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Microbial sulfate reduction (SR) by sulfate-reducing micro-organisms (SRM) is a primary environmental mechanism of anaerobic organic matter mineralization, and as such influences carbon and sulfur cycling in many natural and engineered environments. In industrial systems, SR results in the generation of hydrogen sulfide, a toxic, corrosive gas with adverse human health effects and significant economic and environmental consequences. Therefore, there has been considerable interest in developing strategies for mitigating hydrogen sulfide production, and several specific inhibitors of SRM have been identified and characterized. Specific inhibitors are compounds that disrupt the metabolism of one group of organisms, with little or no effect on the rest of the community. Putative specific inhibitors of SRM have been used to control sulfidogenesis in industrial and engineered systems. Despite the value of these inhibitors, mechanistic and quantitative studies into the molecular mechanisms of their inhibition have been sparse and unsystematic. The insight garnered by such studies is essential if we are to have a more complete understanding of SR, including the past and current selective pressures acting upon it. Furthermore, the ability to reliably control sulfidogenesis - and potentially assimilatory sulfate pathways - relies on a thorough molecular understanding of inhibition. The scope of this review is to summarize the current state of the field: how we measure and understand inhibition, the targets of specific SR inhibitors and how SRM acclimatize and/or adapt to these stressors.

A novel marine sulfur-oxidizing bacterium, designated strain eps51 T , was isolated from a surface rock sample collected from the hydrothermal field of Suiyo Seamount on the Izu-Bonin Arc in the Western Pacific Ocean. This bacterium was Gram-staining-negative, non-motile and rod-shaped. Strain eps51 T grew chemolithoautotrophically, by sulfur-oxidizing respiration with elemental sulfur and thiosulfate as electron donors and used only carbon dioxide as a carbon source. Oxygen and nitrate were used as its electron acceptors. The isolate grew optimally at 30 °C, at pH 7.0 and with 3 % NaCl. The predominant fatty acids were C16 : 1ω7c, C18 : 1ω7c and C16 : 0. The respiratory quinone was menaquinone-6 and the genomic DNA G+C content was 40.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequence revealed that eps51 T represented a member of the genus Sulfurovum and the closest relative was Sulfurovum aggregans (96.7 %). Based on its phylogenetic position along with its physiological and chemotaxonomic characteristics, the name Sulfurovum denitrificans sp. nov. is proposed, with the type strain eps51 T (=NBRC 102602 T =DSM 19611 T ).

The strain BerOc1 T was isolated from brackish sediments contaminated with hydrocarbons and heavy metals. This strain has been used as a model strain of sulfate-reducer to study the biomethylation of mercury. The cells are vibrio-shaped, motile and not sporulated. Phylogeny and physiological traits placed this strain within the genus Pseudodesulfovibrio. Optimal growth was obtained at 30 °C, 1.5 % NaCl and pH 6.0-7.4. The estimated G+C content of the genomic DNA was 62.6 mol%. BerOc1 T used lactate, pyruvate, fumarate, ethanol and hydrogen. Terminal electron acceptors used were sulfate, sulfite, thiosulfate and DMSO. Only pyruvate could be used without a terminal electron acceptor. The major fatty acids were C18 : 0, anteiso-C15 : 0, C16 : 0 and C18 : 1ω7. The name Pseudodesulfovibrio hydrargyri sp. nov. is proposed for the type strain BerOc1 T (DSM 10384 T =JCM 31820 T ).

A novel Gram-stain-negative, chemolithoautotrophic sulfur oxidizer, strain JG42T, was isolated from a hot spring microbial mat. As an electron donor for autotrophic growth, strain JG42T utilized sulfide, thiosulfate, tetrathionate and elemental sulfur. Cells of strain JG42T were oxidase-positive and catalase-negative. The G+C content of the genomic DNA was 65 mol%. The predominant cellular fatty acid was C16 : 0. Phylogenetic analysis of the 16S rRNA gene indicated that strain JG42T belonged to the order Chromatiales, but sequence similarities to the known species were less than 94 %. On the basis of its properties, strain JG42T (=DSM 104776T=NBRC 112696T) is proposed as the type strain of a novel species of a new genus, Sulfurivermis fontis gen. nov., sp. nov., which belongs to the family Thioalkalispiraceae. A new family, Thioprofundaceae fam. nov., is also proposed to accommodate the genus Thioprofundum, transferred from the family Thioalkalispiraceae.

In previous studies, two hydrocarbon-degrading sulfate-reducing bacteria, strains PP31T and PL12T, were obtained from oil-polluted marine sediments of Shuaiba, Kuwait. They had been reported as organisms capable of anaerobic degradation of p-xylene and n-alkanes, respectively. The 16S rRNA gene sequence of strain PP31T showed 98.8 % sequence similarities to that of Desulfosarcina variabilis'Montpellier'T. Strains PL12T had 97.8 % of sequence similarity to Desulfosarcina ovata oXys1T. They both have been partially characterized, but not been validly published as new species of the genus Desulfosarcina. In this study, additional characterizations of these strains were made to describe them as two new species of the genus Desulfosarcina. Major cellular fatty acids of strain PP31T were C15 : 0 (25.9 %) and anteiso-C15 : 0 (22.3 %), whereas those of strain PL12T were C15 : 0 (21.3 %), C16 : 0 (17.8 %) and anteiso-15 : 0 (11.6 %). The phylogenetic tree based on 16S rRNA gene revealed that these isolates should not be classified as any of the known species in the genus Desulfosarcina. On the basis of phenotypic and phylogenetic analyses, these two sulfate reducers are proposed to form two novel species of the genus Desulfosarcina : Desulfosarcina widdelii sp. nov. (PP31T=JCM 31729T=DSM 103921T) and Desulfosarcina alkanivorans sp. nov. (PL12T=JCM 31728T=DSM 103901T). In addition, emended description of the genus Desulfosarcina is presented in this study.

A novel alkaliphilic spore-forming bacterium was isolated from the benthic sediments of the highly mineralized steppe Lake Khilganta (Transbaikal Region, Russia). Cells of the strain, designated Х-07-2T, were straight to slightly curved rods, Gram-stain-positive and motile. Strain Х-07-2T grew in the pH range from 7.0 to 10.7 (optimum pH 9.6-10.3). Growth was observed at 25-47 °C (optimum 30 °C) and at an NaCl concentration from 5 to 150 g l-1 with an optimum at 40 g l-1. Strain Х-07-2T was a chemo-organoheterotroph able to reduce amorphous ferric hydroxide, Fe(III) citrate and elemental sulfur in the presence of yeast extract as the electron donor. It used tryptone, peptone and trypticase with Fe(III) citrate as the electron acceptor. The predominant fatty acids in cell walls were C16:1ω8, iso-C15:0, C14 : 0 3-OH and C16 : 0. The DNA G+C content was 32.6 mol%. 16S rRNA gene sequence analysis revealed that strain Х-07-2T was related most closely to members of the genus Alkaliphilus within the family Clostridiaceae. The closest relative was Alkaliphilus peptidifermentans Z-7036T (96.4 % similarity). On the basis of the genotypic, chemotaxonomic and phenotypic data, strain Х-07-2T represents a novel species in the genus Alkaliphilus, for which the name Alkaliphilus namsaraevii sp. nov. is proposed. The type strain is Х-07-2T (=VKM В-2746Т=DSM 26418Т).

A novel sulfur-reducing bacterium, strain K6013T, was isolated from a sulfide sample collected at a depth of 2771 m from a high-temperature hydrothermal vent in the Indian Ocean. Cells were Gram-stain-negative, anaerobic, motile rods (0.9-2.2×0.4-0.6 µm). The strain grew at NaCl concentrations ranging from 1 to 4.5 % (w/v) (optimum 2.5 %), at pH 5 to 8 (optimum pH 6), and at temperatures between 40 and 75 °C (optimum 65 °C). K6013T was an obligate chemolithoautotroph, using thiosulfate, sulfur and nitrate as terminal electron acceptors in the presence of H2 but not sulfate, sulfite nor nitrite. The major cellular fatty acids were C16 : 0 (17.4 %), C18 : 1ω7c/C18 : 1ω6c (ummed feature 8, 37.91 %), C18 : 0 (18.29 %) and C14 : 0 3-OH/iso-C16: 1I (summed feature 2, 8.56 %). The DNA G+C content was 38.2 mol%. The results of phylogenetic 16S rRNA gene sequence analyses indicated that K6013T represents a member of the genus Desulfurobacterium within the class Aquificae, with highest sequence similarity of 96.93 % to Desulfurobacterium atlanticum SL22T. On the basis of genotypic and phenotypic data, K6013T is considered to represent a novel species of the genus Desulfurobacterium, for which the name Desulfurobacterium indicum sp. nov. is proposed, with the type strain K6013T (=DSM 101677T=MCCC 1A01868T).

