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Evolution d'une famille d'éléments intégratifs potentiellement conjugatifs et/ou mobilisables de Streptococcus thermophilus

Abstract : In this work, four types of genomic islands related to ICESt1 were characterized. They are integrated in the same location as ICESt1 in seven other strains of S. thermophilus. One of these elements, ICESt3, is probably an ICE. Two other types of elements, CIME19258 and CIME302, are flanked by site-specific attachment sites closely related to attL and attR of ICESt1 and ICESt3 whereas DCIME308 only possesses a putative attR site. They have arisen from ICEs by deletion of there conjugation and recombination modules. Comparisons between ICE and CIME (cis-mobilizable element) from Streptococcus thermophilus and functional analysis, using plasmids harbouring the entire or a part of the recombination module of ICESt1, suggest that these elements evolve by a novel model.). The circular form of an ICE, acquired by conjugation, integrates by site-specific in the attR site of the CIME, leading to the structure attL-CIME-attI'-ICE-attR'. Then partial or entire deletion of the attI site would stabilise the composite element. The whole structure would be a novel ICE and could be excised by recombination between attL and attR and transferred to a new host bacterium. This suggests that ICEs have acquired novel modules by a new mechanism : accretion / mobilization of CIMEs. In conclusion, ICE and probably CIME would be important in the evolution of bacterial genomes by horizontal gene transfer and contribute to the acquisition of new functions by these genomes.
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https://hal.univ-lorraine.fr/tel-01746802
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Submitted on : Thursday, March 29, 2018 - 10:45:07 AM
Last modification on : Friday, April 2, 2021 - 3:31:30 AM

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  • HAL Id : tel-01746802, version 1

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Guillaume Pavlovic. Evolution d'une famille d'éléments intégratifs potentiellement conjugatifs et/ou mobilisables de Streptococcus thermophilus. Génétique. Université Henri Poincaré - Nancy 1, 2004. Français. ⟨NNT : 2004NAN10009⟩. ⟨tel-01746802⟩

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