Scanning electron micrograph of Lactobacillus. The anaerobic bacterium Lactobacillus is shown here. As suggested by its name, this genus of bacteria ferments glucose into lactic acid and is widely used in the food industry. Lactobacillus is also a component of the normal human bacterial flora of the urogenital tract where, because of its ability to generate an acidic environment, it prevents the growth of harmful bacteria.

[Power and Syred/Science Photo Library.]