Lactobacillus acidophilus is one of the most well-known and extensively studied species of probiotic bacteria. Here's a breakdown of key information about it:
A Gram-positive, rod-shaped (bacillus) bacterium.
Naturally lactic acid-producing (ferments sugars into lactic acid).
Part of the normal commensal microbiota in the human and animal gastrointestinal tract (primarily the small intestine), mouth, and vagina.
Classified as a probiotic: "live microorganisms which when administered in adequate amounts confer a health benefit on the host" (WHO/FAO definition).
Where it's Found Naturally & in Products:
Human Body: Gut (especially small intestine), mouth, vagina.
Fermented Foods: Most famously in yogurt (look for "live and active cultures"), but also in kefir, sauerkraut, kimchi, miso, tempeh, and some cheeses.
Dietary Supplements: Available widely in capsules, tablets, powders, and liquids, often combined with other probiotic strains. Strain specificity matters for claimed benefits.