Bacteriocines are small peptides with anti-bacterial properties. They are produced both by Gram-positive and Gram-negative bacteria. Until now, a few hundred bacteriocines were described. Classification of bacteriocines undergoes continuous alterations, as new developments regarding their structure, amino acid sequence and recognised mechanism of their action are available. Some of bacteriocins (lantibiotics) contain atypical amino acids, such as lantionine (Lan), methyllantionine (MeLan), dehydroalanine (Dha), dehydrobutyrine (Dhb), or D-alanine (D-Ala). The best recognized bacteriocines are produced by lactic acid bacteria, including nisine produced by strains of Lactococcus lactis. These bacteriocines have been recognized to be fully safe for humans. At present, nisine is used in food industry, as a preserving agent. Other lactic acid bacteria bacteriocines and probiotic preparations provide an alternative for antibiotics, and are used in food and in animal feed.