The Azores are characterized by intense volcanic activity, creating unique environments such as fumarole sites, where geothermal gases and high temperatures drive distinct chemical and biological processes. To investigate small-scale heterogeneity within such a site, six visually distinct samples were collected within a 30 cm radius at an active fumarole on São Miguel Island. The samples were analyzed for elemental and mineralogical composition, bacterial lipid biomarkers (PLFAs), and microbial community structure using a novel DNA separation technique to specifically target the living microbiome. Despite mineralogical similarities across all samples—predominantly composed of alunite, alkali-feldspar, and quartz—significant microbial heterogeneity was observed. Both PLFA and bacterial iDNA analyses revealed distinct microbial communities associated with specific conditions indicated by the specific colors: red and brown samples were dominated by Proteobacteria and Actinobacteriota, yellow and green by Thermoplasmatota and Actinobacteriota, and white and gray by Crenarchaeota. Interestingly, the gray samples exhibited a broader microbial composition, sharing some taxa with all other samples. These striking color variations are likely driven by differences in both specific mineral composition and microbial pigmentation, reflecting localized biogeochemical processes. Our findings demonstrate that extreme microbial heterogeneity can occur over remarkably small spatial scales within fumarolic systems, underscoring the complex interplay between chemical and biological factors in these dynamic volcanic habitats.

Abstract. In marine environments, small hydrocarbon (HC) fluxes through organic-poor sediments are often fully degraded by microorganisms before reaching the seabed. Yet, these fluxes influence sediment geochemistry by stimulating microbial activity. We analyzed 50 gravity cores from the southwestern Barents Sea, covering zones affected by inconspicuous HC seepage and unaffected reference zones. Using various organic and inorganic geochemical analyses of the sediment along with pore water geochemistry, we assess the effects of low-intensity seepage and identify potential geochemical signatures. While analysis of the organic geochemical analyses provided limited insights, inorganic geochemical analyses revealed formation of minerals such as carbonates and sulfides, linked to microbial reductive processes. Element concentrations suggested that HC degradation leaves distinct signatures, particularly in redox-sensitive minerals. Pore water profiles in HC-affected zones showed significant variation, indicating carbonate precipitation. In contrast, sediments not affected by HC seepage displayed more uniform pore water profiles. Estimated fluxes of sulfate, calcium, and alkalinity varied notably between cores, particularly in HC-affected zones, suggesting local and potentially transient differences in seepage intensity. While microbial HC degradation likely occurs deeper than our sampling interval, high-resolution geochemical analysis of both sediment fractions and pore water revealed a clear imprint of HC seepage. This imprint, reflected in authigenic minerals and pore water gradients, allows identification of past and present seepage activity, with authigenic minerals providing evidence for past seepage, and pore water profiles informing about ongoing seepage.

The preservation of organic compounds under extreme environmental conditions remains a critical challenge for both terrestrial ecology applications on Earth and astrobiology. In a novel long-term field experiment over 8 months, we exposed biomolecules and a model organism to natural hyperarid conditions of the Atacama Desert, one of the best Mars analog environments. We used custom-designed sample plates for long-term exposure to simulate environmental stresses that biomolecules are exposed naturally in a hyperarid environment. The multiple stressors included extreme temperature fluctuations, associated humidity changes, and intense solar irradiation. Our field experiment complements and extends the insights obtained from previously conducted short-term laboratory experiments. To investigate biomolecule stability, we embedded adenosine triphosphate (ATP), chlorophyll-a, and the cyanobacterium Chrooccoccidiopsis in various Mars-relevant sediments with addition of chloride and perchlorate. Our findings, which include the rapid degradation of these biomolecules, the detection of more stable degradation products, and the identification of non-enzymatic degradation pathways, reveal the critical influence of substrate and salt types on biomolecule stability. Valuable insights into biosignature preservation under extreme terrestrial conditions and a better understanding of organic signal interpretations were gained, which will provide critical insights for future Mars missions, especially when searching for past or present life.

