Colonization and probiotic function of Bifidobacterium longum

[Display omitted] •B. longum abundance is associated with the delivery mode, feeding type, age, etc.•Carbohydrate utilization partly determinates the colonization of B. longum.•Selection pressures caused by the host influence the colonization of B. longum.•Cell surface proteins and secretory substances of B. longum play a role in health.•Factors that acids and bile salts resistance, adhesion ability influence colonization of B. longum in the intestine.•Cell surface proteins and secretory substances of B. longum have important effects on host health. Bifidobacterium longum, a common member of the gut microbiota throughout the human lifespan, has been widely reported to play a role in host health and disease. However, colonization of B. longum in the host intestine is the basis for its probiotic function. The colonization and abundance of B. longum in the human gut varies significantly among individuals, which have been suggested to be associated with the delivery mode, feeding type, age, geography, and physiological status. Moreover, the colonization of the species results from selective pressures imposed by the host, such as available carbon resources, acids, bile salts and Immune environment. The advancements of 'omics techniques' have facilitated the genetic and functional studies of B. longum. They have revealed a molecular basis for metabolizing different carbohydrates and resisting selective pressures imposed by the host, which likely contribute to the colonization and persistence of B. longum in the colon.