<p>The antimicrobial activity of probiotics is thought to be accounted for, in large part, by their ability to colonize the colon and reinforce the barrier function of the intestinal mucosa. In addition, some probiotics have been found to secrete antimicrobial substances known as bacteriocins. It reduced gastrointestinal pH through stimulation of lactic acid producing bacteria and provides a direct antagonistic action on GI pathogen. Lactobacillus acidophilus, Lactobacillus bulgaricus and Bifidobaterium, have also demonstrated antioxidative ability. Mechanisms include chelation of metal ions (iron, copper), scavenging of reactive oxygen species and reducing activity.</p>