^BLactobacillus bulgaricus.^b Coloured scanning electron micrograph of the bacteria ^ILactobacillus ^Ibulgaricus^i (pink), taken from live yoghurt. They are rod-shaped, Gram-positive bacteria. They grow in acid media and produce lactic acid from the fermentation of carbohydrates. Lactic acid produced by the fermentation of milk is responsible for the preservation and flavour of cheese, yoghurt and other fermented milk products. The bacteria are found in fermenting animal and plant products and in the alimentary tract and vagina of humans and other animals, where they inhibit the growth of more pathogenic bacteria. Magnification: x3,150 at 5x7cm size. x10,500 at 10x8"