A novel sulfur-oxidizing autotrophic bacterium, strain J1AT was isolated from a hot spring microbial mat. The cells were Gram-stain-negative, catalase-negative and oxidase-positive. As sole electron donor for chemolithoautotrophic growth, strain J1AT utilized sulfide, thiosulfate, elemental sulfur, and tetrathionate. The G+C content of the genomic DNA was 66 mol%. Major cellular fatty acids (>40 % of total) were C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The predominant quinone was Q-8. Phylogenetic analysis of the 16S rRNA gene indicated that strain J1AT is a relative of species of the genus Thiobacillus, but shares only 93 % or lower sequence similarities with them. On the basis of its properties, strain J1AT represents a novel species of a new genus, for which the name Sulfuritortus calidifontis gen. nov., sp. nov. is proposed. The type strain of the type species is J1AT (=DSM 103923T=NBRC 112474T).

A novel, mesophilic, strictly anaerobic, sulfate-reducing and propionate-oxidizing bacterium, strain Prop6T, was enriched and isolated from a municipal anaerobic sewage sludge digester. Cells were Gram-stain-negative, catalase-positive, oval rods, motile by means of amphitrichous flagella, non-spore-forming and contained menaquinone MK-5(H2) as the major respiratory quinone. The genomic DNA G+C content was 51.7 mol%. The optimal NaCl concentration, temperature and pH were 2-5 g l-1, 35 °C and pH 7.6, respectively. Strain Prop6T could only oxidize propionate, lactate and pyruvate (weakly) with sulfate, sulfite or thiosulfate, mainly to acetate. Strain Prop6T fermented pyruvate and lactate to acetate and propionate. The predominant cellular fatty acids were C14 : 0, C16 : 0, C16 : 1ω7, C16 : 1ω5, C17 : 1ω6 and C18 : 1ω7. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the newly isolated strain was a member of the genus Desulfobulbus, with Desulfobulbus elongatus DSM 2908T, Desulfobulbus propionicus DSM 2032T and Desulfobulbus rhabdoformis DSM 8777T as closest relatives among species with validly published names. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, it is proposed that the isolate represents a novel species, Desulfobulbus oligotrophicus sp. nov. The type strain is Prop6T (=DSM 103420T=JCM 31535T).

A novel sulfate-reducing bacterium, strain J2T, was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2T clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95 %) to the type species Desulfovibrio desulfuricans DSM 642T. It was most closely related to Desulfovibrio portus MSL79T (96.96 %), followed by Desulfovibrio aespoeensis Aspo-2T (96.11 %), Desulfovibrio piezophilus C1TLV30T (96.04 %) and Desulfovibrio profundus DSM 11384T (95.17 %). Other available sequences shared less than 93.33 % 16S rRNA gene sequence similarity. Cells were Gram-staining-negative, anaerobic, motile vibrios (2-6×0.4-0.6 µm). Growth was observed at salinities ranging from 0.2 to 6 % (optimum 2.5 %), from pH 5 to 8 (optimum pH 6.5-7) and at temperatures between 9 and 40 °C (optimum 30-35 °C). J2T was piezophilic, growing optimally at 10 MPa (range 0-30 MPa). J2T used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate and nitrate were used as terminal electron acceptors. Lactate and pyruvate were fermented. The main fatty acids were iso-C15 : 0, anteiso-C15 : 0, summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl) and iso-C17 : 0. The DNA G+C content of strain J2T was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2T represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2T (=MCCC 1A01867T = DSM 101483T). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as Pseudodesulfovibrio profundus comb. nov., D. portus as Pseudodesulfovibrio portus comb. nov. and D. aespoeensis as Pseudodesulfovibrio aespoeensis comb. nov.

A novel sulfate-reducing bacterium, strain S606T, was isolated from a sulfide sample collected at a depth of 2764 m from a deep-sea vent chimney wall in the Indian Ocean. Phylogenetic 16S rRNA gene sequence analyses placed strain S606T within the genus Thermodesulfatator, with highest sequence similarity of 98.2 % to Thermodesulfatator indicus DSM 15286T, followed by Thermodesulfatator atlanticus AT1325T (97.4 %). The average nucleotide identity (ANI) values between S606T and the two other type strains (T. indicus DSM 15286T and T. atlanticus AT1325T) were 79.2 % and 71.5 %, respectively. The digital DNA-DNA hybridization estimate values between S606T and these two type strains were 22.7±2.4 % and 18.1±2.3 %, respectively. Cells were Gram-stain-negative, anaerobic, motile rods (1-1.8×0.5-0.7 µm). The novel isolate grew at NaCl concentrations ranging from 1.5 to 4.5 % (optimum 2.5-3 %), from pH 5.5 to 8 (optimum 6.5-7.0) and at temperatures between 50 and 80 °C (optimum 65-70 °C). S606T grew chemolithoautotrophically in an H2/CO2 atmosphere (80 : 20, v/v; 200 kPa), used sulfate as a terminal electron acceptor, but not sulfur, sulfite nor thiosulfate. The predominant fatty acids were C16 : 0 (24.2 %), summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c, 26.3 %), C18 : 0 (22.2 %) and C18 : 1ω9c (9.2 %). The DNA G+C content of the chromosomal DNA was 43.1 mol%. The combined genotypic, chemotaxonomic and phenotypic traits show that S606T should be described as representing a novel species of the genus Thermodesulfatator, for which the name Thermodesulfatator autotrophicus sp. nov. is proposed. The type strain is S606T (=DSM 101864T=MCCC 1A01871T).

A chemolithotrophic sulfur-oxidizing bacterium, strain aks1T, was isolated from sediment of a brackish lake in Japan. The cells were curved rod-shaped and Gram-stain-negative. The G+C content of the genomic DNA was 53 mol%. The major components in the cellular fatty acid profile were C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). As electron donor for chemolithoautotrophic growth, strain aks1T oxidized thiosulfate, sulfide, and elemental sulfur. The strain could utilize oxygen and nitrate as an electron acceptor for thiosulfate oxidation. Growth was observed at a temperature range of 5-34 °C, with optimum growth at 30-32 °C. Growth of the strain was observed at a pH range of 6.4-8.7. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain is related to members of the family Granulosicoccaceae within the order Chromatiales, with sequence similarities around 92 %. On the basis of phylogenetic and phenotypic properties, strain aks1T represents a novel species of a new genus, for which the name Sulfuriflexus mobilis gen. nov., sp. nov. is proposed. The type strain of the type species is aks1T (=DSM 102939T=NBRC 111889T).

A novel sulfur-oxidizing bacterium designated strain mst6T was isolated from spring water of Masutomi hot spring in Japan. The cells were rod-shaped (1.2-4.0 × 0.5-0.7 μm) and Gram-stain-negative. The G+C content of genomic DNA was around 52.6 mol%. The isolate possessed summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C12 : 0 as major cellular fatty acids. Strain mst6T grew by inorganic carbon fixation and oxidation of inorganic sulfur compounds with oxygen as an electron acceptor. The isolate grew over a temperature range of 5-34 °C, a NaCl concentration range of 0-110 mM and a pH range of 4.6-8.1. Optimum growth occurred at 32 °C, in the absence of NaCl and at pH 5.9-6.2. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain mst6T belongs to the family Sulfuricellaceae in the class Betaproteobacteria. The closest cultured relative was Sulfuriferula multivorans TTNT with a 16S rRNA gene sequence similarity of 97.0 %. On the basis of the data obtained in this study, strain mst6T represents a novel species of the genus Sulfuriferula, for which the name Sulfuriferula thiophila sp. nov. is proposed. The type strain is mst6T ( = NBRC 111150T = DSM 101871T). In addition, we propose correcting the name Sulfuriferula plumbophilus Watanabe, Kojima and Fukui 2015 to Sulfuriferula plumbiphila corrig. based on Rule 12c, Rule 61 and Appendix 9 of the International Code of Nomenclature of Prokaryotes.

A novel sulfur oxidizer, strain wk12T, was isolated from an industrially synthesized lead (II) sulfide. The G+C content of the genomic DNA was around 58.5 mol%. The major components in the cellular fatty acid profile were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). The strain oxidized lead sulfide, thiosulfate and tetrathionate as electron donors to support autotrophic growth. Cells of strain wk12T were motile, rod-shaped (0.5-1.0 × 0.7-2.2 μm), and Gram-stain-negative. For growth, the temperature range was 5-37 °C, and optimum growth was observed at 28-32 °C. The pH range for growth was 5.8-8.7, with optimum growth at pH 6.4-7.1. Optimum growth of the isolate was observed in medium without NaCl, and no growth was observed in the medium containing 0.5 M or more NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belongs to the class Acidithiobacillia. The closest relative with a validly published name was Thermithiobacillus tepidarius DSM 3134T, with a 16S rRNA gene sequence similarity of 96 %. On the basis of phylogenetic and phenotypic properties, strain wk12T represents a novel species of the genus Thermithiobacillus, for which the name Thermithiobacillus plumbiphilus sp. nov. is proposed. The type strain is wk12T ( = NBRC 111508T = DSM 101799T).

