Search

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

In this study, heat-pretreated sulfate-reducing bacteria (SRBs) were evaluated for simultaneous sulfate and nitrate removal in a bioelectrochemical system (BES). The effect of the applied potential of 20 mV to SRBs was evaluated at a sulfate concentration of 3 g/L and/or nitrate concentration of 0.5 g/L supplemented before heat pretreatment for sulfate and nitrate removal. The highest H 2 production of 2.24 ± 0.04 mM/L in heat-pretreated culture was observed in the presence of sulfate at an applied potential of 20 mV (BHE-S). Simultaneous reduction of sulfate and nitrate was significant in BESs supplemented with either sulfate or nitrate during heat-shock pretreatment of the culture. The highest SO 4 2- removal of 88.91 ± 0.8% was found in culture heat pretreated with NO 3 - and applied with 20 mV potential (BHE-N). The kinetics of heat-pretreated culture showed higher R 2 and ultimate potential for H 2 on the continuous application of 20 mV potential., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Lipopolysaccharides also called endotoxins are an integral component of the outer membrane of Gram-negative bacteria. When released from the bacterial surface, they interact with a host immune system, triggering excessive inflammatory response. Lipid A is the biologically most active part of endotoxin, and its activity is modulated by the quantity, quality and arrangement of its fatty acids. Desulfovibrio desulfuricans is sulfate-reducing, Gram-negative bacterium that is supposed to be opportunistic pathogens of humans and animals. In the present study, chemical composition of lipid A from various strains of D. desulfuricans was analyzed by gas chromatography/mass spectrometry. It was found that the fatty acid component of the lipid A contains dodecanoic, tetradecanoic, 3-hydroxytetradecanoic and hexadecanoic acids, and its carbohydrate core is composed of glucosamine. The analysis of 3-acyloxyacyl residue of the lipid A revealed the presence of amide-bound 3-(dodecanoyloxy)tetradecanoic and 3-(hexadecanoyloxy)tetradecanoic acids and ester-bound 3-(tetradecanoyloxy)tetradecanoic acid. It was concluded that both fatty acid and 3-acyloxyacyl residue profiles of the lipid A from the studied bacteria were similar to those of E. coli and S.enterica. [ABSTRACT FROM AUTHOR]

The outer membrane proteins of Desulfovibrio piger and Bilophila wadsworthia (Omp-DP and Omp-BW, respectively) and the genes encoding them ( omp-DP and omp-BW) were isolated and characterized. Native Omp-DP and Omp-BW form a trimeric structure of approximately 120 kDa. These proteins disaggregated into monomers with a molecular weight of approximately 53 kDa after heating at 95°C for 10 min. The pore-forming abilities of these oligomeric proteins demonstrated that they form small nonspecific channels with an exclusion limit of 260–300 Da. The omp-DP and omp-BW genes were cloned and sequenced. Sequence analyses revealed an open reading frame of 1,512 bp for omp-DP and 1,440 bp for omp-BW. The mature Omp-DP protein consisted of 480 amino acids and had a calculated MW of 53,290 Da. The mature Omp-BW protein consisted of 456 amino acids and had a calculated MW of 50.050 Da. Alignment of Omp-DP with Omp-BW revealed 54% homology, whereas alignment with other known porins showed a low level of homology. Analysis of the secondary structures indicated that both proteins span the outer membrane 18 times with amphipathic β-strands. This research presents porins which were isolated and characterized for the first time from bacteria belonging to the Desulfovibrionaceae family. [ABSTRACT FROM AUTHOR]

Sulfate-reducing bacteria (SRB) are anaerobes readily found in oxic–anoxic interfaces. Multiple defense pathways against oxidative conditions were identified in these organisms and proposed to be differentially expressed under different concentrations of oxygen, contributing to their ability to survive oxic conditions. In this study, Desulfovibrio vulgaris Hildenborough cells were exposed to the highest concentration of oxygen that SRB are likely to encounter in natural habitats, and the global transcriptomic response was determined. Three hundred and seven genes were responsive, with cellular roles in energy metabolism, protein fate, cell envelope and regulatory functions, including multiple genes encoding heat shock proteins, peptidases and proteins with heat shock promoters. Of the oxygen reducing mechanisms of D. vulgaris only the periplasmic hydrogen-dependent mechanism was up-regulated, involving the [NiFeSe] hydrogenase, formate dehydrogenase(s) and the Hmc membrane complex. The oxidative defense response concentrated on damage repair by metal-free enzymes. These data, together with the down-regulation of the ferric uptake regulator operon, which restricts the availability of iron, and the lack of response of the peroxide-sensing regulator operon, suggest that a major effect of this oxygen stress is the inactivation and/or degradation of multiple metalloproteins present in D. vulgaris as a consequence of oxidative damage to their metal clusters. [ABSTRACT FROM AUTHOR]

Cell suspensions ofMethanobrevibacter arboriphiluscatalyzed the reduction of O2 with H2 at a maximal specific rate of 0.4 U (µmol/min) per mg protein with an apparentKm for O2 of 30 µM. The reaction was not inhibited by cyanide. The oxidase activity was traced back to a coenzyme F420-dependent enzyme that was purified to apparent homogeneity and that catalyzed the oxidation of 2 F420H2 with 1 O2 to 2 F420 and 2 H2O. The apparentKm for F420 was 30 µM and that for O2 was 2 µM with aVmax of 240 U/mg at 37°C and pH 7.6, the pH optimum of the oxidase. The enzyme did not use NADH or NADPH as electron donor or H2O2 as electron acceptor and was not inhibited by cyanide. The 45-kDa protein, whose gene was cloned and sequenced, contained 1 FMN per mol and harbored a binuclear iron center as indicated by the sequence motifH-X-E-X-D-X62-H-X18-D-X60-H. Sequence comparisons revealed that the F420H2 oxidase fromM. arboriphilusis phylogenetically closely related to FprA fromMethanothermobacter marburgensis(71% sequence identity), a 45-kDa flavoprotein of hitherto unknown function, and to A-type flavoproteins from bacteria (30-40%), which all have dioxygen reductase activity. With heterologously produced FprA fromM. marburgensisit is shown that this protein is also a highly efficient F420H2 oxidase and that it contains 1 FMN and 2 iron atoms. The presence of F420H2 oxidase in methanogenic archaea may explain why some methanogens, e.g., theMethanobrevibacterspecies in the termite hindgut, cannot only tolerate but thrive under microoxic conditions. [ABSTRACT FROM AUTHOR]

