Bacterial chemolithoautotrophy in ultramafic plumes along the Mid-Atlantic Ridge.

Hydrothermal vent systems release reduced chemical compounds that act as an important energy source in the deep sea. Chemolithoautotrophic microbes inhabiting hydrothermal plumes oxidize these compounds, in particular, hydrogen and reduced sulfur, to obtain the energy required for CO2 fixation. Here, we analysed the planktonic communities of four hydrothermal systems located along the Mid-Atlantic Ridge: Irinovskoe, Semenov-2, Logatchev-1, and Ashadze-2, by combining long-read 16S rRNA gene analysis, fluorescence in situ hybridization, meta-omics, and thermodynamic calculations.

Inactive hydrothermal vent microbial communities are important contributors to deep ocean primary productivity.

Active hydrothermal vents are oases for productivity in the deep ocean, but the flow of dissolved substrates that fuel such abundant life ultimately ceases, leaving behind inactive mineral deposits. The rates of microbial activity on these deposits are largely unconstrained. Here we show primary production occurs on inactive hydrothermal deposits and quantify its contribution to new organic carbon production in the deep ocean.

Putative novel hydrogen- and iron-oxidizing sheath-producing Zetaproteobacteria thrive at the Fåvne deep-sea hydrothermal vent field.

Knowledge on microbial iron oxidation is important for understanding the cycling of iron, carbon, nitrogen, nutrients, and metals. The current study yields important insights into the niche sharing, diversification, and Fe(III) oxyhydroxide morphology of , an iron- and hydrogen-oxidizing Zetaproteobacteria representative belonging to Zetaproteobacteria operational taxonomic unit 9. The study proposes that exhibits a more extensive morphology of Fe(III) oxyhydroxide than previously observed.

Volcanically hosted venting with indications of ultramafic influence at Aurora hydrothermal field on Gakkel Ridge.

The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across-unusually large for a volcanically hosted vent on a slow-spreading ridge and more comparable to tectonically hosted systems that require large time-integrated heat-fluxes to form. The hydrothermal plume emanating from Aurora exhibits much higher dissolved CH/Mn values than typical basalt-hosted hydrothermal systems and, instead, closely resembles those of high-temperature ultramafic-influenced vents at slow-spreading ridges.

Heterotrophic Proteobacteria in the vicinity of diffuse hydrothermal venting.

Deep-sea hydrothermal vents are highly dynamic habitats characterized by steep temperature and chemical gradients. The oxidation of reduced compounds dissolved in the venting fluids fuels primary production providing the basis for extensive life. Until recently studies of microbial vent communities have focused primarily on chemolithoautotrophic organisms.

Methane cycling. Nonequilibrium clumped isotope signals in microbial methane.

Methane is a key component in the global carbon cycle, with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply substituted "clumped" isotopologues (for example, (13)CH3D) has recently emerged as a proxy for determining methane-formation temperatures. However, the effect of biological processes on methane's clumped isotopologue signature is poorly constrained.

Microbial lipids reveal carbon assimilation patterns on hydrothermal sulfide chimneys.

Sulfide 'chimneys' characteristic of seafloor hydrothermal venting are diverse microbial habitats. ¹³C/¹²C ratios of microbial lipids have rarely been used to assess carbon assimilation pathways on these structures, despite complementing gene- and culture-based approaches. Here, we integrate analyses of the diversity of intact polar lipids (IPL) and their side-chain δ¹³C values (δ¹³ C(lipid)) with 16S rRNA gene-based phylogeny to examine microbial carbon flow on active and inactive sulfide structures from the Manus Basin.

The origin of methanethiol in midocean ridge hydrothermal fluids.

Simple alkyl thiols such as methanethiol (CH3SH) are widely speculated to form in seafloor hot spring fluids. Putative CH3SH synthesis by abiotic (nonbiological) reduction of inorganic carbon (CO2 or CO) has been invoked as an initiation reaction for the emergence of protometabolism and microbial life in primordial hydrothermal settings. Thiols are also presumptive ligands for hydrothermal trace metals and potential fuels for associated microbial communities.