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PublicationBook Chapter Pollution affecting cyanobacteria in aquatic habitats(Springer International Publishing, 2021) Abha Pandey; Sonal Mishra; Neha Kumari; Vidya Singh; Rajeshwar P. SinhaAquatic ecosystems comprise the largest portion (~72%) of the biosphere and play a crucial role in stabilizing the global climate as well as providing a large array of services for a fast-growing human population. Nowadays, there is a growing amount of data that prove that many anthropogenic pollutants from agricultural, urban and industrial wastes are dumped in the aquatic ecosystems and accumulate in many environments, including the habitats of marine and freshwater cyanobacteria. Cyanobacteria, as a natural part of phytoplankton assemblages, are known for their role as dominant primary producers and base of aquatic food webs. These microorganisms are continuously exposed to various concentrations of the pollutants that are present in their habitats and affect cyanobacterial communities at different levels such as abundance, growth strategies, succession patterns and dominance. Even if no direct changes in cyanobacterial communities are visible, the pollutants may accumulate in cyanobacteria and be passed onto higher trophic levels in a cascading manner, resulting in biomagnifications of certain pollutants. The most common pollutants in aquatic ecosystems are heavy metals, herbicides, pesticides, nutrients, pharmaceuticals, polycyclic aromatic hydrocarbons and microplastics. It is important to determine their concentrations in cyanobacterial cells and in their environment to know the possibility of contaminants that might be transferred to higher trophic levels. However, some strains of cyanobacteria are capable of metabolizing these pollutants that makes them less toxic or sometimes they even remove pollutants from the environment. This chapter highlights the toxic effects of different types of pollution (both point sources and non-point sources) on cyanobacterial communities in aquatic habitats. The anthropocentric concept of "pollution" and the links between pollution, eutrophication and harmful algal blooms (HABs) are also analyzed. An understanding of the synergistic interactions between these aspects and climate change effects will be useful to devise suitable remediation strategies for future use. © Springer Nature Switzerland AG 2021. All rights reserved.PublicationArticle 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 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 GC constituents and relative codon expressed amino acid composition in cyanobacterial phycobiliproteins(Elsevier, 2014) Vinod K. Kannaujiya; Rajesh P. Rastogi; Rajeshwar P. SinhaThe genomic as well as structural relationship of phycobiliproteins (PBPs) in different cyanobacterial species are determined by nucleotides as well as amino acid composition. The genomic GC constituents influence the amino acid variability and codon usage of particular subunit of PBPs. We have analyzed 11 cyanobacterial species to explore the variation of amino acids and causal relationship between GC constituents and codon usage. The study at the first, second and third levels of GC content showed relatively more amino acid variability on the levels of G3. +. C3 position in comparison to the first and second positions. The amino acid encoded GC rich level including G rich and C rich or both correlate the codon variability and amino acid availability. The fluctuation in amino acids such as Arg, Ala, His, Asp, Gly, Leu and Glu in α and β subunits was observed at G1C1 position; however, fluctuation in other amino acids such as Ser, Thr, Cys and Trp was observed at G2C2 position. The coding selection pressure of amino acids such as Ala, Thr, Tyr, Asp, Gly, Ile, Leu, Asn, and Ser in α and β subunits of PBPs was more elaborated at G3C3 position. In this study, we observed that each subunit of PBPs is codon specific for particular amino acid. These results suggest that genomic constraint linked with GC constituents selects the codon for particular amino acids and furthermore, the codon level study may be a novel approach to explore many problems associated with genomics and proteomics of cyanobacteria. © 2014 Elsevier B.V.PublicationBook Chapter Mechanisms of Photoprotection in Cyanobacteria(Elsevier, 2018) Jainendra Pathak; Haseen Ahmed; Prashant R. Singh; Shailendra P. Singh; Donat-P. Häder; Rajeshwar P. SinhaCyanobacteria represent a unique group of prokaryotes that are able to perform oxygenic photosynthesis and constitute crucial microflora with respect to total biomass and productivity in terrestrial and aquatic ecosystems. They are natural biofertilizers and also serve as potent source of natural products of industrial and medicinal values. Harvesting of light for photosynthesis exposes cyanobacteria to unpredictable changes in light intensity and harmful doses of solar ultraviolet radiation (UVR). High light intensity induces