Bifidobacterium is a genus of gram-positive, nonmotile, often branched anaerobic bacteria. They are ubiquitous inhabitants of the gastrointestinal tract though strains have been isolated from the vagina and mouth of mammals, including humans. Bifidobacteria are one of the major genera of bacteria that make up the gastrointestinal tract microbiota in mammals. Some bifidobacteria are used as probiotics.
Bifidobacterium
Some of the Bifidobacterium animalis bacteria found in a sample of Activia yogurt: The numbered ticks on the scale are 10 micrometres apart.
Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host interactions and unwanted side effects in rare cases. There is some evidence that probiotics are beneficial for some conditions, but there is little evidence for many of the health benefits claimed for them.
A bottle of Yakult, a probiotic drink containing Lactobacillus paracasei
Élie Metchnikoff first suggested the possibility of colonizing the gut with beneficial bacteria in the early 20th century.
