Alcohol conversion by Desulfobulbus propionicus Lindhorst in the presence and absence of sulfate and hydrogen

Ethanol was rapidly degraded to mainly acetate in anaerobic freshwater sediment slurries. Propionate was produced in small amounts. Desulfovibrio species were the dominant bacteria among the ethanol-degrading organisms. The propionate-producing Desulfobulbus propionicus came to the fore under iron-limited conditions in an ethanol-limited chemostat with excess sulfate inoculated with anaerobic intertidal freshwater sediment. In the absence of sulfate, ethanol was fermented by D. propionicus Lindhorst to propionate and acetate in a molar ratio of 2.0.l-Propanol was intermediately produced during the fermentation of ethanol. In the presence of H₂ and CO₂, ethanol was quantitatively converted to propionate. H₂-plus sulfate-grown cells of D. propionicus Lindhorst were able to oxidize l-propanol and l-butanol to propionate and butyrate respectively with the concomitant reduction of acetate plus CO₂ to propionate. Growth was also observed on acetate alone in the presence of H₂ and CO₂ D. propionicus was able to grow mixotrophically on H₂ plus an organic compound. Finally, a brief discussion has been given of the ecological niche of D. propionicus in anaerobic freshwater sediments.     

Glycerol and propanediols degradation by Desulfovibrio alcoholovorans in pure culture in the presence of sulfate, or in syntrophic association with Methanospirillum hungatei

Abstract In a mineral medium containing sulfate as terminal electron acceptor, the sulfate-reducing bacterium Desulfovibrio alcoholovorans oxidized stoichiometrically 1 mol glycerol to 1 mol acetate and 1 mol 1,3-propanediol to 1 mol acetate with the concomitant reduction of 0.75 and 1 mol sulfate, respectively; 1 mol 1,2-propanediol was degraded to 0.8 mol acetate and 0.1 mol proprionate, with the reduction of approximately 1 mol sulfate. The maximum specific growth rates (μ_max in h⁻¹) were 0.22, 0.086 and 0.09 with glycerol, 1,3-propanediol and 1,2-propanediol, respectively. The growth yields were 12.7 g, 11.1 g and 7.2 g dry weight/mol 1,3-propanediol, glycerol and 1,2-propanediol degraded, respectively. The growth yields and maximum specific growth rates of the H₂-transferring associations were also calculated. In the absense of sulfate, all these reduced substrates were degraded to acids and methane when D. alcoholovorans was cocultured with Methanospirillum hungatei . Changes in the metabolic pathway were observed in the degradation of 1,2- and 1,3-propanediol. The metabolic efficiency of D. alcoholovorans to degrade glycerol, 1.2- and 1,3-propanediol is discussed.     

Microbial cultures in the utilization of cellulosic materials

This review elaborates on the most recent microbial development in saccharification of cellulose and cellulase formation. A particular highlight is a new genetic-immunochemical approach investigating the mechanism of adhesion of bacterial cellulase to cellulose during cellulose conversion. New developments and recent reviews in hemicellulose and lignin degradation are also covered.     

Biooxidation of pyrite by defined mixed cultures of moderately thermophilic acidophiles in pH-controlled bioreactors: significance of microbial interactions

The oxidative dissolution of pyrite (FeS2) by pure and mixed cultures of moderately thermophilic acidophiles was studied in shake flask cultures and in pH-controlled bioreactors, incubated at 45 degrees C. Various combinations of seven eubacteria (a Leptospirillum sp. (MT6), Acidimicrobium ferrooxidans, Acidithiobacillus caldus, an Alicyclobacillus sp. (Y004), and three Sulfobacillus spp.) and one archaeon (Ferroplasma sp. MT17) were examined. Pyrite dissolution was determined by measuring changes in soluble iron and generation of acidity, and microbial populations were monitored using a combined culture-dependent (plate counts) and culture-independent (fluorescent in situ hybridization) approach. In pure cultures, the most efficient pyrite-oxidizing acidophile was Leptospirillum MT6, which was unique among the prokaryotes used in being obligately autotrophic. Mixed cultures of Leptospirillum MT6 and the sulfur-oxidizer At. caldus generated more acidity than pure cultures of the iron-oxidizer, though this did not necessarily enhance pyrite dissolution. In contrast, a mixed culture of Leptospirillum MT6 and the obligate heterotroph Alicyclobacillus Y004 oxidized pyrite more rapidly and more completely than a pure culture of Leptospirillum MT6, in synchronized bioreactors. Although the autotroph, At. caldus, and the "heterotrophically inclined" iron-oxidizer, Am. ferrooxidans, were both ineffective at leaching pyrite in pure culture, a mixed culture of the two bacteria was able to accelerate dissolution of the mineral. Concentrations of dissolved organic carbon accumulated to >100 mg/L in some mixed cultures, and the most effective bioleaching systems were found to be consortia containing both autotrophic and heterotrophic moderate thermophiles. A mixed culture comprising the autotrophs Leptospirillum MT6 and At. caldus, and the heterotroph Ferroplasma MT17, was the most efficient of all of those examined. Mutualistic interactions between physiologically distinct moderately thermophilic acidophiles, involving transfer of organic and inorganic carbon and transformations of iron and sulfur, were considered to have critical roles in optimizing pyrite dissolution.     