photooxidative damage of the reaction centers due to the generation of reactive oxygen species and hence, is lethal for cyanobacteria. UVR adversely affects several biological processes, such as growth, development, orientation and motility, photosynthesis, pigmentation, CO2 assimilation, enzyme activity, and N2 fixation. DNA shows absorption in the UV range, hence, is one of the prime targets of UVR. Inclusive survival of cyanobacteria in diverse ecological niches and adaptive diversification have compelled them to evolve an array of survival strategies to compete and sustain successfully in different environments with high light intensity together with UV fluxes on the Earth. Photoprotective mechanisms such as avoidance, nonphotochemical quenching to dissipate excess excited-state energy as heat, synthesis of photoactive proteins such as orange carotenoid protein, fluorescence recovery protein, early shock proteins, late acclimation proteins, antioxidative enzymes, sunscreens such as scytonemin and mycosporine-like amino acids, repair, and programmed cell death are adapted by cyanobacteria to counteract the damage caused by high light conditions and UVR. This chapter provides an in-depth account of important mechanisms involved in photoprotection in cyanobacteria. © 2019 Elsevier Inc. All rights reserved.PublicationArticle UV-induced physiological changes and biochemical characterization of mycosporine-like amino acid in a rice-field cyanobacterium Fischerella sp. strain HKAR-13(Elsevier B.V., 2022) Vidya Singh; Jainendra Pathak; Abha Pandey; Haseen Ahmed; Rajneesh; Deepak Kumar; Rajeshwar P. SinhaMycosporine-like amino acids (MAAs) are valuable secondary metabolite with notable photoprotective potential. The present study investigateS the imрасts of рhоtоsynthetiс асtive rаdiаtiоn (РАR) and ultraviolet radiation (UVR) on various physiological processes in the cyanobacterium Fischerella sp. strain HKAR-13. Cell viability was reduced by 36 and 65% after 72h of exроsure to РАR+UV-А (PA) and РАR+UV-А+UV-B (PAB) radiations respectively. Significant decline in Chl a content was observed during PA and PAB exposure after 36h. Carotenoid content increased significantly after 48h of exposure, thereafter began to decline. Cultures exposed to PAB showed maximum detrimental effect on protein synthesis. In PAB and PA, the levels of intracellular reactive oxygen species (ROS) increased significantly. Fluorescence microscopic images of cyanobacteria revealed generation of ROS in UVR as indicated by increase in green fluorescence. Besides, Fischerella sp. strain HKAR-13 was also tested for the рresenсe of MААs and their induction under UVR. UV-Vis spectrophotometry and high-рerfоrmаnсe liquid сhrоmаtоgrарhy аnаlyses revealed the рresenсe of a MAA having absorption maxima λmax 334 nm and retention time of 1.5 min. Maximum induction of MAA was found in samples exposed to PAB followed by PA. Based on electrospray ionization-mass sрeсtrоsсорy (m/z: 333+1), fourier transform infrared and nuclear magnetic resоnаnсe sрeсtrоsсорy, the MAA was identified as shinorine. Shinorine was found to be highly stable under some abiotic stress factors such as UV-B, temperature and H2O2. It also showed efficient antioxidant activity in a dose-dependent manner as depicted by in vitro antioxidant assays. © 2022 SAABPublicationReview Photoprotective compounds from marine organisms(Springer Verlag, 2010) Rajesh P. Rastogi; Richa; Rajeshwar P. Sinha; Shailendra P. Singh; Donat-P. HäderThe substantial loss in the stratospheric ozone layer and consequent increase in solar ultraviolet radiation on the earth's surface have augmented the interest in searching for natural photoprotective compounds in organisms of marine as well as freshwater ecosystems. A number of photoprotective compounds such as mycosporine- like amino acids (MAAs), scytonemin, carotenoids and several other UV-absorbing substances of unknown chemical structure have been identified from different organisms. MAAs form the most common class of UVabsorbing compounds known to occur widely in various marine organisms; however, several compounds having UV-screening properties still need to be identified. The synthesis of scytonemin, a predominant UV-A- photoprotectivepigment, is exclusively reported in cyanobacteria. Carotenoids are important components of the photosynthetic apparatus that serve both light-harvesting and photoprotective functions, either by direct quenching of the singlet oxygen or other toxic reactive oxygen species or by dissipating the excess energy in the photosynthetic apparatus. The production of photoprotective compounds is affected by several environmental factors such as different wavelengths of UVR, desiccation, nutrients, salt concentration, light as well as dark period, and still there is controversy about the biosynthesis of various photoprotective compounds. Recent studies have focused on marine organisms as a source of natural bioactive molecules having a photoprotective