Desulfoferula mesophilus gen. nov. sp. nov., a mesophilic sulfate-reducing bacterium isolated from a brackish lake sediment.

A novel sulfate-reducing bacterium (strain 12FAKT) was isolated from sediment sampled from a brackish lake in Japan. Respiratory growth was observed with formate and pyruvate as an electron donor. Sulfate, thiosulfate, elemental sulfur and dimethyl sulfoxide were utilized as an electron acceptor. The isolate grew over a temperature range of 18-42 °C (optimum 35-37 °C), a NaCl concentration range of 50-450 mM (optimum 150-300 mM) and a pH range of 6.6-7.5. The 12FAKT genome consists of a circular chromosome with a length of 4.5 Mbp and G + C content of 63.6%. Based on 16S rRNA gene sequence similarity, the closest cultured relative was Desulfarculus baarsii 2st14T (92.2%). Genome-based phylogenetic analysis placed strain 12FAKT within the family Desulfarculaceae but did not affiliate the strain with any existing genus. Taken together, we propose a novel species of a novel genus, Desulfoferula mesophilus gen. nov. sp. nov. with the type strain 12FAKT (= DSM 115219T = JCM 39399T).

Desulfoluna limicola sp. nov., a sulfate-reducing bacterium isolated from sediment of a brackish lake.

A novel sulfate-reducing bacterium, strain ASN36T, was isolated from sediment of a brackish lake in Japan. Cells of strain ASN36T were not motile and rod-shaped, with length of 2.0-4.9 µm and width of 0.6-0.9 µm. Growth was observed at 5-35 °C with an optimum growth temperature of 25-30 °C. The pH range for growth was 6.6-8.8 with an optimum pH of 7.3. Major fatty acids were C16:1 ω7c and C16:0. Under sulfate-reducing conditions, strain ASN36T utilized lactate, malate, pyruvate, butyrate, ethanol, butanol, glycerol, yeast extract and H2/CO2 as growth substrate. Fermentative growth occurred on malate and pyruvate. The novel isolate used sulfate, sulfite and thiosulfate as electron acceptors. The genome of strain ASN36T is composed of a chromosome with length of 6.3 Mbp and G + C content of 55.1 mol%. Analyses of the 16S rRNA gene indicated that strain ASN36T is related to Desulfoluna species. Overall genome relatedness indices indicated that strain ASN36T does not belong to any existing species. In contrast to the closest relatives, strain ASN36T lacks genes for reductive dehalogenase required for organohalide respiration and does not use halogenated aromatics as electron acceptors. On the basis of its genomic and phenotypic properties, strain ASN36T (= DSM 111985 T = JCM 39257 T) is proposed as the type strain of a new species, Desulfoluna limicola sp. nov.

Desulfofustis limnaeus sp. nov., a freshwater sulfate-reducing bacterium isolated from marsh soil.

A novel sulfate-reducing bacterium, strain PPLLT, was isolated from marsh soil. Cells of strain PPLLT were rod-shaped with length of 1.5 µm and width of 0.7 µm. Growth was observed at 22-37 °C (optimum 35 °C) and pH 6.8-8.4 (optimum 7.3). Lactate, succinate, fumarate, formate and malate were utilized as electron donors for sulfate reduction. Fermentative growth was not observed on tested organic acids. Besides sulfate, sulfite, thiosulfate and elemental sulfur were utilized as electron acceptors. Hydrogen is used only in the presence acetate or yeast extract. The major fatty acid was C16:0. The complete genome of strain PPLLT was composed of a circular chromosome with length of 4.2 Mbp and G + C content of 57.7 mol%. Sequence analysis of the 16S rRNA gene showed that strain PPLLT was affiliated with the genus Desulfofustis in the family Desulfocapsaceae. On the basis of differences in the phylogenetic and phenotypic properties between the strain and the type strain of the genus Desulfofustis, strain PPLLT (DSM 110475T = JCM 39161T) is proposed as the type strain of a new species, with name of Desulfofustis limnaeus sp. nov.

Thiomicrorhabdus immobilis sp. nov., a mesophilic sulfur-oxidizing bacterium isolated from sediment of a brackish lake in northern Japan.

