Acid and Bile Resistance and Stress

Members of the genus Bifidobacterium are Gram-positive bacteria which are commonly found in the gastrointestinal tract (GIT) of mammals, including humans. Because of their probiotic properties they are frequently incorporated as functional ingredients in food products. From probiotic production to storage and GIT delivery, bifidobacteria encounter a plethora of stresses, which negatively affect their viability and consequently their probiotic activity. In order to cope with these environmental challenges they need to protect themselves through stress-induced adaptative responses. A range of publications have investigated stress response in bifidobacteria and, from these published results, it has emerged that these bacteria employ an interacting network to manage their response to various environmental stresses. This chapter summarizes the current knowledge on the molecular mechanisms used by bifidobacteria to tolerate the deleterious action of acid, heat and bile on their physiology.