Endemic and cosmopolitan bacteria from microbial mats in maritime Antarctica: Antagonism and antibiotic resistance

Abstract

This is the first study to demonstrate a relationship between antagonistic interactions and antibiotic resistance among bacterial species with different biogeographical ranges, found in freshwater microbial mats in Antarctica. The isolated strains originated from ephemeral freshwater bodies of the periglacial zone of the Ecology Glacier (King George Island, maritime Antarctica). Among the 47 isolates, species with different biogeographical ranges were identified: 22 strains belonging to 12 endemic (EN) bacterial species, and 25 strains belonging to 16 cosmopolitan (CO) species. All the cosmopolitan strains and 82% of the endemic strains produced antimicrobial compounds. The cosmopolitan strains were twice as active antagonistically in relation to the endemic strains, and a reverse relationship was noted in the sensitivity of the cosmopolitan species to antagonism. The endemic strains were twice as sensitive to antagonism as compared to the cosmopolitan strains. The bacterial strains derived from microbial mats exhibited broad resistance to all the antibiotics applied. Most isolates (94%) were resistant to at least one of the 25 used antibiotics. The CO and EN species were characterised by a different spectrum of antibiotic resistance. Among others, strains from the COgroup exhibited greater, statistically significant resistance to antibiotics inhibiting protein synthesis (p<0.05). More than half of all the isolates were multidrug-resistant (MDR) strains. Statistically, cosmopolitan MDR strains showed broader resistance (p>0.05). A relationship was demonstrated between the antagonistic potential and sensitivity to antagonistic interactions, and antibiotic resistance in cosmopolitan bacterial species. The individual patterns of antagonistic interactions and antibiotic resistance observed among isolates showed a clear relationship with the biogeographical ranges of individual species. Strains of cosmopolitan species characterised by broad antagonism and resistance to antibiotics were identified. These specific “biological contaminants” may be the source and propagator of new traits in endemic populations of polar mat microbiocenoses.