A novel sulfur-oxidizing bacterium, strain Am19T, was isolated from sediment of a brackish lake. Strain Am19T grew chemolithoautotrophically on inorganic sulfur compounds, and heterotrophic growth was not observed. Cells were rod-shaped with length of 1.1-3.0 µm and diameter of 0.5-0.8 µm. Growth was observed at 5-37 °C with an optimum growth temperature of 30 °C. The pH range for growth was 5.6-8.5 with an optimum pH of 6.6-7.0. Major fatty acids were summed feature 3 (C16: 1ω7c and/or C16: 1ω6c), summed feature 8 (C18: 1ω7c and/or C18: 1ω6c) and C16: 0. The sole respiratory quinone was ubiquinone-8. The complete genome of strain Am19T is composed of a circular chromosome with length of 2.5 Mbp and G + C content of 42.7 mol%. Phylogenetic analysis based on genomic data indicated that strain Am19T belongs to the genus Thiomicrorhabdus but is distinct from any existing species. Analysis of the 16S rRNA gene supported creation of a new species to accommodate strain Am19T. On the basis of genomic and phenotypic characteristics, strain Am19T (= NBRC 114602 T = BCRC 81336 T) is proposed as the type strain of a new species, with name of Thiomicrorhabdus immobilis sp. nov.

Sulfuricystis multivorans gen. nov., sp. nov. and Sulfuricystis thermophila sp. nov., facultatively autotropic sulfur-oxidizing bacteria isolated from a hot spring, and emended description of the genus Rugosibacter.

Strains J5BT and M52T are facultatively autotrophic sulfur-oxidizing bacteria isolated from a microbial mat from a hot spring. They were isolated and partially characterized in previous studies, as facultative anaerobes which use nitrate as electron acceptor. In this study, additional characterizations were made to determine their taxonomic status. In both strains, major cellular fatty acids were C16:1 (C16:1ω7c and/or C16:1ω6c) and C16:0. Their chemolithoautotrophic growth was supported by thiosulfate and elemental sulfur. They used some organic acids as growth substrates. Their 16S rRNA gene sequences indicated the highest sequence identities to species in the family Sterolibacteriaceae, but the identities were 95% or lower. Phylogenetic analysis indicated that these strains do not belong to any existing genera. Values of average nucleotide identity and digital DNA-DNA hybridization between strains J5BT and M52T were 87.93% and 34.3%, respectively. On the basis of phenotypic and genomic characteristics, Sulfuricystis multivorans gen. nov. sp. nov., and Sulfuricystis thermophila sp. nov. are proposed, with type strains of J5BT and M52T, respectively. An emended description of the genus Rugosibacter is also proposed, for its reclassification to the family Sterolibacteriaceae.

Sulfurimonas aquatica sp. nov., a sulfur-oxidizing bacterium isolated from water of a brackish lake.

A novel chemolithoautotrophic bacterium, strain H1576T, was isolated from water of a brackish lake. Strain H1576T grew aerobically on inorganic sulfur compounds. Hydrogen gas did not support autotrophic growth, and heterotrophic growth was not observed. Cells were rod shaped, motile, 1.5-2.7 µm in length and 0.6-0.7 µm in width. Growth was observed at 3-22 °C with an optimum growth temperature of 13-15 °C. The pH range for growth was 6.0-7.4 with an optimum pH of 6.6-6.8. Major fatty acids were summed feature 3 (C16: 1ω7c and/or C16: 1ω6c). The complete genome of strain H1576T consists of a circular chromosome and a plasmid, with total length of 2.8 Mbp and G+C content of 46.4 mol%. Phylogenetic analyses indicated that strain H1576T belongs to the genus Sulfurimonas but distinct from representatives of existing species. On the basis of genomic and phenotypic characteristics, a new species named Sulfurimonas aquatica sp. nov. is proposed with the type strain of strain H1576T (= BCRC 81254T = JCM 35004T).

Poplar leaf abscission through induced chlorophyll breakdown by Mg-dechelatase.

Chlorophyll breakdown is observed during senescence. The first step in chlorophyll breakdown is the removal of central Mg by Mg-dechelatase. This reaction is the rate-limiting step in the chlorophyll breakdown pathway. We evaluated the effect of induced chlorophyll breakdown on abscission through the removal of Mg by Mg-dechelatase. Poplar transformants carrying the dexamethasone-inducible Mg-dechelatase gene were prepared using the Arabidopsis Stay-Green1 cDNA. When leaves were treated with dexamethasone, chlorophyll was degraded, photosynthetic capacity was reduced, and an abscission zone was formed, resulting in leaf abscission. In addition, ethylene, which plays an important role during senescence, was produced in this process. Thus, chlorophyll breakdown induces the phenotype in the same way as commonly observed during leaf senescence. This study suggests a physiological role of chlorophyll breakdown in the leaf abscission of deciduous trees. Furthermore, this study shows that the dexamethasone-inducible gene expression system is an available option for deciduous tree studies.

