Antimicrobial activity and resistance to heavy metals and antibiotics of heterotrophic bacteria isolated from sediment and soil samples collected from two Antarctic islands1

In this study, 24 Antarctic bacteria, isolated from sediment and soil samples from Deception and Galindez Islands, were characterized for their antimicrobial activity and response to 13 antibiotics and seven heavy metals. Multiple antibiotic resistance was observed for 67% of sediment isolates and 92% of soil isolates, suggesting medium anthropogenic impact in these Antarctic regions. The results revealed a varying response of the Antarctic bacteria to the tested heavy metals. All isolates showed multiple metal resistance towards two to six heavy metals, with minimum inhibitory concentrations ranging from 1.0 mM to 23.2 mM. The majority of the strains in both groups were resistant to lead, nickel, copper and zinc. Plasmids were detected in 21% of isolates. A consortium of highly metal-resistant bacteria could be developed with potential application for biological treatment of wastewaters. Strains that are highly sensitive to cadmium would be promising for developing biosensors to detect this highly toxic heavy metal in environmental samples. All Antarctic bacteria were found to inhibit the growth of one to all eight of the tested indicator bacteria, and 87% inhibited the growth of one to all four of the yeast indicator cultures. Promising psychrotolerant strains were detected as a valuable source of new antimicrobial compounds.