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 Blue and red light significantly aid in the recovery of damaged cells of the cyanobacterium Synechocystis sp. PCC 6803 exposed to ultraviolet radiation(Springer Nature, 2025) Prashant R. Singh; Ashish P. Singh; Amit Gupta; Shailendra P. Singh; Rajeshwar Prasad SinhaCyanobacteria are the most promising models for CO2 sequestration, production of chemicals, and renewal energy. Being photosynthetic organisms, they are continuously exposed to different intensities and wavelengths of light, including ultraviolet radiation (UVR). In the present investigation, we studied photosynthetically active radiation (PAR + UV−A + UV−B (PAB) effects on the cyanobacterium Synechocystis sp. PCC 6803 and its recovery under different wavelengths of light, such as PAR, blue light (BL), green light (GL), and red light (RL). The Chl a and total carotenoid content recovered maximally under BL and RL, whereas phycocyanin (PC) under BL. Maximum recovery in the photosynthetic performance was observed under GL and RL, whereas the least recovery was under BL. After 48 h of PAB irradiation, minimum ROS was found under dark conditions. The maximum number of non-viable cells was found in 24 h PAB, and in the recovery phase, it was found in BL and RL. Thus, it was evident that PAB negatively affects the growth, development, and overall fitness of Synechocystis sp. PCC 6803. The different wavelengths of light play a significant role in the recovery of the cyanobacterium Synechocystis sp. PCC 6803. © The Author(s), under exclusive licence to the European Photochemistry Association, European Society for Photobiology 2025.PublicationArticle Green and blue light-dependent morphogenesis, decoupling of phycobilisomes and higher accumulation of reactive oxygen species and lipid contents in Synechococcus elongatus PCC 7942(Elsevier B.V., 2023) Pankaj K. Maurya; Soumila Mondal; Vinod Kumar; Shailendra P. SinghCyanobacteria are one of the emerging model systems for the sequestration of CO2 and sustainable production of bioenergy and chemicals. However, the spectral composition of light, which changes greatly in a dynamic light environment, could affect their fitness, growth and development. We studied the photobiology of the model cyanobacterium Synechococcus elongatus PCC 7942 using different lights such as white light (WL), red light (RL), green light (GL) and blue light (BL) to investigate the response of the organism to different wavelengths of photosynthetic active radiation. Results obtained suggested that S. elongatus PCC 7942 can not efficiently utilize green and blue wavelengths of light, and the two light colors compromised the fitness and growth of the organism by inducing high levels of reactive oxygen species (ROS). GL and BL, interestingly, increased the lipid content in the biomass and caused decoupling of phycobilisomes from the thylakoid membranes. We report light quality-dependent morphogenesis in S. elongatus PCC 7942 where GL and BL caused cell elongation while RL induced small cell morphology. Gene expression analysis suggested that GL and BL could regulate cell shape by altering the expression of cytoskeleton protein-encoding morphogenes. Thus, it is evident that the growth and fitness of S. elongatus PCC 7942 can be compromised in dense culture or at higher depths in the water column where GL and/or BL-enriched environment prevails. However, decreased fitness is offset by increased lipid content and elongated cellular morphology. © 2022 Elsevier B.V.PublicationArticle Computational studies on photolyase (Phr) proteins of cyanobacteria(Canadian Science Publishing, 2022) Rajneesh; Soumila Mondal; Jainendra Pathak; Prashant R. Singh; Shailendra P. Singh; Rajeshwar P. SinhaPhotolyases (Phrs) are enzymes that utilize the blue/ultraviolet (UV-A) region of light for repairing UV-induced cyclopyramidine dimers. We studied Phr groups by bioinformatic analyses as well as active-site and structural modeling. Analysis of 238 amino acid sequences from 85 completely sequenced cyanobacterial genomes revealed five classes of Phrs, CPD Gr I, 6-4 Phrs/cryptochrome, Cry-DASH, Fe-S bacteria Phrs, and a group with fewer amino acids (276–385) in length. The distribution of Phr groups in cyanobacteria belonging to the order Synechococcales was found to be influenced by the habitats of the organisms. Class V Phrs are exclusively present in cyanobacteria. Unique