Pseudodesulfovibrio sediminis sp. nov., a mesophilic and neutrophilic sulfate-reducing bacterium isolated from sediment of a brackish lake.

A novel mesophilic and neutrophilic sulfate-reducing bacterium, strain SF6T, was isolated from sediment of a brackish lake in Japan. Cells of strain SF6T were motile and rod-shaped with length of 1.2-2.5 µm and width of 0.6-0.9 µm. Growth was observed at 10-37 °C with an optimum growth temperature of 28 °C. The pH range for growth was 5.8-8.2 with an optimum pH of 7.0. The most predominant fatty acid was anteiso-C15:0. Under sulfate-reducing conditions, strain SF6T utilized lactate, ethanol and glucose as growth substrate. Chemolithoautotrophic growth on H2 was not observed, although H2 was used as electron donor. Fermentative growth occurred on pyruvate. As electron acceptor, sulfate, sulfite, thiosulfate and nitrate supported heterotrophic growth of the strain. The complete genome of strain SF6T is composed of a circular chromosome with length of 3.8 Mbp and G+C content of 54 mol%. Analyses of the 16S rRNA gene and whole genome sequence indicated that strain SF6T belongs to the genus Pseudodesulfovibrio but distinct form all existing species in the genus. On the basis of its genomic and phenotypic properties, strain SF6T (= DSM111931T = NBRC 114895T) is proposed as the type strain of a new species, with name of Pseudodesulfovibrio sediminis sp. nov.

Dissimilatory microbial sulfur and methane metabolism in the water column of a shallow meromictic lake.

Lake Harutori is a brackish meromictic lake with a steep physicochemical gradient in shallow water. Anoxic water below the chemocline has been characterized by high concentrations of sulfide (>10 mM) and methane (>1.5 mM). Previously, we reported that uncultured bacteria in the SEEP-SRB1 group were major sulfate reducers in the lake [21], but knowledge of sulfur oxidation and methane metabolism was scarce. In this current study, the Lake Harutori microbial community structure in the mixolimnion (at depths of 1.5 m and 3.0 m), upper chemocline (3.5 m), and monimolimnion (4.5 m) was further investigated by 16S rRNA gene amplicon sequencing and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH). Reads of type I and II methanotrophs were retrieved mainly from 3.5 m and above. Methanotrophic bacteria detected by CARD-FISH accounted for 3.1% of DAPI-stained cells at 3.5 m. Detection frequencies of reads affiliated with the genera Sulfurimonas and Thiomicrorhabdus, which are known to comprise sulfur oxidizers, were relatively high at 3.5 m. Methanogenic archaeal reads were retrieved from the monimolimnion and they affiliated with the genus Methanosaeta. CARD-FISH counts indicated that the cells of Methanosaeta/Methanosarcina/Methanomicrobiales accounted for up to 0.8% of the DAPI-stained cells in the monimolimnion. On the other hand, many of the reads retrieved primarily from the monimolimnion were affiliated with phylogenetically novel uncultured groups.

Mariniplasma anaerobium gen. nov., sp. nov., a novel anaerobic marine mollicute, and proposal of three novel genera to reclassify members of Acholeplasma clusters II-IV.

A novel strictly anaerobic chemoorganotrophic bacterium, designated Mahy22T, was isolated from sulfidic bottom water of a shallow brackish meromictic lake in Japan. Cells of the strain were Gram-stain-negative, non-motile and coccoid in shape with diameters of about 600-800 nm. The temperature range for growth was 15-37 °C, with optimum growth at 30-32 °C. The pH range for growth was pH 6.2-8.9, with optimum growth at pH 7.2-7.4. The strain grew with NaCl concentrations of 5% or below (optimum, 2-3%). Growth of the strain was enhanced by the addition of thiosulfate. The major cellular fatty acids were C16:0 and anteiso-C15:0. Respiratory quinones were not detected. The complete genome sequence of strain Mahy22T possessed a 1 885 846 bp circular chromosome and a 12 782 bp circular genetic element. The G+C content of the genome sequence was 30.1 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that the novel strain belonged to the family Acholeplasmataceae, class Mollicutes. The closest relative of strain Mahy22T with a validly published name was Acholeplasma palmae J233T with a 16S rRNA gene sequence similarity of 90.5%. Based on the results of polyphasic analysis, the name Mariniplasma anaerobium gen. nov., sp. nov. is proposed to accommodate strain Mahy22T, along with reclassification of some Acholeplasma species into Alteracholeplasma gen. nov., Haploplasma gen. nov. and Paracholeplasma gen. nov.

