An extremely thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S95^T) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center, Pacific Ocean, at a depth of 1910 m. Cells of strain S95^Twere oval to short Gram-negative rods, 0.5–0.6 µm in diameter and 1.0–1.5 µm in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50–92 °C, with an optimum at 74 °C. The pH range for growth was 5.5–8.0, with an optimum at pH 7.0. Growth of strain S95^Twas observed at NaCl concentrations ranging from 1.5 to 3.5 % (w/v). Strain S95^Tgrew anaerobically with elemental sulfur as an energy source and bicarbonate/CO₂as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline iron(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S95^Twas also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the phylum Thermodesulfobacteria . On the basis of its physiological properties and results of phylogenetic analyses, it is proposed that the isolate represents the sole species of a new genus,Thermosulfurimonas dismutansgen. nov., sp. nov.; S95^T( = DSM 24515^T = VKM B-2683^T) is the type strain of the type species. This is the first description of a thermophilic micro-organism that disproportionates elemental sulfur.

— Microorganisms disproportionating inorganic sulfur compounds are involved in biogeochemical cycles of elements in the modern biosphere. Sulfur-disproportionating prokaryotes are represented...

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S69^T) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center and Valu Fa Ridge, Pacific Ocean, at a depth of 1910 m using anoxic medium with elemental sulfur as the only energy source. Cells of strain S69^T were Gram-negative short rods, 0.4–0.6 µm in diameter and 1.0–2.5 µm in length, motile with a single polar flagellum. The temperature range for growth was 28–70 °C, with an optimum at 61 °C. The pH range for growth was 5.6–7.9, with optimum growth at pH 6.8. Growth of strain S69^T was observed at NaCl concentrations ranging from 0.9 to 5.0 %, with an optimum at 1.8–2.7 (w/v). Strain S69^T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO₂ as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline Fe(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S69^T was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor either with H₂ or with organic electron donors. Analysis of the 16S rRNA gene sequence revealed that the isolate formed a distinct phylogenetic branch within the Deltaproteobacteria . On the basis of its physiological properties and results of phylogenetic analyses, strain S69^T is considered to represent a novel species of a new genus, for which the name Dissulfuribacter thermophilus gen. nov., sp. nov. is proposed. The type strain of Dissulfuribacter thermophilus is S69^T ( = DSM 25762^T = VKM B-2760^T).

Respiratory ammonification of nitrate is the microbial process that determines the retention of nitrogen in an ecosystem. To date, sulfur-dependent dissimilatory nitrate reduction to ammonium has been demonstrated only with sulfide as an electron donor. We detected a novel pathway that couples the sulfur and nitrogen cycles. Thermophilic anaerobic bacteria Thermosulfurimonas dismutans and Dissulfuribacter thermophilus, isolated from deep-sea hydrothermal vents, grew autotrophically with elemental sulfur as an electron donor and nitrate as an electron acceptor producing sulfate and ammonium. The genomes of both bacteria contain a gene cluster that encodes a putative nitrate ammonification enzyme system. Nitrate reduction occurs via a Nap-type complex. The reduction of produced nitrite to ammonium does not proceed via the canonical Nrf system because nitrite reductase NrfA is absent in the genomes of both microorganisms. The genome of D. thermophilus encodes a complete sulfate reduction pathway, while the Sox sulfur oxidation system is missing, as shown previously for T. dismutans. Thus, in high-temperature environments, nitrate ammonification with elemental sulfur may represent an unrecognized route of primary biomass production. Moreover, the anaerobic oxidation of sulfur compounds coupled to growth has not previously been demonstrated for the members of Thermodesulfobacteria or Deltaproteobacteria, which were considered exclusively as participants of the reductive branch of the sulfur cycle.

A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain Sh68T) was isolated from a hydrothermal pond at Uzon Caldera, Kamchatka, Russia, using anoxic medium with elemental sulfur as the only energy source. Cells of strain Sh68T were Gram-stain-negative rods, 0.5–0.8 μm in diameter and 1.2–2.0 μm in length, motile by means of flagella. The temperature range for growth was 30–65 °C, with an optimum at 50–52 °C. The pH range for growth was 5.2–7.5, with optimum growth at pH 6.0–6.2. Growth of strain Sh68T was observed at NaCl concentrations ranging from 0 to 2.3 % (w/v). Strain Sh68T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline Fe(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain Sh68T was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor either with H2 or with organic electron donors. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the class Deltaproteobacteria and is related most closely to Dissulfuribacter thermophilus S69T (90.0 % similarity). On the basis of its physiological properties and results of phylogenetic analyses, strain Sh68T is considered to represent a novel species of a new genus, for which the name Dissulfurimicrobium hydrothermale gen. nov., sp. nov. is proposed. The type strain of Dissulfurimicrobium hydrothermale is Sh68T ( = JCM 19990T = VKM B-2854T). This is the first description of a sulfur-disproportionating thermophile from a terrestrial ecosystem.

Terrestrial mud volcanoes (TMVs) are important natural sources of methane emission. The microorganisms inhabiting these environments remain largely unknown. We studied the phylogenetic composition and metabolic potential of the prokaryotic communities of TMVs located in the Taman Peninsula, Russia, using a metagenomic approach. One of the examined sites harbored a unique community with a high abundance of anaerobic methane-oxidizing archaea belonging to ANME-3 group (39% of all 16S rRNA gene reads). The high number of ANME-3 archaea was confirmed by qPCR, while the process of anaerobic methane oxidation was demonstrated by radioisotopic experiments. We recovered metagenome-assembled genomes (MAGs) of archaeal and bacterial community members and analyzed their metabolic capabilities. The ANME-3 MAG contained a complete set of genes for methanogenesis as well as of ribosomal RNA and did not encode proteins involved in dissimilatory nitrate or sulfate reduction. The presence of multiheme c-type cytochromes suggests that ANME-3 can couple methane oxidation with the reduction of metal oxides or with the interspecies electron transfer to a bacterial partner. The bacterial members of the community were mainly represented by autotrophic, nitrate-reducing, sulfur-oxidizing bacteria, as well as by fermentative microorganisms. This study extends the current knowledge of the phylogenetic and metabolic diversity of prokaryotes in TMVs and provides a first insight into the genomic features of ANME-3 archaea.