Atmospheric trace gases support primary production in Antarctic desert surface soil

Cultivation-independent surveys have shown that the desert soils of Antarctica harbour surprisingly rich microbial communities. Given that phototroph abundance varies across these Antarctic soils, an enduring question is what supports life in those communities with low photosynthetic capacity. Here we provide evidence that atmospheric trace gases are the primary energy sources of two Antarctic surface soil communities. We reconstructed 23 draft genomes from metagenomic reads, including genomes from the candidate bacterial phyla WPS-2 and AD3. The dominant community members encoded and expressed high-affinity hydrogenases, carbon monoxide dehydrogenases, and a RuBisCO lineage known to support chemosynthetic carbon fixation. Soil microcosms aerobically scavenged atmospheric H2 and CO at rates sufficient to sustain their theoretical maintenance energy and mediated substantial levels of chemosynthetic but not photosynthetic CO2 fixation. We propose that atmospheric H2, CO2 and CO provide dependable sources of energy and carbon to support these communities, which suggests that atmospheric energy sources can provide an alternative basis for ecosystem function to solar or geological energy sources. Although more extensive sampling is required to verify whether this process is widespread in terrestrial Antarctica and other oligotrophic habitats, our results provide new understanding of the minimal nutritional requirements for life and open the possibility that atmospheric gases support life on other planets.

Three surface soils were initially sampled from Robinson Ridge (Wilkes Land) 11 (Extended Data Fig. 1). Physicochemical analysis showed that the soils were low in total organic carbon (0.13 -0.24%), nitrogen (0.012 -0.023%), and moisture (4.0 -5.6%) content (Supplementary Table 1). We used shotgun DNA sequencing to produce a 264-MB metagenome from these soils, comprising 208,233 predicted genes (Supplementary Table 2) and 451 predicted 16S/18S rRNA operational taxonomic units (OTUs) (Supplementary Table 3). The communities were dominated by Actinobacteria, Chloroflexi, Proteobacteria, Acidobacteria, and two candidate phyla, AD3 and WPS-2 (Fig. 1a). Identified phototrophs were limited to Cyanobacteria, with an average relative abundance of 0.28% (Fig. 1a). Consistent with other studies 5,11,14 , the low photosynthetic capacity and organic carbon content of Robinson Ridge soils contrasts with the inferred bacterial diversity, suggesting that alternative energy sources support these communities. To gain a deeper understanding of ecosystem function, we applied differential coverage binning 15 , which has been used to construct genomes of uncultured inhabitants of diverse environments 15-18 . We constructed 23 draft genomes from the Robinson Ridge metagenome, including two WPS-2 and three AD3 genomes ( Fig. 1b; Supplementary Table 4). These candidate phyla affiliate with the Terrabacteria superphylum 16 and are sister lineages to Chloroflexi and Armatimonadetes 19 (Extended Data Fig. 2).
Collectively, the metagenome data suggest that Antarctic surface soil microbial communities have the capacity to scavenge H 2 , CO 2 and CO from the atmosphere for use as energy and carbon sources. We confirmed this theory by detecting both the expression and activity of the enzymes catalysing these processes in Robinson Ridge soils. Reverse transcription (RT)-PCR confirmed the expression of the genes encoding type IE RuBisCO (rbcL1E), high-affinity hydro genase (hhyL), and carbon monoxide dehydrogenases (coxL) (Extended Data Fig. 7). Gas chromatography experiments showed that the soil communities aerobically oxidized atmospheric H 2 and CO (threshold of 190 parts per billion by volume (p.p.b.v.) H 2 and 20 p.p.b.v. CO; rate of 3.49 nmol atmospheric H 2 per hour per gram dry weight and 0.42 nmol atmospheric CO per hour per gram dry weight) ( Fig. 3a; Extended Data Fig. 6b; Supplementary Table 10), with H 2 oxidation also measurable at − 12 °C (Extended Data Fig. 5b). However, we did not observe atmospheric methane oxidation, despite recovering the genome of a putative alpha proteobacterial methanotroph. We next measured the capacity of the soils to fix carbon by tracing assimilation of 14 C-labelled CO 2 . Although basal levels of CO 2 fixation were variable (Extended Data Fig. 4c, d), the addition of H 2 stimulated CO 2 fixation by an average of twofold (Fig. 3b). By contrast, light stimulation had no consistent effect (Fig. 3b).
