Gunter Wegener

MARUM Center for Marine Environmental Sciences

The anaerobic oxidation of alkanes is a microbial process that mitigates the flux of hydrocarbon seeps into the oceans. In marine archaea, the process depends on sulphate-reducing bacterial partners to exhaust electrons, and it is generally assumed that the archaeal CO2-forming enzymes (CO dehydrogenase and formylmethanofuran dehydrogenase) are cou...

Hydrothermal vents emit hot fluids enriched in energy sources for microbial life. Here, we compare the ecological and biogeochemical effects of hydrothermal venting of two recently discovered volcanic seamounts, Polaris and Aurora of the Gakkel Ridge, in the ice-covered Central Arctic Ocean. At both sites, persistent hydrothermal plumes increased u...

Methanogenic hydrocarbon degradation can be carried out by archaea that couple alkane oxidation directly to methanogenesis, or by syntrophic associations of bacteria with methanogenic archaea. However, metagenomic analyses of methanogenic environments have revealed other archaea with potential for alkane degradation but apparent inability to form m...

Methanogenic biodegradation of crude oil is a common process in subsurface biodegraded oil reservoirs. This process was previously assigned to syntrophy of hydrocarbon-degrading bacteria, and methanogenic archaea. Recent studies showed that archaea of the Candidatus Methanoliparum named as alkylotrophic methanogens coupled hydrocarbon degradation a...

Deep-sea hydrothermal systems are particularly difficult to locate and investigate in the ice-covered Arctic Ocean. Here we report findings of a system in the ultraslow-spreading Lena Trough at 81°22'N, from Expedition PS137 of the icebreaker R/V Polarstern in the summer of 2023. The site, named 'Lucky B', was first discovered after the recovery of...

The anaerobic ethane oxidation performed by seafloor archaea and sulfate-reducing partner bacteria involves largely uncharted biochemistry. This study deciphers the molecular basis of the CO 2 -generating steps by characterizing the native archaeal enzymes isolated from a thermophilic enrichment culture. While other microorganisms couple these step...

Hadarchaeota inhabit subsurface and hydrothermally heated environments, but previous to this study, they had not been cultured. Based on metagenome-assembled genomes, most Hadarchaeota are heterotrophs that grow on sugars and amino acids, or oxidize carbon monoxide or reduce nitrite to ammonium. A few other metagenome-assembled genomes encode alkyl...

Hydrothermal vents transport hot fluids rich in potential microbial energy sources into the water column. Here, we describe two deep-sea mounds with hydrothermal venting on the Gakkel Ridge in the ice-covered Central Arctic Ocean. Both mounds showed fresh pillow basalts and mineralization of metal sulfides. Vent fauna were rare, but locally filter...

3-D Dynamics of a natural gas hydrate system in the western Black Sea

Unsubstituted aromatic hydrocarbons (UAHs) are recalcitrant molecules abundant in crude oil, which is accumulated in subsurface reservoirs and occasionally enters the marine environment through natural seepage or human-caused spillage. The challenging anaerobic degradation of UAHs by microorganisms, in particular under thermophilic conditions, is p...

Methanogenic and methanotrophic archaea produce and consume the greenhouse gas methane, respectively, using the reversible enzyme methyl-coenzyme M reductase (Mcr). Recently, Mcr variants that can activate multicarbon alkanes have been recovered from archaeal enrichment cultures. These enzymes, called alkyl-coenzyme M reductase (Acrs), are widespre...

Members of the bacterial genus Sulfurimonas (phylum Campylobacterota) dominate microbial communities in marine redoxclines and are important for sulfur and nitrogen cycling. Here we used metagenomics and metabolic analyses to characterize a Sulfurimonas from the Gakkel Ridge in the Central Arctic Ocean and Southwest Indian Ridge, showing that this...

Background Gas hydrate-bearing subseafloor sediments harbor a large number of microorganisms. Within these sediments, organic matter and upward-migrating methane are important carbon and energy sources fueling a light-independent biosphere. However, the type of metabolism that dominates the deep subseafloor of the gas hydrate zone is poorly constra...