The distribution pattern and occurrence of aromatic hydrocarbons as influenced by thermal maturity and the nature of Aptian to Campanian source rocks from the Orange Basin were investigated to gain more understanding of the petroleum generation and accumulation potential of the basin. Gas chromatography- mass spectrometry was used to determine the aromatic hydrocarbon content of rock extracts. The aromatic hydrocarbon composition showed abundant alkylated aromatic hydrocarbons. The most abundant of the naphthalene series is trimethylnaphthalene, and the most abundant of the phenanthrenes is methylphenanthrene. The distribution of the aromatic hydrocarbons across the seven wells investigated in this basin revealed that the naphthalenes are relatively more abundant than the phenanthrenes. Both the naphthalene and the phenanthrene distribution patterns are strongly controlled by thermal maturity of the organic matter. The type of organic matter and age of the rock also have a significant impact on the distribution and abundance of the aromatic hydrocarbons. The distribution of both naphthalenes and phenanthrenes indicates strong input of marine organic matter. The rock samples have enhanced concentrations of 1,2,5-trimethylnaphthalene compared with 1,2,7-trimethylnaphthlene, which is a typical characteristic of mature rocks. The values of methylnaphthalene ratio and dimethylnaphthalene ratio of the rock samples from the seven wells investigated revealed that Coniacian, Albian, and Aptian source rocks are more thermally mature than other source rocks in this basin that are not of these ages. Phenanthrene thermal maturity indices indicate that Turonian source rocks are the least thermally mature, whereas Santonian, Coniacian, Albian, and Aptian source rocks have a relatively higher thermal maturity. The effect of burial depth on thermal maturity of the source rocks appears to be more significant than the age of the rocks.

Climate warming in the Arctic results in thawing permafrost and associated processes like thermokarst, especially in ice-rich permafrost regions. Since permafrost soils are one of the largest organic carbon reservoirs of the world, their thawing leads to the release of greenhouse gases due to increasing microbial activity with rising soil temperature, further exacerbating climate warming. To enhance the predictions of potential future impacts of permafrost thaw, a detailed assessment of changes in soil characteristics in response to thermokarst processes in permafrost landscapes is needed, which we investigated in this study in an Arctic coastal lowland. We analysed six sediment cores from the Arctic Coastal Plain of northern Alaska, each representing a different landscape feature along a gradient from upland to thermokarst lake and drained basin to thermokarst lagoon in various development stages. For the analysis, a multiproxy approach was used, including sedimentological (grain size, bulk density, ice content), biogeochemical (total organic carbon (TOC), TOC density (TOCvol), total nitrogen (TN), stable carbon isotopes (delta 13C), TOC/TN ratio, mercury (Hg)), and lipid biomarker (n-alkanes, n-alkanols, and their ratios) parameters. We found that a semi-drained state of thermokarst lakes features the lowest OC content, and TOC and TN are generally higher in unfrozen deposits, hinting at a more intact state of organic matter. Indicated by the average chain length (ACL), delta 13C, Paq, and Pwax, we found a stronger influence of aquatic organic matter (OM) in the OM composition in the soils covered by water compared to those not covered by water. Moreover, the results of the delta 13C, TOC/TN ratio, and CPI indicate that the saline deposits contain stronger degraded OM than the deposits not influenced by saltwater. Additionally, we found positive correlations between the TOC and TOCvol and the Hg content in the deposits. The results indicate that thermokarst-influenced deposits tend to accumulate Hg during thawed periods and thus contain more Hg than the upland permafrost deposits that have not been impacted by lake formation. Our findings offer valuable insights into the dynamics of carbon storage and vulnerability to decomposition in coastal permafrost landscapes, reflecting the interplay of environmental factors, landform characteristics, and climate change impacts on Arctic permafrost environments.

This study investigates the impact of large herbivores on soil organic matter (OM) stability in Arctic permafrost and seasonally frozen ground ecosystems, focusing on the potential preservation effect of grazing. Soil samples were collected from Siberian and Finnish permafrost and nonpermafrost areas and organic carbon content, carbon-to-nitrogen ratio, stable carbon isotopes as well as the content of n-alkanes and n-alcohols were analysed to assess OM stability. The results suggest that grazing activity, particularly in permafrost environments, preserves soil OM by reducing decomposition. Permafrost soils exhibit higher functionalized to nonfunctionalized biomarker ratios, indicating in general better preservation under frozen conditions. While differences in grazing intensities had minor effects, the data also showed variability due to soil heterogeneity, especially in seasonally frozen ground ecosystems. Nevertheless, there are slight trends toward enhanced OM preservation with increasing grazing intensity, especially in permafrost, emphasising the potential role of grazing in locally preserving Arctic soil OM. This pilot study offers initial insights into the impact of large herbivores on OM stability in cold-region ecosystems, suggesting that significant effects may require prolonged, intensive grazing pressure.

