Protective bacterium in normal vagina is :

Ans. is b i.e. Lactobacillus "Doderlein's bacillus" is a large gram-positive rod shaped organism which grows anaerobically on acid media. The Doderlein's bacillus appears in the vagina 3 to 4 days after bih and disappears after 1 - 14 days. It appears again at pubey and disappears after menopause. It probably comes from intestine and its presence is dependent on estrogen. its function is to conve the glycogen present in the vaginal mucosa into lactic acid so that the vaginal pH is maintained towards acidic side. This acid pH prevents growth of the other pathogenic organisms.