DESPITE THE TRANSIENT NATURE OF THIS ORGANISM IN THE DIGESTIVE TRACT, THE CHANGES THIS LACTIC ACID BACILLUS PRODUCES SHIFT THE ENVIRONMENT IN SUPPORT OF A COMPLEX GASTROINTESTINAL FLORA.THE MECHANISM OF ACTION IS PRESUMED TO BE A RESULT OF IMPROVING GASTROINTESTINAL ECOLOGY BY REPLENISHING THE QUANTITY OF DESIRABLE OBLIGATE MICROORGANISMS AND ANTAGONIZING PATHOGENIC MICROBES. TWO ISOMERIC FORMS OF LACTIC ACID CAN BE PRODUCED BY LACTIC ACID-PRODUCING BACTERIA -DEXTROROTATORY (D (-)) LACTIC ACID AND LEVOROTATORY (L(-T-)) LACTIC ACID. L. SPOROGENES IS ASSUMED TO PRODUCE BACTERIOCINS AND SHORT CHAIN FATTY ACIDS.