Carbohydrate stress-related response in Bifidobacterium pseudolongum subsp. globosum

Abstract

Bifidobacteria are indigenous components of hu- man and animal gastrointestinal microbiota, and their health-promoting benefits have long been recognized. Of the 36 currently described species of the Bifidobacterium genus, 8 contain plasmids, most of which are cryptic. It is possible that plasmid presence is related very closely to environmental change, so in conditions of stress this pres- ence could be specifically controlled. For plasmid-positive Bifidobacterium pseudolongum subsp. globosum RU809/1, the influence of the type and concentration of the carbohy- drate source is evident in the dramatic pVS809 curing effect when growth is conducted in the presence of 0.15% (w/v) glucose, lactose, maltose, melibiose, raffinose or starch. The effect is linked to carbohydrate starvation, not to carbohy- drate abundance, and is independent of biomass growth. Plasmid curing was achieved after one or two consecutive transfers, also in cells grown on medium containing 0.15% arabinose, fructose, galactose and sucrose, but not mannose, ribose or xylose. Knowing plasmid behavior in stressful conditions, like carbon source availability, has allowed an early insight into carbohydrate starvation as a curing agent for bifidobacteria. Furthermore, knowledge of plasmid be- havior in stressful conditions could be important not only in genetics and ecology but also in food-grade and pharma- ceutical applications for the development of cloning and expression vector systems for bifidobacteria.