Cytochrome c3 of Desulfovibrio desulfuricans strain G20 is an electron carrier for uranium (VI) reduction. When D. desulfuricans G20 was grown in medium containing a non-lethal concentration of uranyl acetate (1 mM), the rate at which the cells reduced U(VI) was decreased compared to cells grown in the absence of uranium. Western analysis did not detect cytochrome c3 in periplasmic extracts from cells grown in the presence of uranium. The expression of this predominant tetraheme cytochrome was not detectably altered by uranium during growth of the cells as monitored through a translational fusion of the gene encoding cytochrome c3 (cycA) to lacZ. Instead, cytochrome c3 protein was found tightly associated with insoluble U(IV), uraninite, after the periplasmic contents of cells were harvested by a pH shift. The association of cytochrome c3 with U(IV) was interpreted to be non-specific, since pure cytochrome c3 adsorbed to other insoluble metal oxides, including cupric oxide (CuO), ferric oxide (Fe2O3), and commercially available U(IV) oxide. [ABSTRACT FROM AUTHOR]

During screening for antigenic proteins in Burkholderia pseudomallei, a novel insertion sequence, ISBp1, was found by sequence similarity searches. ISBp1 contains two overlapping ORFs of 261 bp (orfA) and 852 bp (orfB), encoding 87 and 284 amino acid residues, respectively, and an imperfect inverted repeat. The putative protein encoded by orfA (OrfA) is similar to the OrfA in insertion sequences of the IS3 family in other bacteria, showing 49% and 76% amino acid identity and similarity, respectively, with the transposase encoded by ISD1 of Desulfovibrio vulgaris vulgaris. The putative protein encoded by orfB (OrfB) is similar to the OrfB in insertion sequences of the IS3 family in other bacteria, showing 43% and 62% amino acid identity and similarity, respectively, with the transposase encoded by IS1222 of Enterobacter agglomerans. Sequence analysis of OrfA showed the presence of an α-helix-turn-α-helix motif, as well as the putative leucine zipper at its 3′ end, for possible DNA binding to the terminal inverted repeats. Sequence analysis of OrfB showed the presence of a DDE motif of aspartic acid, aspartic acid, and glutamic acid, a highly conserved motif present in OrfB of other members of the IS3 family. Furthermore, several other conserved amino acid residues, including the arginine residue located seven amino acids downstream from the glutamic acid residue, were observed. PCR amplification of the ISBp1 gene showed a specific band in 65% of the 26 B. pseudomallei strains tested. Southern blot hybridization after XhoI or SacI digestion showed nine different patterns of hybridization. The number of copies of ISBp1 in those strains that possessed the insertion sequence ranged from three to 12. Using several insertion sequences and a combination of insertion-sequence-based and non-insertion-sequence-based methods such as ribotyping will probably increase the discriminatory power of molecular typing in B. pseudomallei. [ABSTRACT FROM AUTHOR]

Washed cells of Desulfovibrio vulgaris strain Marburg (DSM 2119) reduced oxygen to water with H2 as electron donor at a mean rate of 253 nmol O2 min–1 (mg protein)–1. After separating the periplasm from the cells, more than 60% of the cytochrome c activity and 90% of the oxygen-reducing activity were found in the periplasmic fraction. Oxygen reduction and the reduction of cytochrome c with H2 were inhibited by CuCl2. After further separation of the periplasm by ultrafiltration (exclusion sizes 30, 50, and 100 kDa), oxygen reduction with H2 occurred with the retentates only. Ascorbate plus tetramethyl-p-phenylenediamine (TMPD), however, were also oxidized by the filtrates. The stoichiometry of 1 mol O2 reduced per 2 mol ascorbate oxidized indicated the formation of water. Our experiments present evidence that in D. vulgaris periplasmic hydrogenase and cytochrome c play a major role in oxygen reduction. Preliminary studies with other Desulfovibrio species indicated a similar function of periplasmic c-type cytochromes in D. desulfuricans CSN and D. termitidis KH1. [ABSTRACT FROM AUTHOR]

The hmc operon of Desulfovibrio vulgaris subsp. vulgaris Hildenborough encodes a transmembrane redox protein complex (the Hmc complex) that has been proposed to catalyze electron transport linking periplasmic hydrogen oxidation to cytoplasmic sulfate reduction. We have replaced a 5-kb DNA fragment containing most of the hmc operon by the cat gene. The resulting chloramphenicol-resistant mutant D. vulgaris H801 grows normally when lactate or pyruvate serve as electron donors for sulfate reduction. Growth with hydrogen as electron donor for sulfate reduction (acetate and CO2 as the carbon source) is impaired. These results confirm the importance of the Hmc complex in electron transport from hydrogen to sulfate. Mutant H801 is also deficient in low-redox-potential niche establishment. On plates, colony development takes 14 days longer than colony development of the wild-type strain, when the cells use hydrogen as the electron donor. This result suggests that, in addition to transmembrane electron transport from hydrogen to sulfate, the redox reactions catalyzed by the Hmc complex are crucial in establishment of the required low-redox-potential niche that allows single cells to grow into colonies. [ABSTRACT FROM AUTHOR]

