EN
The paper was aimed at synthetic presentation of results of own studies into the occurrence and function of Aeromonas hydrophila bacteria in aquatic environments with different degrees of contamination. This species belongs to the class of gamma proteobacteria, the order of Aeromonadales and the family of Aeromonadaceae. Results of own long-term studies confirm the thesis on the ubiquity of A. hydrophila bacteria, whose occurrence reflects the trophy and contamination degree of aquatic environments, especially. Despite the relatively low numbers of these microorganisms, in environmental studies their percentage in the total bacteria count reached up to 30% in water samples and even up to 41.5% in fish samples. Taking all this into account, it seems justified to consider A. hydrophila bacteria as a potential indicator in the anthropogenic contamination of waters.