Soil microbes drive ecosystem function and play a critical role in how ecosystems respond to global change. Research surrounding soil microbial communities has rapidly increased in recent decades, and substantial data relating to phospholipid fatty acids (PLFAs) and potential enzyme activity have been collected and analysed. However, studies have mostly been restricted to local and regional scales, and their accuracy and usefulness are limited by the extent of accessible data. Here we aim to improve data availability by collating a global database of soil PLFA and potential enzyme activity measurements from 12,258 georeferenced samples located across all continents, 5.1% of which have not previously been published. The database contains data relating to 113 PLFAs and 26 enzyme activities, and includes metadata such as sampling date, sample depth, and soil pH, total carbon, and total nitrogen. This database will help researchers in conducting both global- and local-scale studies to better understand soil microbial biomass and function.

A new green method for extraction of carbazoles from petroleum source rocks was developed using surfactant solution. A three-level full factorial design of experiment (DoE) which involved extraction temperature, extraction time and concentration of surfactant solution led to the development of a new extraction method avoiding organic solvents. All carbazoles extraction experiments were carried out with the assistance of a microwave oven. The carbazoles in the surfactant extracts were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS). The results showed that temperature, time and concentration of surfactant solution have significant influence on the extraction yields of the carbazoles. The highest extraction yields for most of the carbazoles were obtained at the optimal conditions of extraction temperature of 110 degrees C, extraction time of 25 min and surfactant concentration of 0.02 M. In comparison with a fast organic solvent-based extraction method (accelerated solvent extraction, ASE) the microwave assisted surfactant extraction (MASE) method was more efficient with a very good reproducibility.

Life in hyperarid regions has adapted to extreme water scarcity through mechanisms like salt deliquescence. While halite (NaCl) crusts have been intensively studied and identified as one of the last habitats under hyperarid conditions, other less common hygroscopic salt crusts remain unexplored. Here, we investigated newly discovered deliquescent soil surfaces in the Atacama Desert, containing substantial amounts of nitrates, to evaluate their habitability for microorganisms. We characterized the environment with respect to water availability and biogeochemistry. Microbial abundances and composition were determined by cell cultivation experiments, 16S rRNA gene sequencing, and membrane phospholipid fatty acid (PLFA) analysis, while microbial activity was assessed by analyzing adenosine triphosphate (ATP) and the molecular composition of organic matter. Our findings reveal that, while the studied hygroscopic salts provide temporary water, microbial abundances and activity are lower in the studied soil surfaces than in non-deliquescent soil surfaces. Intriguingly, the deliquescent crusts are enriched in geochemically degraded organic matter, indicated by the molecular composition. We conclude that high nitrate concentrations in the hyperarid soils suppress microbial activity but preserve eolian-derived biomolecules. These insights are important for assessing the habitability and searching for life in hyperarid environments on Earth and beyond.

Abstract Ratios of glycerol dialkyl glycerol tetraethers (GDGT), which are membrane lipids of bacteria and archaea, are at the base of several paleoenvironmental proxies. They are frequently applied to soils as well as lake‐ and marine sediments to generate records of past temperature and soil pH. To derive meaningful environmental information from these reconstructions, high analytical reproducibility is required. Based on submitted results by 39 laboratories from across the world, which employ a diverse range of analytical and quantification methods, we explored the reproducibility of brGDGT‐based proxies (MBT′5ME, IR, and #ringstetra) measured on four soil samples and four soil lipid extracts. Correct identification and integration of 5‐ and 6‐methyl brGDGTs is a prerequisite for the robust calculation of proxy values, but this can be challenging as indicated by the large inter‐interlaboratory variation. The exclusion of statistical outliers improves the reproducibility, where the remaining uncertainty translates into a temperature offset from median proxy values of 0.3–0.9°C and a pH offset of 0.05–0.3. There is no apparent systematic impact of the extraction method and sample preparation steps on the brGDGT ratios. Although reported GDGT concentrations are generally consistent within laboratories, they vary greatly between laboratories. This large variability in brGDGT quantification may relate to variations in ionization efficiency or specific mass spectrometer settings possibly impacting the response of brGDGTs masses relative to that of the internal standard used. While ratio values of GDGT are generally comparable, quantities can currently not be compared between laboratories.

