Bacterial community composition in relation to bedrock type and macrobiota in soils from the Sør Rondane Mountains, East Antarctica

Abstract

Antarctic soils are known to be oligotrophic and of having low buffering capacities. It is expected that this is particularly the case for inland high-altitude regions. We hypothesized that the bedrock type and the presence of macrobiota in these soils enforce a high selective pressure on their bacterial communities. To test this, we analyzed the bacterial community structure in 52 soil samples from the western Sør Rondane Mountains (Dronning Maud Land, East Antarctica), using the Illumina MiSeq platform in combination with ARISA fingerprinting. The samples were taken along broad environmental gradients in an area covering nearly 1000 km(2) Ordination and variation partitioning analyses revealed that the total organic carbon content was the most significant variable in structuring the bacterial communities, followed by pH, electric conductivity, bedrock type and the moisture content, while spatial distance was of relatively minor importance. Acidobacteria (Chloracidobacteria) and Actinobacteria (Actinomycetales) dominated gneiss derived mineral soil samples, while Proteobacteria (Sphingomonadaceae), Cyanobacteria, Armatimonadetes and candidate division FBP-dominated soil samples with a high total organic carbon content that were mainly situated on granite derived bedrock.

Soil microbial biomass, activity and community composition along altitudinal gradients in the High Arctic (Billefjorden, Svalbard)

“…To date, only a few studies assessing altitudinal trends in soil microbial properties have been conducted in the Scandinavian Arctic (Löffler et al, 2008;Männistö et al, 2007). Research on spatial variation in microbial community composition and activity in polar regions was conducted mainly within a narrow elevation range (Oberbauer et al, 2007;Trevors et al, 2010;Björk et al, 2008;Chu et al, 2010;Van Horn et al, 2013;Blaud et al, 2015;Tytgat et al, 2016) or was focused on initial soil development following glacier retreat (Bekku et al, 2004;Yoshitake et al, 2007;Schütte et al, 2010). The majority of studies on elevational patterns in microbial community structure (MCS) and activity have been carried out in mountain regions of the lower latitudes from the tropics to the temperate zones.…”

Diversity of Phototrophic Genes Suggests Multiple Bacteria May Be Able to Exploit Sunlight in Exposed Soils from the Sør Rondane Mountains, East Antarctica

“…Roseobacter has been found to be important in sulfur cycling in aquatic environments (González and Moran, 1997; Buchan et al, 2005; Wagner-Döbler and Biebl, 2006). However, the absence of Roseobacter 16S rRNA sequences in this study area (Tytgat et al, 2016) and in terrestrial Antarctic systems in general (based on metagenome data available in NCBI, MG-RAST, Wilke et al, 2016 and IMG/M Markowitz et al, 2014) suggests the presence of other microorganisms, containing PufM highly similar to that of Roseobacter , in our samples. The remainder of the PufM diversity in our samples, although recovered in small relative numbers, also mainly related to aquatic photoheterotrophic taxa.…”

“…Given the distance to the ocean (~200 km) and the extent of the surrounding ice cover, bacteria in exposed soils of the Sør Rondane Mountains, East Antarctica, are faced with very low availability of organic matter (Osanai et al, 2013; Zazovskaya et al, 2015; Tytgat et al, 2016) and might thus be expected to use alternative energy sources such as sunlight. During an initial survey using libraries of ~100 clones, phototrophy genes were investigated for the first time in this terrestrial Antarctic location (Tahon et al, 2016).…”

“…Actinorhodopsin, a similar light-driven proton pump, was originally retrieved from aquatic Actinobacteria (Sharma et al, 2008) and little is known about its presence in terrestrial environments. Because Illumina data of partial 16S rRNA genes previously showed the samples investigated here to contain diverse Actinobacteria (6.26–23.48% of reads and 20.73–34.60% of OTUs, Tytgat et al, 2016) [Tahon et al, under review], we used several primer sets (Table 2) to amplify actinorhodopsin genes from our samples. While our attempts failed, this does not necessarily imply that these systems are absent in the terrestrial Antarctic bacterial communities.…”

“…Although most of the ice-free regions are found in the Antarctic Peninsula and the Transantarctic Mountains, inland mountain ranges, such as the Sør Rondane Mountains (Dronning Maud Land), also represent an important fraction of the exposed surface area (Convey et al, 2008; Cary et al, 2010). The absence of vascular plants in continental Antarctica combined with the extreme environmental conditions have led to depleted soils with low availability of nutrients, especially of organic carbon, and nitrogen, and water (Kennedy, 1993; Cary et al, 2010; Tytgat et al, 2016). As a result, the mainly microscopic life in these areas (Cowan et al, 2014; Tytgat et al, 2014; Obbels et al, 2016) may thus be expected to use alternative energy sources to overcome these limitations.…”