The recently isolated sulfate reducer Desulfovibrio inopinatus oxidizes hydroxyhydroquinone (1,2,4-trihydroxybenzene; HHQ) to 2 mol acetate and 2 mol CO2 (mol substrate)–1, with stoichiometric reduction of sulfate to sulfide. None of the key enzymes of fermentative HHQ degradation, i.e. HHQ-1,2,3,5-tetrahydroxybenzene transhydroxylase or phloroglucinol reductase, were detected in cell-free extracts of D. inopinatus, indicating that this bacterium uses a different pathway for anaerobic HHQ degradation. HHQ was reduced with NADH in cell-free extracts to a nonaromatic compound, which was identified as dihydrohydroxyhydroquinone by its retention time in HPLC separation and by HPLC-mass spectrometry. The compound was identical with the product of chemical reduction of HHQ with sodium borohydride. Dihydrohydroxyhydroquinone was converted stoichiometrically to acetate and to an unknown coproduct. HHQ reduction was an enzymatic activity which was present in the cell-free extract at 0.25–0.30 U (mg protein)–1, with a pH optimum at 7.5. The enzyme was sensitive to sodium chloride, potassium chloride, EDTA, and o-phenanthroline, and exhibited little sensitivity towards sulfhydryl group reagents, such as copper chloride or p-chloromercuribenzoate. [ABSTRACT FROM AUTHOR]

Bacteria are important participants in sulfur cycle of the extremely haloalkaline environment, e.g. soda lake. The effects of physicochemical factors on the composition of sulfide-oxidizing bacteria (SOB) and sulfate-reducing bacteria (SRB) in soda lake have remained elusive. Here, we surveyed the community structure of total bacteria, SOB and SRB based on 16S rRNA, soxB and dsrB gene sequencing, respectively, in five soda lakes with different physicochemical factors. The results showed that the dominant bacteria belonged to the phyla Proteobacteria, Bacteroidetes, Halanaerobiaeota, Firmicutes and Actinobacteria. SOB and SRB were widely distributed in lakes with different physicochemical characteristics, and the community composition were different. In general, salinity and inorganic nitrogen sources (NH 4 + -N, NO 3 - -N) were the most significant factors. Specifically, the communities of SOB, mainly including Thioalkalivibrio, Burkholderia, Paracoccus, Bradyrhizobium, and Hydrogenophaga genera, were remarkably influenced by the levels of NH 4 + -N and salinity. Yet, for SRB communities, including Desulfurivibrio, Candidatus Electrothrix, Desulfonatronospira, Desulfonatronum, Desulfonatronovibrio, Desulfonatronobacter and so on, the most significant determinants were salinity and NO 3 - -N. Besides, Rhodoplanes played a significant role in the interaction between SOB and SRB. From our results, the knowledge regarding the community structures of SOB and SRB in extremely haloalkaline environment was extended., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A new halotolerant Desulfovibrio, strain CVLT (T = type strain), was isolated from a solar saltern in California. The curved, gram-negative, nonsporeforming cells (0.3 × 1.0–1.3 μm) occurred singly, in pairs, or in chains, were motile by a single polar flagellum and tolerated up to 12.5% NaCl. Strain CVLT had a generation time of 60 min when grown in lactate-yeast extract medium under optimal conditions (37°C, pH 7.6, 2.5% NaCl). It used lactate, pyruvate, cysteine, or H2/CO2 + acetate as electron donors, and sulfate, sulfite, thiosulfate, or fumarate as electron acceptors. Elemental sulfur, nitrate, or oxygen were not used. Sulfite and thiosulfate were disproportionated to sulfate and sulfide. The G+C content of the DNA was 62 mol%. Phylogenetic analysis revealed that Desulfovibrio fructosovorans was the nearest relative. Strain CVLT is clearly different from other Desulfovibrio species, and is designated Desulfovibrio senezii sp. nov. (DSM 8436). [ABSTRACT FROM AUTHOR]

The aldehyde dehydrogenase activity of the sulfate-reducing bacterium Desulfovibrio simplex strain DSM 4141 was characterized in cell-free extracts. Oxygen-sensitive, constitutive aldehyde dehydrogenase activity was found in cells grown on l(+)-lactate, hydrogen, or vanillin with sulfate as the electron acceptor. A 1.83- to 2.6-fold higher specific activity was obtained in cells grown in media supplemented with 1 μM WO4 2–. The aldehyde dehydrogenase in cell-free extracts catalyzed the oxidation of aliphatic ( K m < 20 μM) and aromatic aldehydes ( K m < 0.32 mM) using methyl viologen as the electron acceptor. Flavins (FMN and FAD) were also active and are proposed to be the natural cofactors, while no activity was obtained with NAD+ or NADP+. 185WO4 2– was incorporated in vivo into D. simplex; it was found exclusively in the soluble fraction (≥ 98%). Anionic-exchange chromatography demonstrated coelution of 185W with two distinct peaks, the first one containing hydrogenase and formate dehydrogenase activities, and the second one aldehyde dehydrogenase activity. [ABSTRACT FROM AUTHOR]

