Response of a rice-field cyanobacterium Anabaena sp. HKAR-7 upon exposure to ultraviolet-B radiation and ammonium chlori
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ORIGINAL ARTICLE
Response of a rice‑field cyanobacterium Anabaena sp. HKAR‑7 upon exposure to ultraviolet‑B radiation and ammonium chloride Deepak Kumar Singh1,2 · Jainendra Pathak3 · Abha Pandey1 · Vidya Singh1 · Haseen Ahmed1,4 · Deepak Kumar1 · Rajneesh1 · Rajeshwar Prasad Sinha1 Received: 26 November 2019 / Revised: 30 August 2020 / Accepted: 3 November 2020 © Society for Environmental Sustainability 2020
Abstract Interactive effects of ultraviolet radiation (UVR), photosynthetically active radiation (PAR) and exogenously supplied ammonium chloride ( NH4Cl) was studied in the rice-field cyanobacterium Anabaena sp. HKAR-7. The cyanobacterium was cultured under varying N H4Cl concentrations i.e., 0, 50, 200, 500, 1000 and 5000 μM and 200 μM (concentration) was found to be optimum for the growth of the cyanobacterium. Detrimental effects of UV-B exposure were observed on photosynthetic pigments such as chlorophyll a (Chl a), carotenoids and phycocyanin (PC). However, damage to these pigments was less in the cyanobacterial samples supplemented with N H4Cl. Contents of Chl a and PC in cyanobacterial cells decreased upon UV-B exposure but decrement was less in the samples supplemented with N H4Cl. Upon UV-B exposure, carotenoids content enhanced initially (till 15 days) during the course of treatment (21 days) but significant decrease (in carotenoids content) was observed in later phase of the experiment. From the results of photosynthetic activity, maximum quantum efficiency of PSII (Fv/Fm) and maximum electron transport rate ( ETRmax), it could be concluded that exogenous supplementation of N H4Cl (optimum concentration) helped in protecting the cyanobacterial cells from highly energetic UVR to certain extent. Another interesting observation was significantly higher levels of biosynthesis and accumulation of mycosporine-like amino acids (MAAs) in the cyanobacterial cells supplemented with N H4Cl in comparison to non-supplemented cells. The purified MAA was identified to be phorphyra-334 as evidenced by UV/VIS absorption spectra, high performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI–MS). Keywords Ammonium chloride · Cyanobacteria Anabaena · Mycosporine-like amino acids · Photoprotection · Ultraviolet radiation
Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42398-020-00146-6) contains supplementary material, which is available to authorized users. * Rajeshwar Prasad Sinha [email protected]; [email protected] 1
Laboratory of Photobiology and Molecular Microbiology, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi 221005, India
2
Department of Botany, Acharya Narendra Deo Kisan P. G. College, Gonda 271313, India
3
Department of Botany, Pt. Jawaharlal Nehru College, Banda 210001, India
4
Department of Botany, Government Girls PG College, Satna 485001, India
Ultraviolet radiation (UVR), the comparatively low waveband radi
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