Microbial diversity and functional capacity in polar soils

Abstract

Global change is disproportionately affecting cold environments (polar and high elevation regions), with potentially negative impacts on microbial diversity and functional processes. In most cold environments the combination of low temperatures, and physical stressors, such as katabatic wind episodes and limited water availability result in biotic systems, which are in trophic terms very simple and primarily driven by microbial communities. Metagenomic approaches have provided key insights on microbial communities in these systems and how they may adapt to stressors and contribute towards mediating crucial biogeochemical cycles. Here we review, the current knowledge regarding edaphic-based microbial diversity and functional processes in Antarctica, and the Artic. Such insights are crucial and help to establish a baseline for understanding the impact of climate change on Polar Regions. AddressCentre for Microbial Ecology and Genomics, Department of Genetics, University of Pretoria, Pretoria 0028, South Africa Corresponding author: Cowan, Don Arthur (don.cowan@up.ac.za) IntroductionThe Congress of Parties (COP) 21 meeting in Paris (November 2015) highlighted the urgency of global climate change, and the critical need to reduce global average temperatures through curbing greenhouse gas emissions [1]. Nowhere are the effects of global change more apparent than in cold environments (polar and alpine regions), which are subject to accelerated rates of warming compared to other ecosystems [2 ,3]. Climatic models have predicted that temperatures in high latitude regions of the Northern Hemisphere are likely to increase by between 0.38C and 4.88C before the end of the twenty first century [4]. There is also evidence that regions in the Southern Hemisphere have experienced the fastest warming globally, with average increases of as much as 2.48C in the last fifty years [5].A major consequence of climate change in cold environments is the thawing of submerged and surface ice, which alters the hydrology of the systems and may have adverse effects on microbial processes [6 ]. In cold environments, microorganisms (bacteria, archaea and fungi) are major constituents of the total biomass, and are estimated to mediate the cycling of key biogeochemical elements such as nitrogen and carbon, with potentially important implications for the productivity of these systems [7]. Although the precise contribution of microbial processes to global change processes are not well known, there are efforts to incorporate biological processes into Earth systems models with the realization that they may be crucial in regulating soil organic matter (SOM) [8 ]. For instance, permafrost (defined as ground which remains frozen for at least two years) in cold environments stores roughly 1600 Pg of carbon, which if released would significantly contribute towards increasing global CO 2 levels [9]. The current contribution of microbial communities to constraining carbon losses in permafrost and the influence on CO 2 levels remains virtually unknown. In ...

Prokaryotic community shifts during soil formation on sands in the tundra zone

“…The prokaryotic communities of all samples were dominated by phyla Acidobacteria and Proteobacteria , which was previously observed for other soils of the tundra zone [42,49].…”

“…All OTUs belonging to Thaumarchaeota were uncultivable Archaea and were previously observed in other terrestrial environments. Among all Archaeal phyla, Thaumarchaeota are known to be predominate in Arctic and Antarctic soils [49]. We suggest that the relative abundance of Thaumarchaeota , but not their absolute number, decreased from unfixed sands to mature soils because archaeal gene abundances in the unfixed sands were a hundred-fold lower than in the mature soils.…”

Phages actively challenge niche communities in the Antarctic soils

“…Antarctic terrestrial environments including open soils, permafrost and the surface and interior of rocks, are typically oligotrophic and dominated by psychrophilic and psychrotolerant microbial communities (1–4). It has been suggested that the extreme abiotic pressures of the environment such as temperature, desiccation stress and UV radiation are dominant drivers of both the diversity and function of cold-adapted bacterial communities in terrestrial polar deserts (5–7).…”

Nutrient parsimony shapes diversity and functionality in hyper-oligotrophic Antarctic soils

“…Just over half of the ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) ( n =79) and phosphoribulokinase ( prk B) ( n =48) genes identified were assigned to Cyanobacteria (Fig. 3), which are the dominant photosynthetic carbon fixers in most desert soils [10, 48, 49], and were relatively common here. The remaining 83 gene assignments belonged to potentially chemosynthetic guilds, including Actinobacteria, Bacteroidetes, Proteobacteria and Planctomycetes (Table S6), which may together serve as important primary producers in soil, and is consistent with the known importance of alternative primary producers in Antarctic soils [50].…”

“…In Antarctic soils, the extremely low levels of C and N, consistent with definitions for very low Redfield ratio values substantially constrain microbial growth and activity [7]. Nevertheless, the limited abundance of higher eukaryotes in continental Antarctica soil habitats [8, 9] ensures that the microbial communities are the dominant suppliers of ecosystem services [10]. The extent to which very low Redfield ratios may limit productivity in these systems has not been explored.…”