Yogurt is prepared with the addition of culture of bacteria to milk. The bacteria put away sugar in the milk, and ooze lactic acid that helps curdle the milk. Yogurt has live bacteria or active cultures, along with organisms like Streptococcus thermophilus, Lacto-bacillus acidophilus and Lactobacilluys bulgaricus, called pro-biotics packed with health benefits that shield the body from dangerous bacteria.