We isolated a strictly anaerobic bacterium, strain GRZCYSA, from a sludge digestor for its ability to ferment cysteate (2-amino-3-sulfopropionate). The organism also fermented the organosulfonates isethionate (2-hydroxyethanesulfonate) and aminomethanesulfonate, but taurine (2-aminoethanesulfonate) was not a substrate. Strain GRZCYSA, a gram-negative, oxidase-negative and catalase-positive vibrio that could reduce sulfate and contained desulfoviridin, was tentatively identified as Desulfovibrio sp. Utilization of cysteate as a substrate for fermentative growth led to the formation of four products identified as acetate, ammonia, and equimolar amounts of sulfide and sulfate. The fermentation was in balance. Some reactions involved in this novel process were detected in cell-free extracts in which ammonia and acetate were formed from cysteate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The presence of one periplasmic [NiFe] hydrogenase, one periplasmic [Fe] hydrogenase, and one cytoplasmic NADP-reducing hydrogenase has been previously established in Desulfovibrio fructosovorans. In the present work, marker-exchange mutagenesis was performed to determine the function of the tetrameric NADP-reducing hydrogenase encoded by the hndA, B, C, and D genes. The mutations performed were not lethal to the cells, although the H2-dependent NADP reduction was completely abolished. The double-mutated DM4 (Δ hynABC, Δ hndD) strain was still able to grow on hydrogen plus sulfate as the sole energy source. The growth may have occurred under these culture conditions because of the presence of the remaining [Fe] hydrogenase. The cells grew differently on various substrates depending on whether fructose, lactate, or pyruvate was used in the presence of sulfate. The ( hnd mutant growth rates were 25–70% lower than those of the wild-type strain, although the molar growth yield remained unchanged. By contrast, mutants devoid of both [NiFe] hydrogenase and NADP-reducing hydrogenase had 24-38% lower growth yields and showed a corresponding drop in the growth rates. We concluded that each of the three hydrogenases may contribute to the energy supply in D. fructosovorans and that the loss of one enzyme might be compensated for by another. However, the loss of two hydrogenases affected the phosphorylation accompanying the metabolism of fructose, lactate, and pyruvate. [ABSTRACT FROM AUTHOR]

The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate. [ABSTRACT FROM AUTHOR]

A sulfate-reducing bacterium, strain HDv, was isolated from the anoxic soil of a ricefield using lactate as electron donor. Cells were gram-negative, motile, nonsporulating curved rods, with single polar flagella. Substrates were incompletely oxidized to acetate and included glycerol, 1,2-and 1,3-propanediol. Sulfate, sulfite, thiosulfate, elemental sulfur, fumarate, maleate, and malate were utilized as electron acceptors. Pyruvate, fumarate, maleate, malate and dihydroxyacetone were fermented. Desulfoviridin and c-type cytochromes were present. The DNA base composition was 66.6 ± 0.3 mol% G+C. The isolate was identified as a Desulfovibrio sp.; its metabolic properties were somewhat different from those of previously described Desulfovibrio species. Comparative biochemical study of 1,2-propanediol dissimilation by the new isolate and Desulfovibrio alcoholovorans showed that NAD-dependent dehydrogenases play a key role in the catabolism of this substrate. The hypothetical pathways of 1,2-propanediol degradation by Desulfovibrio spp. are presented. [ABSTRACT FROM AUTHOR]

The localization of hydrogenase protein in Desulfovibrio gigas cells grown either in lactate-sulfate or hydrogen-sulfate media, has been investigated by subcellular fractionation with immunoblotting and by electron microscopic immunocytochemistry. Subcellular fractionation experiments suggest that no integral membrane-bound hydrogenase is present in D. gigas. About 40% of the hydrogenase activity could be extracted by treatment of D. gigas cells with Tris-EDTA buffer. The rest of the soluble hydrogenase activity (50%) was found in the soluble fraction which was obtained after disruption of Tris-EDTA extracted cells and high speed centrifugation. Both soluble hydrogenase fractions purified to homogeneity showed identical molecular properties including the N-terminal aminoacid sequences of their large and small subunits. Polyacrylamide gel electrophoresis of the proteins of the subcellular fractions revealed a single band of hydrogenase activity exhibiting the same mobility as purified D. gigas hydrogenase. Western blotting carried out on these subcellular fractions revealed crossreactivity with the antibodies raised against (NiFe) hydrogenase. The lack of crossreactivity with antibodies against (FE) or (NiFeSe) hydrogenases, indicated that only (NiFe) type hydrogenase is present in D. gigas. Immunocytolocalization in ultrathin frozen sections of D. gigas cells grown either in lactate-sulfate, pyruvate-sulfate or hydrogen-sulfate media showed only a (NiFe) hydrogenase located in the periplasmic space. The bioenergetics of D. gigas are discussed in the light of these findings. [ABSTRACT FROM AUTHOR]

Desulfovibrio strain SPSN was isolated from an anaerobic industrial fermenter fed with waste water from the alcohol industry. The isolate was a gram-negative, non-spore-forming, curved organism, the motility of which is provided by a single polar flagellum. The oxidation of substrates was incomplete and included glycerol and 1,3-propanediol. Sulfate, sulfite, thiosulfate, and sulfur were utilized as electron acceptors. Pyruvate, fumarate and malate could be fermented. The DNA base composition was 64.5±0.3% G+C. Cytochrome c and desulfoviridin were present. On the basis of these characteristics and because strain SPSN could not be ascribed to any of the existing species, the isolate is established as a new species of the genus Desulfovibrio, and the name Desulfovibrio alcoholovorans is proposed. [ABSTRACT FROM AUTHOR]

Enzyme measurements were carried out with crude cell-free extracts of the propionate oxidizing coculture of Syntrophobacter wolinii and Desulfovibrio G11. Using cell-free extracts of a pure culture of Desulfovibrio G11 as a blank, most of the enzymes involved in the methylmalonyl-CoA pathway for propionate oxidation, including a propionyl-CoA: oxaloacetate transcarboxylase, were demonstrated in S. wolinii. [ABSTRACT FROM AUTHOR]

