs was visualized under ultraviolet radiation (UVR) in contrast to the photosynthetically active radiation (PAR). The MAAs (palythine and porphyra-334) had a significant dose-dependent free radical scavenging capacity. The findings show that MAAs perform a dynamic role in the survival and photoprotection of cyanobacteria in hostile environments under high solar UV irradiances. These photoprotective compounds may have various biotechnological applications as well as role in the development of natural sunscreens. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.PublicationBook Chapter Bioprospection of Photoprotective Compounds from Cyanobacteria(Springer Nature, 2023) Prashant R. Singh; Ashish P. Singh; Rajneesh; Amit Gupta; Rajeshwar P. Sinha; Jainendra PathakCyanobacteria are one of the oldest photosynthetic nitrogen fixers of the terrestrial as well as aquatic ecosystems. Cyanobacteria and microalgae produce a large number of secondary metabolites having biomedical, industrial, and biotechnological importance. Due to their presence in vast habitats, cyanobacteria and microalgae were exposed to variety of harsh environmental factors such as salt, desiccation, temperature, heavy metals, and ultraviolet radiation (UVR). In response, cyanobacteria have developed different mechanisms to cope these harsh environmental conditions. Photosynthetic nature of cyanobacteria continuously exposes them to lethal doses of UVR coming with solar radiation which affects their physiology, photosynthetic efficiency, productivity by reactive oxygen species (ROS) generation inside the cell and ultimately leads to cell death. In response to these stresses cyanobacteria have developed different protective mechanisms such as avoidance, enzymatic and non-enzymatic defence system and synthesis of novel secondary metabolites such as mycosporine-like amino acids (MAAs) and scytonemin. MAAs are water-soluble molecules that absorb short wavelength of solar UVR which release the energy in the form of heat. Scytonemin is a small hydrophobic alkaloid pigment present in the extracellular sheath of some cyanobacteria that acts as UVR protectant. Scytonemin and MAAs are highly photostable therefore, they primarily function as UV-screening compounds. They also show antioxidative properties. The capability of cyanobacteria to produce large number of secondary metabolites which serve as natural sunscreens, antibiotic, antifungal, anticancer and antiviral agents make them economically important organisms. These are readily biotechnologically exploitable in the cosmetics and other industrial sectors for the creation of novel medications and drugs. Hence, bioprospection of these photoprotective compounds and other secondary metabolites from cyanobacteria and microalgae becomes crucial. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023.PublicationBook Chapter Bioprospecting and Evolutionary Significance of Photoprotectors in Non-flowering Lower Plants(Springer Nature, 2023) Amit Gupta; Ashish P. Singh; Niharika Sahu; Jyoti Jaiswal; Neha Kumari; Prashant R. Singh; Rajeshwar P. SinhaEnvironmental change as well as the continued increase in UV radiation (UVR; 280–400 nm) has a significant impact on terrestrial and aquatic ecosystems. The majority of sun-exposed species are negatively affected by solar UVR. This may be the strong reason behind the evolution of photoprotectants like phenylpropanoids, flavonoids, mycosporines, scytonemin, mycosporine-like amino acids (MAAs), parietin, xanthophyll, phycobiliproteins etc. It is mainly found in cyanobacteria, algae, fungi, lichens and other non-flowering lower plants. These photoprotectors have their own evolutionary significance. To reduce photochemical damage, carotenoids are being considered as UV-protective additives. Carotenoids are major light-harvesting and photoprotective components of the photosynthetic apparatus, and work as quencher of singlet oxygen species. Many other UV-absorbing compounds are also known for their multifunctional capabilities, such as flavonoids, which have antioxidative and antibacterial potentials. The study of these photoprotectants has resulted in the identification of new sunscreen classes and their distribution throughout various microbes and non-flowering lower plants. These natural photoprotectants play an important role in different forms such as scytonemin and MAAs operate as the third line of defence in cyanobacteria, mycosporines are critical for UV-induced photodamage in fungi. Lichens possess a wide range of primary and secondary metabolites, in which MAAs and parietin have major photoprotective effects. Moreover, these photoprotectants aid in diffusing heat from absorbed radiation without generating reactive oxygen species (ROS). This chapter deals with the evolutionary significance of photoprotectors and their possible modes of action. