Desulfomonile tiedjei gen. nov. and sp. nov., a novel anaerobic,dehalogenating, sulfate-reducing bacterium

An anaerobic, dehalogenating, sulfate-reducing bacterium, strain DCB-1, is described and nutritionally characterized. The bacterium is a Gram-negative, nonmotile, non-sporeforming large rod with an unusual morphological feature which resembles a collar. The microorganism reductively dehalogenates meta substituted halobenzoates and also reduces sulfate, sulfite and thiosulfate as electron acceptors. The bacterium requires nicotinamide, 1,4-naphthoquinone and thiamine for optimal growth in a defined medium. The microorganism can grow autotrophically on H₂:CO₂ with sulfate or thiosulfate as terminal electron acceptors. It can also grow heterotrophically with pyruvate, several methoxybenzoates, formate plus sulfate or benzoate plus sulfate. It ferments pyruvate to acetate and lactate in the absence of other electron acceptors. The bacterium is inhibited by MoO _inf4 ^sup2- or SeO _inf4 ^sup2- as well as tetracycline, chloramphenicol, kanamycin or streptomycin. Cytochrome c₃ and desulfoviridin have been purified from cells grown in defined medium. 16S rRNA sequence analysis indicates the organism is a new genus of sulfate-reducing bacteria in the delta subdivision of the class Proteobacteria. We propose that the strain be named Desulfomonile tiedjei.Non-standard abbreviations PIPES piperazine-N,N-bis[2-ethanesulfonic acid] - MES 2-[N-morpholino]ethanesulfonic acid - TES N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid - HQNO 2-N-heptyl-4-hydroxy-quinoline-N-oxide - CCCP carbonyl-cyanide-m-chlorophenylhydrazine - CM carboxymethyl     

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids II. Incomplete oxidation of propionate by Desulfobulbus propionicus gen. nov., sp. nov.

A new type of sulfate-reducing bacteria with ellipsoidal to lemon-shaped cells was regularly enriched from anaerobic freshwater and marine mud samples when mineral media with propionate and sulfate were used. Three strains (1pr3, 2pr4, 3pr10) were isolated in pure culture. Propionate, lactate and alcohols were used as electron donors and carbon sources. Growth on H₂ required acetate as a carbon source in the presence of CO₂. Stoichiometric measurements revealed that oxidation of propionate was incomplete and led to acetate as an endproduct. Instead of sulfate, strain 1pr3 was shown to reduce sulfite and thiosulfate to H₂S; nitrate also served as electron acceptor and was reduced to ammonia. With lactate or pyruvate, all three strains were able to grow without external electron acceptor and formed propionate and acetate as fermentation products. None of the strains contained desulfoviridin. In strain 1pr3 cytochromes of the b- and c-type were identified. Strain 1pr3 is described as type strain of the new species and genus, Desulfobulbus propionicus.     

Anaerobic degradation of 1,3-propanediol by sulfate-reducing and by fermenting bacteria

Three strains of strictly anaerobic Gram-negative, non-sporeforming, motile bacteria were enriched and isolated from freshwater sediments with 1,3-propanediol as sole energy and carbon source. Strain OttPdl was a sulfate-reducing bacterium which grew also with lactate, ethanol, propanol, butanol, 1,4-butanediol, formate or hydrogen plus CO₂, the latter only in the presence of acetate. In the absence of sulfate, most of these substrates were fermented to the respective fatty acids in syntrophic cooperation with Methanospirillum hungatei. Sulfur, thiosulfate, or sulfite were reduced, nitrate not. The other two isolates degraded propanediol only in coculture with Methanospirillum hungatei. Strain OttGlycl grew in pure culture with acetoin and with glycerol in the presence of acetate. Strain WoAcl grew in pure culture only with acetoin. Both strains did not grow with other substrates, and did not reduce nitrate, sulfate, sulfur, thiosulfate or sulfite. The isolates were affiliated with the genera Desulfovibrio and Pelobacter. The pathways of propanediol degradation and the ecological importance of this process are discussed.     

