Molecular Biology of Gene in Extremophiles  

Dr ELMERICH Claudine / Dr GRIBALDO Simonetta / LACERDA Nuno / Dr LUCAS-STAAT Soizick / MAURA Damien / PINA Mery / Dr PRANGISHVILI David / Dr REDDER Peter / Dr SEZONOV Guennadi / TERRAS Chloé

  Annual Report

The division of the cellular living word into three domains, Archaea, Bacteria and Eukarya, has opened a new area in the exploration of the microbial world and in evolutionary studies. The major research axis in our unit is the study of viruses from hyperthermophilic archaea. D. Prangishvili has discovered and/or described several new families of viruses infecting Sulfolobus or Acidianus species: the Rudiviridae, the Lipothrixviridae, the Globuloviridae, the Ampullaviridae (Figure 1), and the Bicaudaviridae (which exhibits a unique developmental cycle of the virion).

These viruses exhibit unique morphotypes, raising new questions about the origin of viruses and their relationships with cellular organisms. We are now looking for new viruses in extremely hot environments (Kamtchatka, Clermont-Ferrand and Iceland hot springs) and we are studying DNA replication and transcription in our previously described viruses. We started studies on viral diversity in high salt environments in Senegal dominated by extremely halophilic archaea.

Most genes of hyperthermophilic viruses encode unknown proteins. We have initiated, in collaboration with external laboratories, two structural genomic projects to identify their structures and possible functions.

Our interest for microbial viruses led us to incubate a new project on phage therapy led by L. Debarbieux. Several new viruses infecting pathogenic bacteria have been isolated and a mouse model has been successfully tested to help establishing rational approaches for phage therapy.

In parallel to these experimental studies, S. Gribaldo and P. Forterre supervise in silico research projects to tackle fundamental evolutionary questions. We have set up a new method based on comparative genomics to detect integrated viruses in archaeal and bacterial genomes. Our results suggest that integration of viral and plasmids are even more frequent than currently thought. Furthermore, our analysis indicates that most ORFans in archaeal and acterial genomes are of viral origin. We also performed several phylogenomic analyses to understand the origin and evolution of major molecular mechanisms in the three domains of life. Our phylogenies of the translation and transcription apparatus help to set up a robust phylogeny of the archaeal domain and led to the proposal of a new archaeal phylum.

Keywords: Archaea, Viruses, Phage therapy, Comparative genomics, Replication, Transcription, Molecular phylogeny, Evolution


The ampullavirus ABVAcidianus Bottle-shaped Virus.


Forterre P. 2006. Three RNA cells for ribosomal lineages and three DNA viruses to replicate their genomes: A hypothesis for the origin of cellular domain. Proc. Natl. Acad. Sci. USA, vol. 103 (no. 10) : 3669 -3674.

Häring M., Vestergaard G., Brügger K., Rachel R., Garrett R.A. and Prangishvili D. 2005.Independent virus development outside a host. Nature 436:1101-1102.

Kessler A., Sezonov G., Guijarro J.I., Desnoues N., Rose T., Delepierre M., Bell S. and Prangishvili D. 2006. A novel archaeal regulatory protein, Sta1, activates transcription from viral promoters. Nucleic Acids Research 34:4837-4845.

Prangishvili D., Forterre P. and Garrett R.A. 2006. Viruses of the Archaea: a unifying view. Nature Reviews Microbiology 4:837-848.

Prangishvili, D., Vestergaard G., Häring M., Aramayo R., Basta T., Rachel R. and Garrett, R. A. 2006. Structural and genomic properties of the hyperthermophilic archaeal virus ATV with an extracellular stage of the reproductive cycle. Journal of Molecular Biology 359:1203-1216.

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Activity Reports 2007 - Institut Pasteur
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