Periplasmic extract from Desulfovibrio desulfuricans (NCIMB 8372) was found to contain two different c-type cytochromes. One is tetraheme cytochrome c and the other is monoheme cytochrome c. Cytochrome c could be purified by a procedure involving only one chromatographic step, whereas cytochrome c required several such steps. Cytochrome c was found to have a relative molecular mass of 14300 and an isoionic point higher than 9. Analysis of the redox potentials indicated one heme at -260 mV and three hemes around -330 mV. Cytochrome c had a relative molecular mass of 7200, an isoionic point higher than 9 and a redox potential of 0 mV. [ABSTRACT FROM AUTHOR]

Four out of five Desulfovibrio strains tested were able to oxidize l-malate to acetate in the presence of sulfate. Fumarate and succinate were also oxidized to acetate by these strains, but growth with the latter substrate was marginal. During growth on malate high NADP-dependent malic enzyme and NADPH DH activities were found in all strains. These activities were lower in lactate-or pyruvate-grown cells. An NADPH DH from D. gigas was partially purified. It was oxygen-labile, very sensitive to heavy metal ions and highly specific for NADPH. Growth yield studies indicated that energy conservation occurred during the transport of reducing equivalents from NADPH to the sulfate reduction pathway. [ABSTRACT FROM AUTHOR]

During growth of ethanol plus sulfate Desulfovibrio gigas and three other Desulfovibrio strains tested contained high NAD-dependent alcohol dehydrogenase activities and dye-linked aldehyde dehydrogenase activities. In lactate-grown cells these activities were lower or absent. In D. gigas an NADH dehydrogenase activity was found which was higher during growth on ethanol than during growth on lactate. The NADH dehydrogenase activity appeared to consist of at least three different soluble enzymes. The aldehyde dehydrogenase activity in D. gigas was highest with benzylviologen as an acceptor and was strongly stimulated by potassium ions. Coenzyme A or phosphate dependency could not be shown, indicating that acetyl-CoA or acetyl phosphate are not intermediates in the conversion of acetaldehyde to acetate. In the absence of sulfate D. gigas was able to convert ethanol to acetate by means of interspecies hydrogen transfer to a methanogen. This conversion, however, did not lead to growth of the Desulfovibrio. [ABSTRACT FROM AUTHOR]

The localization of APS reductase and bisulfite reductase in Desulfovibrio gigas, D. vulgaris Hildenborough and D. thermophilus was studied by immunoelectron microscopy. Polyclonal antibodies were raised against the purified enzymes from each strain. Cells fixed with formaldehyde/glutaraldehyde were embedded and ultrathin sections were incubated with antibodies and subsequently labeled with protein A-gold. The bisulfite reductase in all three strains and APS reductase in d. gigas and D. vulgaris were found in the cytoplasm. The labeling of d. thermophilus with APS reductase antibodies resulted in a distribution of gold particles over the cytoplasmic membrane region. The localization of the two enzymes is discussed with respect to the mechanism and energetics of dissimilatory sulfate reduction. [ABSTRACT FROM AUTHOR]

The capacity of mesophilic sulfate-reducing bacteria to grow lithoautotrophically with H, sulfate and CO was investigated with enrichment cultures and isolated species. (a) Enrichments in liquid mineral media with H, sulfate and CO consistently yielded mixed cultures of nonautotrophic, acetate-requiring Desulfovibrio species and autotrophic, acetate-producing Acetobacterium species (cell ratio approx. 20:1). (b) By direct dilution of mud samples in agar, various non-sporing sulfate reducers were isolated in pure cultures that did grow autotrophically. Two oval cell types (strains HRM2, HRM4) and one curved cell type (strain HRM6) from marine sediment were studied in detail. The strains grew in mineral medium supplemented only with vitamins (biotin, p-aminobenzoate, nicotinate). Carbon autotrophy was evident (i) from comparative growth experiments with non-autotrophic, acetate-requiring species, (ii) from high cell densities ruling out a cell synthesis from organic impurities in the mineral media, and (iii) by demonstrating that 96-99% of the cell carbon was derived from C-labelled CO. Autotrophic growth occurred with a doubling time of 16-20 h at 24-28°C. Formate, fatty acids up to palmitate, ethanol, lactate, succinate, fumarate, malate and other organic acids were also used and completely oxidized. The three strains possessed cytochromes of the b-and c-type, but no desulfoviridin. Strain HRM2 is described as a new species of a new genus, Desulfobacterium autotrophicum. (c) The capacity for autotrophic growth was also tested with sulfate-reducing bacteria that originally had been isolated on organic substrates. The incompletely oxidizing, non-sporing types such as Desulfovibrio and Desulfobulbus species and Desulfomonas pigra were confirmed to be obligate heterotrophs that required acetate for growth with H and sulfate. In contrast, several of the completely oxidizing sulfate reducers were facultative autotrophs, such as Desulfosarcina variabilis, Desulfonema limicola, Desulfococcus niacini, and the newly isolated Desulfobacterium vacuolatum and Desulfobacter hydrogenophilus. The only incompletely oxidizing sulfate reducer that could grow autotrophically was the sporing Desulfotomaculum orientis, which obtained 96% of its cell carbon from C-labelled CO. Desulfovibrio baarsii and Desulfococcus multivorans may also be regarded as types of facultative autotrophs; they could not oxidize H, but grew on sulfate with formate as the only organic substrate. [ABSTRACT FROM AUTHOR]

