Bifidobacteria are common commensals of the mammalian gastrointestinal tract. Previous studies have suggested that a bifidobacterial myosin cross reactive antigen (MCRA) protein plays a role in bacterial stress tolerance, while this protein has also been linked to the biosynthesis of conjugated linoleic acid (CLA) in bifidobacteria. In order to increase our understanding on the role of MCRA in bifidobacteria we created and analyzed an insertion mutant of the MCRA-encoding gene ofB. breveNCFB 2258. Our results demonstrate that the MCRA protein ofB. breveNCFB 2258 does not appear to play a role in CLA production, yet is an oleate hydratase, which contributes to bifidobacterial solvent stress protection.