role, their biosynthesis and commercial application. However, there is a need for extensive work to explore the photoprotective role of various UVabsorbing compounds from marine habitats so that a range of biotechnological and pharmaceutical applications can be found. © Society for Industrial Microbiology 2010.PublicationArticle Physiological responses of the cyanobacterium Synechocystis sp. PCC 6803 under rhythmic light variations(Springer Nature, 2023) Prashant R. Singh; Jainendra Pathak; Rajneesh; Haseen Ahmed; Donat-P. Häder; Rajeshwar P. SinhaCyanobacteria are challenged by daily fluctuations of light intensities and photoperiod in their natural habitats, which affect the physiology and fitness of cyanobacteria. Circadian rhythms (CRs), an important endogenous process found in all organisms including cyanobacteria, control their physiological activities and helps in coping with 24-h light/dark (LD) cycle. In cyanobacteria, physiological responses under rhythmic ultraviolet radiation (UVR) are poorly studied. Therefore, we studied the changes in photosynthetic pigments, and physiological parameters of Synechocystis sp. PCC 6803 under UVR and photosynthetically active radiation (PAR) of light/dark (LD) oscillations having the combinations of 0, 4:20, 8:16, 12:12, 16:8, 20:4, and 24:24 h. The LD 16:8 enhanced the growth, pigments, proteins, photosynthetic efficiency, and physiology of Synechocystis sp. PCC6803. Continuous light (LL 24) of UVR and PAR exerted negative impact on the photosynthetic pigments, and chlorophyll fluorescence. Significant increase in reactive oxygen species (ROS) resulted in loss of plasma membrane integrity followed by decreased viability of cells. The dark phase played a significant role in Synechocystis to withstand the LL 24 under PAR and UVR. This study offers detailed understanding of the physiological responses of the cyanobacterium to changing light environment. © 2023, The Author(s), under exclusive licence to European Photochemistry Association, European Society for Photobiology.PublicationArticle Molecular characterization of hot spring cyanobacteria and evaluation of their photoprotective compounds(2012) Rajesh P. Rastogi; Sunita Kumari; Richa; Taejun Han; Rajeshwar P. SinhaPhylogenetic analysis of 4 cyanobacterial strains isolated from hot springs in Rajgir, India, was carried out using the 16S rRNA gene (1400 bp). These strains were identified as members of Chroococcales (Cyanothece sp. strain HKAR-1) and Nostocales (Nostoc sp. strain HKAR-2, Scytonema sp. strain HKAR-3, and Rivularia sp. strain HKAR-4). Furthermore, we evaluated the presence of ultraviolet-screening and (or) photoprotective compounds, such as mycosporine-like amino acids (MAAs) and scytonemin, in these cyanobacteria by using high-performance liquid chromatography. Well-characterized MAAs, including the critical and highly polar compounds shinorine, porphyra-334, and mycosporine-glycine, as well as several unknown MAAs, were found in these hot-spring-inhabiting microorganisms. The presence of scytonemin was detected only in Scytonema sp. strain HKAR-3 and Rivularia sp. strain HKAR-4. The results indicate that hot spring cyanobacteria, namely Cyanothece, Nostoc, Scytonema, and Rivularia, belonging to different groups possess various photoprotective compounds to cope up with the negative impacts of damaging radiations.PublicationArticle Photoheterotrophic growth unprecedentedly increases the biosynthesis of mycosporine-like amino acid shinorine in the cyanobacterium Anabaena sp., isolated from hot springs of Rajgir (India)(2014) Shailendra P. Singh; Sun-yong Ha; Rajeshwar P. Sinha; Donat-P. HäderCyanobacteria are known to biosynthesize mycosporine-like amino acids (MAAs) as photoprotective compounds against ultraviolet radiation. Anabaena sp., isolated from the hot springs of Rajgir, India, produces a single MAA shinorine (retention time = 2.2 min and absorption maximum at 334 nm) as purified by high-performance liquid chromatography. The MAA biosynthesis was under constitutive control in this cyanobacterium; however, PAR + UV-A + UV-B radiation was found to have highest impact on MAA synthesis. MAA biosynthesis is dependent on photosynthesis for the carbon source since the inhibitory effect of DCMU on MAA synthesis was overcome by externally added fructose. Our results suggest that there is no direct involvement of photosystem II dependent linear electron transport in MAA biosynthesis. However, utilization of energy derived from photosystem I dependent cyclic electron transport in MAA biosynthesis cannot be ruled out. This study also reveals that photoheterotrophic growth can support highest MAA biosynthesis under laboratory conditions in comparison with photoautotrophic and photomixotrophic growth. Thus, photoheterotrophic growth condition can be used for the large-scale production of pharmaceutically important MAAs from cyanobacteria for an industrial application. © 2013 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.