Antibiotic Resistance Genes from Mat and Planktonic Microbiomes of Antarctic Lake Fryxell and Lake Bonney, and a Mat-forming Culture of Rhodoferax antarcticus

The Antarctic Taylor Valley Lakes Fryxell and Bonney harbor oligotrophic microbial communities that are separated geographically from other aquatic systems. Their microbiomes include planktonic as well as lift-off mat communities that float to the underside of the perennial ice cover and eventually emerge at the surface. We investigated the antibiotic resistance genes (ARGs) from metagenomes of lift-off mats emerging from ice, from filtered water samples of Lake Fryxell, and from filtered water samples of Lake Bonney. ARG sequence markers were designed by ShortBRED-Identify using the Comprehensive Antibiotic Resistance Database (CARD). The overall proportion of ARG hits in the metagenomes was found to be similar to that found in temperate-zone rural water bodies with moderate human inputs (0.0002-0.0007%). The specific ARGs found showed distinct distributions for the two lakes, and for mat versus planktonic sources. An enrichment culture of Rhodoferax antarcticus from a Lake Fryxell mat sample showed a mat-forming phenotype not previously reported for this species. Its genome showed no ARGs associated with Betaproteobacteria, but had ARGs consistent with a Pseudomonas minor component. The Antarctic lake mats and water showed specific ARGs distinctive to the mat and water sources, but overall ARG levels were similar to those of temperate water bodies.