During growth on glycerol two marine Desulfovibrio strains that can grow on an unusually broad range of substrates contained high activities of glycerol kinase, NAD(P)-independent glycerol 3-phosphate dehydrogenase and the other enzymes necessary for the conversion of dihydroxyacetone phosphate to pyruvate. Glycerol dehydrogenase and a specific dihydroxyacetone kinase were absent. During growth on dihydroxyacetone, glycerol kinase is involved in the initial conversion of this compound to dihydroxyacetone phosphate which is then further metabolized. Some kinetic properties of the partially purified glycerol kinase were determined. The role of NAD as electron carrier in the energy metabolism during growth of these strains on glycerol and dihydroxyacetone is discussed. Glycerol also supported growth of three out of four 'classical' Desulfovibrio strains tested. D. vulgaris strain Hildenborough grew slowly on glycerol and contained glycerol kinase, glycerol 3-phosphate dehydrogenase and enzymes for the dissimilation of dihydroxyacetone phosphate. In D. gigas which did not grow on glycerol the enzymes glycerol kinase and glycerol 3-phosphate dehydrogenase were absent in lactate-grown cells. [ABSTRACT FROM AUTHOR]

Desulfovibrio HL21 is unable to grow with amino acids as energy substrates. Alanine, serine, aspartate and to some extent glutamate were used as carbon and nitrogen sources in the presence of hydrogen as the energy substrate. Dense cell suspensions converted alanine stoichiometrically to acetate, NHand presumably HCO, but at a very low rate. Desulfovibrio HL21 cells grown with alanine as carbon and nitrogen source contained increased levels of NAD(P)-dependent l-alanine dehydrogenase as compared to cells grown with NHCl as nitrogen source. Unfavourable kinetic properties of this alanine dehydrogenase, repression of the synthesis of the enzyme by NHand a low rate of NADH oxidation all have a negative effect on the rate of degradation of alanine and may partly explain the inability of the strain to grow with alanine as an energy substrate. [ABSTRACT FROM AUTHOR]

Rates of nitrate and nitrite reduction by cultures and washed suspensions of both natural isolates and culture collection strains of sulphate-reducing bacteria have been determined. Neither activity was detected in the Desulfotomaculum strains, but all Desulfovibrio strains reduced nitrite. Only the Desulfovibrio natural isolate FBA 20a was also able to reduce nitrate. Nitrate reduction by washed suspensions of strain FBA 20a was far more rapid than previously reported rates for sulphate-reducing bacteria [6.6 μmol NOreduced h (mg dry weight)] and was regulated by nitrate induction and sulphate repression: it was insensitive to the product of nitrate reduction, ammonium ions. Cell yields from sulphate-limited cultures were proportional to the concentration of nitrate added with a yield coefficient of 28.0 g bacterial dry weight per mol of nitrate reduced. These results indicate that although the ability of strain FBA 20a to reduce nitrate is a physiologically significant process, it is a specialized property of only a few strains of Desulfovibrio isolates. [ABSTRACT FROM AUTHOR]

A sulfate reducing bacterium isolated from sewage sludge was capable of degrading methanol after growth on pyruvate, malate, or fumarate. C-Methanol was completely oxidized to carbon dioxide but not incorporated into the cellular material. The organism is a member of the genus Desulfovibrio. [ABSTRACT FROM AUTHOR]

Methanogenesis from ethanol was studied in batch cocultures of a proton-reducing acetogenic Desulfovibrio sp. together with one of eight methanogenic bacteria representing five genera. A mathematical model of mutualistic cocultures predicts an equalisation in the specific growth rates of the two species which defines a specific growth rate for the coculture. At non-limiting ethanol concentrations the model predicts that the specific growth rate of the coculture is dependent upon the K (H) of the methanogen and its maximum specific growth rate in axenic culture when utilising H as the energy source. We demonstrate experimentally that with methanogens known to have similar K (H) values, the specific growth rates of methanogenic mutualistic cocultures are dependent upon the maximum specific growth rates of the methanogens. [ABSTRACT FROM AUTHOR]

Apparent half-saturation constants ( K) and maximum uptake rates ( V) for sulfate were determined in four species of Desulfovibrio of freshwater and marine origin using aS-sulfate tracer technique. The lowerst K (5 μM) was found in the freshwater species Desulfovibrio vulgaris (Marburg) and the highest K (77 μM) in the marine species Desulfovibrio salexigens. Maximum specific rates of sulfate uptake (i.e., V) were proportional to the growth rates observed in batch cultures. The halophilic Desulfovibrio salexigens did not change its K and V between 1 and 6,000 μM SO, and apparently did not induce a low-affinity uptake system at high sulfate concentrations. The low half-saturation constants measured for sulfate uptake explain why high rates of bacterial sulfate reduction occur in surface sediments of freshwater lakes, and why sulfate reduction can be a quantitatively important process in anaerobic carbon mineralization in low-sulfate environments. The results shows that extremely low sulfate concentrations must occur before sulfate reduction is completely outcompeted by methanogenesis. [ABSTRACT FROM AUTHOR]

An indirect enzyme-linked immunoadsorption assay (ELISA) was developed for cytochrome c using antisera to the cytochromes from Desulfovibrio africanus Benghazi, Desulfovibrio vulgaris Hildenborough and Desulfovibrio salexigens British Guiana. The ELISA system was used to test for cross-reactions between these antisera and the heterologous antigens. In contrast to previous experiments using the Ouchterlony technique, all of the cytochromes c tested exhibited some degree of cross-reaction. Considerable variation was seen in cross-reactions for cytochromes c from differing strains of D. desulfuricans. This observation raises questions about the taxonomic relatedness of these strains. No cross-reaction was seen with eukaryotic cytochrome c or with D. vulgaris cytochrome c. The data demonstrate that cytochrome c is capable of undergoing nonprecipitating cross-reactions, and thus may not be as immunologically unique as was once thought. [ABSTRACT FROM AUTHOR]