Desulforhopalus vacuolatus gen. nov., sp. nov., a new moderately psychrophilic sulfate-reducing bacterium with gas vacuoles isolated from a temperate estuary

A new type of gas-vacuolated, sulfate-reducing bacterium was isolated at 10° C from reduced mud (E₀ < 0) obtained from a temperate estuary with thiosulfate and lactate as substrates. The strain was moderately psychrophilic with optimum growth at 18–19° C and a maximum growth temperature of 24° C. Propionate, lactate, and alcohols served as electron donors and carbon sources. The organism grew heterotrophically only with hydrogen as electron donor. Propionate and lactate were incompletely oxidized to acetate; traces of lactate were fermented to propionate, CO₂, and possibly acetate in the presence of sulfate. Pyruvate was utilized both with and without an electron acceptor present. The strain did not contain desulfoviridin. The G+C content was 48.4 mol%. The differences in the 16S rRNA sequence of the isolate compared with that of its closest phylogenetic neighbors, bacteria of the genus Desulfobulbus, support the assignment of the isolate to a new genus. The isolate is described as the type strain of the new species and genus, Desulforhopalus vacuolatus. Received: 4 March 1996 / Accepted: 17 June 1996     

Acetonema longum gen.nov.sp.nov., an H2/CO2 acetogenic bacterium from the termite,Pterotermes occidentis

A previously undescribed, H₂-oxidizing CO₂-reducing acetogenic bacterium was isolated from gut contents of the wood-feeding termite, Pterotermes occidentis. Cells of representative strain APO-1 were strictly anaerobic, Gram-negative, endospore-forming motile rods which measured 0.30–0.40×6–60 m. Cells were catalase positive, oxidase negative, and had 51.5 mol percent G+C in their DNA. Optimum conditions for growth on H₂+CO₂ were at 30–33°C and pH (initial) 7.8, and under these conditions cells formed acetate according to the equation: 4 H₂+2 CO₂CH₃COOH+2 H₂O. Other energy sources supporting good growth of strain APO-1 included glucose, ribose, and various organic acids. Acetate and butyrate were major fermentation products from most organic compounds tested, however propionate, succinate, and 1,2-propanediol were also formed from some substrates. Based on comparative analysis of 16S rRNA nucleotide sequences, strain APO-1 was related to, but distinct from, members of the genus Sporomusa. Moreover, physiological and morphological differences between strain APO-1 and the six known species of Sporomusa were significant. Consequently, it is proposed herewith that a new genus, Acetonema, be established with strain APO-1 as the type strain of the new species, Acetonema longum. A. longum may contribute to the nutrition of P. occidentis by forming acetate, propionate and butyrate, compounds which are important carbon and energy sources for termites.     

Fermentation of trihydroxybenzenes by Pelobacter acidigallici gen. nov. sp. nov., a new strictly anaerobic,non-sporeforming bacterium

Five strains of rod-shaped, Gram-negative, non-sporing, strictly anaerobic bacteria were isolated from limnic and marine mud samples with gallic acid or phloroglucinol as sole substrate. All strains grew in defined mineral media without any growth factors; marine isolates required salt concentrations higher than 1% for growth, two freshwater strains only thrived in freshwater medium. Gallic acid, pyrogallol, 2,4,6-trihydroxybenzoic acid, and phloroglucinol were the only substrates utilized and were fermented stoichiometrically to 3 mol acetate (and 1 mol CO₂) per mol with a growth yield of 10g cell dry weight per mol of substrate. Neither sulfate, sulfur, nor nitrate were reduced. The DNA base ratio was 51.8% guanine plus cytosine. A marine isolate, Ma Gal 2, is described as type strain of a new genus and species, Pelobacter acidigallici gen. nov. sp. nov., in the family Bacteroidaceae. In coculture with Acetobacterium woodii, the new isolates converted also syringic acid completely to acetate. Cocultures with Methanosarcina barkeri converted the respective substrates completely to methane and carbon dioxide.     

