Lactobacillus acidophilus and L. casei cultured from a commercial probiotic food gel sold in health food stores claiming to contain 5 billion live bacterial cells. Lactobacilli produce lactocins as a kind of bacteriocins which the bacteria use against other bacteria. SEM. Image width: 8.5 micrometers. Magnification: 11,765x if the image is printed 10 cm wide.