Today, in the cheese production, we use selected microbial cultures which contain lactic acid bacteria, propionic acid bacteria, strains of Brevibacterium linens and blue mold strains. Culture of lactic acid bacteria has the primary role in the production of all cheeses, and the role of other cultures comes to light only in the ripening phase of the cheese, under conditions optimal for a particular type, with constant control and proper nourishment of cheese. Depending on the cheese type, mesophilic or thermophilic cultures of lactic acid bacteria are used. Lactic acid bacteria can also be divided according to the shape of the bacteria into spherical and rounded forms. Propionic acid bacteria are used in the production of hard cheeses at high temperatures and are added in combination with thermophilic lactic acid bacteria. Propionic acid bacteria cultures are responsible for developing distinctive flavors and smells as well as developing "cheese holes". Bacteria Brevibacterium linens grows on the surface of the cheese, for example Romadura, where it forms a red smear. It lives in the alkaline environment and is a strong proteolite. B.linens also participates in the process of secondary cheese ripening. Mold cultures are also used while manufacturing blue cheeses, alongside the mesophilic lactic acid bacteria cultures and sometimes the thermophilic cultures, such as in the manufacture of Gorgonzola (S. thermophilus and Lb. bulgaricus), Camembert and Brie. Cheeses containing precious molds can be divided into two groups. The first group consists of white cheeses, and the other group consists of blue cheeses.