The presumption of the south polar continent, Antarctic, being pristine have posed a serious questioning in response to the recent climatic changes and disintegration of ice shelves into the ocean. Antarctica, claimed to be in the pre-antibiotic era, is uncertain due to the emergence of heavy metal resistant bacteria conferring antibiotic resistance on self-transmissible plasmids via horizontal gene transfer (HGT). Human impaction has not left this arid continent and the ecological distribution of psychrotrophs have elicited various defence mechanism in response to the myriad of stresses. Evolution of buttress microbes has introduced bacterial recalcitrance towards antimicrobial and heavy metal activity. In this study, Antarctic soil bacteria were sampled at two distinct locations- Gourlay Peninsula and Berntsen Point. Selected heavy metal (Lead, Copper and Zinc) resistant bacterial strains with minimum inhibitory concentration (MIC) ranging from 3.0 mM to 20.0 mM were isolated. Evidently, Pb and Zn resistant strains tolerated the highest concentration at 20.0 mM whereas Cu resistant strains at 13.0 mM. The most adapted bacterial strain from each heavy metal was tested with 13 different commercially available antibiotics. Prominent results were observed in isolates resistant to sulphonamides and aminoglycosides classes with a moderate incidence of co-resistance. The growth curve, biochemical characteristics, and cell surface hydrophobicity properties were attained and notable differences in the utilization of oxidase, catalase and bacterial cell adhesion by bacteria were observed post the heavy metal treatment. Promising strains will be subjected to microarray analysis for identification and gene expression profiling. These preliminary results reiterate that the Antarctic may not be exempt from the by-products of anthropogenic influences.
Keywords: Antibiotic resistance, heavy metal resistance, psychrotrophic bacteria. Antarctic soil.