Ice glaciers as reservoirs of xenobiotic degrading strains with potential application in soil bioremediation

Glaciers are extreme environments that recover and preserve for long times many inorganic and organic materials, including bacteria, moulds, algae, pollen, insects, plants, rock debris and chemical pollutants. In particular, in glaciers close to ski resorts, it is possible to find different pollutants at levels significantly higher than background common levels. Two drilling sampling campaigns were conducted in September 2009 and October 2010 in the Glacier Madaccio in the Orthes mountain group, at 3125 m a.s.l., close to summer ski resorts. The first aim of the campaign was to assess the microbial diversity of these environments: culture dependent and culture independent methods were thus applied to analyse the global diversity and isolate culturable strains. Chemical analyses were also conducted, identifying contamination by PAHs and PCBs at ppb levels. A microtiter method was then applied to screen isolates for their ability to degrade phenathrene and other organic xenobiotics. On the isolates positive to this screening test, further assessments were carried out at different temperatures. Twelve strains were isolated, belonging to different genera such as Pseudomonas, Rhodopseudomonas, Arthrobacter, Polaromonas, Methylobacterium and Janthinobacterium. Some of those are indeed degrading phenanthrene and other pollutants, in some cases even more efficiently at 4°C compared to 20 and 30°C. This paves they way for their possible application, in pure or mixed cultures, in soil bioremediation at cold conditions, for example in cryic soils contaminated by oil spillages.