To ensure that the use of H 2 , CO 2 and CO from the atmosphere as energy and carbon sources was not an isolated phenomenon, we sampled another Antarctic site: Adams Flat (Princess Elizabeth Land) (Extended Data Fig. 1). We collected three soils (Supplementary Table 1) with low organic carbon content and high Actinobacteria-low Cyanobacteria communities (Extended Data Fig. 8). Enzymes responsible for trace gas scavenging were expressed and active in these soils ( Fig. 3a; Extended Data Figs 6b, 7; Supplementary Table 10), and H 2 supplementation stimulated carbon fixation by an average of eightfold (P = 0.0039) (Fig. 3b). In further support of the theory that trace gas scavenging operates in a range of Antarctic desert sites, analysis of public metagenomes revealed that hhyL, coxL, and rbcL1E genes are relatively abundant in the McMurdo Dry Valleys region (Extended Data Fig. 9).
On the basis of these findings, we propose that the two Antarctic sites sampled harbour largely dormant microbial communities that conserve energy by oxidation of atmospheric trace gases (Fig. 4). Biochemical studies showed that soils oxidize atmospheric H 2 and CO at rates that are theoretically sufficient to sustain the energy needs of their microbial communities; assuming 1.4 × 10 14 cells per C-mol of biomass (the amount of biomass that contains 1 mol carbon) and a maintenance energy of 1.68 kJ per C-mol biomass per hour at 10 °C 22,26 , the rates of atmospheric H 2 and CO oxidation observed can support 5.5 × 10 7 bacteria per gram of Robinson Ridge soil and 8.0 × 10 7 bacteria per gram of Adams Flat soil (Supplementary Table 10  showing the relative abundance of genes encoding key enzymes involved in carbon fixation and energy conservation. The relative abundance was calculated on the basis of the presence or absence of functional genes within the sequenced genomes from three biologically independent soil samples, and is presented relative to the total number of 16S rRNA gene sequences in the total microbial community.  Moreover, we propose that the primary producers in these communities are bacteria from the phyla Actinobacteria, AD3, and WPS-2 that generate biomass by consuming atmospheric H 2 , CO 2 and CO. Of the draft genomes harbouring group 1h [NiFe]-hydrogenase genes, 55% also contained type IE RuBisCO genes (Fig. 2a, b; Supplementary Table 5), suggesting that some bacteria generate biomass through H 2 -driven CO 2 fixation and others exclusively scavenge H 2 for energy acquisition. The metagenomes suggest that minor community members may also assimilate carbon through the serine pathway (methanotrophs), the 3-hydroxypropionate pathway (ammonia oxidizers), and oxygenic photosynthesis (cyanobacteria). On the basis of the high completeness, minimal contamination, and monophyly of their genomes (Supplementary Table 4), we propose the names Candidatus Eremiobacteraeota (desert bacterial phylum) and Candidatus Dormibacteraeota (dormant bacterial phylum) for candidate phyla WPS-2 and AD3, respectively (Supplementary Information). The type genera Candidatus Eremiobacter and Candidatus Dormibacter are also proposed, based on two of the obtained genome sequences (Ga011786, Ga0137693), as per recent recommendations 29 .
