Browsing by Author "Prashansa Singh"

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Cell Death in Photoautotrophs
(Springer Nature, 2024) Samujjal Bhattacharjee; Prashansa Singh; Alka Bhardwaj; Arun Kumar Mishra
Programmed cell death (PCD) is a genetically controlled mechanism regulating cellular demise. Though commonly associated with multicellular organisms, it has also been observed in unicellular organisms such as photoautotrophs, which are organisms proficient in generating their sustenance through photosynthesis. This chapter delves into the fundamental role of programmed cell death in photoautotrophs, elucidating its pivotal contributions to growth, development, and adaptive responses to environmental challenges. The exploration unveils the sophisticated mechanisms these organisms have evolved to ensure survival and reproductive success amid changing conditions. Through an in-depth analysis of distinct mechanisms and regulatory pathways governing PCD in photoautotrophs, this chapter provides valuable insights into the broader understanding of cell death processes. It accentuates unique features, specific pathways, molecular players, and regulatory elements that PCD in photoautotrophs apart from other systems, particularly animals. Key discoveries underscore the significance of PCD in sculpting the life cycle of photoautotrophs, resonating with implications for plant biology, ecological dynamics, and beyond. Comparative analyses with PCD in diverse organisms shed light on the evolutionary dimensions of cell death mechanisms. The presented findings not only propel our comprehension of PCD in photoautotrophs but also pave the way for future research, unraveling the intricate interplay between cellular life and death in these vital organisms. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
Circadian cycle of cyanobacteria: mechanistic prospect and evolution
(Elsevier, 2023) Prashansa Singh; Alka Bhardwaj; Balkrishna Tiwari
The circadian clock in most of the organisms enable them to synchronize their physiology with the external environmental changes that occur due to the rotation of the Earth on its axis. Cyanobacteria have also developed a posttranslational oscillator system that sustains these circadian rhythms, and has emerged as a key example for understanding circadian timekeeping processes. This protein-based oscillator undergoes an oscillating biochemical cycle that, in turn, gives timing cues to effectuate a 24-hour molecular clock. Our understanding of the cyanobacterial clock system has revolved largely around a single model organism, Synechococcus elongatus PCC 7942. However, other forms of this oscillator, known as the Kai system have been observed among the diversity of cyanobacterial species. Furthermore, the cyanobacterial circadian system has a long and complex evolutionary history, associated with natural selection, multiple lateral transfers, gene duplications, and losses. Its components have undergone numerous changes over years, leading to the assortment of functional forms seen today. Broadly, these fall into three major classes of Kai systems that occur across cyanobacterial phyla, each with a different set of clock components. These Kai-based timing systems have evolved parallelly with the geological history of the Earth, and thus offers a unique opportunity to correlate day-length changes in Earth’s history to the origin of the circadian clock. Overall, this chapter highlights the structure and function of clock components, how this circadian network operates in a cyanobacterial cell, and summarizes the evolution and diversity of the circadian oscillators observed in this unique group of prokaryotic photoautotrophs. © 2024 Elsevier Inc. All rights reserved.
Cyanobacteria: a key player in nutrient cycling
(Elsevier, 2023) Alka Bhardwaj; Prashansa Singh; Neha Gupta; Samujjal Bhattacharjee; Ankit Srivastava; Anirbana Parida; Arun Kumar Mishra
Cyanobacteria are photosynthetic prokaryotic organisms that are found in various aquatic and terrestrial environments. They are one of the oldest and most primitive forms of life on Earth, playing critical role in the biological nutrient cycling of different habitats. The phenomenon of nutrient cycling delineates the continual recycling of essential elements, which are rendered accessible to the biota of an ecosystem. Cyanobacteria possess the ability to fixate atmospheric nitrogen and transform it into a bioavailable form, which can be utilized by other organisms in the ecosystem. This process is called nitrogen fixation, and it helps to increase the availability of nitrogen in the ecosystem, which is an essential nutrient for the growth of different life forms. They also play a key role in carbon cycling by capturing carbon dioxide through photosynthesis and releasing oxygen into the atmosphere. Indeed, cyanobacteria played a significant role in making the early environment aerobic by producing oxygen through photosynthesis. This process helps to regulate the amount of carbon dioxide in the atmosphere, which is important for mitigating the effects of climate change. Additionally, cyanobacteria can contribute to the cycling of other nutrients, such as phosphorus and sulfur, by releasing them from organic matter and making them available for other organisms to use. Overall, cyanobacteria are crucial for the cycling of different nutrients, including nitrogen, carbon, phosphorus, and sulfur, and their impact on the health of the ecosystem cannot be overstated. The presence of these microorganisms is essential for ensuring a stable and thriving environment, and their involvement in nutrient cycling and oxygenic photosynthesis has constituted a critical component in the evolutionary history of life on Earth. © 2024 Elsevier Inc. All rights reserved.