A novel acidotolerant and moderately thermophilic sulfur-reducing bacterium was isolated from sediments of the Tinto River (Spain), an extremely acidic environment. Strain TR1T stained Gram-negative, and was obligately anaerobic, non-spore-forming and motile. Cells were short rods (1.5-2 × 0.5-0.7 μm), appearing singly or in pairs. Strain TR1T was catalase-negative and slightly oxidase-positive. Urease activity and indole formation were absent, but gelatin hydrolysis was present. Growth was observed at 20-52 °C with an optimum close to 50 °C, and a pH range of 3-7 with optimum between pH 6 and 6.5. Yeast extract was essential for growth, but extra vitamins were not required. In the presence of sulfur, strain TR1T grew with acetate, formate, lactate, pyruvate, stearate, arginine and H2/CO2. All substrates were completely oxidized and H2S and CO2 were the only metabolic products detected. Besides elemental sulfur, thiosulfate was used as an electron acceptor. The isolate also grew by disproportionation of elemental sulfur. The predominant cellular fatty acids were saturated components: C16 : 0, anteiso-C17 : 0 and C18 : 0. The only quinone component detected was menaquinone MK-7(H2). The G+C content of the genomic DNA was 34 mol%. The isolate is affiliated to the genus Desulfurella of the class Deltaproteobacteria, sharing 97 % 16S rRNA gene sequence similarity with the four species described in the genus Desulfurella. Considering the distinct physiological and phylogenetic characteristics, strain TR1T represents a novel species within the genus Desulfurella, for which the name Desulfurella amilsii sp. nov. is proposed. The type strain is TR1T ( = DSM 29984T = JCM 30680T).

A novel thermophilic, facultatively autotrophic bacterium, strain S2479T, was isolated from a thermal spring located in a tidal zone of a geothermally heated beach (Kuril Islands, Russia). Cells of strain S2479T were rod-shaped and motile with a Gram-negative cell-wall type. The temperature range for growth was 35-68 °C (optimum 65 °C), and the pH range for growth was pH 5.5-8.8 (optimum pH 6.5). Growth of strain S2479T was observed in the presence of NaCl concentrations ranging from 0.5 to 3.5 % (w/v) (optimum 1.5-2.0 %). The strain oxidized sulfur and thiosulfate as sole energy sources for autotrophic growth under anaerobic conditions with nitrate as electron acceptor. Strain S2479T was also capable of heterotrophic growth by reduction of nitrate with oxidation of low-chain fatty acids and a limited number of other carboxylic acids or with complex proteinaceous compounds. Nitrate was reduced to N2. Sulfur compounds were oxidized to sulfate. Strain S2479T did not grow aerobically during incubation at atmospheric concentration of oxygen but was able to grow microaerobically (1 % of oxygen in gas phase). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain was a member of the family Ectothiorhodospiraceae, order Chromatiales, class Gammaproteobacteria. On the basis of phylogenetic and phenotypic properties, strain S2479T represents a novel species of a new genus, for which the name Inmirania thermothiophila gen. nov., sp. nov. is proposed. The type strain of the type species is S2479T ( = DSM 100275T = VKM B-2962T).

The genus Acidithiobacillus includes three species that conserve energy from the oxidation of ferrous iron, as well as reduced sulfur, to support their growth. Previous work, based on multi-locus sequence analysis, identified a fourth group of iron- and sulfur-oxidizing acidithiobacilli as a potential distinct species. Eleven strains of 'Group IV' acidithiobacilli, isolated from different global locations, have been studied. These were all shown to be obligate chemolithotrophs, growing aerobically by coupling the oxidation of ferrous iron or reduced sulfur (but not hydrogen) to molecular oxygen, or anaerobically by the oxidation of reduced sulfur coupled to ferric iron reduction. All strains were mesophilic, although some were also psychrotolerant. Strain variation was also noted in terms of tolerance to extremely low pH and to elevated concentrations of transition metals. One strain was noted to display far greater tolerance to chloride than reported for other iron-oxidizing acidithiobacilli. All of the strains were able to catalyse the oxidative dissolution of pyrite and, on the basis of some of the combined traits of some of the strains examined, it is proposed that these may have niche roles in commercial mineral bioprocessing operations, such as for low temperature bioleaching of polysulfide ores in brackish waters. The name Acidithiobacillus ferriphilus sp. nov. is proposed to accommodate the strains described, with the type strain being M20T ( = DSM 100412T = JCM 30830T).

A novel sulfur-oxidizing bacterium, strain HA5T, was isolated from sediment of a lake in Japan. The cells were rod-shaped (0.3-0.5 × 1.2-6.0 μm) and Gram-stain-negative. The G+C content of the genomic DNA was 63 mol%. The major components in the cellular fatty acid profile were C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The strain oxidized thiosulfate, tetrathionate and elemental sulfur as electron donors to support autotrophic growth. Growth was observed at a temperature range of 8-37 °C, with optimum growth at 28-32 °C. The pH range for growth was pH 6.1-9.2. Optimum growth of the isolate was observed in medium without NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belongs to the family Acidiferrobacteraceae in the class Gammaproteobacteria. The closest relative was Sulfurifustis variabilis skN76T with the highest 16S rRNA gene sequence similarity of 93 %. On the basis of phylogenetic and phenotypic properties, strain HA5T is proposed to represent a novel species of a new genus, Sulfuricaulis limicola gen. nov., sp. nov. The type strain of the type species is HA5T ( = DSM 100373T = NBRC 110752T).

Strain KhalAKB1T, a mesophilic, anaerobic, rod-shaped bacterium, was isolated from water collected from a mesothermic Tunisian spring. Cells were Gram-staining-positive rods, occurring singly or in pairs and motile by one lateral flagellum. Strain KhalAKB1T grew at 15-45 °C (optimum 30 °C), at pH 5.5-8.5 (optimum pH 7.0) and in the presence of 0-35 g NaCl l- 1 (optimum 1 g NaCl l- 1). It fermented yeast extract and a wide range of carbohydrates including cellobiose, d-glucose, d-ribose, sucrose, d-xylose, maltose, d-galactose and starch as electron donors. Acetate, ethanol, CO2 and H2 were end products of glucose metabolism. It reduced elemental sulfur, but not sulfate, thiosulfate or sulfite, into sulfide. The DNA G+C content was 37.6 mol%. The predominant cellular fatty acids were C14 : 0 and C16 : 0. Phylogenetic analysis of the 16S rRNA gene sequence suggested Fusibacter bizertensis as the closest relative of this isolate (identity of 97.2 % to the type strain). Based on phenotypic, phylogenetic and genotypic taxonomic characteristics, strain KhalAKB1T is proposed to be assigned to a novel species within the genus Fusibacter, order Clostridiales, Fusibacter fontis sp. nov. The type strain is KhalAKB1T ( = DSM 28450T = JCM 19912T).

A marine facultative anaerobe, strain SIP-G1T, was isolated from salt marsh sediments, Falmouth, MA, USA. Phylogenetic analysis of its 16S rRNA gene sequence indicated that it belongs to an unclassified clade of Gammaproteobacteria that includes numerous sulfur-oxidizing bacteria that are endosymbionts of marine invertebrates endemic to sulfidic habitats. Strain SIP-G1T is a member of the genus Sedimenticola, of which there is one previously described isolate, Sedimenticola selenatireducens AK4OH1T. S. selenatireducens AK4OH1T was obtained for further characterization and comparison with strain SIP-G1T. The two strains were capable of coupling the oxidation of thiosulfate, tetrathionate, elemental sulfur and sulfide to autotrophic growth and they produced sulfur inclusions as metabolic intermediates. They showed varying degrees of O2 sensitivity, but when provided amino acids or peptides as a source of energy, they appeared more tolerant of O2 and exhibited concomitant production of elemental sulfur inclusions. The organic substrate preferences and limitations of these two organisms suggest that they possess an oxygen-sensitive carbon fixation pathway(s). Organic acids may be used to produce NADPH through the TCA cycle and are used in the formation of polyhydroxyalkanoates. Cell-wall-deficient morphotypes appeared when organic compounds (especially acetate) were present in excess and reduced sulfur was absent. Levels of DNA-DNA hybridization (∼47%) and phenotypic characterization indicate that strain SIP-G1T represents a separate species within the genus Sedimenticola, for which the name Sedimenticola thiotaurini sp. nov. is proposed. The type strain is SIP-G1T ( = ATCC BAA-2640T = DSM 28581T). The results also justify emended descriptions of the genus Sedimenticola and of S. selenatireducens.

