Développement d'un outil génétique pour Brevibacterium aurantiacum et analyse génomique comparative de souches laitières

Authors: Levesque, Sébastien
Advisor: Moineau, Sylvain
Abstract: Brevibacterium aurantiacum is an orange-pigmented actinobacterium that confers key organoleptic properties to washed-rind cheeses during surface ripening. To date, only two complete and assembled genomes of B. aurantiacum are available and there is currently no genetic tool available to study this industrially relevant species. The acquisition of fundamental knowledge on the gene repertoire of this species and their functions is essential to understand its evolution and its role in cheese ripening In this study, 12 plasmids and 4 synthetic vectors were used to transform 6 B. aurantiacum dairy strains and one B. linens strain in the aim of adapting CRISPR-Cas9 tool for these bacterial species. Different electrocompetent cell preparation and electroporation methods were tested to transform various Brevibacterium strains, but no transformants were recovered with all the experiments. Therefore, it seems that Brevibacterium strains are recalcitrant to genetic transformation We sequenced six additional genomes of Brevibacterium and performed phylogenetic and pan-genome analyses. Our phylogenetic analysis revealed that cheese isolates, previously identified as B. linens, belong to the B. aurantiacum species, making this species a key player in cheese production. B. aurantiacum genomes are composed of 2612 core genes with an open pan-genome reaching now 6259 genes. Horizontal gene transfers (HGT) between cheese actinobacteria were observed in all B. aurantiacum genomes. HGT regions involved in iron acquisition were found in five B. aurantiacum genomes, which suggests cooperative evolution between smear-ripened cheese actinobacteria. Our comparative genomic analysis provides novel insights into the evolution and the adaptation of B. aurantiacum to the cheese ecosystem.
Document Type: Mémoire de maîtrise
Issue Date: 2018
Open Access Date: 18 April 2019
Permalink: http://hdl.handle.net/20.500.11794/34492
Grantor: Université Laval
Collection:Thèses et mémoires

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