Skip to Main content Skip to Navigation
Theses

Biais de codons et régulation de la traduction chez les bactéries et leurs phages

Abstract : This thesis contains some works about the codon bias and its role in bacteria and phages, particularly about regulation of translation and chromosome organization in bacteria. After an introduction describing i) translation processes in prokaryotes, and ii) bases of classification and information theories, a new clustering algorithm designed to classify a set of genes according to their codon usage is presented. Its application to the genomes of E.coli and B. subtilis puts forward multiple phenomena. Their genomes are respectively composed of 4 and 5 groups of genes sharing the same codon usage. The genes of the same group tend to have similar function, and are organized in coherent domains 10 to 15 genes long on the chromosome. This non-trivial organisation could be used to regulate the translation speed of genes depending on their similarity with their genetic context.
In the second part, the codon bias and tRNA content of phages are analyzed, relative to those of their hosts. Statistical tests show that tRNA content in phage genomes is not random, but biased towards the tRNA cognate to the frequent codons in the phage genome. A master equation model shows that this tRNA distribution could be the result of two processes: random acquisition of tRNA among those of the host, and preferential loss of tRNA cognate to codons used less in the phage genome than inside its host. Such a selection could be adaptative by allowing the phage to keep only the tRNAs insufficiently represented inside its host. Eventually, more tRNAs are observed among lytic phages than among temperate ones, which lead to the hypothesis that the selective pressure acting on translation is more important to them.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00200730
Contributor : Marc Bailly-Bechet <>
Submitted on : Friday, December 21, 2007 - 1:16:20 PM
Last modification on : Monday, January 13, 2020 - 5:08:08 PM
Long-term archiving on: : Thursday, September 27, 2012 - 12:15:41 PM

Identifiers

  • HAL Id : tel-00200730, version 1

Collections

Citation

Marc Bailly-Bechet. Biais de codons et régulation de la traduction chez les bactéries et leurs phages. Biophysique [physics.bio-ph]. Université Paris-Diderot - Paris VII, 2007. Français. ⟨tel-00200730⟩

Share

Metrics

Record views

542

Files downloads

4489