title: Impact of the deletion of the six mce operons in Mycobacterium smegmatis.
abstract: The Mycobacterium smegmatis genome contains six operons designated mce (mammalian cell entry). These operons, which encode membrane and exported proteins, are highly conserved in pathogenic and non-pathogenic mycobacteria. Although the function of the Mce protein family has not yet been established in Mycobacterium smegmatis, the requirement of the mce4 operon for cholesterol utilization and uptake by Mycobacterium tuberculosis has recently been demonstrated. In this study, we report the construction of an M. smegmatis knock-out mutant deficient in the expression of all six mce operons. The consequences of these mutations were studied by analyzing physiological parameters and phenotypic traits. Differences in colony morphology, biofilm formation and aggregation in liquid cultures were observed, indicating that mce operons of M. smegmatis are implicated in the maintenance of the surface properties of the cell. Importantly, the mutant strain showed reduced cholesterol uptake when compared to the parental strain. Further cholesterol uptake studies using single mce mutant strains showed that the mutation of operon mce4 was reponsible for the cholesterol uptake failure detected in the sextuple mce mutant. This finding demonstrates that mce4operon is involved in cholesterol transport in M. smegmatis.
authors.affiliation: Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria, Castelar, Buenos Aires, Argentina.
authors.forename: Laura I
authors.initials: LI
authors.lastname: Klepp
authors.forename: Marina A
authors.initials: MA
authors.lastname: Forrellad
authors.forename: Ana V
authors.initials: AV
authors.lastname: Osella
authors.forename: Federico C
authors.initials: FC
authors.lastname: Blanco
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Stella
authors.forename: María Verónica
authors.initials: MV
authors.lastname: Bianco
authors.forename: María de la Paz
authors.initials: Mde L
authors.lastname: Santangelo
authors.forename: Cristopher
authors.initials: C
authors.lastname: Sassetti
authors.forename: Mary
authors.initials: M
authors.lastname: Jackson
authors.forename: Angel A
authors.initials: AA
authors.lastname: Cataldi
authors.forename: Fabiana
authors.initials: F
authors.lastname: Bigi
authors.forename: Héctor R
authors.initials: HR
authors.lastname: Morbidoni
mesh_terms: D002784:Cholesterol / Q000493:pharmacokinetics*; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism; D009876:Operon / Q000235:genetics*; D017384:Sequence Deletion; D014774:Virulence / Q000235:genetics*
chemical_list: D002784:Cholesterol