Bacterial Communities Associated with Deschampsia antarctica in Chronically Diesel-Contaminated Soils: Candidate Taxa...

More than six decades of human activity in Antarctica resulted in chronic diesel contamination of soils surrounding research stations. Phytoremediation assisted by the native vascular plant Deschampsia antarctica is one of the few remediation strategies compatible with the Antarctic Treaty System guidelines. Securing suitable root-associated microbial resources is central to this approach. This work characterized the bacterial communities of the rhizosphere and root endosphere of D. antarctica growing in a chronically diesel-contaminated soil at Carlini Station and in three pristine sites on 25 de Mayo (King George) Island, South Shetland Islands, combining culture-independent 16S rRNA gene amplicon sequencing, PICRUSt2 functional prediction and culture-dependent bacterial strain isolation. The rhizospheric microbial community was consistently more diverse than those inhabiting the endosphere and was more strongly structured by site and associated soil physicochemical variables, with the contaminated site showing the most distinct composition, whereas the endosphere remained comparatively stable and host-selected. The community associated with the chronically contaminated site showed pronounced compositional differences and higher predicted abundances of hydrocarbon-degradation pathways in the rhizosphere. Polaromonas, Rhodococcus, Mycobacterium and Devosia were repeatedly associated with the community from the contaminated site across taxonomic, biomarker and predicted functional analyses. Members of the genera Polaromonas, Rhodococcus and Devosia were also recovered in culture. These taxa represent suitable candidates for the future development of microbe-assisted phytoremediation strategies in Antarctica.