Methyloradius palustris gen. nov., sp. nov., a methanol-oxidizing bacterium isolated from snow.

A novel methylotrophic bacterium, strain Zm11T, was isolated from reddish brown snow collected in a moor in Japan. Cells of the isolate were Gram-stain-negative, motile, and rod-shaped (0.6-0.7 × 1.2-2.7 µm). Growth was observed at 5-32 °C with an optimum growth temperature of 25-28 °C. The pH range for growth was 5.4-7.8 with an optimum pH of 6.8. The strain utilized only methanol as carbon and energy sources for aerobic growth. The major cellular fatty acids (> 40% of total) were summed feature 3 (C16:1ω7c and/or C16:1ω6c) and C16: 0. The predominant quinone was Q-8, and major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The complete genome of strain Zm11T is composed of a circular chromosome (2,800,413 bp), with G + C content of 46.4 mol%. Phylogenetic analyses were conducted based on the 16S rRNA gene sequence and conserved proteins encoded in the genome. The results of analyses indicate that strain Zm11T is a member of the family Methylophilaceae but does not belong to any existing genus. On the basis of its genomic and phenotypic properties, strain Zm11T (= DSM111909T = NBRC114766T) is proposed as the type strain of a new species in a new genus, Methyloradius palustris gen. nov., sp. nov.

Dissulfurispira thermophila gen. nov., sp. nov., a thermophilic chemolithoautotroph growing by sulfur disproportionation, and proposal of novel taxa in the phylum Nitrospirota to reclassify the genus Thermodesulfovibrio.

Recently, presence of sulfur-disproportionating bacterial species belonging to the phylum Nitrospirota was indicated by an enrichment culture-based study. In the present study, a strain representing that species was isolated and characterized. The strain, strain T55JT, was isolated from a microbial mat of a hot spring. The cells were motile, and rods or spiral forms with width of 0.32-0.49 µm. The strain grew autotrophically, only by disproportionation of thiosulfate or elemental sulfur. Growth was observed at a temperature range of 25-60°C, with optimum growth at 53-57°C. The pH range for growth was 5.5-9.0, with optimum pH of 7.0-8.0. The complete genome of strain T55JT is composed of a circular chromosome (2,370,875 bp), with G+C content of 38.7%. Thermodesulfovibrio hydrogeniphilus Hdr5T showed the highest sequence similarity of the 16S rRNA gene to strain T55JT, but it was only 88.2%. On the basis of the phylogenetic and physiologic properties, strain T55JT (= DSM 110365T=NBRC 114245T) is proposed as type strain of a novel species in a new genus, Dissulfurispira thermophila gen. nov., sp. nov. To assign the new genus to family and higher taxa, its taxonomic position was assessed by genome-based phylogeny. As a result, it was shown that the novel genus and Thermodesulfovibrio belong to different families. It was also shown that Thermodesulfovibrio should be reclassified at levels from class to family and creation of some novel taxa is required. Based on these results, Thermodesulfovibrionia class. nov., Thermodesulfovibrionales ord. nov., Thermodesulfovibrionaceae fam. nov., and Dissulfurispiraceae fam. nov. are proposed.

Sulfurimicrobium lacus gen. nov., sp. nov., a sulfur oxidizer isolated from lake water, and review of the family Sulfuricellaceae to show that it is not a later synonym of Gallionellaceae.