Overall, the microbial community structure of the two Antarctic sites sampled appears to be shaped by selection for bacteria that can persist in these physically extreme, chemically deprived environments. Microbial phototrophs are in low abundance, probably restricted by climatic conditions such as low water and nutrient availability, summer radiation, and winter darkness 1 . Instead, most inhabitants are inferred to be dormant heterotrophic aerobic bacteria that support energy generation and, in some cases, carbon fixation by oxidizing atmospheric trace gases. In oligotrophic Antarctic soils, there is evidence that aeolian processes drive some ecosystem recruitment from less hostile microenvironments (for example, hypolithons) and niche processes sub sequently select for the most functionally specialized microorganisms 30 ; hence, the ability to scavenge trace gases is likely to be an important survival-determining trait that may influence ecosystem succession. Given the concurrent findings from Robinson Ridge, Adams Flat, and the public McMurdo Dry Valley metagenomes, trace gas scavenging may be a general mechanism in Antarctic desert soils. However, broader surveys are now needed to determine the distribution, signi ficance, and role of this process in primary production and ecosystem succession in terrestrial Antarctica, particularly in comparison to phototrophy. Indeed, there are diverse Antarctic sites where photo trophs are dominant, including hypolithons and high-latitude or moist soils 2,4 . It is likely that both phototrophy and gas scavenging co-occur in many Antarctic sites, with the balance of these processes shifting depending on physicochemical factors. It will also be of interest to determine whether trace gas scavenging supports primary production in other oligotrophic ecosystems, for example the hyperarid deserts of Atacama, where Actinobacteria harbouring genes for trace gas scavenging are also dominant 17 . Whereas most ecosystems are driven by solar or geologically derived energy, primary production in these Antarctic desert surface soils appears to be supported by atmospheric trace gases.
Online Content Methods, along with any additional Extended Data display items and Source Data, are available in the online version of the paper; references unique to these sections appear only in the online paper.

Figure 3 | Trace gas oxidation and chemosynthetic carbon fixation in
Antarctic desert soils. a, Gas chromatography measurements of oxidation of atmospheric H 2 (mixing ratio, 0.53 parts per million by volume (p.p.m.v.)) at 10 °C. Values shown for two biologically independent soil samples (mean of technical triplicates). b, Ratios of 14 C-labelled CO 2 assimilation following stimulation with light and/or H 2 . Results shown for two biologically independent Robinson Ridge soils (technical quadruplicate) and three biologically independent Adams Flat soils (technical triplicate). Centre values show medians; boxes show upper and lower quartiles; whiskers show maximum and minimum values. Where sample size was appropriate, statistical significance between paired technical replicates was tested using a two-tailed Wilcoxon signed-rank test. Depicted are members of the five microbial phyla that are predicted to persist by trace gas scavenging. These phyla are variably capable of aerobic respiration of atmospheric H 2 (all phyla) or CO (Actinobacteria, Dormibacteraeota), and chemosynthetic fixation of atmospheric CO 2 (Actinobacteria, Dormibacteraeota, Eremiobacteraeota). It remains to be determined whether atmospheric H 2 oxidation supports NAD(P) + reduction through direct coupling or reverse electron transport, although direct coupling remains thermodynamically favourable at 10 °C (Gibbs free energy of reaction (Δ G) = − 19 kJ mol −1 ). The community is also predicted to respire the small amount of soil organic carbon present as it becomes bioavailable.