The new facultatively chemolithoautotrophic, moderately halophilic, sulfate-reducing bacterium Desulfovermiculus halophilus gen. nov., sp. nov., isolated from an oil field

The new mesophilic, chemolithoautotrophic, moderately halophilic, sulfate-reducing bacterium strain 11-6, could grow at a NaCl concentration in the medium of 30–230 g/l, with an optimum at 80–100 g/l. Cells were vibrios motile at the early stages of growth. Lactate, pyruvate, malate, fumarate, succinate, propionate, butyrate, crotonate, ethanol, alanine, formate, and H₂/CO₂ were used in sulfate reduction. Butyrate was degraded completely, without acetate accumulation. In butyrate-grown cells, a high activity of CO dehydrogenase was detected. Additional growth factors were not required. Autotrophic growth occurred, in the presence of sulfate, on H₂/CO₂ or formate without other electron donors. Fermentation of pyruvate and fumarate was possible in the absence of sulfate. Apart from sulfate, sulfite, thiosulfate, and elemental sulfur were able to serve as electron acceptors. The optimal growth temperature was 37°C; the optimum pH was 7.2. Desulfoviridin was not detected. Menaquinone MK-7 was present. The DNA G+C content was 55.2 mol %. Phylogenetically, the bacterium represented a separate branch within the cluster formed by representatives of the family Desulfohalobiaceae in the class Deltaproteobacteria. The bacterium was assigned to a new genus and species, Desulfovermiculus halophilus gen. nov., sp. nov. The type strain is 11-6^T (= VKM B-2364), isolated from the highly mineralized formation water of an oil field.     

Desulfolutivibrio sulfoxidireducens gen. nov., sp. nov., isolated from a pyrite-forming enrichment culture and reclassification of Desulfovibrio sulfodismutans as Desulfolutivibrio sulfodismutans comb. nov

Two strains of sulfate-reducing bacteria (J.5.4.2-L4.2.8^T and J.3.6.1-H7) were isolated from a pyrite-forming enrichment culture and were compared phylogenetically and physiologically to the closest related type strain Desulfovibrio sulfodismutans DSM 3696^T. The isolated strains were vibrio-shaped, motile rods that stained Gram-negative. Growth occurred from 15 to 37 °C and within a pH range of 6.5–8.5. Both strains used sulfate, thiosulfate, sulfite, and dimethyl sulfoxide (DMSO) as electron acceptor when grown with lactate. Lactate was incompletely oxidized to acetate. Formate and H₂ were used as electron donor in the presence of acetate. Dismutation of thiosulfate and pyrosulfite was observed. The two new isolates differed from D. sulfodismutans by the utilization of DMSO as electron acceptor, 82% genome-wide average nucleotide identity (ANI) and 32% digital DNA-DNA hybridization (dDDH), thus representing a novel species. The type strain of the type species Desulfovibrio desulfuricans Essex6^T revealed merely 88% 16S rRNA gene identity and 49% genome-wide average amino acid identity (AAI) to the new isolates as well as to D. sulfodismutans. Furthermore, the dominance of menaquinone MK-7 over MK-6 and the dominance of ai-C_15:0 fatty acids were observed not only in the two new isolated strains but also in D. sulfodismutans. Therefore, the definition of a new genus is indicated for which the name Desulfolutivibrio is proposed. We propose for strains J.5.4.2-L4.2.8^T and J.3.6.1-H7 the name Desulfolutivibrio sulfoxidireducens gen. nov. sp. nov. with strain J.5.4.2-L4.2.8^T defined as type strain. In addition, we propose the reclassification of Desulfovibrio sulfodismutans as Desulfolutivibrio sulfodismutans comb. nov.     