A facultatively anaerobic sulfur-oxidizing bacterium, strain skT11T, was isolated from anoxic lake water of a stratified freshwater lake. As electron donor for chemolithoautotrophic growth, strain skT11T oxidized thiosulfate, tetrathionate, and elemental sulfur under nitrate-reducing conditions. Oxygen-dependent growth was observed under microoxic conditions, but not under fully oxygenated conditions. Growth was observed at a temperature range of 5-37 °C, with optimum growth at 28 °C. Strain skT11T grew at a pH range of 5.1-7.5, with optimum growth at pH 6.5-6.9. Heterotrophic growth was not observed. Major components in the cellular fatty acid profile were C16:1 and C16:0. The complete genome of strain skT11T consisted of a circular chromosome with a size of 3.8 Mbp and G + C content of 60.2 mol%. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that the strain skT11T is related to sulfur-oxidizing bacteria of the genera Sulfuricella, Sulfurirhabdus, and Sulfuriferula, with sequence identities of 95.4% or lower. The analysis also indicated that these three genera should be excluded from the family Gallionellaceae, as members of another family. On the basis of its genomic and phenotypic properties, strain skT11T (= DSM 110711 T = NBRC 114323 T) is proposed as the type strain of a new species in a new genus, Sulfurimicrobium lacus gen. nov., sp. nov. In addition, emended descriptions of the families Gallionellaceae and Sulfuricellaceae are proposed to declare that Sulfuricellaceae is not a later synonym of Gallionellaceae.

Thiosulfativibrio zosterae gen. nov., sp. nov., and Thiosulfatimonas sediminis gen. nov., sp. nov.

Aerobic, Gram-stain-negative, obligately chemolithoautotrophic thiosulfate-oxidizing bacteria, strains AkT22T and aks77T were isolated from a brackish lake in Japan. Strains AkT22T and aks77T were isolated from samples of eelgrass and sediment, respectively. Growth on sulfide, tetrathionate, elemental sulfur, and organic substrates was not observed for both strains. Growth of the strains was observed at 5 °C or higher temperature, with optimum growth at 22 °C. Strain AkT22T grew at a pH range of 5.8-8.0, with optimum growth at pH 6.7-7.8. Strain aks77T grew at a pH range of 5.8-8.5, with optimum growth at pH 7.0-7.9. Major cellular fatty acids (> 10% of total) of strain AkT22T were C16:1, C18:1, and C16:0. The sole respiratory quinone was ubiquinone-8 in both strains. The genome of strain AkT22T consisted of a circular chromosome, with size of approximately 2.6 Mbp and G + C content of 43.2%. Those values of the genome of strain aks77T were ca. 2.7 Mbp and 45.5%, respectively. Among cultured bacteria, Thiomicrorhabdus aquaedulcis HaS4T showed the highest sequence identities of the 16S rRNA gene, to strains AkT22T (94%) and aks77T (95%). On the basis of these results, Thiosulfativibrio zosterae gen. nov., sp. nov. and Thiosulfatimonas sediminis gen. nov., sp. nov. are proposed, with type strains of AkT22T (= BCRC 81184T = NBRC 114012T = DSM 109948T) and aks77T (= BCRC 81183T = NBRC 114013T), respectively.

Aquipluma nitroreducens gen. nov. sp. nov., a novel facultatively anaerobic bacterium isolated from a freshwater lake.

A novel facultatively anaerobic, nitrate-reducing bacterium, designated MeG22T, was isolated from a freshwater lake in Japan. Cells of the strain were straight rods (0.8×2.5-10 µm), motile, and Gram-stain-negative. For growth, the optimum NaCl concentration was 0 % and the optimum temperature was 30 °C. Under anoxic conditions, strain MeG22T reduced nitrate to nitrite. Major cellular fatty acids were C15 : 1 ω6c (13.6 %), C17 : 0 (11.9 %), anteiso-C15 : 0 (10.6 %) and iso-C15 : 0 (10.6 %). The major respiratory quinone was menaquinone-7. The genome sequence of strain MeG22T consists of 5 712 279 bp with a G+C content of 40.3 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that the novel strain belonged to the family Prolixibacteraceae within the phylum Bacteroidetes. The closest relative of strain MeG22T was Sunxiuqinia faeciviva strain JAM-BA0302T with a 16S rRNA gene sequence similarity of 90.9 %. On the basis of phylogenetic and phenotypic characterization, Aquipluma nitroreducens, gen. nov., sp. nov., belonging to the family Prolixibacteraceae is proposed with the type strain MeG22T (=NBRC 112896T=DSM 106262T).

Proposal of Desulfosarcina ovata subsp. sediminis subsp. nov., a novel toluene-degrading sulfate-reducing bacterium isolated from tidal flat sediment of Tokyo Bay.