Oil-source and oil-oil correlations are challenging when the primary chemical composition of petroleum was altered or destroyed by biodegradation. Biomarkers that are bound to macromolecular matrices rather than being in a free form are largely protected from alteration and may therefore offer a solution to the challenges. Using Microscale Sealed Vessel Catalytic Hydrogenation (MSSV-Hy), the bound biomarkers of two North Sea and two Barents Sea oil samples, with varying levels of biodegradation, were released from their respective asphaltenes. Despite biodegradation having changed the relative concentrations of steranes (C27-C30 steranes) and hopanes (C29-C30 hopanes) in the free biomarker fraction to varying degrees, the asphaltene-bound biomarkers were protected and show pristine ratios unaffected by biodegradation, e.g., the relative content of C27-C29 steranes, the C30/C29 sterane ratio, and the C29/C30 hopane ratio. Empirical calibration then allows these bound biomarkers to be converted into regular biomarker ratios. The MSSV-Hy technique has been shown to be an efficient and effective tool for releasing asphaltene-bound biomarkers from biodegraded oil and revealing genetic information when free biomarkers are altered by biodegradation.

The Atacama Desert in Chile is one of the driest and most inhospitable places on Earth. To analyze the diversity and distribution of microbial communities in such an environment, one of the most important and challenging steps is DNA extraction. Using commercial environmental DNA extraction protocols, a mixture of living, dormant, and dead cells of microorganisms is extracted, but separation of the different DNA pools is almost impossible. To overcome this problem, we applied a novel method on soils across a west-east moisture transect in the Atacama Desert to distinguish between extracellular DNA (eDNA) and intracellular DNA (iDNA) at the cell extraction level. Here, we show that a large number of living and potentially active microorganisms, such as Acidimicrobiia, Geodermatophilaceae, Frankiales, and Burkholderiaceae, occur in the hyperarid areas. We observed viable microorganisms involved as pioneers in initial soil formation processes, such as carbon and nitrogen fixation, as well as mineral-weathering processes. In response to various environmental stressors, microbes coexist as generalists or specialists in the desert soil environment. Our results show that specialists compete in a limited range of niches, while generalists tolerate a wider range of environmental conditions. Use of the DNA separation approach can provide new insights into different roles within viable microbial communities, especially in low-biomass environments where RNA-based analyses often fail.IMPORTANCEThe novel e- and iDNA separation technique offers insights into the living community at the cell extraction level in the hyperarid Atacama Desert. This approach provides a new framework for analyzing the composition and structure of the potentially active part of the microbial communities as well as their specialization, ecological network and community assembly process. Our findings underscore the significance of utilizing alternative genomic techniques in low-biomass environments where traditional DNA- and RNA-based analyses may not be feasible. The results demonstrate the viability of the proposed study framework and show that specialized microorganisms are important in initial soil formation processes, including microbial-driven mineral weathering, as well as the fixation of carbon and nitrogen.