motifs and binding sites were reported in groups II and III. The Fe-S protein binding site was only present in group V and the active site residues and putative CPD/6-4PP binding residues are charged amino acids present on the surface of the proteins. The majority of hydrophilic amino acid residues were present on the surface of the Phrs. Sequence analysis confirmed the diverse nature of Phrs, although sequence diversity did not affect the overall three-dimensional structure. Protein–ligand interaction analysis identified novel CPD/6-4PP binding sites on Phrs. This structural information of Phrs can be used for the preparation of efficient Phr-based formulations. © 2021 The Author(s).PublicationArticle Flow Cytometry-based Measurement of Reactive Oxygen Species in Cyanobacteria(Bio-protocol LLC, 2022) Soumila Mondal; Shailendra P. SinghCyanobacteria are Gram-negative oxygen-producing photosynthetic bacteria that are useful in the pharmaceutical and biofuel industries. Monitoring of oxidative stress under fluctuating environmental conditions is important for determining the fitness, survival, and growth of cyanobacteria in the laboratory as well as in large scale cultivation systems. Here, we provide a protocol developed using unicellular Synechococcus elongatus PCC 7942 and filamentous Fremyella diplosiphon BK14 cyanobacteria for high-throughput oxidative stress measurement by 2′,7′-dichlorodihydrofluorescein-diacetate (DCFH-DA) and flow cytometry (FCM). We also provide details for the optimization of cell number, dye concentration, and FCM parameters for each organism before it can be utilized to quantify reactive oxygen species (ROS). FCM-based method can be used to measure ROS in a large population of cyanobacterial cells in a high-throughput manner. © 2022 The Authors; exclusive licensee Bio-protocol LLC.PublicationArticle Light-dependent impact of salinity on the ecophysiology of Synechococcus elongatus PCC 7942: Genetic and comparative protein structure analyses of UV-absorbing mycosporine-like amino acids (MAAs) biosynthesis(Elsevier B.V., 2021) Vinod Kumar; Soumila Mondal; Anjali Gupta; Pankaj K. Maurya; Rajeshwar P. Sinha; Donat-P. Häder; Shailendra P. SinghCyanobacteria are subjected to a dynamic light environment in their natural habitat or artificial cultivation system. The fluctuating light environment is associated with increased salinity stress due to the evaporation of the growth medium. Therefore, it is important to understand the physiology of the organisms under a dynamic environment of light and salinity which together affect the fitness and overall performance of the organism. We studied the growth behavior and other physiological parameters of Synechococcus elongatus PCC 7942 in the presence of different NaCl concentrations (0, 50, 100 and 200 mM) and light conditions such as low PAR (LPAR), high PAR (HPAR) and PAR + UVR using diurnal and continuous photoperiods. We also investigated the ability of S. elongatus PCC 7942 to biosynthesize UV-absorbing mycosporine-like amino acids (MAAs) and conducted genetic and comparative protein structure analyses to better understand its biosynthesis. Results obtained suggest that the impact of salinity stress caused by NaCl on growth behavior and physiological parameters such as photosynthetic pigments, the effective quantum yield of PSII and oxidative stress is dependent on the light environment. These parameters were affected differently by the quality and quantity of light and photoperiods, and the negative effect of salinity was alleviated by a high light environment. S. elongatus PCC 7942 does not biosynthesize MAAs due to the absence of MAAs biosynthesizing genes cluster in its genome. Results from genomic and comparative protein structure analyses suggested that DDGS and DHQS enzymes are different and DDGS but not DHQS is required for MAAs biosynthesis. Understanding the light-dependent impact of salinity stress may help in developing strategies for outdoor cultivation of cyanobacteria for bioenergy and valuable chemicals production by balancing absorbed and utilized radiant energy. © 2021 Elsevier B.V.PublicationArticle Phylogenetic distribution and structural analyses of cyanobacterial glutaredoxins (Grxs)(Elsevier Ltd, 2020) Soumila Mondal; Vinod Kumar; Shailendra P. SinghGlutaredoxins (Grxs), the oxidoreductase proteins, are involved in several cellular processes, including maintenance of cellular