Lactobacillus bacteria. Coloured scanning electron micrograph (SEM) of Lactobacillus sp. bacteria (grey/blue). Unidentified spherical cocci (green) are also seen. Both types of bacteria are an important constituent of the oral and intestinal flora, fermenting glucose to lactic acid. For this reason they are used extensively in the food industry, for the preparation of milk products and sauerkraut among other foods. These bacteria are a cause of tooth decay. If too much sugar is consumed in the diet the excess lactic acid produced by them can damage tooth enamel. Magnification: x12,000 at 6x7cm size.