Illustrate typical fields for each milk product showing all observed morphologies of bacteria. Yogurt is produced by a mixed culture of two types of bacteria. The illustrations at the top of the page are micrographs I took of a Gram stain of yogurt. The purple rods are Lactobacillus , the purple spheres are Streptococcus . The pink globs are casein, milk protein.
Bacteria are less numerous than in buttermilk.