Anaerobic Bacteria and Archaea in Cold Ecosystems

Permanently cold environments are very common on Earth. For example, the average temperature in bottom waters of the largest fraction of the world oceans is 5°C or less and including terrestrial habitats about 80% of the Earth's biosphere is to be found in permanently cold habitats (Russell 1990). In addition to being cold, many of these environments are also oxygen-free, thus supporting exclusively facultative or obligately anaerobic microbial life. Anoxic permanently cold environments are very diverse and include the marine sea floor (Rysgaard et al. 1998; Sagemann et al. 1998; Bowman et al. 2003; Vandieken et al. 2006b), microbial mats (Mueller et al. 2005; Fernández-Valiente et al. 2007), endolithic communities in sandstones (Friedmann 1982), permafrost soils of the Arctic and Antarctic regions (Kobabe et al. 2004; Gilichinsky et al. 2005; Steven et al. 2007), and chilled food (Broda et al. 2000a, 2000b, 2002). It has also been demonstrated that these habitats harbor extensive microbial communities, including many microorganisms that are phylogenetically affiliated with obligately anaerobic organisms in culture (Ravenschlag et al. 1999; Purdy et al. 2003; Ganzert et al. 2007). Despite their ecological and economical significance very little is known about anaerobic bacteria and archaea that live in these environments and the mechanisms by which they thrive or survive under in situ conditions.