Strain 28bB2TT is a sulfate-reducing bacterium isolated in a previous study, obtained from a p-xylene-degrading enrichment culture. Physiological, phylogenetic and genomic characterizations of strain 28bB2TT were performed to establish the taxonomic status of the strain. Cells of strain 28bB2TT were short oval-shaped (0.8-1.2×1.2-2.7µm), motile, and Gram-negative. For growth, the optimum pH was pH 6.5-7.0 and the optimum temperature was 28-32°C. Strain 28bB2TT oxidized toluene but could not utilize p-xylene. Sulfate and thiosulfate were used as electron acceptors. The G+C content of the genomic DNA was 53.8mol%. The genome consisted of an approximately 8.3 Mb of chromosome and two extrachromosomal elements. On the basis of 16S rRNA gene analysis, strain 28bB2TT was revealed to belong to the genus Desulfosarcina, with high sequence identities to Desulfosarcina ovata oXyS1T (99.5%) and Desulfosarcina cetonica DSM 7267T (98.7%). Results of Average Nucleotide Identity (ANI) calculation and digital DNA-DNA hybridization (dDDH) analysis showed that the strain 28bB2TT should be classified as a subspecies under D. ovata. Based on physiological and phylogenetic data, strain 28bB2TT (=NBRC 106234 =DSM 23484) is proposed as the type strain of a novel species in genus Desulfosarcina, Desulfosarcina ovata subsp. sediminis subsp. nov.

Disproportionation of inorganic sulfur compounds by a novel autotrophic bacterium belonging to Nitrospirota.

The phylum Nitrospirota (previously known as Nitrospirae or Nitrospira) currently encompasses a limited number of bacterial species with validly published names, including sulfate-reducing bacteria (SRB) of the genus Thermodesulfovibrio. Some metagenome-assembled genomes (MAGs) of bacteria occur in this phylum, and genes involved in dissimilatory sulfur metabolism have been identified in them. Currently, however, there is no established way to discriminate SRB and sulfur-disproportionating bacteria (SDB), which obtain energy from the disproportionation of inorganic sulfur compounds. In this study, a thiosulfate-disproportionating enrichment culture was established from a hot spring microbial mat. The culture was dominated by a single species belonging to the phylum Nitrospirota, and growth of the novel bacterium was supported by disproportionation of thiosulfate and elemental sulfur. Its growth was not observed under sulfate-reducing conditions. Therefore, a comparative genomic analysis of SDB and SRB was performed using its draft genome sequence, in order to identify any genetic element that could be used as a marker for SDB. As a result, a characteristic gene cluster was identified as a putative genetic element that characterized the genomes of SDB. The gene cluster was found in some MAGs of the phylum Nitrospirota, and their corresponding bacteria may also be capable of the disproportionation of inorganic sulfur compounds.

Sulfuriferula nivalis sp. nov., a sulfur oxidizer isolated from snow and emended description of Sulfuriferula plumbiphila.

A chemolithoautotrophic sulfur-oxidizing bacterium, strain SGTMT was isolated from snow collected in Japan. As electron donors for growth, SGTMT oxidized thiosulfate, tetrathionate and elemental sulfur. Heterotrophic growth was not observed. Growth of the novel isolate was observed at a temperature range of 5-28 °C, with optimum growth at 18 °C. SGTMT grew at a pH range of 4.3-7.4, with optimum growth at pH 6.1-7.1. Major components in the cellular fatty acid profile were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The complete genome of SGTMT consisted of a circular chromosome of approximately 3.4 Mbp and two plasmids. Phylogenetic analysis based on the 16S rRNA gene indicated that SGTMT represented a member of the genus Sulfuriferula, and its closest relative is Sulfuriferula thiophila mst6T with a sequence identity of 98 %. A comparative genome analysis showed dissimilarity between the genomes of SGTMT and S. thiophila mst6T, as low values of average nucleotide identity (74.9 %) and digital DNA-DNA hybridization (20.4%). On the basis of its genomic and phenotypic properties, SGTMT (=DSM 109609T=BCRC 81185T) is proposed as the type strain of a novel species, Sulfuriferula nivalis sp. nov. Some characteristics of another species in the same genus, Sulfuriferula plumbiphila, were also investigated to revise and supplement its description. The type strain of S. plumbiphila can grow on thiosulfate, tetrathionate and elemental sulfur. The strain showed optimum growth at pH 6.3-7.0 and shared major cellular fatty acids with the other species of the genus Sulfuriferula.