environmental samples
The soil core (Eur3, Steven et al., 2008) was collected in May 2003 near Eureka, in the Canadian High Arctic (80*0.029 N, 85*50.367 W). Core samples were kept frozen during transport and stored at -20*C until further analysis. Soil subsamples for molecular analyses were collected under sterile conditions from the center of the core. Control of microbiological contamination during coring and subsampling was monitored as previously described (Juck et al., 2005). The active layer and 2 m deep permafrost soils were used in the present study.