Bacteria from Antarctic environments: diversity and detection of antimicrobial, antiproliferative, and antiparasitic activities

Abstract

Microorganisms dominate most of Antarctic ecosystems and play a crucial role in their functioning. They are called extremophilic microorganisms with unique and versatile metabolic properties with possible biotechnological applications in several areas. The aim of the present study was to identify psychrotolerant microorganisms from Antarctic continent samples and to screen them for antimicrobial effects. Phylogenetic analyses revealed that most isolates were closely related to recognized species, including those recovered previously from Antarctica, which belonged to the major phyla Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria (classes Alpha, Beta, and Gammaproteobacteria). A total of 326 bacterial isolates, distributed in 39 different genera, were recovered and identified based on sequencing of the 16S rRNA gene. The main representative genera were Arthrobacter, Psychrobacter, Pseudoalteromonas, and Rhodococcus. Antimicrobial screening revealed fifteen isolates capable of inhibiting growth of at least one of the indicator strains: Escherichia coli, Micrococcus luteus, Staphylococcus aureus, Bacillus subtilis, and Candida albicans. One psychrotolerant bacterium, Pseudomonas sp. isolate 99, showed a broad antimicrobial range, in addition to antiproliferative and antiparasitic activity. Overall, the small number of antibiotic-producing isolates obtained and the weakness of their inhibition halos corroborated previous findings suggesting that cold-loving bacteria from Antarctica are not as good as their relatives from mesophilic environments for antimicrobial prospecting. Nonetheless, antiproliferative and antiparasitic results observed are promising and suggest that there is an untapped wealth in Antarctic environments for bioprospecting compounds with pharmaceutical potential application.