MEthODS
No statistical methods were used to predetermine sample size. The experiments were not randomized and the investigators were not blinded to allocation during experiments and outcome assessment. Site description and sample collection. This study focused on two coastal ice-free sites in different regions of eastern Antarctica. Robinson Ridge (− 66.367739, 110.585262), located 10 km south of Casey station in the Windmill Islands coast of Wilkes Land (Extended Data Fig. 1a, b), is part of a pristine polar desert (Extended Data Fig. 1c). Adams Flat (− 68.5502, 78.02106) is located 242 km from Davis station in the Vestfold Hills regions of Princess Elizabeth Land (Extended Data Fig. 1d). Both sites are devoid of vascular plants, but harbour a limited diversity of macrofauna, with tardigrades and nematodes shown to be present in Robinson Ridge 31 . Three surface soil samples (100 g) from the top 10 cm of the soil profile were collected in December 2005 for a previous study on Robinson Ridge 1 and January 2014 for Adams Flat. For both sites, samples were collected along a spatially explicit sampling design comprised of three 300-m-long transects 1,11,32 separated by 2-m distances from each other. As these soils were included in the Australian Antarctic Divisions polar soil archive, samples were sieved down to 63 μ m, aliquoted into 5-25-g subsamples, and stored at − 80 °C until analysis. Physicochemical analysis. Latitude, longitude, slope, aspect and elevation were recorded for each sample taken using ARC GIS software (ESRI). For all soils, detailed physical and chemical data were analysed in-house using standard procedures. Total carbon, nitrogen, and phosphorus, pH, water-holding capacity, grain size, and conductivity were recorded 1 . In addition, extractable ions were meas- ) and X-ray fluorescence elemental analysis was conducted (SiO 2 , TiO 2 , Al 2 O 3 , Fe 2 O 3 , MnO, MgO, CaO, Na 2 O, K 2 O, P 2 O 5 , SO 3 and Cl). The soils were low in total organic carbon content (average 0.17% for Robinson Ridge, 0.09% for Adams Flat) and moisture measured as dry matter fraction (average 4.4% for Robinson Ridge, 0.42% for Adams Flat) (Supplementary Table 1). Community DNA extraction. Total community DNA was extracted from the six soil samples for microbial community profiling and functional metagenomic analysis. In all cases, DNA was extracted from 0.25-0.3 g of each sample in technical triplicate using the FastDNA SPIN Kit for Soil (MP Biomedicals). All DNA extracts were quantified and DNA lysate quality was evaluated using automated ribosomal intergenic spacer analysis (ARISA) as described 32 . Metagenome sequencing, assembly, and binning. For the three Robinson Ridge samples, DNA was extracted in triplicate and used for shotgun meta genome sequencing. Metagenome libraries were prepared using the Nextera DNA Library Preparation Kit (Illumina) and sequenced using three-fifths of an Illumina HiSeq2000 flowcell lane at the Institute for Molecular Biosciences (University of Queensland). The raw reads (2 × 100-bp reads, 14.9 Gb) were processed using Trimmomatic 33 for adaptor removal and quality filtering, and BBMap to merge overlapping reads. The processed reads were combined into a large co-assembly using the de novo assembly algorithm in CLC Genomics Workbench v8 (CLC Bio) and gaps within scaffolds were closed using abyss-sealer 34 . Processed reads from each dataset were mapped onto the co-assembly with BamM. The scaffolds were binned on the basis of differential coverage profiles, k-mer frequencies, and GC content using GroopM 35 and MetaBAT 36 . Population genome bins obtained with GroopM were further refined using the GroopM refine function. The genome completeness and contamination were estimated with CheckM 37 by calculating the presence of lineage-specific single-copy marker genes. The two sets of population genomes from the GroopM and MetaBAT binning were compared using RefineM to identify possible duplicates. Twenty-three genomes (> 50% completeness, < 10% contamination) were selected for further analysis and accounted for 56-65% of total reads obtained from the three soil samples. Of these, 11 genomes were estimated to be more than 90% complete and less than 5% contaminated (Supplementary Table 4). Community analysis. We determined the microbial community structure of the three soil samples from Robinson Ridge and three from Adams Flat. For both sites, the bacterial and archaeal community structure was determined by 16S rRNA gene amplicon sequencing as described previously 32,38 . Community alpha diversity was inferred from the amplicon sequencing data by calculating observed richness, Chao1, and the Shannon index (H′ ) as described 11 . For the Robinson Ridge samples only, bacterial, archaeal, and eukaryote community structure was also determined by retrieving 16S and 18S rRNA genes from the metagenomes. Community composition profiles were generated with CommunityM by mapping reads onto a database of bacterial, archaeal and eukaryotic 16S and 18S rRNA genes (that is, the SILVA 39 and GreenGenes 40 databases clustered at 97% similarity). To infer the phylogeny of WPS-2 and AD3, a genome tree was generated using 38 universal conserved marker genes 41 from 4,624 bacterial and archaeal genomes retrieved from the Integrated Microbial Genomes database (IMG) 42 together with the recovered population genomes. A concatenated alignment of the marker genes was used to generate the genome tree with FastTree 43 and the tree was visualized in iTOL 44 . Functional analysis. The population genomes derived from Robinson Ridge were functionally annotated using Prokka 45 and the KEGG Orthology database (Kyoto Encyclopedia of Genes and Genomes) 46 . Genes specifically involved in carbohydrate metabolism were identified using dbCAN, an HMM-based database for carbohydrate-active enzyme (CAZy) 47 annotation. Potential secondary metabolite biosynthesis gene clusters were identified using antiSMASH 48 .