A novel sulfate-reducing bacterium, designated strain Pf12BT, was isolated from sediment of meromictic Lake Harutori in Japan. Cells were vibroid (1.0 × 3.0-4.0 μm), motile and Gram-stain-negative. For growth, the optimum pH was 7.0-7.5 and the optimum temperature was 42-45 °C. Strain Pf12BT used sulfate, thiosulfate and sulfite as electron acceptors. The G+C content of the genomic DNA was 55.4 mol%. Major cellular fatty acids were C16 : 0 and C18 : 0. The strain was desulfoviridin-positive. Phylogenetic analysis based on the 16S rRNA gene revealed that the novel strain belonged to the order Desulfovibrionales in the class Deltaproteobacteria. The closest relative was Desulfomicrobium baculatum DSM 4028T with which it shared 91 % 16S rRNA gene sequence similarity. On the basis of phylogenetic and phenotypic characterization, a novel species of a new genus belonging to the family Desulfomicrobiaceae is proposed, Desulfoplanes formicivorans gen. nov., sp. nov. The type strain of Desulfoplanes formicivorans is Pf12BT ( = NBRC 110391T = DSM 28890T).

A strictly anaerobic, mesophilic, sulfate-reducing bacterial strain (DS(T)), isolated from river sediment contaminated with volatile organic compounds, was characterized phenotypically and phylogenetically. Cells were Gram-reaction-negative, non-motile short rods. For growth, optimum NaCl concentration was 0.9 g l(-1), optimum temperature was 30 °C and optimum pH was 7.2. Strain DS(T) utilized phenol, benzoate, 4-hydroxybenzoate, 4-methylphenol, 4-chlorophenol, acetate, butyrate and pyruvate as electron donors for sulfate reduction. Electron donors were completely oxidized. Strain DS(T) did not utilize sulfite, thiosulfate or nitrate as electron acceptors. The genomic DNA G+C content of strain DS(T) was 58.9 mol%. Major cellular fatty acids were iso-C14 : 0, anteiso-C15 : 0 and C18 : 1ω7c. Phylogenetic analyses based on the 16S rRNA gene indicated its closest relatives were strains of Desulfobacterium anilini (about 98-99 % sequence similarity) but the DNA-DNA hybridization value with Desulfobacterium anilini Ani1(T) was around 40 %. Although strain DS(T) and its relatives shared most phenotypic and chemotaxonomic characteristics, the utilization of 4-chlorophenol, the range of electron acceptors and the optimum growth conditions differed. Strain DS(T) is closely related to strains of Desulfobacterium anilini, but constitutes a different species within the genus. Based on phylogeny, phenotypic characteristics and chemotaxonomic characteristics, strain DS(T) and Desulfobacterium anilini were clearly different from strains of other species of the genus Desulfobacterium. We thus propose the reclassification of Desulfobacterium anilini within a new genus, Desulfatiglans gen. nov., as Desulfatiglans anilini comb. nov. We also propose Desulfatiglans parachlorophenolica sp. nov. to accommodate strain DS(T). The type strain is DS(T) ( = JCM 19179(T) = DSM 27197(T))., (© 2014 IUMS.)

A novel, strictly anaerobic, sulfate-reducing bacterium, designated strain SCBM(T), was isolated from water extracted from a coal bed in Indiana, USA. The isolate was characterized by a polyphasic taxonomic approach that included phenotypic and genotypic characterizations. Cells of strain SCBM(T) were vibrio-shaped, polarly flagellated, Gram-negative, motile, oxidase-negative and weakly catalase-positive. Growth of strain SCBM(T) was observed at NaCl concentrations ranging from 0 to 300 mM. However, no growth was observed when 1 M or more NaCl was present. Growth was observed at 16-37 °C, with optimal growth at 30 °C. The optimum pH for growth was 7, although growth was observed from pH 6.5 to 8. The doubling time under optimal growth conditions (30 °C, pH 7, 2.5 mM benzoate, 14 mM sulfate) was 2.7 days. Bicarbonate, HEPES, PIPES and MES were effective buffers for growth of strain SCBM(T), but citrate inhibited growth. When sulfate was provided as the electron acceptor, strain SCBM(T) grew autotrophically with hydrogen as the electron donor and heterotrophically on benzoate, formate, acetate, pyruvate, butyrate, fumarate, succinate and palmitate. None of the substrates tested supported fermentative growth. Thiosulfate and sulfate were used as electron acceptors coupled to benzoate oxidation, but sulfite, elemental sulfur, DMSO, anthraquinone 2,6-disulfonate, nitrate, nitrite, ferric citrate, hydrous iron oxide and oxygen were not. The G+C content of genomic DNA was 62.5 mol%. The major cellular fatty acids were anteiso-C(15 : 0) and C(18 : 1)ω7c. Phylogenetic analysis based on 16S rRNA gene sequencing placed strain SCBM(T) into a distinct lineage within the class Deltaproteobacteria. The closest, cultivated phylogenetic relative of strain SCBM(T) was Desulfarculus baarsii DSM 2075(T), with only 91.7% 16S rRNA gene sequence identity. On the basis of phenotypic and genotypic analyses, strain SCBM(T) represents a novel genus and species of sulfate-reducing bacteria, for which the name Desulfocarbo indianensis gen. nov., sp. nov. is proposed. The type strain of Desulfocarbo indianensis is SCBM(T) ( = DSM 28127(T) = JCM 19826(T)). Desulfocarbo is the second genus of the order Desulfarculales., (© 2014 IUMS.)

A novel sulfate-reducing bacterium designated strain BE2801(T) was isolated from oil-polluted estuarine sediments (Berre Lagoon, France). Cells were Gram-stain-negative, motile, slightly curved or vibrioid rods. Optimal growth of strain BE2801(T) occurred at 30-32 °C, 0.5-1.5% NaCl (w/v) and pH 7.2-7.4. Strain BE2801(T) grew with C4 to C20 fatty acids or C12 to C20 n-alkenes as electron donors. Acetate and carbon dioxide were the oxidation products. The major cellular fatty acids were C16 : 0, C(16 : 1)ω7c and C(18 : 1)ω7. The DNA G+C content was 50.2 mol%. 16S rRNA and dsrAB gene sequence analysis indicated that strain BE2801(T) was a member of the family Desulfobacteraceae within the class Deltaproteobacteria. DNA-DNA hybridization with the most closely related taxon demonstrated 14.8 % relatedness. Based on phenotypic and phylogenetic evidence, strain BE2801(T) ( = DSM 25524(T) = JCM 18157(T)) is proposed to be a representative of a novel species of the genus Desulfatiferula, for which the name Desulfatiferula berrensis sp. nov. is suggested.

A novel anaerobic, chemo-organotrophic, sulfate-reducing bacterium, designated strain Olac 40(T), was isolated from a Tunisian wastewater digestor. Cells were curved, motile rods or vibrios (5.0-7.0×0.5 µm). Strain Olac 40(T) grew at temperatures between 15 and 50 °C (optimum 40 °C), and between pH 5.0 and 9.0 (optimum pH 7.1). It did not require NaCl for growth but tolerated it up to 50 g l(-1) (optimum 2 g l(-1)). In the presence of sulfate or thiosulfate, strain Olac 40(T) used lactate, pyruvate and formate as energy sources. Growth was observed on H2 only in the presence of acetate as carbon source. In the presence of sulfate or thiosulfate, the end products of lactate oxidation were acetate, sulfide and CO2. Sulfate, thiosulfate and sulfite were used as terminal electron acceptors, but not elemental sulfur, nitrate or nitrite. The genomic DNA G+C content of strain Olac 40(T) was 70 mol%. The profile of polar lipids consisted of phosphatidylglycerol, phosphatidylethanolamine, aminophospholipid and four phospholipids. The main fatty acids were C16 : 0, anteiso-C15 : 0 and iso-C15 : 0. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Olac 40(T) was affiliated with the family Desulfovibrionaceae within the class Deltaproteobacteria. On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain Olac 40(T) is proposed to be assigned to a novel species of the genus Desulfocurvus, for which the name Desulfocurvus thunnarius is proposed. The type strain is Olac 40(T) ( = DSM 26129(T) = JCM 18546(T)).

