A bile-inducible membrane protein mediates bifidobacterial bile resistance.
Bottom Line: The high level of similarity to bile efflux pumps from other bifidobacteria suggests a significant and general role for Bbr_0838 in bile tolerance.Insertional inactivation of Bbr_0838 in B. breve UCC2003 resulted in a strain, UCC2003:838(800) , which exhibited reduced survival upon cholate exposure as compared with the parent strain, a phenotype that was reversed when a functional, plasmid-encoded Bbr_0838 gene was introduced into UCC2003:838(800) .This study represents the first in-depth analysis of a bile-inducible locus in bifidobacteria, identifying a key gene relevant for bifidobacterial bile tolerance.
Affiliation: Departamento de Microbiología y Bioquímica de Productos Lácteos, Instituto de Productos Lácteos de Asturias, Villaviciosa, Asturias, Spain.Show MeSH
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Mentions: The bile‐inducibility of Bbr_0838 (Fig. 1C) coupled with its homology to reported bile efflux systems in other bifidobacteria (> 98% identity to betA from B. longum NCC2705) suggests a role for Bbr_0838 in supporting B. breve UCC2003 bile tolerance. In support of this theory, our previous work demonstrated the ability of Bbr_0838 to enhance bile survival of recombinant Lactococcus lactis clones expressing the Bbr_0838 (Ruiz et al., 2011). In order to further investigate the physiological role of Bbr_0838 in B. breve, two Bbr_0838 insertion mutant strains designated UCC2003::838800 and UCC2003::8381000, were constructed (see Experimental procedures). Southern hybridization using EcoRI‐digested genomic DNA and pORI19‐8381000‐tetW as a probe unequivocally confirmed that the disruptions of Bbr_0838 were the result of site‐specific homologous recombination events (Fig. 2). Moreover, the stability of the integrated plasmid in UCC2003::838800 and UCC2003::8381000 strains was analysed following 50 generations in the absence of the selective antibiotic, showing that at least 96% of the cells retained the insertion.
Affiliation: Departamento de Microbiología y Bioquímica de Productos Lácteos, Instituto de Productos Lácteos de Asturias, Villaviciosa, Asturias, Spain.