Exploration of the thermophilic viral communities of the hot ecosystems of the French Southern and Antartic lands

• Main Author: Parikka, Kaarle Joonas
• Other Authors: Laboratoire de Microbiologie des Environnements Extrêmophiles (LM2E), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Marc Le Romancer
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Bacteria; Archaea; Phage; Thermophile; Viral induction; Lysogeny; Hot spring; Abundance; Bactérie; Archée; Induction virale; Lysogénie; Source chaude; Abondance; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; Antarctic; Antarc*; Antarctique*; antartic*
• Online Access: https://theses.hal.science/tel-01629201; https://theses.hal.science/tel-01629201/document; https://theses.hal.science/tel-01629201/file/These-2013-EDSM-Microbiologie-PARIKKA_Kaarle_Joonas.pdf

Viruses thrive in all types of ecosystems where life is found. They represent the most abundant biological entity of our biosphere. Though several studies have been conducted on viral abundance and dynamics in mesophilic aquatic ecosystems, these aspects remain largely unexplored in extremophilic environments, such as hot springs. In this study, prokaryotic and associated viral communities of the French Southern and Antarctic Lands hot springs were explored. First, prokaryotic cells and Virus-like particles (VLP) were enumerated in several terrestrial and inshore hot springs. The results reveal an abundance of 105 - 106 particles/ml in both types of hot springs studied. The virus-to-prokaryote ratios (VPR) were generally low, confirming thus actual knowledge in these types of ecosystems. The morphological diversity of VLP was then studied in raw samples as well as in enrichment cultures containing Thermococcales and Thermotogales. Several isolates obtained from these samples were then screened for viral particles which led to the discovery and description of a temperate phage (GTV1) of a thermophilic bacterium belonging to the genus Geobacillus. The effect of NaCl and anoxic stress on the viral production was studied. The genomic characterization of the GTV1 was started and revealed a 38441 bp genome with 71 predicted ORF. Finally, microbial diversity studies led also to the discovery of a new extremely thermophilic bacterium, Calditerricola clavaformis sp.nov. Les virus peuvent être retrouvés dans tous les écosystèmes où de la vie est présente. Ils constituent l’entité biologique la plus abondante de la biosphère. Si de nombreuses données sont disponibles sur l’abondance et la dynamique virale dans les écosystèmes aquatiques tempérés, peu d’études ont été menées sur ces aspects dans les milieux extrêmes, dont les sources hydrothermales. Dans l’étude présentée dans ce manuscrit, les communautés procaryotiques et virales des sources hydrothermales des Terres australes et antarctiques françaises (TAAF) ont été ...