The basis for the outcome of competition between sulfidogens and methanogens for H was examined by comparing the kinetic parameters of representatives of each group separately and in co-culture. Michaelis-Menten parameters ( V and K) for four methanogens and five sulfate-reducing bacteria were determined from H-depletion data. Further, Monod growth parameters (μ, K, Y) for Desulfovibrio sp. G11 and Methanospirillum hungatei JF-1 were similarly estimated. H K values for the methanogenic bacteria ranged from 2.5 μM ( Methanospirillum PM1) to 13 μM for Methanosarcina barkeri MS; Methanospirillum hungatei JF-1 and Methanobacterium PM2 had intermediate H K estimates of 5 μM. Average H K estimates for the five sulfidogens was 1.2 μM. No consistent difference among the V estimates for the above sulfidogens (mean=100 nmol H min mg protein) and methanogens (mean=110 nmol H min mg protein) was found. A two-term Michaelis-Menten equation accurately predicted the apparent H K values and the fate of H by resting co-cultures of sulfate-reducers and methanogens. Half-saturation coefficients ( K) for H-limited growth of Desulfovibrio sp. G11 (2-4 μM) and Methanospirillum JF-1 (6-7 μM) were comparable to H K estimates obtained for these organisms. Maximum specific growth rates for Desulfovibrio sp. G11 (0.05 h) were similar to those of Methanospirillum JF-1 (0.05-0.06 h); whereas G11 had an average yield coefficient 4 x that of JF-1. Calculated μ and V/ K values for the methanogens and sulfidogens studied predict that the latter bacterial group will process more H whether these organisms are in a growing or resting state, when the H concentration is in the first-order region. [ABSTRACT FROM AUTHOR]

The occurrence of organic storage compounds in six strains of sulfate-reducing bacteria was investigated. In Desulfovibrio HL21 and Desulfovibrio vulgaris NCIB 8303 accumulation of polyglucose was brought about by limiting the Fe or NHconcentration in the growth medium. Desulfobulbus propionicus 1pr3 and especially Desulfovibrio gigas NCIB 9332 already synthesized large amounts of polyglucose in normal media, whereas the synthesis of polyglucose in two strains of Desulfovibrio desulfuricans was far less pronounced. Suspensions of Desulfovibrio HL21 cells in media without an energy source and sulfate degraded the polyglucose to acetate, hydrogen and small amounts of ethanol and succinate; Desulfobulbus propionicus formed acetate, propionate and some hydrogen under these conditions. In the presence of sulfate both strains produced acetate and corresponding amounts of sulfide. None of the strains synthesized PHB as a storage polymer. [ABSTRACT FROM AUTHOR]

Four strains of Desulfovibrio produced ammonium during growth on a defined medium containing 100 μg NO-N/ml in the presence of 1 mM sulfate. Ammonium was not produced by cultures grown in media devoid of sulfate nor in media containing 35 mM sulfate. The four strains of Desulfovibrio studied reduced 32.7-46% of the available nitrate to ammonium in 21 days incubation. Ammonium production from nitrate was confirmed by recovering N-enriched ammonium when N-enriched Ca(NO) was utilized as the substrate for the reduction. [ABSTRACT FROM AUTHOR]

An indirect fluorescent antibody technique was used as a method of rapidly assessing and identifying sulphate-reducing bacteria. Five specific antisera and one polyvalent serum were raised and tested against 44 strains of the genera Desulfovibrio and Desulfotomaculum along with 4 control organisms. Immunofluorescence was found to be mainly strain specific with the sulphate-reducing bacteria although weak fluorescence was seen both within and between recognised groups. A polyvalent antiserum was successfully used to detect sulphate-reducing bacteria. No interference from 4 control organisms was found. [ABSTRACT FROM AUTHOR]

Colony counts of acetate-, propionate- and l-lactate-oxidizing sulfate-reducing bacteria in marine sediments were made. The vertical distribution of these organisms were equal for the three types considered. The highest numbers were found just beneath the border of aerobic and anaerobic layers. Anaerobic mineralization of acetate, propionate and l-lactate was studied in the presence and in the absence of sulfate. In freshwater and in marine sediments, acetate and propionate were oxidized completely with concomitant reduction of sulfate. l-Lactate was always fermented. Lactate-oxidizing, sulfate-reducing bacteria, belonging to the species Desulfovibrio desulfuricans, and lactate-fermenting bacteria were found in approximately equal amounts in the sediments. Acetate-oxidizing, sulfate-reducing bacteria could only be isolated from marine sediments, they belonged to the genus Desulfobacter and oxidized only acetate and ethanol by sulfate reduction. Propionate-oxidizing, sulfate-reducing bacteria belonged to the genus Desulfobulbus. They were isolated from freshwater as well as from marine sediments and showed a relatively large range of usable substrates: hydrogen, formate, propionate, l-lactate and ethanol were oxidized with concomitant sulfate reduction. l-Lactate and pyruvate could be fermented by most of the isolated strains. [ABSTRACT FROM AUTHOR]

Desulfovibrio vulgaris (Marburg) was grown on hydrogen plus sulfate as sole energy source and acetate plus CO as the sole carbon sources. The incorporation of U-C acetate into alanine, aspartate, glutamate, and ribose was studied. The labelling data show that alanine is synthesized from one acetate (C-2 + C-3) and one CO (C-1), aspartate from one acetate (C-2 + C-3) and two CO (C-1 + C-4), glutamate from two acetate (C-1−C-4) and one CO (C-5), and ribose from 1.8 acetate and 1.4 CO. These findings indicate that in Desulfovibrio vulgaris (Marburg) pyruvate is formed via reductive carboxylation of acetyl-CoA, oxaloacetate via carboxylation of pyruvate or phosphoenol pyruvate, and α-ketoglutarate from oxaloacetate plus acetyl-CoA via citrate and isocitrate. Since C-5 of glutamate is derived from CO, citrate must have been formed via a (R)-citrate synthase rather than a(S)-citrate synthase. The synthesis of ribose from 1.8 mol of acetate and 1.4 mol of CO excludes the operation of the Calvin cycle in this chemolithotrophically growing bacterium. [ABSTRACT FROM AUTHOR]