Desulfovibrio vietnamensissp.nov., a Halophilic Sulfate-Reducing Bacterium from Vietnamese Oil Fields

From samples collected in crude oil storage tanks and oil production waters near the coastal town of Vung Tau in Southern Vietnam, several strains of sulfate-reducing bacteria were isolated and maintained in pure culture. Strain G3 100 consisted of vibrio-shaped, motile, non-sporulating, Gram-negative, desulfoviridin-containing cells. It grew optimally at 5% NaCl. It utilized a range of organic acids as electron donors in the presence of sulfate, including lactate, malate, formate and fumarate. Ethanol and glycerol were also used. In the presence of lactate, thiosulfate, sulfite, sulfate and fumarate were used as electron acceptors. Organic substrates were not fermented. The DNA base composition of G3 100 was 60·6 mol % G + C. On the basis of 16S rRNA sequence data, G3 100 should be included in the genusDesulfovibrio. However, its physiology, whole-cell protein pattern and susceptibility to antibiotics were different from other members of this genus. Therefore, G3 100 should be recognized as a new species, for which we propose the nameDesulfovibrio vietnamensis.     

Culturable diversity of lithotrophic haloalkaliphilic sulfate-reducing bacteria in soda lakes and the description of Desulfonatronum thioautotrophicum sp. nov., Desulfonatronum thiosulfatophilum sp. nov., Desulfonatronovibrio thiodismutans sp. nov., and Desulfonatronovibrio magnus sp. nov

Soda lake sediments usually contain high concentrations of sulfide indicating active sulfate reduction. Monitoring of sulfate-reducing bacteria (SRB) in soda lakes demonstrated a dominance of two groups of culturable SRB belonging to the order Desulfovibrionales specialized in utilization of inorganic electron donors, such as formate, H₂ and thiosulfate. The most interesting physiological trait of the novel haloalkaliphilic SRB isolates was their ability to grow lithotrophically by dismutation of thiosulfate and sulfite. All isolates were obligately alkaliphilic with a pH optimum at 9.5–10 and moderately salt tolerant. Among the fifteen newly isolated strains, four belonged to the genus Desulfonatronum and the others to the genus Desulfonatronovibrio. None of the isolates were closely related to previously described species of these genera. On the basis of phylogenetic, genotypic and phenotypic characterization of the novel soda lake SRB isolates, two novel species each in the genera Desulfonatronum and Desulfonatronovibrio are proposed.     

Oxalobacter formigenes gen. nov., sp. nov.: oxalate-degrading anaerobes that inhabit the gastrointestinal tract

This report describes a new group of anaerobic bacteria that degrade oxalic acid. The new genus and species, Oxalobacter formigenes, are inhabitants of the rumen and also of the large bowel of man and other animals where their actions in destruction of oxalic acid may be of considerable importance to the host. Isolates from the rumen of a sheep, the cecum of a pig, and from human feces were all similar Gram-negative, obligately anaerobic rods, but differences between isolates in cellular fatty acid composition and in serologic reaction were noted. Measurements made with type strain OxB indicated that 1 mol of protons was consumed per mol of oxalate degraded to produce approximately 1 mol of CO₂ and 0.9 mol of formate. Substances that replaced oxalate as a growth substrate were not found.     

Desulfotomaculum geothermicum sp. nov., a thermophilic,fatty acid-degrading,sulfate-reducing bacterium isolated with H2 from geothermal ground water