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023.PublicationArticle Characterization of UV-screening pigment scytonemin from cyanobacteria inhabiting diverse habitats of Varanasi, India(Springer Science and Business Media Deutschland GmbH, 2023) Neha Kumari; Abha Pandey; Amit Gupta; Sonal Mishra; Rajeshwar P. SinhaScytonemin is a yellow-brown ultraviolet screening compound present in the sheath of several cyanobacteria. In this investigation, biological crusts from various natural habitats were examined for the presence of the photoprotective compound scytonemin. Cyanobacteria such as Scytonema sp., Anabaena sp., Nostoc sp., Fischerella sp. and Lyngbya sp. were present in these biological crusts. Analysis of photosynthetic pigments such as Chl a and carotenoids was done by UV-VIS spectrophotometer. The Chl a and carotenoid contents were found to be maximum in Scytonema sp. isolated from the wall of the excavated area of Sarnath. Identification and characterization of scytonemin were done through High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FTIR) and High Resolution Mass Spectrometry (HRMS). Scytonemin was present in all samples and HPLC chromatograms showed absorption maxima at 386 nm having retention time ranging from 5.3 to 5.9 min. It also absorbs significantly at 252, 278 and 300 nm. HRMS showed [M + H]+m/z: 545.1) divulged scytonemin. From the present study, it can be concluded that synthesis of photoprotective compound scytonemin counteracts the harmful effects of solar radiation which enable cyanobacteria to colonize and survive in extreme environmental conditions such as rocks and walls of buildings that face prolonged high intensity solar radiation. Scytonemin as strong UV-shielding and antioxidant molecule can be considered as a key ingredient in various pharmaceutical industries for the development of novel drugs and natural Sun protection cream. © 2022, The Author(s), under exclusive licence to Plant Science and Biodiversity Centre, Slovak Academy of Sciences (SAS), Institute of Zoology, Slovak Academy of Sciences (SAS), Institute of Molecular Biology, Slovak Academy of Sciences (SAS).PublicationArticle Phylogenetic distribution, structural analysis and interaction of nucleotide excision repair proteins in cyanobacteria(Elsevier B.V., 2023) Prashant R. Singh; Amit Gupta; Rajneesh; Jainendra Pathak; Rajeshwar P. SinhaCyanobacteria are photosynthetic Gram-negative, oxygen evolving prokaryotes with cosmopolitan distribution. Ultraviolet radiation (UVR) and other abiotic stresses result in DNA lesions in cyanobacteria. Nucleotide excision repair (NER) pathway removes the DNA lesions produced by UVR to normal DNA sequence. In cyanobacteria, detailed knowledge about NER proteins is poorly studied. Therefore, we have studied the NER proteins in cyanobacteria. Analyses of 289 amino acids sequence from 77 cyanobacterial species have revealed the presence of a minimum of one copy of NER protein in their genome. Phylogenetic analysis of NER protein shows that UvrD has maximal rate of amino acid substitutions which resulted in increased branch length. The motif analysis shows that UvrABC proteins is more conserved than UvrD, Further, UvrA with UvrB protein interacts with each other and form stable complex which have DNA binding domain on the surface of the complex. UvrB also have DNA binding domain. Positive electrostatic potential was found in the DNA binding region, which is followed by negative and neutral electrostatic potential. Additionally, the surface accessibility values at the DNA strands of T5-T6 dimer binding site were maximal. Protein nucleotide interaction shows the strong binding of T5-T6 dimer with NER proteins of Synechocystis sp. PCC 6803. This process repairs the UV-induced DNA lesions in dark when photoreactivation is inactive. Regulation of NER proteins protect cyanobacterial genome and maintain the fitness of organism under different abiotic stresses. © 2023 Elsevier B.V.