The methane-rich areas, the Loki's Castle vent field and the Jan Mayen vent field at the Arctic Mid Ocean Ridge (AMOR), host abundant niches for anaerobic methane-oxidizers, which are predominantly filled by members of the ANME-1. In this study, we used a metagenomic-based approach that revealed the presence of phylogenetic and functional different...

In seafloor sediments, the anaerobic oxidation of methane (AOM) consumes most of the methane formed in anoxic layers, preventing this greenhouse gas from reaching the water column and finally the atmosphere. AOM is performed by syntrophic consortia of specific anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria (SRB). Cultures...

The methyl-coenzyme M reductase (Mcr) enables archaea to produce and oxidize methane, critically impacting the global greenhouse gas budget. Recently cultured archaea activate short- and long-chain n -alkanes with divergent Mcr variants, termed alkyl-coenzyme M reductases (Acrs). Here, we probed the anaerobic oxidation of mid-chain petroleum alkane...

Alkanes are saturated apolar hydrocarbons that range from its simplest form, methane, to high-molecular-weight compounds. Although alkanes were once considered biologically recalcitrant under anaerobic conditions, microbiological investigations have now identified several microbial taxa that can anaerobically degrade alkanes. Here we review recent...

Consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria mediate the anaerobic oxidation of methane (AOM) in marine sediments. However, even sediment-free cultures contain a substantial number of additional microorganisms not directly related to AOM. To track the heterotrophic activity of these community members and their...

Background Gas hydrate-bearing subseafloor sediments harbor a large number of microorganisms. Sedimentary organic matter and upward methane fluids represent two important sources of carbon and energy for deep biosphere. However, which metabolism dominates the deep subseafloor of gas hydrate zone is poorly constrained. Here we studied the microbial...

Members of the genus Sulfurimonas (phylum Campylobacterota) dominate microbial communities of benthic and pelagic redox clines, playing a key role in the biogeochemistry of these environments. Investigating neutrally buoyant hydrothermal plumes of the Central Arctic Ocean, we found a novel type of Sulfurimonas that inhabits hydrogen-rich and oxygen...

The methanogenic degradation of oil hydrocarbons can proceed through syntrophic partnerships of hydrocarbon-degrading bacteria and methanogenic archaea1,2,3. However, recent culture-independent studies have suggested that the archaeon ‘Candidatus Methanoliparum’ alone can combine the degradation of long-chain alkanes with methanogenesis4,5. Here we...

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate-reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure c...

Elemental carbon exists in different structural forms including graphite, diamond, fullerenes, and amorphous carbon. In nature, these materials are produced through abiotic chemical processes under high temperature and pressure but are considered generally inaccessible to biochemical synthesis or breakdown. Here, we identified and characterized ele...

The anaerobic oxidation of methane coupled to sulfate reduction is a microbially mediated process requiring a syntrophic partnership between anaerobic methanotrophic (ANME) archaea and sulfate reducing bacteria (SRB). Based on genome taxonomy, ANME lineages are polyphyletic within the phylum Halobacterota, none of which have been isolated in pure c...

The flanking regions of Guaymas Basin, a young marginal rift basin located in the Gulf of California, are covered with thick sediment layers that are hydrothermally altered due to magmatic intrusions. To explore environmental controls on microbial community structure in this complex environment, we analyzed site- and depth-related patterns of micro...

The surficial hydrothermal sediments of Guaymas Basin harbor complex microbial communities where oxidative and reductive nitrogen, sulfur, and carbon-cycling populations and processes overlap and coexist. Here, we resolve microbial community profiles in hydrothermal sediment cores of Guaymas Basin on a scale of 2 millimeters, using Denaturing Gradi...

How to feed an enzyme ethane When released from ocean floor seeps, small hydrocarbons are rapidly consumed by micro-organisms. Methane is highly abundant and is both produced and consumed by microbes through well understood biochemical pathways. Less well understood is how ethane, also a major natural component of gaseous hydrocarbons, is metaboliz...

