Heterogeneity of Microbial Communities in Soils From the Antarctic Peninsula Region

Abstract

Ice-free areas represent less than 1% of the Antarctic surface. However, climate change models predict a significant increase in temperatures in the coming decades, triggering a relevant reduction of the ice-covered surface. Microorganisms, adapted to the extreme and fluctuating conditions, are the dominant biota. In this article we analyze the diversity and composition of soil bacterial communities in 52 soil samples on three scales: (i) fine scale, where we compare the differences in the microbial community between top-stratum soils (0–2 cm) and deeper-stratum soils (5–10 cm) at the same sampling point; (ii) medium scale, in which we compare the composition of the microbial community of top-stratum soils from different sampling points within the same sampling location; and (iii) coarse scale, where we compare communities between comparable ecosystems located hundreds of kilometers apart along the Antarctic Peninsula. The results suggest that in ice-free soils exposed for longer periods of time (millennia) microbial communities are significantly different along the soil profiles. However, in recently (decades) deglaciated soils the communities are not different along the soil profile. Furthermore, the microbial communities found in soils at the different sampling locations show a high degree of heterogeneity, with a relevant proportion of unique amplicon sequence variants (ASV) that appeared mainly in low abundance, and only at a single sampling location. The Core90 community, defined as the ASVs shared by 90% of the soils from the 4 sampling locations, was composed of 26 ASVs, representing a small percentage of the total sequences. Nevertheless, the taxonomic composition of the Core80 (ASVs shared by 80% of sampling points per location) of the different sampling locations, was very similar, as they were mostly defined by 20 common taxa, representing up to 75.7% of the sequences of the Core80 communities, suggesting a greater homogeneity of soil bacterial taxa among distant locations.

Growth Forms and Functional Guilds Distribution of Soil Fungi in Coastal Versus Inland Sites of Victoria Land, Antarctica

“…Among these, soil granulometry, strongly influencing nutrient availability in such limiting conditions, showed a prominent effect. Preferences for different sized soil particles (clay, silt, and sand) have already been reported for different bacterial phyla, strongly contributing to the spatial heterogeneity and bacterial diversity found [71,72]. In fact, the almost always greater percentage of sand in all samples results in a lower ability to retain nutrient, cations, and water, and even small changes in pH or soil water content can affect the community composition.…”

Insight Into Ecology, Metabolic Potential, and the Taxonomic Composition of Bacterial Communities in the Periodic Water Pond on King George Island (Antarctica)

“…Tychonema is a genus of filamentous Cyanobacteria, that is unable to fix nitrogen. It was identified in e.g., microbiome in Perennially Ice-Covered Lake Untersee in East-Antarctic (Weisleitner et al, 2019), cryoconite hole in Untersee Oasis (Weisleitner et al, 2020), Biscoe and Elephant Point in Soils From the Antarctic Peninsula Region (Almela et al, 2021), where it represented the most abundant Cyanobacteria. Luteolibacter represents the phylum Verrumicrobia -a group of microorganisms found in a wide range of habitats, most of which are eutrophic (Schlesner et al, 2006), Persicitalea, Petrimonas, and Flavobacterium represent Bacteroidetes which play an important role in the degradation of organic compounds, including insoluble polymeric substrates (Thomas et al, 2011), whereas Firmicutes represented by Tissierella are involved in the degradation of biopolymers (Mahowald et al, 2009;Flint et al, 2012), and Psychrobacter represents Proteobacteria, which frequent occurrence is thought to reflect their adaptability to environmental changes, including extreme environments (Edwards et al, 2014).…”

Geomicrobiological Heterogeneity of Lithic Habitats in the Extreme Environment of Antarctic Nunataks: A Potential Early Mars Analog

“…Thus, they represent unique, mostly pristine environments that can be considered as ideal natural laboratories for polar studies. Although nunataks can be found in continental and peninsular (including archipelagos close to it) regions of Antarctica, they have received little attention from a biological perspective, with only a few studies analysing nunatak microbiology in the last decades [e.g., (Brinkmann et al, 2007;Yergeau et al, 2009), both studying Coal Nunatak in Alexander Island, 72°03' S 68°31' W, and (Almela et al, 2021), not focused but including samples from Clark Nunatak, Byers Peninsula, Livingston Island].…”

“…Within lithic environments, soils are characterized by having an enormous heterogeneity in geochemical parameters that leads to niche partitioning, including variations in vertical profiles in the scale of a few centimeters (Cary et al, 2010;Bottos et al, 2014;Bockheim et al, 2015;Almela et al, 2021). Consequently, these ecosystems usually contain high microbial diversity -discoveries of novel lineages are frequent -with reduced space for the different populations to develop, and a higher influence of stochastic events on the inhabiting communities (Bottos et al, 2014;Feeser et al, 2018).…”

“…Consequently, these ecosystems usually contain high microbial diversity -discoveries of novel lineages are frequent -with reduced space for the different populations to develop, and a higher influence of stochastic events on the inhabiting communities (Bottos et al, 2014;Feeser et al, 2018). To date, microbial communities from exposed Antarctic soils have received moderate attention, despite their importance to ecosystem function (Cary et al, 2010;Bottos et al, 2014;Niederberger et al, 2015;Feeser et al, 2018;Lambrechts et al, 2019;Garrido-Benavent et al, 2020;Almela et al, 2021). These microbial communities are mainly composed of psychrotolerant organisms, with maximum growth rates at temperatures below 20°C.…”