Lactobacillus helveticusis a lactic-acid producing, rod-shaped bacterium of the genusLactobacillus. It is most commonly used in the production ofAmerican Swiss cheeseandEmmental cheese, but is also sometimes used in making other styles of cheese, such asCheddar,Parmesan,Romano,provolone, andmozzarella. The primary function ofL. helveticusculture is to prevent bitterness and produce nutty flavors in the final cheese. InEmmental cheeseproduction,L. helveticusis used in conjunction with aPropionibacterculture, which is responsible for developing the holes (known as "eyes") through production of carbon dioxide gas.