A strictly anaerobic, thermophilic, fatty acids-degrading, sporulating sulfate-reducing bacterium was isolated from geothermal ground water. The organism stained Gram-negative and formed gas vacuoles during sporulation. Lactate, ethanol, fructose and saturated fatty acids up to C₁₈ served as electron donors and carbon sources with sulfate as external electron acceptor. Benzoate was not used. Stoichiometric measurements revealed a complete oxidation of part of butyrate although growth with acetate as only electron donor was not observed. The rest of butyrate was oxidized to acetate. The strain grew chemolithoautotrophically with hydrogen plus sulfate as energy source and carbon dioxide as carbon source without requirement of additional organic carbon like acetate. The strain contained a c-type cytochrome and presumably a sulfite reductase P582. Optimum temperature, pH and NaCl concentration for growth were 54°C, pH 7.3–7.5 and 25 to 35 g NaCl/l. The G+C content of DNA was 50.4 mol %. Strain BSD is proposed as a new species of the spore-forming sulfate-reducing genus Desulfotomaculum, D. geothermicum.     

New types of acetate-oxidizing,sulfate-reducing Desulfobacter species,D. hydrogenophilus sp. nov., D. latus sp. nov., and D. curvatus sp. nov.

Sulfate-reducing bacteria with oval to rod-shaped cells (strains AcRS1, AcRS2) and vibrio-shaped cells (strains AcRM3, AcRM4, AcRM5) differing by size were isolated from anaerobic marine sediment with acetate as the only electron donor. A vibrio-shaped type (strain AcKo) was also isolated from freshwater sediment. Two strains (AcRS1, AcRM3) used ethanol and pyruvate in addition to acetate, and one strain (AcRS1) grew autotrophically with H₂, sulfate and CO₂. Higher fatty acids or lactate were never utilized. All isolates were able to grow in ammonia-free medium in the presence of N₂. Nitrogenase activity under such conditions was demonstrated by the acetylene reduction test. The facultatively lithoautotrophic strain (AcRS1), a strain (AcRS2) with unusually large cells (2×5 m), and a vibrio-shaped strain (AcRM3) are described as new Desulfobacter species, D. hydrogenophilus, D. latus, and D. curvatus, respectively.     

Desulfacinum subterraneumsp. nov., a New Thermophilic Sulfate-Reducing Bacterium Isolated from a High-Temperature Oil Field

A new thermophilic sulfate-reducing bacterium isolated from the high-temperature White Tiger oil field (Vietnam) is described. Cells of the bacterium are oval (0.4–0.6 by 0.6–1.8 m), nonmotile, non-spore-forming, and gram-negative. Growth occurs at 45 to 65°C (with an optimum at 60°C) at NaCl concentrations of 0 to 50 g/l. In the course of sulfate reduction, the organism can utilize lactate, pyruvate, malate, fumarate, ethanol, salts of fatty acids (formate, acetate, propionate, butyrate, caproate, palmitate), yeast extract, alanine, serine, cysteine, and H₂+ CO₂(autotrophically). In addition to sulfate, the bacterium can use sulfite, thiosulfate, and elemental sulfur as electron acceptors. In the absence of electron acceptors, the bacterium can ferment pyruvate and yeast extract (a yet unrecognized capacity of sulfate reducers) with the formation of acetate and H₂. The G+C content of DNA is 60.8 mol %. The level of DNA–DNA hybridization of the isolate (strain 101^T) and Desulfacinum infernum(strain BG1^T) is as low as 34%. Analysis of the nucleotide sequence of 16S rDNA places strain 101^Tin the phylogenetic cluster of the Desulfacinumspecies within the sulfate reducer subdivision of the delta subclass of Proteobacteria. All these results allowed the bacterium studied to be described as a new species, Desulfacinum subterraneumsp. nov., with strain 101 as the type strain.     