A novel spore-forming, sulfate-reducing bacterium, strain SR45(T), was isolated from sediment of a freshwater lake, Lake Mizugaki, in Japan. Cells of strain SR45 were rod-shaped (1.0-1.5×2.0-5.0 µm) and weakly motile; Gram staining and the KOH lysis test were negative. For growth, the optimum pH was 6.4-6.8 and the optimum temperature was 42-45 °C. Strain SR45(T) used sulfate, thiosulfate, sulfite and elemental sulfur as electron acceptors but not Fe(III). The G+C content of the genomic DNA was 41.1 mol%. Phylogenetic analyses based on genes for the 16S rRNA and DNA gyrase (gyrB) revealed that the isolated strain belonged to the family Peptococcaceae in the class Clostridia. The closest relative is Desulfotomaculum acetoxidans 5575(T), with 16S rRNA gene sequence similarity of 92-94 %. It is suggested that the strain is the second isolated member of Desulfotomaculum subcluster Ie. The isolate had multiple 16S rRNA gene copies, with 13 different sequences. On the basis of phylogenetic and phenotypic characterization, the name Desulfotomaculum intricatum sp. nov. is proposed, with the type strain SR45(T) ( = NBRC 109411(T) = DSM 26801(T)).

A sulfate-reducing bacterium, designated JHA1(T), was isolated from a permanently cold marine sediment sampled in an Artic fjord on the north-west coast of Svalbard. The isolate was originally enriched at 4 °C in a highly diluted liquid culture amended with hydrogen and sulfate. Strain JHA1(T) was a psychrophile, growing fastest between 14 and 16 °C and not growing above 20 °C. Fastest growth was found at neutral pH (pH 7.2-7.4) and at marine concentrations of NaCl (20-30 g l(-1)). Phylogenetic analysis of 16S rRNA gene sequences revealed that strain JHA1(T) was a member of the family Desulfobacteraceae in the Deltaproteobacteria. The isolate shared 99 % 16S rRNA gene sequence similarity with an environmental sequence obtained from permanently cold Antarctic sediment. The closest recognized relatives were Desulfobacula phenolica DSM 3384(T) and Desulfobacula toluolica DSM 7467(T) (both <95 % sequence similarity). In contrast to its closest phylogenetic relatives, strain JHA1(T) grew chemolithoautotrophically with hydrogen as an electron donor. CO dehydrogenase activity indicated the operation of the reductive acetyl-CoA pathway for inorganic carbon assimilation. Beside differences in physiology and morphology, strain JHA1(T) could be distinguished chemotaxonomically from the genus Desulfobacula by the absence of the cellular fatty acid C16 : 0 10-methyl. Phylogenetic differentiation from other genera was further supported by DsrAB and AprBA sequence analysis. Based on the described phylogenetic and phenotypic differences between strain JHA1(T) and its closest relatives, the establishment of a novel genus and a novel species, Desulfoconvexum algidum gen. nov., sp. nov. is proposed. The type strain is JHA1(T) ( = DSM 21856(T)  = JCM 16085(T)).

A novel anaerobic, gram-positive, spore-forming, curved rod-shaped, mesophilic and sulfate-reducing bacterium was isolated from pore water collected in a borehole at -490 m in Bure (France). This strain, designated BSREI1(T), grew at temperatures between 5 °C and 30 °C (optimum 25 °C) and at a pH between 6 and 8 (optimum 7). It did not require NaCl for growth, but tolerated it up to 1.5 % NaCl. Sulfate, thiosulfate and elemental sulfur were used as terminal electron acceptors. Strain BSREI1(T) used crotonate, formate, lactate, pyruvate, fructose, glycerol and yeast extract as electron donors in the presence of sulfate. The sole quinone was MK-7. The G+C content of the genomic DNA was 43.3 mol%. Strain BSREI1(T) had the type strains of Desulfosporosinus lacus (16S rRNA gene sequence similarity of 96.83 %), Desulfosporosinus meridiei (96.31 %) and Desulfosporosinus hippei (96.16 %) as its closest phylogenetic relatives. On the basis of phylogenetic and physiological properties, strain BSREI1(T) is proposed as a representative of a novel species of the genus Desulfosporosinus, Desulfosporosinus burensis sp. nov.; the type strain is BSREI1(T) ( = DSM 24089(T) = JCM 17380(T)).

A novel sulfate-reducing bacterium, strain S28bF(T), was isolated from tidal flat sediment from Tokyo Bay, Japan. Cells of strain S28bF(T) were rod-shaped (0.5-0.6×1.7-3.8 µm), motile and Gram-stain-negative. For growth, the optimum pH was pH 6.8-7.3 and the optimum temperature was 34-42 °C. Strain S28bF(T) used sulfate and thiosulfate as electron acceptors, but not nitrate. The G+C content of the genomic DNA was 56.6 mol%. The fatty acid profile of strain S28bF(T) was characterized by the presence of anteiso-C(15 : 0) and C(16 : 0) as the major components. Phylogenetic analyses based on genes for 16S rRNA, the alpha subunit of dissimilatory sulfite reductase (dsrA) and adenosine-5'-phosphosulfate reductase (aprA) revealed that the isolated strain belonged to the class Deltaproteobacteria. Its closest relative was Desulfosarcina cetonica DSM 7267(T) with a 16S rRNA gene sequence similarity of 93.3 %. Two other strains, S28OL1 and S28OL2 were also isolated from the same sediment. These strains were closely related to S28bF(T) with 16S rRNA gene sequence similarities of 99 %, and the same physiological characteristics were shared with strain S28bF(T). On the basis of phylogenetic and phenotypic characterization, a novel species in a new genus, Desulfatitalea tepidiphila gen. nov., sp. nov., is proposed to accommodate the strains obtained in this study. The type strain is S28bF(T) ( = NBRC 107166(T) = DSM 23472(T)).

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 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(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) (=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.

Two types of heterotrophic sulfate-reducing bacteria (SRB) were isolated from anoxic sediments of hypersaline soda lakes in Kulunda Steppe (Altai, Russia). The isolates used propionate as an energy and carbon source. Strain APT2(T) was enriched and isolated with thiosulfate as the electron acceptor. Strains APS1(T) and ASS1 were isolated with sulfate. Strain APT2(T) was a short rod and motile with a single subpolar flagellum, while strains APS1(T) and ASS1 were lemon-shaped oval rods and motile with a single polar flagellum and thin flagella-like filaments. Strain APT2(T) grew by complete oxidation of C(3)-C(8) fatty acids with thiosulfate or sulfate as the electron acceptor, while strains APS1(T) and ASS1 were much less versatile and utilized only propionate and pyruvate as the electron donor and carbon source with sulfate or sulfite as the electron acceptor. Furthermore, strains APS1(T) and ASS1 oxidized propionate incompletely to form acetate. All of the isolates were moderately halophilic and obligately alkaliphilic. Phylogenetic analysis based on 16S rRNA gene sequences placed the isolates in the order Desulfobacterales of the class Deltaproteobacteria. Strain APT2(T) belonged to the family Desulfobacteraceae and clustered with a halophilic SRB, Desulfosalsimonas propionicica PropA(T). Strains APS1(T) and ASS1 were closely related to each other and clustered with the genus Desulfobulbus of the family Desulfobulbaceae. On the basis of phenotypic and phylogenetic analysis, the isolates are proposed to represent two novel taxa, Desulfonatronobacter acidivorans gen. nov., sp. nov. (type strain of the type species APT2(T) = DSM 24257(T) = UNIQEM U853(T)) and Desulfobulbus alkaliphilus sp. nov. (type strain APS1(T) = DSM 24258(T) = UNIQEM U900(T)).

Lateral gene transfer (LGT) is an important mechanism by which micro-organisms acquire new functions. This process has been suggested to be central to prokaryotic evolution in various environments. However, the influence of geographical constraints on the evolution of laterally acquired genes in microbial metabolic evolution is not yet well understood. In this study, the influence of geographical isolation on the evolution of laterally acquired dissimilatory sulphite reductase (dsr) gene sequences in the sulphate-reducing micro-organisms (SRM) was investigated. Sequences on four continental blocks related to SRM known to have received dsr by LGT were analysed using standard phylogenetic and multidimensional statistical methods. Sequences related to lineages with large genetic diversity correlated positively with habitat divergence. Those affiliated to Thermodesulfobacterium indicated strong biogeographical delineation; hydrothermal-vent sequences clustered independently from hot-spring sequences. Some of the hydrothermal-vent and hot-spring sequences suggested to have been acquired from a common ancestral source may have diverged upon isolation within distinct habitats. In contrast, analysis of some Desulfotomaculum sequences indicated they could have been transferred from different ancestral sources but converged upon isolation within the same niche. These results hint that, after lateral acquisition of dsr genes, barriers to gene flow probably play a strong role in their subsequent evolution.

