Abstract:
Climate change has the potential to induce dramatic shifts in the biodiversity and functionality of soil
microorganisms in polar hyperarid ecosystems. In these depauperate soil ecosystems, microbial communities
are vital as they represent the dominant input sources of essential nutrients. However, the
effects of changing climate on extreme edaphic environments, such as the McMurdo Dry Valleys of
Antarctica, remain poorly understood. To better understand these effects, we constructed soil microcosms
and simulated temperature shifts over a 40-day period. Soil physicochemical analysis revealed low
levels of key nutrients, with mean organic carbon and nitrogen contents of <0.1% and 11.55 ppm,
respectively. We also applied 16S rRNA gene amplicon sequencing to determine taxonomic composition
and enzyme assays to measure in situ activity. Our data showed a prevalence of ubiquitous soil taxa
(Actinobacteria, Chloroflexi and Deinococcus-Thermus), with a smaller proportion of autotrophic phyla
(i.e. Cyanobacteria). None of the major phyla showed relative abundance changes in response to temperature.
We found very low extracellular enzyme activity levels across all samples and observed no
significant differences among temperature treatments. Functional predictions (using PICRUSt) revealed
the putative presence of key genes implicated in the cycling of carbon (ppc, rbcl) and nitrogen (nifH, nirK),
in stress response and in DNA repair throughout all treatments. Overall, our results suggest that shortterm
temperature fluctuations do not alter microbial biodiversity and functionality in Antarctic soils. This
study provides the first evidence that microbial communities within this edaphic extreme environment
may be functionally redundant, adapted and resistant to short term climatic perturbations.