Isolation and characterization of Thermanaerothrix daxensis gen. nov., sp. nov., a thermophilic anaerobic bacterium pertaining to the phylum "Chloroflexi", isolated from a deep hot aquifer in the Aquitaine Basin

A new strictly anaerobic thermophilic multicellular filamentous bacterium (0.2–0.3 μm × >100 μm), designated GNS-1^T, was isolated from a deep hot aquifer in France. It was non-motile, and stained Gram-negative. Optimal growth was observed at 65 °C, pH 7.0, and 2 g L⁻¹ of NaCl. Strain GNS-1^T was chemoorganotrophic fermenting ribose, glucose, galactose, arabinose, fructose, mannose, maltose, sucrose, xylose, raffinose, pyruvate, and xylan. Yeast extract was required for growth. The end products of glucose fermentation were lactate, acetate, CO₂, and H₂. The G + C content of the DNA was 57.6 mol%. Its closest phylogenetic relative was Bellilinea caldifistulae with 92.5% similarity. Based on phylogenetic, genotypic and phenotypic characteristics, strain GNS-1^T (DSM 23592^T, JCM 16980^T) is proposed to be assigned to a novel species of a novel genus within the class Anaerolineae (subphylum I), phylum “Chloroflexi”, Thermanaerothrix daxensis gen. nov., sp. nov. The GenBank accession number is HM596746.     

Thermodesulforhabdus norvegicus gen. nov., sp. nov., a novel thermophilic sulfate-reducing bacterium from oil field water

A novel gram-negative, thermophilic, acetate-oxidizing, sulfate-reducing bacterium, strain A8444, isolated from hot North Sea oil field water, is described. The rod-shaped cells averaged 1 μm in width and 2.5 μm in length. They were motile by means of a single polar flagellum. Growth was observed between 44 and 74°C, with an optimum at 60°C. Spores were not produced. Sulfate and sulfite were used as electron acceptors. Sulfur, thiosulfate, nitrate, fumarate, and pyruvate were not reduced. In the presence of sulfate, growth was observed with acetate, lactate, pyruvate, butyrate, succinate, malate, fumarate, valerate, caproate, heptanoate, octanoate, nonadecanoate, decanoate, tridecanoate, pentadecanoate, palmitate, heptadecanoate, stearate, and ethanol. Pyruvate, lactate, and fumarate did not support fermentative growth. Cytochromes of the c-type were present. Desulfoviridin, desulforubidin, P582, and desulfofuscidin were not present. The G+C content of the DNA was 51 mol%. Sequence analysis of 16S rDNA showed that phylogenetically strain A8444 belongs to the delta subdivision of the Proteobacteria. The closest relatives are Desulfacinum infernum and Syntrophobacter wolinii. Strain A8444 is described as the type strain of the new taxon Thermodesulforhabdus norvegicus gen. nov., sp. nov. Received: 4 May 1995 / Accepted: 11 July 1995     

Malonomonas rubra gen. nov. sp. nov., a microaerotolerant anaerobic bacterium growing by decarboxylation of malonate

From anoxic marine sediment samples, new anaerobic, microaerotolerant, Gram-negative, non-sporeforming bacteria were isolated which grew in mineral medium with malonate as sole source of carbon and energy. Cells were motile thin rods, often forming large aggregates. Malonate was decarboxylated to acetate with concomitant growth yields of 1.9–2.1 g dry cell matter per mol malonate degraded. Fumarate and malate were fermented to succinate and CO₂. No other substrates were used. No inorganic electron acceptors were reduced. At least 150 mM NaCl was required for growth with either substrate. High amounts of a periplasmic cytochrome c were detected, as well as small amounts of a membrane-bound cytochrome b. All enzymes of the citric acid cycle were found to be present. The DNA base ratio was 48.3 mol% guanine plus cytosine. Since this new bacterium cannot be affiliated with any of the known genera and species, a new genus and species, Malonomonas rubra is proposed.     