Anaerobic degradation of benzene in BTX mixtures dependent on sulfate reduction

Abstract Enrichment cultures from marine sediments mineralized benzene while using sulfate as the terminal electron acceptor. Parallel cultures using river marsh sediment displayed no activity. Mineralization was confirmed by release of ¹⁴CO₂ from radiolabeled benzene. The dependence on sulfate reduction was demonstrated by stoichiometric balances and the use of specific inhibitors. This work supports recent observations that anaerobic benzene degradation takes place coupled to sulfate reduction.     

Fe(III) as an electron acceptor for H2 oxidation in thermophilic anaerobic enrichment cultures from geothermal areas

Six sustainable enrichment cultures of thermophilic H₂-oxidizing microorganisms utilizing Fe(III) as an electron acceptor were obtained from geothermally heated environments located on two continents (America, Eurasia) and on islands in the Northern (Iceland) and Southern (Fiji) hemispheres, demonstrating the wide distribution of these microorganisms. The main products of amorphic Fe(III) oxide reduction were magnetite and siderite. The observed temperature range for Fe(III) reduction in growing cultures was from 55°C to 87°C, extending the known limits for growth of Fe(III)-reducing microorganisms producing extracellular magnetite to nearly 90°C. Received: August 13, 1996 / Accepted: January 17, 1997     

Characterization of sulfate transport in Desulfovibrio desulfuricans

Uptake of ³⁵S-labelled sulfate was studied with a new isolate of Desulfovibrio desulfuricans, strain CSN. Micromolar additions of sulfate (1–10 M or nmol/mg protein) to cell suspensions incubated in 150 mM KCl at-1°C were almost completely taken up and accumulated about 5,000-fold. Accumulation was not influenced by incubation in NaCl instead of KCl, by acidic pH (5.5) or by incubation under air for 10 min. In alkaline milieu (pH 8.5), after prolonged contact with air (2 h), or after growth with excess sulfate or thiosulfate as electron acceptor, the amount taken up was diminished approximately by half. Pasteurization inhibited sulfate uptake completely. With increasing concentrations of added sulfate (0.1 to 2.5 mM) the intracellular concentration increased only slowly up to 25 mM, and the accumulation factor decreased down to 8. Sulfate transport was reversible. Accumulated sulfate was rapidly lost from the cells after addition of excess non-labelled sulfate or after addition of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). The ATPase inhibitor dicyclohexylcarbodiimide (DCCD) specifically inhibited sulfate reduction but had no immediate influence on sulfate accumulation. Addition of the phosphate analogue arsenate (5 mM) was without effect. These results were not in favour of an ATP-dependent transport system. The K⁺-H⁺-antiporter nigericin (in 150 mM KCl) and the Na⁺-H⁺-antiporter monensin (in 150 mM NaCl) caused partial inhibition of sulfate accumulation, whereas the K⁺-transporter valinomycin (in 150 mM KCl) and the Na⁺-H⁺ exchange inhibitor amiloride (2 mM) were without effect. The permeant thiocyanate anion (150 mM) inhibited sulfate uptake by 60% at pH 7, and completely at pH 8.5. Although the effects of the different ionophores on the chemiosmotic gradients have not been studied so far, the results indicated that probably both, pH and drive sulfate accumulation and that sulfate is taken up electrogenically in symport with more than 2 protons. The structural sulfate analogues tungstate and molybdate (0.1 mM, each) did not affect sulfate accumulation, although molybdate inhibited sulfate reduction. Chromate completely blocked both of these activities. Sulfite and selenite caused little or no decrease of sulfate accumulation, whereas with thiosulfate and selenate significant inhibition was observed.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - DCCD dicyclohexylcarbodiimide     