A novel halophilic Gram-negative sulfate-reducing bacterium affiliated with the deltaproteobacterial family Desulfobacteraceae, strain PropA(T), was isolated from the extreme hypersaline sediment of the northern arm of Great Salt Lake, Utah, USA. Comparative 16S rRNA gene sequence analysis showed that strain PropA(T) is the first cultured representative of a clade of phylotypes that have been retrieved from a range of geographically and ecologically distinct hypersaline environments. Strain PropA(T) shared < or =90 % 16S rRNA gene sequence identity with cultured strains within the family Desulfobacteraceae. Cells of strain PropA(T) were rod-shaped and sometimes motile. The strain required NaCl for growth and grew at salinities up to 200 g NaCl l(-1) (optimum 60 g l(-1)). Growth was observed at 15-40 degrees C, optimum growth occurred at about 40 degrees C, while growth was absent at 10 and 45 degrees C. The pH range for growth was pH 6.0-8.3. Yeast extract (0.1 g l(-1)) was required for growth. C(2-4) alcohols, C(3-4) carboxylic acids, yeast extract and H(2)/acetate supported growth with sulfate as electron acceptor. Sulfate, thiosulfate and sulfite served as electron acceptors, but not elemental sulfur, nitrate or fumarate. The DNA G+C content of strain PropA(T) was 54.1 mol%. Based on the genotypic and physiological properties, we propose that strain PropA(T) represents a novel species within a novel genus, Desulfosalsimonas propionicica gen. nov., sp. nov. The type strain of Desulfosalsimonas propionicica is PropA(T) (=DSM 17721(T) =VKM B-2385(T)).

The phylogenetic placement of Thermodesulfovibrio yellowstonii was investigated on the basis of gene order data from completely sequenced bacterial genomes. T. yellowstonii was found to share four gene arrangements characteristic of the Proteobacteria, Aquificae, Planctomycetes, Spirochaetes, Bacteroidetes, Chlorobi, Acidobacteria, Verrucomicrobia and termite group 1, the presence of which defines superphylum 2. The remaining phyla show sets of alternative gene arrangements and form superphylum 1. An analysis of conserved gene pairs showed that the overall genome organization of T. yellowstonii is most similar to that of deltaproteobacteria. Three arrangements that suggest gene translocations were identified that are likely to have occurred in a common ancestor of T. yellowstonii and the Proteobacteria exclusive of virtually all other major bacterial phyla. The translocation events suggest the closest evolutionary relationship between T. yellowstonii and the Proteobacteria.

The bacterial strain SR-1(T) was isolated from subsurface sediments of a uranium-contaminated site in Shiprock, New Mexico, USA. Cells are vibrioid and motile by means of a single polar flagellum. Strain SR-1(T) grows on sulfate, oxidizing formate, lactate and H2, but not malate, and ferments pyruvate. The DNA sequences of the 16S rRNA gene and the 16S-23S internal transcribed spacer of strain SR-1(T) showed 99.9 and 99.4 % similarity, respectively, to those of the type strain Desulfovibrio africanus DSM 2603(T). The DNA sequence of the ITS region is 300 bases in length and contains two tRNA genes (tRNA(Ile), tRNA(Ala)). The partial DNA sequence of the dsrAB gene showed 94.6 % amino acid sequence similarity to that of D. africanus. The DNA G+C content of strain SR-1(T) was 62.4 mol% and it showed 72 % DNA-DNA similarity to D. africanus. DNA typing methods that target gene clusters and whole genomes revealed characteristic genomic fingerprints for strain SR-1(T). A small plasmid was detected by gel electrophoresis. On the basis of distinct phenotypic and genotypic characteristics, strain SR-1(T) represents a novel subspecies of D. africanus, for which the name Desulfovibrio africanus subsp. uniflagellum subsp. nov. is proposed. The type strain is SR-1(T) (=JCM 15510(T) =LS KCTC 5649(T)).

A moderately halophilic, obligately chemolithoautotrophic, sulfur-oxidizing bacterium, designated strain HRh1(T), was obtained from mixed sediment samples from hypersaline chloride-sulfate lakes in the Kulunda Steppe, in south-western Siberia (Russia), using aerobic enrichment culture at 1 M NaCl with thiocyanate as substrate. Cells of the isolate were short, non-motile rods with a Gram-negative type of cell wall. The bacterium was an obligate aerobe capable of chemolithoautotrophic growth with thiocyanate and thiosulfate. With thiosulfate, it grew at NaCl concentrations of 0.2-3.0 M (optimum 0.5 M) and at pH 6.3-8.0 (optimum pH 7.3-7.5). During growth on thiocyanate, cyanate was identified as an intermediate. The dominant cellular fatty acids were C(16 : 0) and C(18 : 1)omega7. Phylogenetic analysis based on 16S rRNA gene sequencing placed the isolate in the class Gammaproteobacteria as an independent lineage, with an unclassified marine sulfur-oxidizing bacterium as the closest culturable relative (93 % sequence similarity). A single cbbL gene (coding for the key enzyme of the Calvin-Benson cycle of autotrophic CO(2) assimilation) with relatively low similarity to any homologous genes found in chemolithoautotrophs was detected in strain HRh1(T). On the basis of our phenotypic and phylogenetic analysis, the halophilic isolate is proposed to represent a new genus and novel species, Thiohalobacter thiocyanaticus gen. nov., sp. nov. The type strain of Thiohalobacter thiocyanaticus is HRh1(T) (=DSM 21152(T) =UNIQEM U249(T)).

A novel strictly anaerobic, endospore-forming, rod-shaped, Gram-positive bacterium, designated strain SGB2(T), was isolated from a mixed culture from a pond sediment during screening for sulfate-reducing bacteria capable of degrading cyanophycin (CGP). In this study, the taxonomic characterization of this mesophilic, proteolytic Clostridium isolate and the role which it, and its phylogenetic relatives, may play in peptide degradation and in the sulfur cycle are reported. Strain SGB2(T) was a commensal strain, utilizing CGP degradation products produced by other micro-organisms. Cells were motile until sporulation, forming oval, terminal spores that swell the cells. It showed optimum growth at 34 degrees C, pH 6.6 and in the absence of NaCl. Strain SGB2(T) utilized proteinaceous compounds such as peptone, Casamino acids, gelatin and trypticase soy, in addition to several amino acids and pyruvate. Utilization of many of these compounds was enhanced in the presence of thiosulfate. The isolate was unable to use any of the carbohydrates or alcohols investigated or CGP as carbon and energy sources. Thiosulfate and elemental sulfur were used as terminal electron acceptors. Phylogenetic analysis revealed that strain SGB2(T) belongs to the low-G+C-containing Clostridiales group. It exhibited 99 % 16S rRNA gene sequence similarity to its closest relatives Clostridium thiosulfatireducens Lup21(T) and Clostridium subterminale DSM 6970(T). DNA-DNA hybridization values with these two strains were 39.4 and 42.1 %, respectively. Based on phenotypic, genotypic and phylogenetic characteristics, we conclude that the isolate represents a novel species of the genus Clostridium, Clostridium sulfidigenes sp. nov. The type strain is SGB2(T) (=DSM 18982(T) =ATCC BAA-1538(T)).

A novel strictly anaerobic, thermophilic, sulfur-reducing bacterium, designated PH1209(T), was isolated from an East Pacific Rise hydrothermal vent (1 degrees N) sample and studied using a polyphasic taxonomic approach. Cells were Gram-negative, motile rods (approx. 1.60 x 0.40 microm) with a single polar flagellum. Strain PH1209(T) grew at temperatures between 33 and 65 degrees C (optimum 60 degrees C), from pH 5.0 to 8.0 (optimum 6.0-6.5), and between 2 and 4 % (w/v) NaCl (optimum 3 %). Cells grew chemolithoautotrophically with H(2) as an energy source, S(0) as an electron acceptor and CO(2) as a carbon source. Strain PH1209(T) was also able to use peptone and yeast extract as carbon sources. The G+C content of the genomic DNA was 35 mol%. Phylogenetic analyses based on 16S rRNA gene sequencing showed that strain PH1209(T) fell within the order Nautiliales, in the class Epsilonproteobacteria. Comparative 16S rRNA gene sequence analysis indicated that strain PH1209(T) belonged to the genus Nautilia and shared 97.2 and 98.7 % 16S rRNA gene sequence identity, respectively, with the type strains of Nautilia lithotrophica and Nautilia profundicola. It is proposed, from the polyphasic evidence, that the strain represents a novel species, Nautilia abyssi sp. nov.; the type strain is PH1209(T) (=DSM 21157(T)=JCM 15390(T)).

