6533b834fe1ef96bd129d25a

RESEARCH PRODUCT

Identification des gènes impliqués lors de l'établissement de Lactobacillus casei dans l'intestin et caractérisation de l'opéron LSEI_0219-0221

subject

description

In bacteria which are in direct contact with their environment, genes transcription and proteins synthesis are efficiently regulated at each change of environmental parameters to allow cell survival. For intestinal commensal bacteria, these regulations must also allow symbiotic interactions and colonization whose molecular mechanisms, so far little known, are probably related, among others, to the bacteria surface (molecules exposed and secreted…). Lactobacillus casei, a commensal bacterium, has about 330 predicted genes involved in the composition and functionality of the cell surface. To have a global view of the whole genes involved in the establishment of L. casei in the gut, a reverse genetics approach was performed. For that, a library of L. casei random labeled-mutants by Signature-Tagged Mutagenesis was generated then annotated and reassembled thanks to the sequencing of transposon insertion sites. Mutants were screened for their ability to establish themselves in the rabbit ligated ileal loop and quantified by qPCR. Among the 47 genes identified as involved in the in vivo establishment, three genes in an operon encoding a two-component system and a penicillin-binding protein were characterized. These three genes are involved in the cell surface modulation and particularly in the regulation of peptidoglycan hydrolases which are required for the bacteria protection in the intestinal environment.