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.     

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.     

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     

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.     

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.     

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     

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.     

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.     

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.     

A sulfate-reducing bacterium from the oxic layer of a microbial mat from Solar Lake (Sinai), Desulfovibrio oxyclinae sp. nov.

In an investigation on the oxygen tolerance of sulfate-reducing bacteria, a strain was isolated from a 10⁷-fold dilution of the upper 3-mm layer of a hypersaline cyanobacterial mat (transferred from Solar Lake, Sinai). The isolate, designated P1B, appeared to be well-adapted to the varying concentrations of oxygen and sulfide that occur in this environment. In the presence of oxygen strain P1B respired aerobically with the highest rates [260 nmol O₂ min^–1 (mg protein)^–1] found so far among marine sulfate-reducing bacteria. Besides H₂ and lactate, even sulfide or sulfite could be oxidized with oxygen. The sulfur compounds were completely oxidized to sulfate. Under anoxic conditions, it grew with sulfate, sulfite, or thiosulfate as the electron acceptor using H₂, lactate, pyruvate, ethanol, propanol, or butanol as the electron donor. Furthermore, in the absence of electron donors the isolate grew by disproportionation of sulfite or thiosulfate to sulfate and sulfide. The highest respiration rates with oxygen were obtained with H₂ at low oxygen concentrations. Aerobic growth of homogeneous suspensions was not obtained. Additions of 1% oxygen to the gas phase of a continuous culture resulted in the formation of cell clumps wherein the cells remained viable for at least 200 h. It is concluded that strain P1B is oxygen-tolerant but does not carry out sulfate reduction in the presence of oxygen under the conditions tested. Analysis of the 16S rDNA sequence indicated that strain P1B belongs to the genus Desulfovibrio, with Desulfovibrio halophilus as its closest relative. Based on physiological properties strain P1B could not be assigned to this species. Therefore, a new species, Desulfovibrio oxyclinae, is proposed. Received: 7 August 1996 / Accepted: 29 January 1997     

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.     

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).     

Isolation and characterization of a thermophilic sulfate-reducing bacterium Desulfotomaculum thermoacetoxidans sp. nov.

An obligately anaerobic thermophilic sporeforming sulfate-reducing bacterium, named strain CAMZ, was isolated from a benzoate enrichment from a 58°C thermophilic anaerobic bioreactor. The cells of strain CAMZ were 0.7 m by 2–5 m rods with pointed ends, forming single cells or pairs. Spores were central, spherical, and caused swelling of the cells. The Gram stain was negative. Electron donors used included lactate, pyruvate, acetate and other short chain fatty acids, short chain alcohols, alanine, and H₂/CO₂. Lactate and pyruvate were oxidized completely to CO₂ with sulfate as electron acceptor. Sulfate was required for growth on H₂/CO₂, and both acetate and sulfide were produced from H₂/CO₂-sulfate. Sulfate, thiosulfate, or elemental sulfur served as electron acceptors with lactate as the donor while sulfite, nitrate, nitrite, betaine, or a hydrogenotrophic methanogen did not. The optimum temperature for growth of strain CAMZ was 55–60°C and the optimum pH value was 6.5. The specific activities of carbon monoxide dehydrogenase of cells of strain CAMZ grown on lactate, H₂/CO₂, or acetate with sulfate were 7.2, 18.1, and 30.8 mol methyl viologen reduced min^–1 [mg protein]^–1, respectively, indicating the presence of the CO/Acetyl-CoA pathway in this organism. The mol%-G+C of strain CAMZ's DNA was 49.7. The new species name Desulfotomaculum thermoacetoxidans is proposed for strain CAMZ.     

Complete oxidation of catechol by the strictly anaerobic sulfate-reducing Desulfobacterium catecholicum sp. nov.

From an anaerobic enrichment culture with vanillate as substrate, a catechol-degrading lemon-shaped nonsporing sulfate-reducing bacterium, strain NZva20, was isolated in pure culture. Growth occurred in defined, bicarbonate-buffered, sulfide-reduced freshwater medium with catechol as sole electron donor and carbon source. Catechol was completely oxidized to CO₂ with an average growth yield of 31 g cell dry mass per mol of catechol, corresponding to 9.5 g cell dry mass per mol of sulfate reduced. Further substrates utilized as electron donors and carbon sources were resorcinol, hydroquinone, benzoate and several other aromatic compounds, hydrogen plus carbon dioxide, formate, lactate, pyruvate, alcohols including methanol, dicarboxylic acids, acetate, propionate and higher fatty acids up to 18 carbon atoms. Instead of sulfate, sulfite, thiosulfate, dithionite or nitrate served as electron acceptors. Nitrate was reduced to ammonium. Strain NZva20 is the first bacterium in which the complete oxidation of organic substrates is linked to the ammonification of nitrate. Elemental sulfur was not utilized as electron acceptor. In the absence of an electron acceptor slow growth occurred on pyruvate or fumarate. The G+C content of the DNA of strain NZva20 was 52.4 mol%. Cytochromes were present. Desulfoviridin could not be detected. Strain NZva20 is described as type strain of a new species, Desulfobacterium catecholicum sp. nov.Affectionately dedicated to Professor Ralph S. Wolfe on the occassion of his 65th birthday     

Desulfovibrio mexicanus sp. nov., a Sulfate-reducing Bacterium Isolated from an Upflow Anaerobic Sludge Blanket (UASB) Reactor Treating Cheese Wastewaters

A mesophilic sulfate-reducing bacterium, designated strain Lup1^T(T=type strain) was isolated from a Mexican UASB digester treating cheese factory wastewater. The non-motile, Gram-negative, curved and non-spore-forming cells (1.7–2.5×0.5 μm) existed singly or in chains. Optimum growth occurred at 37°C and pH 7.2 in a medium containing lactate and thiosulfate. Strain Lup1^Tused pyruvate, formate, Casamino acids, serine, cysteine, H₂and ethanol as electron donors in the presence of thiosulfate as an electron acceptor and fermented pyruvate, Casamino acids, cysteine, and serine. Sulfate, elemental sulfur, and sulfite also served as electron acceptors but not nitrate or fumarate. Thiosulfate was disproportionated to sulfate and sulfide. The G+C content of the DNA was 66 mol%. Phylogenetic analysis based on 16S rDNA revealed that strain Strain Lup1^Twas a member of the genus Desulfovibrio withDesulfovibrio aminophilus being the closest relative (similarity value of 91%). As strain Lup1^Tis physiologically and phylogenetically different from other Desulfovibrio species, it is designated Desulfovibrio mexicanus sp. nov. (=DSM 13116).