AbstractWe studied dynamic changes in anthropogenic bacterial communities at a summer-operated Czech research base (theMendelResearch Station) in the Antarctic during 2012 and 2013. We observed an increase in total numbers of detected bacteria between the beginning and the end of each stay in the Antarctic. In the first series of samples, bacteria ofBacillussp. predominated. Surprisingly, high numbers of Gram-positive cocci and coliforms were found (including opportunistic human pathogens), although the conditions for bacterial life were unfavourable (Antarctic winter). In the second series of samples, coliforms and Gram-positive cocci predominated. Dangerous human pathogens were also detected.Yersinia enterocoliticawas identified as serotype O:9. Antibiotic susceptibility testing showed medium-to-high resistance rates to ampicillin, cefalotin, cefuroxime, amoxicillin-clavulanate and gentamicin in Enterobacteriaceae. 16S rRNA sequencing showed high rates of accordance between nucleotide sequences among the tested strains. Three conclusions were drawn: (1) Number of anthropogenic bacteria were able to survive the harsh conditions of the Antarctic winter (inside and outside the polar station). Under certain circumstances (e.g.impaired immunity), the surviving bacteria might pose a health risk to the participants of future expeditions or to other visitors to the base. (2) The bacteria released into the outer environment might have impacts on local ecosystems. (3) New characteristics (e.g.resistance to antibiotics) may be introduced into local bacterial communities.