title: Coccomyxa actinabiotis sp. nov. (Trebouxiophyceae, Chlorophyta), a new green microalga living in the spent fuel cooling pool of a nuclear reactor.
abstract: Life can thrive in extreme environments where inhospitable conditions prevail. Organisms which resist, for example, acidity, pressure, low or high temperature, have been found in harsh environments. Most of them are bacteria and archaea. The bacterium Deinococcus radiodurans is considered to be a champion among all living organisms, surviving extreme ionizing radiation levels. We have discovered a new extremophile eukaryotic organism that possesses a resistance to ionizing radiations similar to that of D. radiodurans. This microorganism, an autotrophic freshwater green microalga, lives in a peculiar environment, namely the cooling pool of a nuclear reactor containing spent nuclear fuels, where it is continuously submitted to nutritive, metallic, and radiative stress. We investigated its morphology and its ultrastructure by light, fluorescence and electron microscopy as well as its biochemical properties. Its resistance to UV and gamma radiation was assessed. When submitted to different dose rates of the order of some tens of mGy · h-1to several thousands of Gy · h-1, the microalga revealed to be able to survive intense gamma-rays irradiation, up to 2,000 times the dose lethal to human. The nuclear genome region spanning the genes for small subunit ribosomal RNA-Internal Transcribed Spacer (ITS) 1-5.8S rRNA-ITS2-28S rRNA (beginning) was sequenced (4,065 bp). The phylogenetic position of the microalga was inferred from the 18S rRNA gene. All the revealed characteristics make the alga a new species of the genus Coccomyxa in the class Trebouxiophyceae, which we name Coccomyxa actinabiotis sp. nov.
authors.affiliation: Commissariat à l'Energie Atomique et aux Energies Alternatives, LPCV, CNRS, CEA, INRA, Univ. Grenoble-Alpes, BIG, F-38000, Grenoble, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Rivasseau
authors.affiliation: Institut Laue-Langevin, F-38009, Grenoble, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Farhi
authors.affiliation: Institut Laue-Langevin, F-38009, Grenoble, France.|CEA, LPCV, CNRS, INRA, Univ. Grenoble-Alpes, F-38000, Grenoble, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Compagnon
authors.affiliation: Institut Laue-Langevin, F-38009, Grenoble, France.|CEA, LPCV, CNRS, INRA, Univ. Grenoble-Alpes, F-38000, Grenoble, France.
authors.forename: Diane
authors.initials: D
authors.lastname: de Gouvion Saint Cyr
authors.affiliation: CNRS, BIP, Univ. Aix-Marseille, F-13402, Marseille, France.
authors.forename: Robert
authors.initials: R
authors.lastname: van Lis
authors.affiliation: CNRS, LPCV, CEA, INRA, Univ. Grenoble-Alpes, F-38000, Grenoble, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Falconet
authors.affiliation: CNRS, LPCV, CEA, INRA, Univ. Grenoble-Alpes, F-38000, Grenoble, France.
authors.forename: Marcel
authors.initials: M
authors.lastname: Kuntz
authors.affiliation: CNRS, Laboratoire de Bioénergétique et Ingénierie de Protéines, Univ. Aix-Marseille, F-13402, Marseille, France.
authors.forename: Ariane
authors.initials: A
authors.lastname: Atteia
authors.affiliation: Muséum National d'Histoire Naturelle, UMR7245, F-75005, Paris, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Couté
mesh_terms: D000460:Chlorophyta / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure; D048028:DNA, Algal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D058086:Microalgae / Q000145:classification* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009688:Nuclear Reactors; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D062065:Wastewater
chemical_list: D048028:DNA, Algal; D021903:DNA, Ribosomal Spacer; D012337:RNA, Ribosomal, 18S; D062065:Wastewater
keywords: 
  Coccomyxa
  ; extremophiles; green microalga; ionizing radiation; radioresistance