Seasonal oscillation of microbial iron and sulfate reduction in saltmarsh sediments (Sapelo Island, GA, USA)

Seasonal variations in anaerobic respiration pathways were investigated at three saltmarsh sites using chemical data, sulfate reduction rate measurements, enumerations of culturable populations of anaerobic iron-reducing bacteria (FeRB), and quantification of in situ 16S rRNA hybridization signals targeted for sulfate-reducing bacteria (SRB). Bacterial sulfate reduction in the sediments followed seasonal changes in temperature and primary production of the saltmarsh, with activity levels lowest in winter and highest in summer. In contrast, a dramatic decrease in the FeRB population size was observed during summer at all sites. The collapse of FeRB populations during summer was ascribed to high rates of sulfide production by SRB, resulting in abiotic reduction of bioavailable Fe(III) (hydr)oxides. To test this hypothesis, sediment slurry incubations at 10, 20 and 30 °C were carried out. Increases in temperature and labile organic carbon availability (acetate or lactate additions) increased rates of sulfate reduction while decreasing the abundance of culturable anaerobic FeRB. These trends were not reversed by the addition of amorphous Fe(III) (hydr)oxides to the slurries. However, when sulfate reduction was inhibited by molybdate, no decline in FeRB growth was observed with increasing temperature. Addition of dissolved sulfide adversely impacted propagation of FeRB whether molybdate was added or not. Both field and laboratory data therefore support a sulfide-mediated limitation of microbial iron respiration by SRB. When total sediment respiration rates reach their highest levels during summer, SRB force a decline in the FeRB populations. As sulfate reduction activity slows down after the summer, the FeRB are able to recover.     

Characterization of a soluble oxidoreductase from the thermophilic bacterium Carboxydothermus ferrireducens

An NAD(P)H-dependent oxidoreductase has been purified approximately 40-fold from the soluble protein fraction of the dissimilatory iron-reducing, anaerobic, thermophilic bacterium Carboxydothermus ferrireducens. The enzyme, a flavoprotein, has broad-substrate specificity—reducing Fe³⁺, Cr⁶⁺, and AQDS with rates of 0.31, 0.33, and 3.3 U mg⁻¹ protein and calculated NADH oxidation turnover numbers of 0.25, 0.25, and 2.5 s⁻¹, respectively. Numerous quinones are reduced via a two-electron transfer from NAD(P)H to quinone, thus participating in managing oxidative stress by avoiding the formation of semiquinone radicals.     

Investigation of a sulfate transfer during autohydrolysis of a fucoidan from the brown alga Fucus evanescens by tandem ESIMS

A fucoidan from the brown alga Fucus evanescens was effectively depolymerized by autohydrolysis. Negative-ion electrospray ionization mass spectrometry (ESIMS) revealed that the mixture contained sulfated mono- and oligosaccharides with polymerization degree (DP) up to 6, having from 1 to 4 sulfate groups per molecule. The prevalence of oligosaccharides with even DP was observed. It could be explained by the tendency of the 3-linked α-l-fucopyranose residues to hydrolyze faster than 4-linked ones. The intermolecular sulfate transfer during autohydrolysis was detected by ESIMS, when equimolar quantities of d-Rib and d-Glc were added as acceptors. The products were singly-sulfated and hexose was about four times more effective as an acceptor, than pentose. It was impossible to record MS/MS spectra of the sulfate transfer products, since intensities of their ions were too low.     

废黄河口盐沼土硫酸盐还原速率的研究

本文报道了江苏省北部废黄河口滩面盐沼土中的硫酸盐还原速率。两年内,用同位素标记法测定了两块试验地的硫酸盐还原速率。结果表明,它们均有较高的还原速率。积分得大米草地和互花米草地年总还原值分别为77.75mol SO_4~(2-)·m~(-2)和110.3mol SO_4~(2-)·m~(-2)。硫酸盐还原速率高可能有3个原因:①米草地下部分向上层提供大量有机物;②SO_4~(2-)可由渗透潮水补充,不会因SO_4~(2-)亏损而影响还原率;③硫化物浓度保持在低于引起毒害的水平。硫酸盐还原主要终产物是FeS_2。FeS_2作为被还原的临时贮存库,其浓度有季节性变化。此外,还讨论了硫酸盐还原在有机碳矿化中的作用及在盐沼生态系统中能流的意义。     

