Abstract
Tolerance of gut commensals to bile salt exposure is an important feature for their survival in and colonization of the intestinal environment. A transcriptomic approach was employed to study the response of Bifidobacterium breve UCC2003 to bile, allowing the identification of a number of bile-induced genes with a range of predicted functions. The potential roles of a selection of these bile-inducible genes in bile protection were analyzed following heterologous expression in Lactococcus lactis. Genes encoding three transport systems belonging to the major facilitator superfamily (MFS), Bbr_0838, Bbr_0832, and Bbr_1756, and three ABC-type transporters, Bbr_0406-0407, Bbr_1804-1805, and Bbr_1826-1827, were thus investigated and shown to provide enhanced resistance and survival to bile exposure. This work significantly improves our understanding as to how bifidobacteria respond to and survive bile exposure.