A novel weakly halotolerant, sulfate-reducing bacterium, designated strain RB22(T), was isolated from exhaust water of a Tunisian oil refinery. Cells of strain RB22(T) were Gram-negative, motile, vibrio-shaped or sigmoid and non-spore-forming, and occurred singly or in chains. Strain RB22(T) grew between 15 and 45 degrees C (optimum, 37 degrees C) and at pH 4.5 to 9 (optimum, pH 7). NaCl was not required for growth, but the strain tolerated high NaCl concentrations (up to 70 g l(-1)) with an optimum of 40 g l(-1). Sulfate, thiosulfate, sulfite and elemental sulfur served as electron acceptors, but not fumarate. Nitrate and nitrite were not reduced. Strain RB22(T) utilized lactate, formate, fumarate, succinate, glycerol, H(2)+CO(2) and methanol as substrates. The DNA G+C content was found to be 59.6 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that the isolate was a member of the genus Desulfovibrio, with no close relatives at the species level (16S rRNA gene sequence similarity of less than 95 %). Strain RB22(T) exhibited levels of 16S rRNA gene sequence similarity of 94.6 and 94.12 % to the type strains of the closely related species Desulfovibrio aespoeensis and Desulfovibrio dechloracetivorans, respectively. On the basis of genotypic and phylogenetic characteristics, and significant phenotypic differences, we suggest that strain RB22(T) represents a novel species, for which the name Desulfovibrio tunisiensis sp. nov. is proposed. The type strain is RB22(T) (=NCIMB 14400(T)=JCM 15076(T)=DSM 19275(T)).

A novel mesophilic sulfate-reducing bacterium, EMSSDQ(4)(T), was isolated from olive mill wastewater in the semi-arid region of Morocco (Marrakech). Cells were Gram-negative, catalase-positive, straight rods that were non-motile and non-spore-forming and contained cytochrome c(3) and desulfoviridin. The DNA G+C content was 65.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate was a member of the genus Desulfovibrio with Desulfovibrio carbinoliphilus D41(T), Desulfovibrio alcoholivorans SPSN(T), Desulfovibrio fructosivorans JJ(T) and Desulfovibrio carbinolicus EDK82(T) as the most closely related strains with validly published names. In addition to the classical substrates used by Desulfovibrio species, the isolate oxidized 1,4-tyrosol, one of the most abundant phenolic compounds occurring in olive mill wastewater, to 4-hydroxyphenylacetate without ring cleavage. D. alcoholivorans SPSN(T) was also found to carry out this reaction. Under air, strain EMSSDQ(4)(T) exhibited limited growth on lactate and yeast extract in the absence of sulfate. On the basis of genotypic and phenotypic characteristics, it is proposed that the isolate represents a novel species, Desulfovibrio marrakechensis sp. nov. The type strain is EMSSDQ(4)(T) (=DSM 19337(T) =ATCC BAA-1562(T)).

Four obligately anaerobic, thermophilic, sulfate-reducing bacterial strains, designated TGE-P1(T), TDV(T), TGL-LS1 and TSL-P1, were isolated from thermophilic (operated at 55 degrees C) methanogenic sludges from waste and wastewater treatment. The optimum temperature for growth of all the strains was in the range 55-60 degrees C. The four strains grew by reduction of sulfate with a limited range of electron donors, such as hydrogen, formate, pyruvate and lactate. In co-culture with the hydrogenotrophic methanogen Methanothermobacter thermautotrophicus DeltaH(T), strains TGE-P1(T), TGL-LS1 and TSL-P1 were able to utilize lactate syntrophically for growth. The DNA G+C contents of all the strains were in the range 34-35 mol%. The major cellular fatty acids of the strains were iso-C(17 : 0), iso-C(16 : 0), C(16 : 0) and anteiso-C(15 : 0). Phylogenetic analyses based on 16S rRNA gene sequences revealed that the strains belong to the Thermodesulfovibrio clade of the phylum 'Nitrospirae'. On the basis of their physiological, chemotaxonomic and genetic properties, strains TGL-LS1 (=JCM 13214) and TSL-P1 (=JCM 13215) were classified as strains of Thermodesulfovibrio islandicus. Two novel species of the genus Thermodesulfovibrio are proposed to accommodate the other two isolates: Thermodesulfovibrio aggregans sp. nov. (type strain TGE-P1(T) =JCM 13213(T) =DSM 17283(T)) and Thermodesulfovibrio thiophilus sp. nov. (type strain TDV(T) =JCM 13216(T) =DSM 17215(T)). To examine the ecological aspects of Thermodesulfovibrio-type cells in the sludge from which the strains were originally isolated, an oligonucleotide probe targeting 16S rRNA of all Thermodesulfovibrio species was designed and applied to thin sections of thermophilic sludge granules. Fluorescence in situ hybridization using the probe revealed rod- or vibrio-shaped cells as a significant population within the sludge, indicating their important role in the original ecosystem.

A novel strictly anaerobic, moderately thermophilic, sulfate-reducing bacterium, designated strain Lam5(T), was isolated from a hot spring in north-east Tunisia and was characterized phenotypically and phylogenetically. The isolate stained Gram-negative but had a Gram-positive-type cell wall. The strain comprised endospore-forming, slightly curved rod-shaped cells with peritrichous flagella. It did not possess desulfoviridin. Strain Lam5(T) grew anaerobically at 40-60 degrees C (optimally at 55 degrees C) and at pH 5.8-8.2 (optimally at pH 7.1); it did not require NaCl but tolerated concentrations up to 1.5 % (w/v). It utilized lactate, pyruvate, formate, ethanol, butanol, glycerol, propanol and H(2) (plus acetate) as electron donors. Lactate was oxidized and pyruvate was fermented to acetate. Sulfate, sulfite, thiosulfate, As(V) and Fe(III) (but not elemental sulfur, fumarate, nitrate or nitrite) were used as electron acceptors. The G+C content of the genomic DNA was 46.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain Lam5(T) was a member of the genus Desulfotomaculum, with Desulfotomaculum putei as its closest relative (96 % similarity to the type strain). On the basis of genotypic, phenotypic and phylogenetic data, strain Lam5(T) represents a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum hydrothermale sp. nov. is proposed. The type strain is Lam5(T) (=DSM 18033(T) =JCM 13992(T)).

Our newly designed primers were evaluated for the molecular analysis of specific groups of the sqr gene encoding sulfide : quinone reductase (SQR) in sediment environments. Based on the phylogenetic analysis, we classified the sqr sequences into six groups. PCR primers specific for each group were developed. We successfully amplified sqr-like gene sequences related to groups 1, 2 and 4 from diverse sediments including a marine sediment (SW), a tidal flat (TS), a river sediment (RS) and a lake sediment (FW). We recovered a total of 82 unique phylotypes (based on a 95 % amino acid sequence similarity cutoff) from 243 individual sqr-like gene sequences. Phylotype richness varied widely among the groups of sqr-like gene sequences (group 1>group 2>group 4) and sediments (SW>TS>RS>FW). Most of the sqr-like gene sequences were affiliated with the Proteobacteria clade and were distantly related to the reference sqr gene sequences from cultivated strains (less than approximately 80 % amino acid sequence similarity). Unique sqr-like gene sequences were associated with individual sediment samples in groups 1 and 2. This molecular tool has also enabled us to detect sqr-like genes in a sulfur-oxidizing enrichment from marine sediments. Collectively, our results support the presence of previously unrecognized sqr gene-containing micro-organisms that play important roles in the global biogeochemical cycle of sulfur.

Phenotypic and phylogenetic studies were performed on a novel sulfate-reducing bacterium, strain D41(T), isolated as part of a methanogenic syntrophic culture from a gas condensate-contaminated aquifer undergoing intrinsic bioremediation. The bacterium was a Gram-negative, non-spore-forming, curved rod, motile by a single polar flagellum, which oxidized several alcohols incompletely, including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 3-methyl-1-butanol (isoamyl alcohol), ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, phenylethanol and benzyl alcohol. Additionally, the strain oxidized H(2)/CO(2), formate, lactate, pyruvate, maleate, malate and fumarate. Sulfate, thiosulfate and sulfite were used as electron acceptors. The DNA G+C content was 63 mol%. Based on phylogenetic and phenotypic evidence, the novel species Desulfovibrio carbinoliphilus sp. nov. is proposed. The type strain is D41(T) (=ATCC BAA-1241(T) =DSM 17524(T)).