Methanogens are considered as one of the earliest life forms on Earth, and together with anaerobic methane-oxidizing archaea, they have crucial effects on climate stability. However, the origin and evolution of anaerobic alkane metabolism in the domain Archaea remain controversial. Here, we present evidence that methylotrophic methanogenesis was th...

Coastal sands are biocatalytic filters for dissolved and particulate organic matter of marine and terrestrial origin, thus, acting as centers of organic matter transformation. At high temporal resolution, we accessed the variability of benthic bacterial communities over two annual cycles at Helgoland (North Sea), and compared it with seasonality of...

The anaerobic oxidation of methane (AOM) is performed by methanotrophic archaea (ANME) in distinct sulfate-methane interfaces of marine sediments. In these interfaces, AOM often appears to deplete methane in the heavy isotopes toward isotopic compositions similar to methanogenesis. Here, we shed light on this effect and its physiological underpinni...

Methanogens are considered as one of the earliest life forms on Earth, and together with anaerobic methane-oxidizing archaea, they have crucial effects on climate stability. Yet, the origin and evolution of anaerobic alkane metabolism in the domain Archaea remain controversial. Here, we show that methanogenesis was already present in the common anc...

Cold seeps and hydrothermal vents are seafloor habitats fueled by subsurface energy sources. Both habitat types coexist in Guaymas Basin in the Gulf of California, providing an opportunity to compare microbial communities with distinct physiologies adapted to different thermal regimes. Hydrothermally active sites in the southern Guaymas Basin axial...

Methane is abundant in marine subsurface sediments, sourced from microbial or thermocatalytic production. The relative composition of its isotopologues (12 CH 4 , 13 CH 4 , 12 CH 3 D and 13 CH 3 D) is used to infer its sources and sinks. The anaerobic oxidation of methane (AOM) is an important methane sink reaction carried out by consortia of anaer...

Methane is abundant in marine subsurface sediments, sourced from microbial or thermocatalytic products. The relative composition of its isotopologues (12CH4, 13CH4, 12CH3D and 13CH3D) is used to infer its sources and sinks. The anaerobic oxidation of methane (AOM) is an important methane sink reaction carried out by consortia of anaerobic methanotr...

Dual stable isotope probing has been used to infer rates of microbial biomass production and modes of carbon fixation. In order to validate this approach for assessing archaeal production, the methanogenic archaeon Methanosarcina barkeri was grown either with H2, acetate or methanol with D2O and 13C‐dissolved inorganic carbon (DIC). Our results rev...

Methyl‐coenzyme M reductase (MCR) has been originally identified to catalyze the final step of the methanogenesis pathway. About 20 years ago anaerobic methane‐oxidizing archaea (ANME) were discovered that use MCR enzymes to activate methane. ANME thrive at the thermodynamic limit of life, are slow‐growing, and in most cases form syntrophic consort...

In the seabed, gaseous alkanes are oxidized by syntrophic microbial consortia that thereby reduce fluxes of these compounds into the water column. Because of the immense quantities of seabed alkane fluxes, these consortia are key catalysts of the global carbon cycle. Due to their obligate syntrophic lifestyle, the physiology of alkane-degrading arc...

Cold seeps and hydrothermal vents deliver large amounts of methane and other gaseous alkanes into marine surface sediments. Consortia of archaea and partner bacteria thrive on the oxidation of these alkanes and its coupling to sulfate reduction. The inherently slow growth of the involved organisms and the lack of pure cultures have impeded the unde...

At the Campeche Knolls in the southern Gulf of Mexico large-scale hydrocarbon emissions are associated with numerous salt tectonic structures. A notable feature of this area is the expulsion of highly viscous heavy oils, also referred to as asphalts, which form lava-like flows on the seafloor. These oil and asphalt seeps have been detected via sate...

The flux of methane, a potent greenhouse gas, from the seabed is largely controlled by anaerobic oxidation of methane (AOM) coupled to sulfate reduction (S-AOM) in the sulfate methane transition (SMT). S-AOM is estimated to oxidize 90% of the methane produced in marine sediments and is mediated by a consortium of anaerobic methanotrophic archaea (A...