Cytochromes c of different strains of sulfatereducing bacteria have been purified and tested for their capacity to reduce colloidal sulfur to hydrogen sulfide. The results are in good agreement with the activities reported for the whole cells. Cytochrome c is the sulfur reductase of some strains of sulfate-reducing bacteria such as Desulfovibrio desulfuricans Norway 4 and sulfate-reducing bacterium strain 9974 from which the sulfur reductase activity can be purified with the cytochrome c. In contrast, Desulfovibrio vulgaris Hildenborough cytochrome c is inhibited by the product of the reaction namely hydrogen sulfide. Chloramphenicol has no effect on the sulfur reductase activity of D. desulfuricans Norway 4 when resting cells grown on lactate-sulfate medium are put in the presence of colloidal sulfur. This shows that the sulfur reductase activity is constitutive and corresponds to the fact that colloidal sulfur grown cells do not contain more cytochrome c (or another sulfur reductase) than lactate-sulfate-grown cells. [ABSTRACT FROM AUTHOR]

The yield coefficients for Desulfovibrio vulgaris and D. gigas varied with the electron donoracceptor combinations and with the bacterial strain. The only evidence for electron transport coupled formation of adenosine triphosphate (ATP) was with sulfate as the electron acceptor. With D. vulgaris the ATP formation coupling to electron flow with pyruvate oxidation was 1:4 electrons and with lactate oxidation was 1:8 electrons. With D. gigas these ratios were 1:8 electrons and 1:16 electrons for the oxidation of pyruvate and lactate. The clearest resolution of energy coupling was with D. vulgaris growing on formatesulfate medium where 2 ATP appear to be formed with the transfer of electrons from formate to adenosine phosphosulfate and one ATP with the transfer of electrons from formate to sulfite. [ABSTRACT FROM AUTHOR]

Desulfovibrio vulgaris (Marburg) was grown on H plus sulfate and H plus thiosulfate as the sole energy sources and acetate plus CO as the sole carbon sources. Conditions are described under which the bacteria grew exponentially. Specific growth rates (μ) and molar growth yields ( Y) at different pH were determined. μ and Y were found to be strongly dependent on the pH. Highest growth rates and molar growth yields were observed for growth on H plus sulfate at pH 6.5 (μ=0.15h; Y=8.3g·mol) and for growth on H plus thiosulfate at pH 6.8 (μ=0.21h; YO=16.9g·mol). The growth yields were found to increase with increasing growth rates: plots of 1/ Y versus 1/μ were linear. Via extrapolation to infinite growth rates a Y/max of 12.2g·mol and a YSO/max of 33.5g·mol was obtained. The growth yield data are interpred to indicate that dissimilatory sulfate reduction to sulfide is associated with a net synthesis of 1 mol of ATP and that near to 3 mol of ATP are formed during dissimilatory sulfite reduction to sulfide. [ABSTRACT FROM AUTHOR]

Hydrogen gas stimulated sulphate reduction in a saltmarsh sediment and the importance of H transferred from organotrophic bacteria to the sulphate-reducers is discussed. β-fluorolactate inhibited sulphate reduction whether lactate, ethanol or hydrogen was being used as growth substrate. When added to sediment β-fluorolactate inhibited sulphate reduction with a consequent increase in methane production. Addition of H stimulated methanogenesis in sediment and this stimulation was greater if CO was also present. Hydrogen availability was the primary limitation of methanogenesis but the low concentration of dissolved CO in seawater may limit methane production even if H is available. The removal of inhibition of methanogenesis by the use of fluorolactate to suppress sulphate reduction or by the provision of hydrogen indicates competitive inhibition of methanogens by sulphate reducers utilizing transferred hydrogen. [ABSTRACT FROM AUTHOR]

Two sulfate reducing bacteria (Madison and Marburg strains) that grew on H plus sulfate in a mineral salts medium that contained acetate and CO as sole carbon source were isolated from diverse environments. During growth in this medium 4.2 mol of H were consumed per mol of sulfate reduced to sulfide. Acetate was required for biosynthetic purposes only. Approximately 70% of the cell carbon synthesized was derived from acetate and 30% from CO. Acetate was not involved in dissimilatory sulfate reduction. Growth of the bacteria on H plus sulfate was linear rather than exponential, and a doubling time at the beginning of linear growth of approximately 3 h was observed. The optimal growth temperature was found to be near 35° C. Cultures could be grown up to a density of 500 mg cells (dry weight) per liter. Growth yield studies demonstrated that between 4 and 5 g of cells (dry weight) were formed per mol of sulfate reduced to sulfide. The chemolithotrophically growing sulfate reducing isolates were identified as Desulfovibrio species by being obligately anaerobic, gram negative, non spore forming vibrios that contained desulfoviridin and cytochrome c (350-450 nmol/g protein). The organisms were found to be monopolarly and monotrichously flagellated. The abilities of the two strains to grow on electron donors other than H and to use electron acceptors other than sulfate differed considerably. The DNA base composition of the Madison and Marburg strains were 60 and 63.5 mol % GC, respectively. The taxonomic status of the strains was discussed. [ABSTRACT FROM AUTHOR]