Metabolic and growth characteristics of novel diverse microbes isolated from deep cores collected at the Next Generation Ecosystem Experiment (NGEE)-Arctic site in Barrow, Alaska

The Arctic is characterized by vast amounts of carbon stored in permafrost and is an important focal point for the study of climate change as increasing temperature may accelerate microbially mediated release of Carbon stored in permafrost into the atmosphere as CO2 and CH4. Yet surprisingly, very little is known about the vulnerability of permafrost and response of microorganisms in the permafrost to their changing environment. This deficiency is largely due to the difficulty in study of largely uncultivated and unknown permafrost microbes. As part of the U.S. Department of Energy (DOE) Next Generation Ecosystem Experiment (NGEE) in the Arctic, we collected permafrost cores in an effort to isolate resident microbes. The cores were from the Barrow Environmental Observatory (BEO), located at the northern most location on the Alaskan Arctic Coastal Plain near Barrow, AK, and up to 3m in depth. In this location, permafrost starts from 0.5m in depth and is characterized by variable water content and higher pH than surface soils. Enrichments for heterotrophic bacteria were initiated at 4°C and 1°C in the dark in several different media types, under both aerobic and anaerobic conditions. Positive enrichments were identified by an increase in optical density and cell counts after incubation period ranging from two to four weeks. After serial transfers into fresh media, individual colonies were obtained on agar surface. Several strains were isolated that include Firmicutes such as Bacillus, Clostridium, Sporosarcina, and Paenibacillus species and Iron-reducing Betaproteobacteria such as Rhodoferax species. In addition, methanogenic enrichments continue to grow and produce methane gas at 2°C. In this study, we present the characterization, carbon substrate utilization, pH, temperature and osmotic tolerance, as well as the effect of increasing climate change parameters on the growth rate and respiratory gas production from these permafrost isolates.