redox potential and iron-sulfur homeostasis. The analysis of 503 amino acid sequences from 167 cyanobacterial species led to the identification of four classes of cyanobacterial Grxs, i.e., class I, II, V, and VI Grxs. Class III and IV Grxs were absent in cyanobacteria. Class I and II Grxs are single module oxidoreductase while class V and VI Grxs are multimodular proteins having additional modules at their C-terminal and N-terminal end, respectively. Furthermore, class VI Grxs were exclusively present in marine cyanobacteria. We also report the identification of class VI Grxs with two novel active site motif compositions. Detailed phylogenetic analysis of all four classes of Grxs revealed the presence of several subgroups within each class of Grx having variable dithiol and/or monothiol catalytic active site motif and putative glutathione binding sites. However, class II Grxs possess CGFS-type highly conserved monothiol catalytic active site motif. Sequence analysis confirmed the highly diverse nature of Grx proteins in terms of their amino acid composition; though, sequence diversity does not affect the overall 3D structure of cyanobacterial Grxs. The active site residues and putative GSH binding residues are uncharged amino acids which are present on the surface of the protein. Additionally, the presence of hydrophilic residues at the surface of Grxs confirms their solubility. Protein-ligand interaction analysis identified novel glutathione binding sites on Grxs. Regulation of Grxs encoding genes expression by light quality and quantity as well as salinity suggests their role in determining the fitness of organisms under abiotic factors. © 2019 Elsevier LtdPublicationArticle Genetic regulation of scytonemin and mycosporine-like amino acids (MAAs) biosynthesis in cyanobacteria(Elsevier B.V., 2019) Jainendra Pathak; Haseen Ahmed; Rajneesh; Shailendra P. Singh; Donat-P. Häder; Rajeshwar P. SinhaScytonemin and mycosporine-like amino acids (MAAs) are important novel secondary metabolites synthesized by cyanobacteria to protect themselves from lethal ultraviolet (UV) radiation. Scytonemin, the extracellular polysaccharide sheath pigment is found in several cyanobacterial species and is a lipid-soluble dimeric pigment consisting of phenolic and indolic subunits linked through an olefinic carbon atom. Structure of MAAs consists of aminocyclohexenone or an aminocyclohexinimine chrompohore conjugated with the nitrogen substituent of an amino acid or its amino alcohol. MAAs are small, colorless water soluble compounds. These UV screening compounds are highly photostable photoprotectant and also serve as potent antioxidants. Multiple environmental signals influence scytonemin and MAAs synthesis and regulation of induction of these UV screening compounds is a part of complex stress response pathway. Hence, proper understanding of genetic regulation and biosynthesis of these microbial sunscreens would not only provide scientific insight in a major class of secondary metabolites but will also help in commercial production of these new age ecofriendly sunscreens. © 2019PublicationArticle In silico study on interaction between human polo-like kinase 1 and cyanobacterial sheath pigment scytonemin by molecular docking approach(AMG Transcend Association, 2019) Jainendra Pathak; Soumila Mondal; Haseen Ahmed; Rajneesh; Shailendra P. Singh; Rajeshwar P. SinhaCancer is one of the major causes of death throughout the globe. It is expected that the number of new reports with cancer cases will reach twenty two million in the coming two decades. Africa, Central and South America and Asia will have more than 60 percent of the world’s new cancer reports and 70 percent of the world’s deaths from cancer will be contributed by these continents. Hence, drug discovery for treatment of cancer is the most worked area of this century. Polo-like kinase 1 (PLK-1) is highly expressed in human tumors and is important target of anti-cancerous drugs owing to its role in cell cycle events. It is crucial in maintenance of stability of genome and during different stages of mitosis. Scytonemin is a lipid-soluble and yellow-brown pigment exclusively synthesized by several cyanobacterial species in response to ultraviolet-A radiation. It functions as a photoprotective compound and can act as noncompetitive and competitive inhibitor of PLK-1. Other kinases such as Myt1, cyclin-dependent kinase 1/cyclin B, checkpoint