Microbial Communities and Processes in Arctic Permafrost Environments

Abstract

In polar regions huge layers of frozen ground are formed -termed permafrost -which covers more than 25 % of the land mass and significant parts of the coastal sea shelfs. Permafrost habitats are controlled by extreme climate and terrain conditions. Particularly, the seasonal freezing and thawing in the upper active layer of permafrost leads to distinct gradients in temperature and geochemistry. Due to the harsh living conditions, microorganisms in permafrost environments have to survive extremely cold temperatures, freeze-thaw cycles, desiccation and starvation under long-lasting background radiation over geological time scales. Although, permafrost microorganisms remains relatively unexplored, recent findings show that microbial communities in this extreme environment are composed by members of all three domains of life (Archaea, Bacteria, Eukarya), with a total biomass comparable to temperate soil ecosystems. This chapter describes the environmental conditions of permafrost and reviews recent studies on microbial processes and diversity in permafrost affected soils as well as the role and significance of microbial communities on the global biogeochemical cycles. 7.1

The functional potential of high Arctic permafrost revealed by metagenomic sequencing, qPCR and microarray analyses

“…This is in line with previous studies from the Canadian Arctic, where type II methanotrophs were not detected among the active microbial community (Martineau et al, 2010). Type II methanotrophs are regularly isolated and can be dominant in Siberian permafrost (Liebner and Wagner, 2007), but PLFA-SIP showed that the communities that were active at low in situ temperatures were dominated by type I methanotrophs (reviewed by Wagner, 2008).…”

“…The genetic potential of the microorganisms present in permafrost is also likely to determine whether permafrost environments will become net sources or sinks of greenhouse gases following warming. However, the microbiology of permafrost remains relatively unexplored (reviewed in Steven et al 2006Steven et al , 2009Wagner, 2008). The concerns about potential largescale positive feedback loops on global warming make it crucial to gain in-depth knowledge of the microbes inhabiting permafrost environments.…”

“…The biological oxidation of methane by methaneoxidizing bacteria (methanotrophs) was shown to be a major sink for methane in the permafrost habitats (Trotsenko and Khmelenina, 2005). However, most of the previous microbiological studies of permafrost focused on 16S rRNA genes, on a few functional genes, on the measurement of general processes or on the isolation and discovery of new microbial species (reviewed in Steven et al 2006Steven et al , 2009Wagner, 2008). Highly parallelized methods such as next-generation sequencing can target all functional genes present in a given sample at once, providing an in-depth assessment of the genetic potential of the microorganisms of an environment.…”

Diversity of Aerobic Methanotrophic Bacteria in a Permafrost Active Layer Soil of the Lena Delta, Siberia

“…In addition, based on the temperature response of potential methane oxidation rates, it was recently shown that methane oxidizing bacteria are well adapted to the temperature regime in permafrost active layer soils of the Lena Delta [37]. However, our knowledge on MOB from high-latitude environments in terms of diversity and composition remains very poor [56].…”

Methanogenesis in Arctic Permafrost Habitats

“…Intensive physico-chemical processes under extreme conditions take place in the active layer and upper permafrost sediments (Ostroumov 2004). In the deeper permafrost layers, conditions have been stable for long periods of time and microbial processes are limited (Wagner, 2008). Permafrost soils (cryosols) have been developed in the upper zone of the cryolithosphere (active layer and upper permafrost sediments) where the temperatures range from -50°C to +30°C (Yershov 1998).…”