High antagonistic activity and antibiotic resistance of flavobacteria of polar microbial freshwater mats on King George Island in maritime Antarctica.

This is the first study to demonstrate a relationship between antagonistic interactions with antibiotic resistance within flavobacterial strains, a component of polar-region microbial mats. These strains were derived from ephemeral freshwater reservoirs, i.e. ponds and streams of the periglacial zone of Ecology Glacier (King George Island, maritime Antarctica). The study demonstrated the strains' surprisingly high phylogenetic diversity, with 20 species among 50 isolates. Flavobacteria were characterised by different patterns of antagonism and sensitivity to antimicrobials. 29 strains produced substances inhibiting the growth of other isolates, with 21 strains being sensitive to such compounds; 34 strains were multidrug-resistant (MDR). The antibiotic resistance index (ARI) demonstrated a significantly higher proportion of MDR strains and ARI ≥ 0.2 in stream mats (87%) as compared to the strains derived from pond mats (55%). A strong correlation was observed between the strains' antagonistic potential and antibiotic resistance. An important role in these phenomena is accomplished by the "super bacteria" strains that effectively accumulate numerous traits associated with antagonistic potential and can be involved in the potential transfer of these traits. The results of the study demonstrate that there are individual patterns of antagonistic interactions and antibiotic resistance among the biotic components of mats.