Biology subjects

Elvert, M.

Publications and source records attributed to Elvert, M..

6 recordsLinked to original sources

bioRxiv2026

Alkane-oxidizing consortia produce substantial amounts of disaccharides

1Consortia of archaea and partner bacteria couple the anaerobic oxidation of alkanes to sulfate reduction. While catabolic pathways in anaerobic alkane-oxidizing archaea (ANKA) are increasingly understood, their anabolic capacities remain poorly characterized. Here, we examined nine enrichment cultures dominated by ANKA and their partner bacteria for small-molecular compounds using solvent extraction and gas chromatographic analysis of derivatized extracts. All hydrocarbon-degrading cultures contained substantial amounts of disaccharides in their metabolite pools. Cold-adapted methane-oxidizing cultures dominated by ANME-2c and Seep-SRB2 contained up to 1.5 mg of trehalose per mg soluble protein. Trehalose was also abundant in ethane-oxidizing cultures of Candidatus Ethanoperedens and its distinct partner SRBs, accounting for up to 75 % of the extracted metabolites. In contrast, thermophilic ANKA cultures dominated by ANME-1 or Ca. Syntropharchaeum and Ca. Desulfofervidus contained an abundant as-yet-unidentified glucose-containing disaccharide. Metagenomic analysis revealed widespread trehalose metabolism genes among partner Desulfobacterota and in ANME-2c and Ca. Ethanoperedens, but a lower potential in ANME-1 and Syntropharchaeum, consistent with metabolite profiles. If exogenous trehalose was added to the Ethane50 culture, we observed rapid metabolization by heterotrophic microorganisms, but poor assimilation by the Ca. Ethanoperedens/ Ca. Desulfofervidus core community, indicating that ANKA/SRB consortia do not consume externally supplied trehalose. Instead, Ca. Ethanoperedens/ Ca. Desulfofervidus, as well as other ANKA/SRB consortia, may use the disaccharides as energy-storage molecules, osmolytes, or components of the extracellular matrix. Notably, the disaccharides produced by the consortia also sustain ancillary heterotrophs, thereby linking alkane oxidation to broader sedimentary carbon cycling.

microbiology↗

bioRxiv2026

Anaerobic oxidation of methane supports a minimal microbial community in a subsurface biofilm at Ginsburg Mud Volcano

Deep marine sediments generate large amounts of methane, but most of this gas is consumed by the anaerobic oxidation of methane (AOM) mediated by microscopic consortia of anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB). In this study, we investigated the AOM within a sulfate-methane transition zone (SMTZ) at a depth of [~]9.6 m at the rim of the Ginsburg mud volcano in the Gulf of Cadiz. The SMTZ is supplied with sulfate from both, overlying seawater and an underlying evaporitic deposit, and it coincides with a fracture zone that hosts a visible biofilm. Here, carbon dioxide shows the strongest 13C-depletion, indicating intense methane consumption. Metagenomic and lipid biomarker analysis of the biofilm revealed an exceptionally simple microbial community dominated by ANME-1b archaea (63%), which predominantly produce strongly 13C-depleted glycerol dialkyl glycerol tetraethers and, to a lesser extent, the less common macrocyclic archaeols. The putative partner bacterium Seep-SRB1c (Desulfobacterota) is less abundant (9%). Additionally, the biofilm contained five low-abundance heterotrophs that likely rely on biomass or metabolites released from the ANME-SRB consortium. Our study highlights the presence of active methanotrophic biofilms in subsurface sediments and suggests that these communities may play an overlooked role in mitigating seafloor methane emissions.

microbiology↗

bioRxiv2025

Diffusive and advective fluid flow shapes chemoautotrophic bacterial communities and sulfur mineralogy in hydrothermal sediments off Milos

Hydrothermal fluid flow not only shapes mineral deposition on the ocean floor but also creates ecological niches by altering temperature and energy availability. In these niches, microbial life thrives and has an additional, often unrecognized impact on mineral formation. In a newly discovered vent field in medium depths off Milos, Greece, we show how contrasting hydrothermal regimes host fundamentally different bacterial metabolisms. Diffusive flow fosters acidic, sulfate-rich conditions that promote kaolinization and pyrite formation. Fatty acid {delta}13C values down to -39{per thousand} indicate acetyl-CoA-based sulfate reduction as the main metabolism, likely contributing to pyrite formation. In contrast, vigorous venting delivers hot, acidic, carbon-rich, and sulfate-depleted fluids that sustain the activity of sulfide-oxidizing chemoautotrophs. Fatty acid {delta}13C values of up to -4{per thousand} and elemental sulfur accumulation provide evidence of their activity. Without such hydrothermal influence, little microbial activity and only quartz-rich sediments can be observed. Combined multivariate lipid analyses highlight Eh as the strongest environmental control, with increasing average chain length of fatty acids as an adaptation to (hydro-)thermal stress. These results illustrate how different types of fluid flow influence the activity of chemoautotrophic bacterial communities that are involved in the formation of characteristic sulfur minerals in hydrothermal environments.

