Lactobacilli and bifidobacteria

Autochthonous L. acidophilus and bifidobacteria strains in humans may remain stable lifelong. With lactobacilli particularly, some succession of strains may be caused by transient species derived from food or from the oral cavity.[2] Multiple combinations of lactobacilli and bifidobacteria abound in the intestinal tracts of breast-feeding infants, and persist in substantially lower logarithmic quantities in adults to promote gastrointestinal health. They are greatly influenced by food and alcohol consumption habits, antibiotic use, and host physiology.[3] L. acidophilus, and only a few strains of bifidobacteria, grow well in the vagina and urethra.[4] While multiple strains of commensal bacteria coexist in large quantities in the ileum and large bowel, lactic acid bacteria use lactose as their main source of carbon to produce energy. L. acidophilus is a rich source of lactase, the enzyme needed to digest milk sugar. Fructo-oligosaccharides (FOS) are naturally occurring carbohydrates that cannot be digested or absorbed by humans. They support the growth of bifidobacteria in the lower colon, where the bifidobacteria thrive on vegetable fiber, and complex sugars, that are included in garlic, onion, artichoke, asparagus, and chicory root.[5] By matching host carbohydrate synthesis with the capacity of these commensal bacteria to produce glycosidases, oligosaccharide outer chains in mammalian glycans may help prime colonization of the developing intestine.