This diploma thesis is focused on microorganisms, which form microbiota of milk, including pathogenic microorganisms and possible natural substances which inhibit undesirable microbiota. The thesis is divided into theoretical and practical part. The theoretical part describes microbiology of raw milk and contaminating microbiota. Furthermore, the work deals with the microbiology of heat-treated milk, where the methods of heat treatment are described and milk bacterial cultures, which are used in the production of dairy products. The last part describes the pathogenic microbiota of milk causing foodborne diseases and possible measures to combat undesirable microorganisms. In the practical part, the inhibitory effect of substances of plant or...