biochemistry↗

bioRxiv2025

Marine cold seep ANME-2/SRB consortia produce their lipid biomass from inorganic carbon

In cold seeps, anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) oxidize methane to inorganic carbon (IC) coupled to sulfate reduction. While catabolic pathways are well resolved, carbon flow into biomass remains unclear. We conducted lipid stable isotope probing (lipid-SIP) experiments with Astoria Canyon sediments dominated by ANME-2/SRB consortia and incubated samples with either 13C-labeled methane (13CH4) or dissolved IC (DI13C). Lipid-specific {delta}13C analysis showed higher 13C incorporation from DI13C than from 13CH4. After 30 days, {delta}13C values were up to +417{per thousand} in SRB-specific fatty acids (e.g., C16:1{omega}5c, cyC17:0{omega}5,6) and +126{per thousand} in ANME-2-specific isoprenoid lipids (e.g., archaeol, crocetane). Based on these values, we calculated carbon assimilation rates and found that both partners primarily assimilate IC. Remarkedly, IC assimilation in SRB lipids was eight times higher than in ANME lipids, suggesting that ANME either rely on fixation of internally generated CO2 from 13C-label-free methane before it can be exchanged with the environment or they utilize an additional, yet unknown carbon source for lipid biosynthesis. By examining the step-wise 13C-enrichment of ANME- and SRB-derived lipids, we further delineate biosynthetic pathways for archaeal and bacterial diether lipid formation and highlight crocetane as a bilayer-modulating isoprenoid hydrocarbon potentially affecting membrane fluidity and proton permeability. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/667857v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@a70354org.highwire.dtl.DTLVardef@cb95acorg.highwire.dtl.DTLVardef@1cf6d5corg.highwire.dtl.DTLVardef@114b912_HPS_FORMAT_FIGEXP M_FIG C_FIG Lipid-SIP experiments in Astoria Canyon sediments revealed that both ANME-2 and SRB primarily assimilate inorganic carbon (IC), not methane, into biomass. SRB-specific lipids showed eightfold higher I13C-assimilation than ANME lipids, suggesting SRB directly assimilate environmental IC, while ANME rely on internally produced CO2 or alternative carbon sources, potential provided by SRBs.

microbiology↗

bioRxiv2019

CO2 conversion to methane and biomass in obligate methylotrophic methanogens in marine sediments

Methyl substrates are important compounds for methanogenesis in marine sediments but diversity and carbon utilization by methylotrophic methanogenic archaea have not been clarified. Here, we demonstrate that RNA-stable isotope probing (SIP) requires 13C-labeled bicarbonate as co-substrate for identification of methylotrophic methanogens in sediment samples of the Helgoland mud area, North Sea. Using lipid-SIP, we found that methylotrophic methanogens incorporate 60 to 86% of dissolved inorganic carbon (DIC) into lipids, and thus considerably more than what can be predicted from known metabolic pathways ([~]40% contribution). In slurry experiments amended with the marine methylotroph Methanococcoides methylutens, up to 12% of methane was produced from CO2, indicating that CO2-dependent methanogenesis is an alternative methanogenic pathway and suggesting that obligate methylotrophic methanogens grow in fact mixotrophically on methyl compounds and DIC. Thus, the observed high DIC incorporation into lipds is likely linked to CO2-dependent methanogenesis, which was triggered when methane production rates were low. Since methylotrophic methanogenesis rates are much lower in marine sediments than under optimal conditions in pure culture, CO2 conversion to methane is an important but previously overlooked methanogenic process in sediments for methylotrophic methanogens.

microbiology↗

bioRxiv2018

Lipid analysis of CO2-rich subsurface aquifers suggests an autotrophy-based deep biosphere with lysolipids enriched in CPR bacteria

Sediment-hosted CO2-rich aquifers deep below the Colorado Plateau (USA) contain a remarkable diversity of uncultivated microorganisms, including Candidate Phyla Radiation (CPR) bacteria that are putative symbionts unable to synthesize membrane lipids. The origin of organic carbon in these ecosystems is unknown and the source of CPR membrane lipids remains elusive. We collected cells from deep groundwater brought to the surface by eruptions of Crystal Geyser, sequenced the community, and analyzed the whole community lipidome over time. Characteristic stable carbon isotopic compositions of microbial lipids suggest that bacterial and archaeal CO2 fixation ongoing in the deep subsurface provides organic carbon for the complex communities that reside there. Coupled lipidomic-metagenomic analysis indicates that CPR bacteria lack complete lipid biosynthesis pathways but still possess regular lipid membranes. These lipids may therefore originate from other community members, which also adapt to high in situ pressure by increasing fatty acid unsaturation. An unusually high abundance of lysolipids attributed to CPR bacteria may represent an adaptation to membrane curvature stress induced by their small cell sizes. Our findings provide new insights into the carbon cycle in the deep subsurface and suggest the redistribution of lipids into putative symbionts within this community.

microbiology↗