Characterization of Radiation-Resistant Yeast Isolated from Radiation-Polluted Areas and Its Potential Application in Bi
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haracterization of Radiation-Resistant Yeast Isolated from Radiation-Polluted Areas and Its Potential Application in Bioremediation T. Liua, b, X. Liua, b, J. Zhuc, Q. Tangc, W. Wangc, L. Zhud, Z. Zhange, Z. Zhangc, *, L. Jianga, **, and H. Huangb aCollege
of Food Science and Light Industry, Nanjing Tech University, Nanjing, 210009 People’s Republic of China b College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 210009 People’s Republic of China c Institute of Microbiology, Xinjiang Academy of Agricultural Sciences, Urumqi, Xinjiang Uigur Autonomous Region, People’s Republic of China dCollege of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, 210009 People’s Republic of China eNanjing Beishengrong Energy Technology Co. Ltd., Nanjing, 210009 People’s Republic of China *e-mail: [email protected] **e-mail: [email protected] Received February 20, 2020; revised April 8, 2020; accepted April 22, 2020
Abstract– Twenty-four yeast isolates were obtained from radiation-polluted areas soils samples exposed to 60Co-γ radiation at a dose of 10 kGy and identified as members of the genus Cryptococcus based on morphological and LSU rDNA D1/D2 domain sequence analysis. Further phylogenetic analysis showed that the isolates were clustered into 4 branches. The investigation of these yeast isolates revealed D10 values for γ radiation of 5 (M2), 5 (M38), 6 (M22) and 7 kGy (M5) and a 4 × 10–3% survival rate at a UV dosage of 200 J/m2. Furthermore, the tolerance of M5 towards Zn2+ was as high as 1.700 mg/L. The isolate M5 was selected for further study, including the distribution of heavy metals within the cells by subcellular fractionation, expression of relevant genes involved in heavy metal resistance by qRT-PCR, and the removal rate by flame atomic absorption spectrometry (FAAS). The results revealed that almost 72.9% of the Zn2+ was absorbed by the cells and deposited mainly in the membrane fraction. Compared to normal conditions, all of the genes in M5 strain related to transport and regulation showed greater than 10.4-fold increases of expression levels upon exposure to heavy metal stress. In the presence of culture medium, a total of 86.5% of the initial concentration of Zn2+ was removed by the M5 strain exhibiting high removal efficiency and providing a potential of radiation-resistant platform strain for the bioremediation of heavy metals in polluted environments in the near future. Keywords: Cryptococcus, radiation resistance, heavy metal resistance, bioremediation DOI: 10.1134/S0003683820050117
The earliest report of the most radio-resistant microorganism known to date, was devoted to bacterium isolated from irradiated meat, which was initially designated as ‘Micrococcus radiodurans’ [1] and then reclassified as Deinococcus radiodurans [2]. Currently, various radiation-resistant organisms are known from several branches of the domains Bacteria, and Archaea, as well as kingdom Fungi. They have been isolated from a variety of environments, including extreme arid envir
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