Recherche Avancée

Thèse soutenue

FR  |  
EN
Auteur / Autrice : Nicolas Soler
Direction : Patrick Forterre
Type : Thèse de doctorat
Discipline(s) : Sciences biologiques
Date : Soutenance en 2007
Etablissement(s) : Paris 11
Partenaire(s) de recherche : autre partenaire : Université de Paris-Sud. Faculté des sciences d'Orsay (Essonne)

Mots clés

FR

Mots clés contrôlés

Virus -- Reproduction (biologie)
Plasmides

Mots clés libres

Archées
Archaea
Hyperthermophiles
Réplication en cercle roulant
Vésicules

Résumé

FR

The study of plasmids and viruses has been critical for increasing the knowledge about molecular mechanisms of life. During the last two decades, very different types of viruses have been discovered in hyperthermophilic Archaea from terrestrial hot springs. In order to investigate whether such viral diversity is also found in marine hyperthermophilic Archaea, I have screened and characterized new extra-chromosomal elements from the hyperthermophilic order Thermococcales. I found four new plasmids. The smallest (pTN1) replicates via the rolling circle mechanism, and I have studied the biochemical activities of the two proteins it encodes. Two other plasmids (pTN2 and pP12-1, c. A. 12 kb) belong to a new family characterized by the presence of a gene encoding a putative superfamily I helicase. Some genes of these plasmids also have homologues in Pyrococcus abyssi virus 1 (PAV1) genome. A fourth plasmid (21,6 kb) revealed many homologous genes within integrated elements found in different genomes of euryarchaeotes. I did not find new viruses. However, I have observed that many Thermococcales strains produce vesicles that are sometimes associated with genomic DNA from the host. This work allowed the discovery of new plasmid families in Thermococcales, revealing evolutive relationships with viruses. In other respects, vesicles (sometimes associated with DNA) might protect extra-cellular DNA at high temperatures ; they might be involved in horizontal gene transfers.