A genus of gram-positive, acid-resistant bacteria in the Lactobacillaceae family. We know of lactobacillus because of its use in making yoghourt and the conventional wisdom of taking it in one form or another after antibiotic therapy, but it is an integral part of the colon and mouth flora, and is the critical acidifying agent in vaginal flora. There is a growing body of rather ignored data showing the value of regular consumption of a lactobacillus-containing food in immunosuppression, slow virus, and candidiasis conditions.