Characterization of Desulfomicrobium escambium sp. nov. and proposal to assign Desulfovibrio desulfuricans strain Norway 4 to the genus Desulfomicrobium

A sulfate-reducing bacterium, designated strain ESC1, was isolated and found to be a new species. Strain ESC1 is a strictly anaerobic, gram-negative, non-sporeforming, motile, short, round-ended rod often occurring in pairs. Of 31 fermentative substrates tested, only pyruvate was utilized. Sulfate enhanced growth with pyruvate and allowed growth with ethanol, lactate, formate and hydrogen. Both sulfate and thiosulfate were reduced. Lactate was incompletely oxidized to acetate and CO₂. The strain was desulfoviridin negative. The G+C content is 59.9%. These data suggested placement of strain ESC1 in the genus Desulfomicrobium. Comparative 16S rRNA analysis showed that strain ESC1 shares 98% rRNA sequence similarity with Desulfomicrobium baculatum and Desulfovibrio desulfuricans strain Norway 4. The latter two strains shared greater than 99% 16S rRNA sequence similarity. Strain ESC1 has been designated as the new species Desulfomicrobium escambium. We also recommend that D. desulfuricans strain Norway 4 be considered for reclassification as a Desulfomicrobium species.     

Anaerobic degradation of indolic compounds by sulfate-reducing enrichment cultures,and description of Desulfobacterium indolicum gen. nov., sp. nov.

Indole (1.5 mmol/l) added to suflate-rich marine mud or sulfate-free sewage digestor sludge was anaerobically degraded within one week. Enrichments from sludge samples in defined indole-containing media with or without sulfate were selective for sulfate-reducing bacteria or mixed methanogenic associations, respectively. Other enrichments of sulfate-reducing bacteria were obtained with skatole, indoleacetate, indolepropionate, quinoline, and pyridine. From a marine enrichment with indole as sole electron donor and carbon source, an oval to rod-shaped, Gram-negative, nonsporing sulfate-reducing bacterium (strain In04) was isolated. Growth occurred in defined bicarbonate-buffered, sulfide-reduced media supplemented with vitamin B₁₂. Furthen aromatic compounds utilized as electron donors and carbon sources were anthranilic acid and quinoline. Nonaromatic compounds used as substrates were formate, acetate, propionate, ethanol, propanol, butanol, pyruvate, malate, fumarate, and succinate. However, growth with substrates other than indole was rather slow. Thiosulfate served as an alternative electron acceptor. Complete oxidation of indole to CO₂ was shown by stoichiometric measurements in batch culture with sulfate as electron acceptor. An average growth yield of 31.3 g cell dry weight was obtained per mol of indole oxidized. Pigment analysis revealed that cytochromes and menaquinone MK-7 (H₂) were present. Desulfoviridin could not be detected. Strain In04 is described as new species of the new genus Desulfobacterium indolicum.     

Haloalkaliphilic spore-forming sulfidogens from soda lake sediments and description of Desulfitispora alkaliphila gen. nov., sp. nov.

An anaerobic enrichment with pyruvate as electron donor and thiosulfate at pH 10 and 0.6 M Na⁺ inoculated with pasteurized soda lake sediments resulted in a sulfidogenic coculture of two morphotypes of obligately anaerobic haloalkaliphilic endospore-forming clostridia, which were further isolated in pure culture. Strain AHT16 was a thin long rod able to ferment sugars and pyruvate and to respire H₂, formate and pyruvate using thiosulfate and fumarate as electron acceptors and growing optimally at pH 9.5. Thiosulfate was reduced incompletely to sulfide and sulfite. The strain was closely related (99% sequence similarity) to a peptolytic alkaliphilic clostridium Natronincola peptidovorans. Strain AHT17 was a short rod with a restricted respiratory metabolism, growing with pyruvate and lactate as electron donor and sulfite, thiosulfate and elemental sulfur as electron acceptors with a pH optimum 9.5. Thiosulfate was reduced completely via sulfite to sulfide. The ability of AHT17 to use sulfite explained the stability of the original coculture of the two clostridia—one member forming sulfite from thiosulfate and another consuming it. Strain AHT17 formed an independent deep phylogenetic lineage within the Clostridiales and is proposed as a new genus and species Desulfitisporum alkaliphilum gen. nov., sp. nov. (=DSM 22410^T = UNIQEM U794^T).