Nitrite-oxidizing bacteria (NOB) catalyze the second step of nitrification, a major process of the biogeochemical nitrogen cycle, but the recognized diversity of this guild is surprisingly low and only two bacterial phyla contain known NOB. Here, we report on the discovery of a chemolithoautotrophic nitrite oxidizer that belongs to the widespread phylum Chloroflexi not previously known to contain any nitrifying organism. This organism, named Nitrolancetus hollandicus , was isolated from a nitrifying reactor. Its tolerance to a broad temperature range (25–63 °C) and low affinity for nitrite ( K s =1 mℳ), a complex layered cell envelope that stains Gram positive, and uncommon membrane lipids composed of 1,2-diols distinguish N. hollandicus from all other known nitrite oxidizers. N. hollandicus grows on nitrite and CO 2 , and is able to use formate as a source of energy and carbon. Genome sequencing and analysis of N. hollandicus revealed the presence of all genes required for CO 2 fixation by the Calvin cycle and a nitrite oxidoreductase (NXR) similar to the NXR forms of the proteobacterial nitrite oxidizers, Nitrobacter and Nitrococcus . Comparative genomic analysis of the nxr loci unexpectedly indicated functionally important lateral gene transfer events between Nitrolancetus and other NOB carrying a cytoplasmic NXR, suggesting that horizontal transfer of the NXR module was a major driver for the spread of the capability to gain energy from nitrite oxidation during bacterial evolution. The surprising discovery of N. hollandicus significantly extends the known diversity of nitrifying organisms and likely will have implications for future research on nitrification in natural and engineered ecosystems.

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Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing ε-proteobacterium isolated from a deep-sea hydrothermal vent where it forms a deep cluster with recently isolated relatives. On the basis of phenotypic and phylogenetic differences between strain 525 T and its closest phylogenetic relatives, it is proposed that the new isolate should be described as a member of a new genus, Nautilia, for which the name Nautilia lithotrophica gen. nov., sp. nov. is proposed. The type strain is strain 525 T (l DSM 13520 T ).

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From 24 samples of hydrothermal venting structures collected at the East Pacific Rise (13 degrees N), 13 enrichments of coccoid cells were obtained which grew on CO, producing H2 and CO2 at 80 degrees C. A hyperthermophilic archaeon capable of lithotrophic growth on CO coupled with equimolar production of H2 was isolated. Based on its 16S rRNA sequence analysis, this organism was affiliated with the genus Thermococcus. Other strains of Thermococcales species ( Pyrococcus furiosus, Thermococcus peptonophilus, T. profundus, T. chitonophagus, T. stetteri, T. gorgonarius, T. litoralis, and T. pacificus) were shown to be unable to grow on CO. Searches in sequence databases failed to reveal deposited sequences of genes related to CO metabolism in Thermococcales. Our work provides the first evidence of anaerobic CO oxidation coupled with H2 production performed by an archaeon as well as the first documented case of lithotrophic growth of a Thermococcales representative.

Thermosulfurimonas dismutans gen. nov., sp. nov., an extremely thermophilic sulfur-disproportionating bacterium from a deep-sea hydrothermal vent 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 T were oval to short Gram-negative rods, 0.5-0.6 mm in diameter and 1.0-1.5 mm in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50-92 6C, with an optimum at 74 6C. The pH range for growth was 5.5-8.0, with an optimum at pH 7.0. Growth of strain S95 T was observed at NaCl concentrations ranging from 1.5 to 3.5 % (w/v). Strain S95 T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO 2 as 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 T was 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 dismutans gen. nov., sp. nov.; S95 T (5DSM 24515 T 5VKM B-2683 T ) is the type strain of the type species. This is the first description of a thermophilic microorganism that disproportionates elemental sulfur.Biogeochemical cycling of sulfur in aquatic environments includes the activities of different aerobic and anaerobic prokaryotes. Bacteria that disproportionate sulfur compounds such as thiosulfate or elemental sulfur (Bak & Cypionka, 1987;Thamdrup et al., 1993) are a unique group of sulfur cycle micro-organisms. Sulfur isotope data from early Archaean rocks and the presence of microfossils in 3.4-billion-year-old geological formations suggest that sulfur disproportionation could be one of the earliest modes of microbial metabolism (Philippot et al., 2007;Wacey et al., 2011). Inorganic sulfur fermentation has been reported for members of the mesophilic genera Desulfovibrio, Desulfobulbus, Desulfocapsa, Desulfonatronum, Desulfonatronospira and Desulfonatronovibrio in the Deltaproteobacteria (Bak & Pfennig, 1987;Lovley & Phillips, 1994;Janssen et al., 1996;Pikuta et al., 2003;Sorokin et al., 2008 Sorokin et al., , 2011. Among thermophiles, Desulfotomaculum thermobenzoicum is the only micro-organism that has been reported to be capable of growth by thiosulfate disproportionation (Jackson & McInerney, 2000). Prior to this report, no thermophiles were known to disproportionate elemental sulfur. S 0 is abundant in thermal ecosystems, including deep-sea hydrothermal vents, where it forms when hydrogen sulfide-rich hydrothermal fluid mixes w...