[NiFe]-hydrogenase, [MoCu]-carbon monoxide dehydrogenase, and RuBisCO enzymes encoded within the metagenome were classified by constructing phylogenetic trees of their catalytic subunits 21,49,50 . The derived protein sequences encoding the catalytic subunits of these enzymes were aligned with reference sequences reported in previous studies 21, 49,50 using ClustalX 51 . Evolutionary relationships were visualized on phylogenetic trees constructed with MEGA7 52 using the maximum-likelihood method. Trees were bootstrapped using 500 replicates and rooted with suitable outgroup sequences. The relative abundance of hhyL, coxL, and rbcL1E in McMurdo Dry Valley samples was determined by retrieving ten public metagenomes through the Joint Genome Institute (JGI IDs 104803, 106649, 35851, 3300002548, 3300012042,  3300012045, 3300012185, 3300012188, 3300012527, and 3300012678). The genes of interest were retrieved from the downloaded metagenomes by BLAST using the hhyL, coxL, and rbcL1E gene sequences identified from the Robinson Ridge metagenome as queries. The identity of the retrieved type I coxL and type IE rbcL large subunit genes was confirmed by constructing phylogenetic trees as described above, whereas genes encoding group 1h [NiFe]-hydrogenase large subunits were identified using HydDB 53 . The relative abundance of the three genes was compared with those in five public forest metagenomes (JGI IDs 66726, 69782, 92543, 94443, 109646). RT-PCR analysis. We used RT-PCR to confirm the expression of the genes of interest by the microbial communities within the six soil samples. RNA was extracted from 2 g from each of the six soil samples using the MoBio PowerSoil Total RNA Isolation kit (MO BIO). All RNA extracts were quantified using the RNA Analysis Kit (Agilent) and cDNA was synthesized using Maxima First Strand cDNA Synthesis Kit (Thermo Fisher Scientific). RT-PCR was used to confirm the expression of the group 1h [NiFe]-hydrogenase large subunit gene hhyL (primers NiFe-244f: 5′-GGGATCTGCGGGGACAACCA-3′; NiFe-568r: 5′-TCTCCCGGGTGTAGCGGCTC-3′) and the type I [MoCu]-carbon monoxide dehydrogenase large subunit gene coxL (primers type1-1288f: 5′-TSKKYACSGGCWSSTA-3′; type1-1540r: 5′-TAYGAYWSSGGYRAYTA-3′) using previously described degenerate primers, mixtures, and thermal cycler conditions 23,54 . Expression of the type IE RuBisCO large subunit gene (rbcL1E) was confirmed using specifically designed primers based on the sequences obtained from Robinson Ridge (rbcL1Ef: 5′-GGACBGTSGTVTGGACSGA-3′; rbcL1Er: 5′-TTGAABCCRAAVACRTTGCC-3′). For this gene, the RT-PCR mixtures were comprised of 1× Promega reaction buffer (Promega), 0.4 mM deoxynucleotide triphosphates, 0.4 nM of each primer, 0.1 mg ml −1 bovine serum albumin, 1.25 U Go-Taq polymerase (Promega), 1 μ l diluted cDNA, and nuclease-free water to a final volume of 25 μ l. A standard PCR protocol was used for the type IE RuBisCO large subunit gene as follows: 95 °C for 5 min; 30 cycles of denaturing at 95 °C for 30 s, annealing at 55 °C for 30 s and extension at 72 °C for 30 s; and a final extension of 72 °C for 5 min. Owing to the high degeneracy of coxL PCR primers, multiple bands were produced after thermal cycling. To confirm the identity of the PCR products, bands were separated by gel electrophoresis, the band of the correct size (780 bp) was excised aseptically, and its DNA was extracted using the Zymoclean Gel DNA Recovery Kit (Zymol). For hydrogenase and RuBisCO, purified PCR products were cloned and transformed using the pGEM-T Easy Vector System (Promega). The purified coxL PCR products and positive hydrogenase and RuBisCO clones were sequenced using Sanger sequencing at the Ramaciotti Center for Gene Function Analysis (Sydney). The identity of all sequenced clones was confirmed using NCBI BLAST against the nucleotide database. Gas chromatography analysis. We used gas chromatography to determine whether the microbial communities in the collected soil samples scavenged atmospheric H 2 , CO, or CH 4 . Soil samples of 1 g were placed into sterile 114-ml serum bottles and sealed with butyl rubber stoppers. H 2 , CO, or CH 4 gas was then added to achieve final initial headspace concentrations of ~ 60 p.p.m.v., ~ 5 p.p.m.v., or ~ 50 p.p.m.v., respectively. Soil incubation temperatures were monitored throughout using a 51II single input digital thermometer (Fluke). Headspaces (1 ml) were sampled in situ using a gas-tight syringe (VICI Precision Sampling). H 2 and CO partial pressures were measured using a PP1 Gas Analyser (Peak Performer) equipped with a reducing compound photometer (RCP: H 2 , CO), flame ionizing detector (FID: CH 4 ), Unibeads 1S 60/80 column, and Molecular Sieve 13X 60/80 column, as previously described 20 . Samples were calibrated against H 2 , CO, and CH 4 standards letter reSeArCH prepared in advance. The experiments each used two biologically independent Robinson Ridge and two biologically independent Adams Flat soil samples. Gas chromatography traces were recorded of technical triplicates for all H 2 measurements and technical duplicates for all CO measurements. Two negative controls, namely heat-killed soils (1 g; 121 °C, 15 p.s.i., 20 min) and serum bottles without soil, were monitored in parallel to regular sampling to ensure that the observed reduction of H 2 and CO concentrations was a consequence of biological oxidation. The theoretical bacterial population sustained by trace gas scavenging (N) was calculated by the methods of Conrad 26 based on the observed trace gas oxidation rate (d), the Gibbs free energy of gas oxidation (Δ G), and the theoretical maintenance energy of the population (m e ). Δ G was calculated to be − 200.9 kJ mol −1 for the reaction H 2 + 0.5 O 2 → H 2 O and − 236.2 kJ mol −1 for the reaction CO + 0.5 O 2 → CO 2 using the Nernst equation (10 °C, ambient gas concentrations). m e was estimated to be 1.68 kJ per C-mol biomass per hour using the Tijhuis equation 55 . Carbon fixation analysis. The soil samples were incubated with radiolabelled carbon dioxide ( 14 CO 2 ) under different conditions to determine whether their microbial communities could mediate chemosynthetic or photosynthetic CO 2 fixation. Each of the soil samples (0.25 g) were added to sterile 4-ml glass vials, sealed with rubber septum lids, and stored on ice before downstream analysis. Gaseous 14 CO 2 (1% v/v) was generated by mixing 75 μ l radiolabelled sodium bicarbonate solution (NaH 14 CO 3 , Perkin Elmer, 53.1 mCi nmol −1 ) with 75 μ l 10% HCl solution in a sealed 4-ml glass vial and incubating for 2 h at room temperature. To each sample, 160 μ l of 14 CO 2 (1% v/v) gas was added using a gas-tight syringe (1 ml, SGE Analytical Science), obtaining initial headspace mixing ratios of 400 p.p.m.v. 14 CO 2 in a headspace otherwise comprised of ambient air. In addition, 40 μ l standard H 2 gas (1% v/v, AirLiquide) was added to half of the sampling cohort to obtain simultaneous mixing ratios of 100 p.p.m.v. H 2 and 400 p.p.m.v. 14 CO 2. Both groups were then incubated under either light (40 μ mol photons m −2 s −1 under constant illumination) or dark conditions (sealed light-proof box) for 96 h at 10 °C. To remove any unfixed 14 CO 2 , incubated soils were transferred to 12-ml scintillation vials, suspended in 2 ml 10% acetic acid in ethanol, and left to dry under a heat lamp at 30 °C for 12 h. Ten millilitres of scintillation cocktail (EcoLume) was added and radioisotope analysis