Detection of a Putative TetR-Like Gene Related to BCG Growth in Cholesterol Using a -Transposon Mutagenesis System.

transposition is a powerful genetic tool for identifying mycobacterial virulence genes and studying virulence factors in relation to the host. Transposon shuttle mutagenesis is a method for constructing stable insertions in the genome of different microorganisms including mycobacteria. Using an IS derivative, we have constructed the Tn, a transposon containing a promoterless green fluorescent protein () gene. This transposon was able to transpose randomly in BCG. Bacteria with a single copy of the gene per chromosome from an BCG::Tngfp library were analyzed and cells exhibiting high levels of fluorescence were detected by flow cytometry. Application of this approach allowed for the selection of a mutant, BCG_2177c::Tn (BCG-Tn), on the basis of high level of long-standing fluorescence at stationary phase. This BCG-Tn mutant showed some particular phenotypic features compared to the wild type strain, mainly during stationary phase, when cholesterol was used as a sole carbon source, thus supporting the relationships of the targeted gene with the regulation of cholesterol metabolism in this bacteria. This approach showed that Tn is a potentially useful tool for studying the involvement of the targeted loci in metabolic pathways of mycobacteria.