kinase 1 and protein kinase C are also inhibited by scytonemin. In the present study, molecular docking approach has been employed for positioning the inhibitor (dimethoxyscytonemin) into the active site of PLK-1 for determining the most probable binding mode. Based on the docking studies, the models which are developed could be utilized for understanding the structure-activity relationships of the scytonemins and for the prescreening and designing of novel inhibitors of PLK-1. © 2019 by the authors.PublicationArticle RcaE-dependent regulation of carboxysome structural proteins has a central role in environmental determination of carboxysome morphology and abundance in Fremyella diplosiphon(American Society for Microbiology, 2018) Brandon A. Rohnke; Shailendra P. Singh; Bagmi Pattanaik; Beronda L. MontgomeryCarboxysomes are central to the carbon dioxide-concentrating mechanism (CCM) and carbon fixation in cyanobacteria. Although the structure is well understood, roles of environmental cues in the synthesis, positioning, and functional tuning of carboxysomes have not been systematically studied. Fremyella diplosiphon is a model cyanobacterium for assessing impacts of environmental light cues on photosynthetic pigmentation and tuning of photosynthetic efficiency during complementary chromatic acclimation (CCA), which is controlled by the photoreceptor RcaE. Given the central role of carboxysomes in photosynthesis, we investigated roles of light-dependent RcaE signaling in carboxysome structure and function. A ΔrcaE mutant exhibits altered carboxysome size and number, ccm gene expression, and carboxysome protein accumulation relative to the wild-type (WT) strain. Several Ccm proteins, including carboxysome shell proteins and core-nucleating factors, overaccumulate in ΔrcaE cells relative to WT cells. Additionally, levels of carboxysome cargo RuBisCO in the ΔrcaE mutant are lower than or unchanged from those in the WT strain. This shift in the ratios of carboxysome shell and nucleating components to the carboxysome cargo appears to drive carboxysome morphology and abundance dynamics. Carboxysomes are also occasionally mislocalized spatially to the periphery of spherical mutants within thylakoid membranes, suggesting that carboxysome positioning is impacted by cell shape. The RcaE photoreceptor links perception of external light cues to regulating carboxysome structure and function and, thus, to the cellular capacity for carbon fixation. © 2018 Rohnke et al.PublicationBook Chapter Enzymatic and non-enzymatic protection strategies of cyanobacteria against ultraviolet radiation(Nova Science Publishers, Inc., 2018) Jainendra Pathak; Rajneesh; Vidya Singh; Deepak Kumar; Haseen Ahmed; Deepak K. Singh; Vinod K. Kannaujiya; Richa; Shailendra P. Singh; Rajeshwar P. SinhaClimate change and enhanced ultraviolet radiation (UVR; 280-400 nm) acts synergistically and strongly affects terrestrial and aquatic ecosystems. Phytoplankton productivity and species composition is expected to change due to altered external conditions such as temperature, nutrient accessibility, pH and exposure to photosynthetically active radiation (PAR; 400-700 nm) and UVR. Cyanobacteria are found in almost every habitat; ranging from oceans to fresh water and from bare rock to soil. They are major biomass producers in aquatic ecosystems representing more than 50% of the biomass in many aquatic ecosystems. These photosynthetic organisms are simultaneously exposed to PAR and UVR in their natural habitats. UVR is one of the most potent genotoxic agents which adversely affect the living organisms by altering their genomic stability. UVR also inhibit number of photochemical and photobiological processes in cyanobacteria. However, cyanobacteria have evolved a number of defense strategies to reduce the direct and indirect damaging effects of UVR. These strategies include scavenging of ROS by non-enzymatic and enzymatic antioxidant molecules, synthesis of UV screening compounds such as scytonemin and mycosporine-like amino acids (MAAs), repair of UV-induced damage of DNA and resynthesis of damaged proteins. Each of these strategies involves enzymatic activity either directly or indirectly. This chapter presents an update on various enzymatic and non-enzymatic defense mechanisms employed by cyanobacteria to withstand UVR stress. © 2018 Nova Science Publishers, Inc.
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