Bacterial and Archaeal Diversity in Permafrost

Abstract

Microorganisms in permafrost survive in an extreme environment characterized by constant subzero temperatures, low water and nutrient availability, and prolonged exposure to background radiation. Despite the harsh conditions, considerable abun- dance and diversity of microorganisms inhabit permafrost. Pioneering studies focusing on permafrost microbiology simply attempted to determine if permafrost harbored viable microorganisms. For example, microorganisms cultured from Canadian (James and Sutherland 1942), Alaskan (Boyd and Boyd 1964) and Antarctic (Cameron and Morelli 1974) permafrost samples were generally poorly character- ized, and the studies were hampered by an inability to demonstrate that drilling and sample handling were performed aseptically. Recent developments using fluid-less drilling (Gilichinsky et al. 1989; Khlebnikova et al. 1990; Juck et al. 2005), tracer microorganisms (Christner et al. 2005; Juck et al. 2005), nucleic acid stains (Christner et al. 2005) and fluorescent microspheres as microbial surrogates (Juck et al. 2005) have greatly improved our ability to recover intact permafrost samples and to monitor exogenous microbiological contamination of pristine permafrost samples. Permafrost also contains various other geomorphological structures including mas- sive ground ice, cryopegs, and ice wedges (Steven et al. 2006) that harbor microbial populations. The description of the abundance, diversity, activity and distribution of microorganisms in permafrost and associated environments will be fundamental to our understanding of how microorganisms survive in permafrost, and how they will respond to future climatic warming and permafrost thawing. Lastly, permafrost micro- organisms and microbial ecosystems are considered significant terrestrial analogs for similar organisms that may inhabit permafrost environments that exist beyond the Earth, especially in light of the recent evidence of massive amounts of shallow ground ice near the surface of Mars (Gilichinsky 2002a; Gilichinsky et al. 2007).