A novel thermophilic, sulfur-reducing chemolithoautotroph, strain ABI70S6(T), was isolated from a deep-sea hydrothermal field at the Yonaguni Knoll IV, Southern Okinawa Trough. Cells of strain ABI70S6(T) were motile rods, 0.9-2.0 microm in length and 0.4-0.8 microm in width. Strain ABI70S6(T) was an obligately anaerobic chemolithotroph, exhibiting hydrogen oxidation coupled with sulfur reduction. Growth was observed at 55-78 degrees C (optimum, 70 degrees C), pH 5.0-7.5 (optimum, pH 5.5-6.0) and 0.5-4.5 % NaCl (optimum, 3.0 % NaCl). H(2) and elemental sulfur were utilized as electron donor and acceptor, respectively. The major fatty acids were C(16 : 0) (40.0 %) and C(20 : 1) (60.0 %). The G+C content of genomic DNA was 44.2 mol%. The physiological attributes of strain ABI70S6(T) are similar to those of species of genera within the family Desulfurobacteriaceae, most of which are thermophilic and chemolithoautotrophic sulfur reducers. However, 16S rRNA gene sequence similarities between the novel isolate and type strains of all species within the family Desulfurobacteriaceae were <87 %, which is close to the similarities found between the novel isolate and members of the family Thermodesulfobacteriaceae (<85 %). Based on physiological and phylogenetic features of the novel isolate, it is proposed that it represents a novel species in a novel genus, Thermosulfidibacter takaii gen. nov., sp. nov., within the phylum Aquificae. The type strain of T. takaii is ABI70S6(T) (=JCM 13301(T)=DSM 17441(T)).

A novel sulfate-reducing bacterium, strain HB1(T), was isolated from an upflow anaerobic sludge blanket (UASB) reactor treating paper-mill wastewater operated at 37 degrees C. Cells of strain HB1(T) were oval to rod-shaped, 1-1.3 microm wide and 2.6-3.5 microm long and Gram-negative. The optimum temperature for growth was 28-30 degrees C. In the presence of sulfate, the isolate was able to grow on H(2)/acetate, formate, ethanol, propionate, fumarate, succinate, butyrate, crotonate, catechol, benzoate, 4-hydroxybenzoate, palmitate and stearate. The isolate only grew on H(2) when acetate was added as a carbon source; when grown on formate, acetate was not required. Growth was also possible on pyruvate and crotonate without an electron acceptor. The isolate showed very poor growth on acetate. Thiosulfate and sulfate were used as electron acceptors. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain HB1(T) represents a novel lineage within the Deltaproteobacteria; sequence similarities between strain HB1(T) and members of other related genera were less than 91%. Strain HB1(T) was also distinguished from members of related genera based on differences in several phenotypic characteristics. It is a member of the family Desulfobacteraceae. The major cellular fatty acids of strain HB1(T) were C(16:0), iso-C(15:0), anteiso-C(15:0) and C(14:0). beta-Hydroxy fatty acids were also present in the range of C(14:0) to C(18:0), of which C(16:0) was the most abundant. The G+C content of the DNA was 55.1 mol%. Based on physiological, biochemical and chemotaxonomic traits together with results of comparative 16S rRNA gene sequence analysis, strain HB1(T) is considered to represent a novel species in a new genus, for which the name Desulfatirhabdium butyrativorans gen. nov., sp. nov. is proposed. The type strain of Desulfatirhabdium butyrativorans is HB1(T) (=DSM 18734(T) =JCM 14470(T)).

A novel anaerobic, long-chain alkene-degrading, sulfate-reducing bacterium, strain LM2801T, was isolated from brackish sediment of a wastewater decantation facility of an oil refinery (Berre lagoon, France). Cells of strain LM2801T were Gram-negative, motile, slightly curved or vibrioid rods. Its optimum growth conditions were 30-36 degrees C, 6-10 g NaCl l(-1) and pH 7.5. Strain LM2801T incompletely oxidized long-chain alkenes (from C14 to C23) and fatty acids (C14 to C24). The DNA G+C content was 45.5 mol%. Sequence analyses of the 16S rRNA and dsrAB genes indicated that the strain was a member of the family Desulfobacteraceae within the Deltaproteobacteria. This novel isolate possesses phenotypic and phylogenetic traits that do not allow its classification as a member of any previously described genus. Therefore, strain LM2801T is described as a member of a new genus, Desulfatiferula gen. nov., of which Desulfatiferula olefinivorans sp. nov. is the type species. The type strain of Desulfatiferula olefinivorans is LM2801T (=DSM 18843T=JCM 14469T).

Newly developed PCR assays were used to PCR-amplify and sequence fragments of the dissimilatory adenosine-5'-phosphosulfate (APS) reductase genes (aprBA) comprising nearly the entire gene locus (2.2-2.4 kb, equal to 92-94 % of the protein coding sequence) from 75 sulfate-reducing prokaryotes (SRP) of a taxonomically wide range. Comparative phylogenetic analysis included all determined and publicly available AprBA sequences from SRP and selected homologous sequences of sulfur-oxidizing bacteria (SOB). The almost identical AprB and AprA tree topologies indicated a shared evolutionary path for the aprBA among the investigated SRP by vertical inheritance and concomitant lateral gene transfer (LGT). The topological comparison of AprB/A- and 16S rRNA gene-based phylogenetic trees revealed novel LGT events across the SRP divisions. Compositional gene analysis confirmed Thermacetogenium phaeum to be the first validated strain affected by a recent lateral transfer of aprBA as a putative effect of long-term co-cultivation with a Thermodesulfovibrio species. Interestingly, the Apr proteins of SRP and SOB diverged into two phylogenetic lineages, with the SRP affiliated with the green sulfur bacteria, e.g. Chlorobaculum tepidum, while the Allochromatium vinosum-related sequences formed a distinct group. Analysis of genome data indicated that this phylogenetic separation is also reflected in the differing presence of the putative proteins functionally associated with Apr, QmoABC complex (quinone-interacting membrane-bound oxidoreductase) and AprM (transmembrane protein). Scenarios for the origin and evolution of the dissimilatory APS reductase are discussed within the context of the dissimilatory sulfite reductase (DsrAB) phylogeny, the appearance of QmoABC and AprM in the SRP and SOB genomes, and the geochemical setting of Archean Earth.

Two strictly anaerobic, mesophilic, sulfate-reducing bacterial strains, Pro1(T) and Pro16, were isolated from an estuarine sediment in the Sea of Japan of the Japanese islands and were characterized by phenotypic and phylogenetic methods. Strains Pro1(T) and Pro16 had almost the same physiological and chemotaxonomic characteristics. Cells of both strains were Gram-negative, motile, non-spore-forming rods. Catalase activity was not detected. The optimum NaCl concentration for growth was 3.0 % (w/v). The optimum temperature for growth was 35 degrees C and the optimum pH was 6.7. Both strains used formate, propionate, pyruvate, lactate, fumarate, malate, ethanol, propanol, butanol, glycerol, alanine, glucose, fructose and H(2) as electron donors for sulfate reduction and did not use acetate, butyrate, succinate, methanol, glycine, serine, aspartate, glutamate, cellobiose or sucrose. Organic electron donors were incompletely oxidized mainly to acetate. Both strains also used thiosulfate as an electron acceptor. Without electron acceptors, both strains fermented pyruvate and lactate. The genomic DNA G+C contents of strains Pro1(T) and Pro16 were 48.6 and 46.0 mol%, respectively. The major respiratory quinone of both strains was menaquinone MK-5(H(2)). Major cellular fatty acids of both strains were C(15 : 0), C(16 : 0), C(17 : 1)omega6 and C(18 : 1)omega7. Phylogenetic analysis based on 16S rRNA gene sequences placed both strains in the class Deltaproteobacteria. The closest recognized relative of strains Pro1(T) and Pro16 was Desulfobulbus mediterraneus with sequence similarities of 95.2 and 94.8 %, respectively. Based on phylogenetic, physiological and chemotaxonomic characteristics, strains Pro1(T) and Pro16 represent a novel species of the genus Desulfobulbus, for which the name Desulfobulbus japonicus is proposed. The type strain is Pro1(T)(=JCM 14043(T)=DSM 18378(T)) and strain Pro16 (=JCM 14044=DSM 18379) is a reference strain.

A novel thermophilic and sulfur-reducing heterotrophic bacterium, strain TFS10-5(T), was isolated from a deep-sea hydrothermal field in Yonaguni Knoll IV, Southern Okinawa Trough. Cells of strain TFS10-5(T) were motile rods, 1.5-5 microm in length and 0.5-0.8 microm in width. Strain TFS10-5(T) was an obligately anaerobic heterotroph and sulfur-reduction stimulated growth. Growth was observed between 30 and 70 degrees C (optimum at 55-60 degrees C), pH 5.0-7.4 (optimum at pH 5.5-5.8), 1.0-5.5 NaCl % (optimum at 3.0-3.5 %). The fatty acid content was C(16 : 0) (71.0 %), C(16 : 1) (6.0 %), C(18 : 0) (21.4 %) and C(18 : 1) (1.6 %). The G+C content of the genomic DNA was 28 mol%. 16S rRNA gene sequence analysis indicated that strain TFS10-5(T) belongs to the genus Marinitoga. Based on the physiological and phylogenetic features of the new isolate, strain TFS10-5(T) represents a novel species in the genus Marinitoga for which the name Marinitoga okinawensis sp. nov. is proposed. The type strain is TFS10-5(T) (=JCM 13303(T)=DSM 17373(T)).