Guaymas Basin, located off the Gulf of California, is a hydrothermally active marginal basin. Due to steep geothermal gradients and localized heating by sill intrusions, microbial substrates like short-chain fatty acids and hydrocarbons are abiotically produced from sedimentary organic matter at comparatively shallow depths. However, the potential of hydrocarbons as microbial substrates for both catabolic and anabolic metabolism remains elusive. We thus analyzed the effect of hydrocarbons on microbial sulfate reduction rates (SRR) and uptake of hydrocarbons by microorganisms using NanoSIMS. Sediment samples were recovered during IODP Exp. 385. Two sites, U1545C and U1546D, have a distance of roughly 1 km, and their sedimentary sequence and current geothermal gradients are almost identical, but Site U1546D experienced the intrusion of a sill. Since emplacement, the sill has thermally equilibrated with the surrounding sediment. For SRR measurements, sediment samples were amended with four aliphatic and four aromatic hydrocarbons or methane. Incubations were carried out at in-situ temperature and pressure for 10 days. For NanoSIMS analysis, sediment samples were incubated with stable-isotope labeled hydrocarbons (hexadecane-d34 + benzene-13C6 or 13C-methane) and 15NH4Cl at in-situ temperature and pressure for 42 days. Our results show that SRR increases upon the addition of either methane and hydrocarbons in samples from near the seafloor at Site U1545C. Methane addition also stimulated SRR around the sulfate-methane transition zone (SMTZ) at Site U1545C. In contrast, SRR did only increase at Site U1546D below the SMTZ, when the sample was incubated with methane, but did not show any reaction on hydrocarbon addition. Despite the relatively short incubation time of only 42 days we succeeded in detecting hydrocarbon and nitrogen uptake in some samples from both sites. Assimilation also mostly occurred in samples near the seafloor. Consequently, these data indicate the potential of microorganisms in Guaymas Basin to metabolize hydrocarbons.

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In the hyper‐arid Atacama Desert, microbial life thrives near its “dry limit” in scarcely distributed habitats. Fracture networks of salt‐poor sand wedges outlining salt‐cemented polygons on alluvial surfaces in the Yungay region (Chile) represent potential microbial habitats. The degree of soil habitability at the surface (0–5 cm depth) and subsurface (10–15 cm depth) of a polygon and adjacent sand wedge was assessed before and up to 42 days after a 20 mm simulated rain experiment through the abundance of phospholipid fatty acids (PLFAs). Mineralogical composition, salinity, pH, electrical and thermal conductivity, water content, and water activity were analyzed for their relevance to habitability. After wetting, the PLFA content exclusively increased steadily with time in the polygon subsurface indicating the growth of an indigenous bacterial community. This increased habitability is presumably related to the soil's ability to retain water for at least 6 weeks at this depth. The lack of a continuous growth signal at the surface is likely due to rapid desiccation. In the sand wedge subsurface, the increase in PLFA content is not continuous despite the water activity being >0.9. The reason for this remains unclear but indicates that not only water availability is relevant for habitability but also the here described soil heterogeneities might impact the detection of the microbial response. Yet, the increasing PLFA trend in the polygon subsurface emphasized its relevance as a saline microbial habitat in an otherwise hostile environment, which could have implications for the assessment of soil habitability on Mars.

Unlike the free biomarkers, which can be routinely recovered via solvent extraction, the bound biomarkers are covalently linked to the kerogen or asphaltene macrostructures and are more resistant to secondary alteration processes. Although similarities have been identified between these two types of biomarkers using different techniques, it remains unclear how the kerogen- and asphaltene-bound biomarkers are complicatedly corelated with their free counterparts, thus limiting the applications of bound biomarkers in geoscience research. In this study, the characteristics of free biomarkers recovered from shale samples, from 10 sedimentary basin around the world, and petroleum samples, from the North Sea, have been systematically compared with their kerogen- and asphaltene-bound biomarkers, which were released by the newly developed Microscale Sealed Vessel Catalytic Hydrogenation (MSSV-Hy) method. Although the kerogen-bound biomarkers are characterized by the absence of rearranged biomarkers (e.g., Ts and diasteranes) and elevated C29/C30 hopane ratios, many key source-related parameters show strong positive correlations between free and bound fractions, including the steranes/ hopane, C27/C29 sterane, C30/C29 sterane, C29/C30 hopane (alpha beta + beta alpha), C35/C34 homohopanes and C24 tetracyclic terpane/C26 tricyclic terpane ratios. These results suggest that bound biomarkers can reveal critical information about deposits and organic matter precursors of source rocks. Thermal maturity indicators, such as C29 sterane beta beta/(alpha alpha + beta beta), C29 sterane S/(S + R), C31 hopane S/R, and T beta/Tm ratios, also display excellent correlations between the free and bound counterparts in the source rocks. Although the correlations are not 1:1, empirical formulae, which are based on the correlations between free and bound biomarkers, can be used to calibrate bound biomarkers into values that can be directly compared to routine free biomarkers. Importantly, asphaltenebound biomarkers of North Sea samples exhibit similar characteristics to kerogen-bound biomarkers, and the conversion between free and bound biomarkers of the source rock and reservoir samples is the same. In summary, the bound biomarkers are found highly effective in determining the organic facies, lithology, and thermal maturity of the parent kerogen and/or asphaltene, and, thus, have a great potential to be widely used in geoscience research when information from free biomarkers is hampered by oil mixing, contamination or biodegradation.