The anaerobic oxidation of methane (AOM) mitigates the flux of methane from marine sediments into the water column. AOM is performed by anaerobic methanotrophic archaea (ANME) that reverse the methanogenesis pathway and partner bacteria that utilize the released reducing equivalents for sulfate reduction. Here, we investigated small-molecule extrac...

Oil-rich sediments from the Gulf of Mexico were found to contain diverse alkane-degrading groups of archaea. The symbiotic, consortium-forming “ Candidatus Argoarchaeum” and “ Candidatus Syntrophoarchaeum” are likely responsible for the degradation of ethane and short-chain alkanes, with the help of sulfate-reducing bacteria. “ Ca. Methanoliparia”...

Consortia of anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria are responsible for the anaerobic oxidation of methane (AOM) in marine sediments. Laboratory enrichments of such consortia have been frequently obtained but were never devoid of community members not involved in AOM, even after years of repeated dilution and inoculat...

Methanogenesis and anaerobic methane oxidation through methyl-coenzyme M reductase (MCR) as a key enzyme have been suggested to be basal pathways of archaea ¹ . How widespread MCR-based alkane metabolism is among archaea, where it occurs and how it evolved remain elusive. Here, we performed a global survey of MCR-encoding genomes based on metagenom...

Seepage of methane (CH4) on land and in the sea may significantly affect Earth’s biogeochemical cycles. However processes of CH4 generation and consumption, both abiotic and microbial, are not always clear. We provide new geochemical and isotope data to evaluate if a recently discovered CH4 seepage from the shallow seafloor close to the Island of E...

Porewater chemistry and isotope compositions (δ13CDIC and δ18OH2O) at gas emission and reference spots 1–3 (locations indicated on map; Fig 1). Samples were taken in 2011. (XLSX)

Additional sulphide and DIC concentrations and δ13CDIC-values of porewater samples taken in 2009 and measured in 2010. (XLSX)

Traditionally, the description of microorganisms starts with their isolation from an environmental sample. Many environmentally relevant anaerobic microorganisms grow very slowly, and often they rely on syntrophic interactions with other microorganisms. This impedes their isolation and characterization by classic microbiological techniques. We deve...

Fig. S1. Phylogenetic affiliation of ANME and partner bacteria clades within Methanomicrobia and Deltaproteobacteria. In the E20 enrichment ANME‐2c forms consortia with Seep‐SRB2, in the G37 enrichment ANME‐1 forms consortia with Seep‐SRB2, and in the G60 enrichment ANME‐1 forms consortia with HotSeep‐1. The phylogenetic trees are modified from Weg...

Table S2. Classification of metagenomic and metatranscriptomic 16S rRNA gene fragments on different phylogenetic levels.

Table S5. Single copy genes identified in ANME draft genomes.

Table S7. Draft genomes and expression data generated in this study.

Table S8. Overview of c‐type cytochromes encoded in the ANME and SRB draft genomes.

The sulfate-dependent, anaerobic oxidation of methane (AOM) is an important sink for methane in marine environments. It is carried out between anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB) living in syntrophic partnership. In this study, we compared the genomes, gene expression patterns and ultrastructures of three phy...

Subseabed CO2 storage is considered a future climate change mitigation technology. We investigated the ecological consequences of CO2 leakage for a marine benthic ecosystem. For the first time with a multidisciplinary integrated study, we tested hypotheses derived from a meta-analysis of previous experimental and in situ high-CO2 impact studies. Fo...

In 2014 and 2016, RV Polarstern expeditions examined two hydrothermally active areas on the Arctic Gakkel Ridge that had been located during the AMORE Expedition in 2001. We report on results of ship-based bathymetry as well as deep-tow visual and sonar survey data collected with the new Ocean Floor Observation and Bathymetry System (OFOBS). The Au...

During the 2016 RV Polarstern expedition exploring the axial volcanic Gakkel Ridge, we employed CTD casts to identify the source and dispersion characteristics of a hydrothermal plume at 87°N, 55°30’E, first identified by the 2001 AMORE expedition. We collected buoyant plume water samples characterized by pronounced Eh and potential temperature ano...