An evaluation of the importance of sulfate reduction and temperature to P fluxes from aerobic-surfaced, lacustrine sediments

We examined the influence of temperature and sulfate reduction rates onP-release from aerobic-surfaced, littoral sediments in a coolingreservoir. Annually, significant differences in P release from sediments at twosites (thermal effluent and non-effluent) were related to differenttemperature regimes, with higher rates of P release and decomposition at highertemperatures. Site-specific differences in solute fluxes were mostpronounced in late summer, when water temperatures reached40°Cat the effluent site and solute fluxes increased dramatically. The thermaleffluent site retained 65% of its annual P load, while thenon-effluent site retained 92%. Relative P release(P-release normalized to inorganic carbon fluxes; RPR) data indicatedthat lake sediments retained P selectively (relative to C) throughout the year,except at the effluent site during late summer when stored P was released inexcess of supply rates.Sulfate reduction rates were often typical of those measured in otherfreshwater lakes, but unusually high rates were measured at thethermal-effluent site especially in early fall and suggested higher DICfluxes than we measured. These high rates suggest that sulfate reduction rateswere overestimated and/or that most sulfide was recycled within the sediments.In any case, the highest sulfate reduction rates did not coincide with thehighest P release rates. Furthermore, the total reduced inorganic sulfurcontentof surficial sediments did not significantly correlate to RPR, althoughconcentrations varied widely throughout the year. Temperature was the onlyvariable examined that significantly correlated to RPR (R² =0.53, P-value = 0.017). Coupling between temperature and sedimentP release was likely mediated through temperature effects on bioturbation andmicrobial metabolic rates.     

Detection of sequences homologous to the highly-conserved HSP70 gene of eukaryotes in thermophilic eubacteria and archaebacteria

Abstract The HSP70 genes of eukaryotes show up to 50% nucleotide sequence homology to the dna K gene of Escherichia coli . This extreme structure conservation implies conservation of a function that may be needed by all cells, suggesting that other bacteria may have sequences related to HSP70 and dna K. Amongst other functions, HSP70-like proteins may act to limit thermal protein denaturation. In this study DNA isolated from thermophilic archaebacteria (from the family Desulfurococcus ) and thermophilic eubacteria (from the families Bacillus and Thermus ) was probed with sequences from a heat shock inducible HSP70 gene of the yeast Saccharomyces cerevisiae . Hybridization was detected under conditions of low stringency, indicating the existence of HSP70-related sequences in the thermophilic bacteria studied.     

Desulfonauticus autotrophicus sp. nov., a novel thermophilic sulfate-reducing bacterium isolated from oil-production water and emended description of the genus Desulfonauticus

A novel moderately thermophilic and halophilic sulfate-reducing bacterium, strain TeSt^T, was isolated from production water of an oil field in Northern Germany near Hamburg. The cells were Gram-negative, straight to slightly curved rods and motile by a single polar flagellum. Only hydrogen and formate served as electron donors, whereas a wide variety of organic substrates and CO₂ could be used as carbon sources. Sulfate, sulfite, thiosulfate and sulfur were used as electron acceptors, but not nitrate or ferric iron. The novel isolate was negative for oxidase, catalase and desulfoviridin enzyme activity. Cytochromes were present and predominantly of the c-type. Whole-cells fatty acid patterns were dominated by the branched-chain fatty acids anteiso-C_15:0, iso-C_15:0, iso-C_17:0 and anteiso-C_17:0. As major respiratory lipoquinones partially saturated derivates of menaquinone 6 [MK-6(H₂) and probably MK-6(H₄)] were identified. The G + C content of the genomic DNA was 41.3 mol% (HPLC method). An analysis of the 16S rRNA gene sequence indicated that strain TeSt^T belongs to the family Desulfohalobiaceae within the class Deltaproteobacteria. The most closely related species with a sequence similarity of 95.0% was Desulfonauticus submarinus suggesting an affiliation of TeSt^T to the genus Desulfonauticus. The novel isolate could be clearly distinguished from Desulfonauticus submarinus by its ability to grow chemolithoautotrophically and hence should be assigned to a novel species for which the name Desulfonauticus autotrophicus sp. nov. is proposed. The type strain is TeSt^T (=DSM 4206^T = JCM 13028^T). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.