Influence of Moderate Hyperosmotic Stress on Ultrastructure and Indicators of Energy Metabolism of Chlorella vulgaris (C
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OPLANKTON, PHYTOBENTHOS, AND PHYTOPERIPHYTON
Influence of Moderate Hyperosmotic Stress on Ultrastructure and Indicators of Energy Metabolism of Chlorella vulgaris (Chlorophyta) A. J. Alyabeva, †, I. N. Andreyevaa, *, A. A. Ponomarevaa, V. V. Salnikova, and M. A. Suslova aKazan
Institute of Biochemistry and Biophysics, Federal Research Center Kazan Scientific Center, Russian Academy of Sciences, Kazan, Russia *e-mail: [email protected] Received June 14, 2018; revised February 6, 2019; accepted December 30, 2019
Abstract—A comparison of the response of freshwater alga Chlorella vulgaris Beijer. on a quantitatively identical change in tonicity of growth medium by different osmotics (NaCl and sucrose) has been studied. Upon an increase in growth-medium osmotic potential (regardless the nature of osmoticum), increased thermogenesis and decreased oxygen absorption by Chlorella is observed first. The difference in the reaction of Chlorella to equiosmotic concentrations of NaCl and sucrose is revealed. Upon an increased salt background, thermogenesis and photosynthetic activity decreases in comparison with the control and the respiration rate is close to the control. In the presence of sucrose, the culture has a higher level of thermogenesis, respiration, and photosynthesis. Sodium chloride does not cause significant changes in ultrastructure of Chlorella and does not lead to significant changes in the diffusional decay of water magnetization in comparison with the control. Under sucrose stress, a change in the cell shape indicating cytorhysis is revealed. The effective waterdiffusion coefficient (according to NMR data) decreases, which also indicates the reduction of cell sizes. Sucrose affects Chlorella as a nonpenetrating osmotically active substance. Under moderate hyperosmotic stress, the toxicity of NaCl is a smaller problem for freshwater microalga Chlorella than the partial dehydration caused by sucrose. Keywords: hyperosmotic stress, freshwater alga, sucrose, cytorhysis, Chlorella vulgaris, NaCl DOI: 10.1134/S1995082920030025
INTRODUCTION The unicellular green alga Chlorella vulgaris Beijer. is common in nature and an important element of a freshwater ecosystem. As a full-fledged plant organism, it can serve as a model for studying the life of an individual plant cell, including adaptive capabilities under changing living conditions. Chlorella is a convenient object both for studying fundamental problems and for solving applied problems, in particular, the environmental monitoring of the state of freshwater bodies and developing food additives and third-generation biofuels (Camuel et al., 2017; Chen et al., 2015). Chlorella, along with other microalgae, is now considered a resource for replenishing the animal feed base, as well as for industrial production, proteins, amino acids, vitamins, lipids, and other physiologically active compounds (Makarova et al., 2009; Almeida et al., 2017; Skjanes et al., 2013). † Deceased.
Abbreviations: NMR, nuclear magnetic resonance; Deff, mean effective water diffusion coef
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