With ongoing climate warming, ice-rich permafrost, such as late Pleistocene Yedoma permafrost, is especially vulnerable to rapid and deep thaw processes. Such permafrost sediments contain a large organic matter storage that becomes increasingly accessible to microbes upon thaw. Only a few studies analysed organic matter in deep (>10 m) permafrost and thawed permafrost sediments. We studied Yedoma sediments from four sites in Yakutia in the Russian Federation: at the Arctic Ocean (Bykovsky Peninsula), inside the Lena Delta (Sobo-Sise Cliff), close to the northern hemisphere’s cold pole (Batagay) and in central Yakutia (Yukechi Alas). We measured biomarker concentrations of sediment cores taken from below thermokarst lakes and sediment samples taken from the headwall of a coastal bluff and a retrogressive thaw slump. In addition, we carried out incubation experiments to quantify greenhouse gas production in thawing permafrost. Here, we present the first molecular biomarker distributions (alkanes and fatty acids) and organic carbon turnover (anaerobic CO2 and CH4 production) data as well as insights in organic matter decomposition processes in deep frozen and thawed Yedoma sediments. We show that biomarker proxies are useful to assess the source and degree of degradation of permafrost organic matter. Furthermore, the organic matter in frozen Pleistocene Yedoma sediments was better preserved than in thawed Holocene sediments. These findings show the relevance of studying organic matter in deep permafrost sediments.

Strain NGK35T is a motile, Gram-stain-negative, rod-shaped (1.0-2.1 µm long and 0.6-0.8 µm wide), aerobic bacterium that was isolated from plastic-polluted landfill soil. The strain grew at temperatures between 6 and 37 °C (optimum, 28 °C), in 0-10 % NaCl (optimum, 1 %) and at pH 6.0-9.5 (optimum, pH 7.5-8.5). It was positive for cytochrome c oxidase, catalase as well as H2S production, and hydrolysed casein and urea. It used a variety of different carbon sources including citrate, lactate and pyruvate. The predominant membrane fatty acids were C16 : 1 cis9 and C16 : 0, followed by C17 : 0 cyclo and C18 : 1 cis11. The major polar lipids were phosphatidylglycerol and phosphatidylethanolamine, followed by diphosphatidyglycerol. The only quinone was ubiquinone Q-8. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NGK35T belongs to the genus Paenalcaligenes (family Alcaligenaceae), appearing most closely related to Paenalcaligenes hominis CCUG 53761AT (96.90 %) and Paenalcaligenes suwonensis ABC02-12T (96.94 %). The genomic DNA G+C content of strain NGK35T was 52.1 mol %. Genome-based calculations (genome-to-genome distance, average nucleotide identity and DNA G+C content) clearly indicated that the isolate represents a novel species within the genus Paenalcaligenes. Based on phenotypic and molecular characterization, strain NGK35T can clearly be differentiated from its phylogenetic neighbours establishing a novel species, for which the name Paenalcaligenes niemegkensis sp. nov. is proposed. The type strain is NGK35T (=DSM 113270T=NCCB 100854T).

Figure S1. Biochemical parameters along main headwall (profile 1 and 2). Depth in meters from top headwall. Upper row: total organic carbon (TOC) content, carbon to nitrogen ratio (C/N), concentration of short n-alkanes (C<20), long n-alkanes, and other alkanes (branched and cyclic alkanes). Bottom row: n-alkane proxy average chain length (ACL), concentration of short n-fatty acids