Browsing by Author "Rinkesh Gupta"

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Carbon concentrating mechanism in cyanobacteria: necessity and evolution
(Elsevier, 2023) Priyul Pandey; Rinkesh Gupta; Sapna Tiwari; Anjali Gupta; Soumila Mondal; Rajeshwar P. Sinha; Shailendra P. Singh
Cyanobacteria are Gram-negative photosynthetic bacteria that produce oxygen similar to eukaryotic algae and higher plants during photosynthesis. These prokaryotes appeared on the Earth when there was no oxygen in the atmosphere, and oxygen produced by them led to the development of present-day aerobic life. However, cyanobacteria lack any subcellular organelles like a nucleus, chloroplast, and mitochondria, and therefore the evolution of the ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) enzyme in the presence of oxygen resulted in the oxygenase activity. Also, CO2 is limiting in aquatic environments where it is readily available in the form of bicarbonate (HCO3 ¯). Thus the oxygenase activity of Rubisco and availability of HCO3 ¯ acted as a selection pressure in the cyanobacteria for the evolution of an efficient CO2 concentrating mechanism (CCM) to minimize photorespiration and utilization of available forms of inorganic carbon. In this chapter, we will discuss different components of cyanobacterial CCM such as carboxysome, carbonic anhydrase, and inorganic carbon transporters. We have also included information on evolutionary pressure that resulted in the development of CCM in cyanobacteria. © 2024 Elsevier Inc. All rights reserved.
Cyanobacterial green chemistry: a blue-green approach for a sustainable environment, energy, and chemical production
(Royal Society of Chemistry, 2025) Priyul Pandey; Deepa Pandey; Anjali Gupta; Rinkesh Gupta; Sapna Tiwari; Shailendra P. Singh
Increased human activity due to the ever-increasing global population has necessitated the urgent need for a sustainable environment, food, and energy. Cyanobacteria, classically known as blue-green algae, are oxygen-producing photosynthetic organisms that are emerging as an option to achieve sustainable development goals. These Gram-negative prokaryotes can efficiently sequester atmospheric CO2 due to an efficient carbon concentrating mechanism and divert it to the production of energy-rich compounds, i.e., biofuel, and other valuable chemicals, using their flexible metabolic chassis. Additionally, cyanobacteria also minimize the emission of methane, which is another greenhouse gas, by providing oxygen to methane-oxidizing bacteria. In recent years, several genetically engineered strains of cyanobacteria have been developed that can produce biofuels and several other valuable chemicals. Strains have also been engineered for bioplastic production and bioremediation purposes. These organisms have gained attention as biofertilizers and can increase the quality and fertility of soil. Thus, cyanobacteria are promising CO2 sinks that can contribute to global efforts in carbon capture and storage initiatives while producing bioenergy, cosmetics, pharmaceuticals, and several other valuable chemicals. Therefore, these blue-green cells can be used for green chemistry while minimizing the atmospheric CO2 concentration. In this review, we present various applications of cyanobacterial biomass to achieve sustainable development goals. We also discuss challenges associated with the wide application of cyanobacteria and the future direction to make full use of these robust organisms to fulfill our future demands in an environment-friendly manner. © 2025 The Author(s)
Flow Cytometry–Based Methods for Estimating DNA Content and Live-Dead Cells in Cyanobacteria
(CRC Press, 2024) Soumila Mondal; Anjali Gupta; Sapna Tiwari; Rinkesh Gupta; Shailendra P. Singh
Cyanobacteria are Gram-negative, photosynthetic, oxygen-producing bacteria that thrive in a variety of harsh environmental conditions (Whitton and Potts 2012). In addition to oxygen production, several cyanobacteria can fix atmospheric nitrogen due to the presence of nitrogenase enzymes. Therefore, cyanobacteria play an important role in sustaining life on Earth. Cyanobacteria are found in different morphological forms such as filamentous, unicellular and colonial forms. Filamentous forms generally show cellular differentiation during their development and may possess different cell types such as heterocysts for nitrogen fixation, akinetes as a resting stage cell and hormogonia as a reproductive short motile filament (Claessen et al. 2014; Herrero et al. 2016). Cyanobacteria are known for the production of industrially important metabolites and biofuels (Jones and Mayfield 2012; Neilan et al. 2013; Wijffels et al. 2013; Oliver and Atsumi 2014). © 2024 selection and editorial matter, Shailendra P. Singh, Rajeshwar P. Sinha and Donat-P. Häder; individual chapters, the contributors.
Photoacclimation strategies in cyanobacterial photosynthesis under dynamic light environments: implications in growth, fitness, and biotechnological applications
(Frontiers Media SA, 2025) Sapna Tiwari; Anjali Gupta; Deepa Pandey; Priyul Pandey; Rinkesh Gupta; Shailendra P. Singh
Cyanobacteria, ancient oxygenic photoautotrophs originated in the Precambrian period, exhibit remarkable adaptability to diverse ecological systems. Light, a critical environmental factor, exerts differential pressures on these organisms. The scattering of white light creates dynamic light environments, which poses a significant ecological challenge. To thrive in dynamic light environment, cyanobacteria have developed several light acclimation strategies. This includes chromatic acclimation, which optimize light harvesting by adjusting pigments. Cyanobacteria also employ robust photoprotective mechanisms against quantitative light stress. Under high light, these organisms activate non-photochemical quenching using the proteins such as orange carotenoid protein, iron starvation-induced protein, and high light-induced proteins to safely dissipate excess excitation energy. Additionally, thylakoid-localized respiratory enzymes alleviate electronic pressure arising from over-reduction of the plastoquinone pool. Under low light conditions, cyanobacteria frequently employ state transitions, reversibly associating their phycobilisomes with PSII and PSI to optimize light harvesting. These natural strategies offer a blueprint for engineering cyanobacteria and algae for their application in biomanufacturing and CO2 sequestration. This review synthesizes the key light acclimation and photoprotective mechanisms, underscoring their importance for both the ecological success of cyanobacteria and their implication in biotechnological applications using engineered strains. © © 2025 Tiwari, Gupta, Pandey, Pandey, Gupta and Singh.
Responding to light signals: a comprehensive update on photomorphogenesis in cyanobacteria
(Springer, 2023) Anjali Gupta; Priyul Pandey; Rinkesh Gupta; Sapna Tiwari; Shailendra Pratap Singh
Cyanobacteria are ancestors of chloroplast and perform oxygen-evolving photosynthesis similar to higher plants and algae. However, an obligatory requirement of photons for their growth results in the exposure of cyanobacteria to varying light conditions. Therefore, the light environment could act as a signal to drive the developmental processes, in addition to photosynthesis, in cyanobacteria. These Gram-negative prokaryotes exhibit characteristic light-dependent developmental processes that maximize their fitness and resource utilization. The development occurring in response to radiance (photomorphogenesis) involves fine-tuning cellular physiology, morphology and metabolism. The best-studied example of cyanobacterial photomorphogenesis is chromatic acclimation (CA), which allows a selected number of cyanobacteria to tailor their light-harvesting antenna called phycobilisome (PBS). The tailoring of PBS under existing wavelengths and abundance of light gives an advantage to cyanobacteria over another photoautotroph. In this work, we will provide a comprehensive update on light-sensing, molecular signaling and signal cascades found in cyanobacteria. We also include recent developments made in other aspects of CA, such as mechanistic insights into changes in the size and shape of cells, filaments and carboxysomes. © 2023, Prof. H.S. Srivastava Foundation for Science and Society.