was carried out using a liquid scintillation spectrometer (Tri-Carb 2810 TR, Perkin Elmer) operating at 95% efficiency, with background luminescence and chemiluminescence corrected through internal calibration standards. Each experiment used two Robinson Ridge soil samples in paired technical quadruplicates (performed in three separate experiments across successive weeks) and three Adams Flat samples in paired technical triplicates (performed in three separate experiments across successive weeks). Control samples were run with soils that were heat-killed for 12 h at 100 °C using a cooled vacuum drying oven (Memmert GmbH). Scintillation counts from heat-killed controls were subtracted and the amount of 14 CO 2 fixed per sample was calculated on the basis of the reported specific radioactivity of the original bicarbonate solution. A control experiment validated that light stimulation caused a 15-fold increase in CO 2 fixation over the dark-incubated samples in a phototroph-containing soil community collected from Mitchell Peninsula in December 2005. Data availability. The raw shotgun sequencing datasets generated during the current study have been deposited in the National Center for Biotechnology Information (NCBI) Sequence Read Archive (RR samples 1, 2 and 3 under accession numbers SRR5223441, SRR5223442 and SRR5223443, respectively). The metagenome data have been deposited into the IMG-M web portal (https://img.    For all figures and tables that use statistical methods, confirm that the following items are present in relevant figure legends (or in the Methods section if additional space is needed).

n/a Confirmed
The exact sample size (n) for each experimental group/condition, given as a discrete number and unit of measurement (animals, litters, cultures, etc.) A description of how samples were collected, noting whether measurements were taken from distinct samples or whether the same sample was measured repeatedly A statement indicating how many times each experiment was replicated The statistical test(s) used and whether they are one-or two-sided (note: only common tests should be described solely by name; more complex techniques should be described in the Methods section) A description of any assumptions or corrections, such as an adjustment for multiple comparisons The test results (e.g. P values) given as exact values whenever possible and with confidence intervals noted A clear description of statistics including central tendency (e.g. median, mean) and variation (e.g. standard deviation, interquartile range) For manuscripts utilizing custom algorithms or software that are central to the paper but not yet described in the published literature, software must be made available to editors and reviewers upon request. We strongly encourage code deposition in a community repository (e.g. GitHub). Nature Methods guidance for providing algorithms and software for publication provides further information on this topic.

Materials and reagents
Policy information about availability of materials 8. Materials availability Indicate whether there are restrictions on availability of unique materials or if these materials are only available for distribution by a for-profit company.
All materials are available. However, only limited quantities remain of the Antarctic soil samples used for this study.

Antibodies
Describe the antibodies used and how they were validated for use in the system under study (i.e. assay and species). c. Report whether the cell lines were tested for mycoplasma contamination.
Not applicable.
d. If any of the cell lines used are listed in the database of commonly misidentified cell lines maintained by ICLAC, provide a scientific rationale for their use.