Measurements and monitoring of the hydrogen and deuterium contents in the plasma of the L-2M stellarator

The program of experiments on ITER includes a sequential change of the plasma isotopic composition from pure hydrogen plasma in the initial stage of research to deuterium and, then, deuterium-tritium plasma with a gradual increase in the tritium content. In this context, the influence of the plasma isotopic composition on the processes of plasma heating and confinement are being actively studied on the existing tokamaks and stellarators. The plasma isotopic composition also depends on the composition of the gas desorbed from the vacuum chamber wall in the course of recycling. Therefore, the rate of change of the plasma isotopic composition after altering the injected gas also depends on the rate of change of the isotopic composition of the gas absorbed in the wall. These effects were studied in the experiments carried out on the L-2M stellarator in which the working gas was changed from hydrogen to deuterium. Spectral measurements of the intensity ratio between the H _α and D _α lines made it possible to monitor the isotopic composition of the plasma in the course of cleaning of the chamber wall from earlier absorbed hydrogen and its replacement with deuterium. After returning to hydrogen, the rate of cleaning of the wall from deuterium was also determined. The results of these experiments show that the plasma isotopic composition varies exponentially with the number N of shots after transition to another isotope, ∼exp(−N/47). Hence, the isotopic composition can be changed almost completely over 2 to 3 working days. This allows one to study the influence of the plasma isotopic composition on plasma confinement during the same experimental session.     

Isotopic fractionation factors of intermolecular hydrogen bonds in water

Association constants for N---H⁺…⁻O hydrogen bond formation between substituted ammonium dications and phenolate ion were measured in water and deuterium oxide at 25°C and 2.0 ionic strength. In combination with isotopic fractionation factors for phenol and the conjugate diacid of 1,2-ethanediamine determined by ¹³C NMR spectroscopy, these yield isotopic fractionation factors for amine dication-phenolate ion hydrogen bonds in water: φ_AB = 0.69 for 1,2-propanediamine dication with a pK difference between donor and acceptor, ΔpK_a = −0.45, φ_AB = 0.88 for 1,2-ethanediamine dication (ΔpK_a = −2.1), and φ_AB = 1.1 for piperizine dication (ΔpK_a = −3.5). The hydrogen bond association constants follow Brønsted correlations α = 0.19 in water and α = 0.27 in deuterium oxide. The results are consistent with a double-minimum potential with a significant barrier for motion across the hydrogen bond.     

Similarity laws for cathode-directed streamers in gaps with an inhomogeneous field at elevated air pressures

Results are presented from experimental studies of cathode-directed streamers in the gap closure regime without a transition into spark breakdown. Spatiotemporal, electrodynamic, and spectroscopic characteristics of streamer discharges in air at different pressures were studied. Similarity laws for streamer discharges were formulated. These laws allow one to compare the discharge current characteristics and streamer propagation dynamics at different pressures. Substantial influence of gas photoionization on the deviations from the similarity laws was revealed. The existence of a pressure range in which the discharges develop in a similar way was demonstrated experimentally. In particular, for fixed values of the product pd and discharge voltage U, the average streamer velocity is also fixed. It is found that, although the similarity laws are violated in the interstreamer pause of the discharge, the average discharge current and the product of the pressure and the streamer repetition period remain the same at different pressures. The radiation spectra of the second positive system of nitrogen (the C³Π _u -B³Π _g transitions) in a wavelength range of 300–400 nm at air pressures of 1–3 atm were recorded. It is shown that, in the entire pressure range under study, the profiles of the observed radiation bands practically remain unchanged and the relative intensities of the spectral lines corresponding to the ³Π _u -B³Π _g transitions are preserved.     

Influence of hydrogen acceptors on growth and energy production ofProteus mirabilis

The generation time ofP. mirabilis in defined and in complex medium is shorter in the presence of hydrogen acceptors than in their absence. In the presence of hydrogen acceptors the molar growth yield for glucose and the acetate production are strongly increased. From the molar growth yield and the acetate production Y_ATP in defined medium was calculated as 5.5 g/mole, whereas in complex medium a value of 12.6 g/mole was obtained. The molar growth yield, the acetate production, the amount of hydrogen acceptor reduced and Y_ATP were used to calculate P/2e⁻ratios for phosphorylation coupled to electron transfer to oxygen, nitrate and tetrathionate as respectively 2.80; 1.48 and 1.23 in defined medium. Under anaerobic conditions in the presence of nitrate or tetrathionate as hydrogen acceptor in complex medium a bend in the growth curve is observed. In the period of rapid growth the P/2e⁻ratio for nitrate reduction is of the same magnitude as that in defined medium, however much lower P/2e⁻ratios are found during the subsequent period of slow growth. The P/2e⁻ratios for tetrathionate reduction in complex medium for both growth periods are lower than those in defined medium. Most probably these results indicate that during this period growth and energy production are uncoupled. Under aerobic conditions in complex medium a constant Y_O value of 32.2 g/atom O is found during a short period of the growth curve. Afterwards when the cell density increases a steady decrease of Y_O is observed.     

Annual cycle of gross primary production and respiration in the Viroin River (Belgium)

Gross primary production, community respiration and reaeration coefficient were determined during an annual cycle on the Viroin River (South Belgium), based on the daily variations of dissolved oxygen concentration. Reaeration coefficient remains remarkably constant (0.26 h⁻¹) during the year in spite of discharge variations. The autotrophic community is dominated by ‘Ranunculus fluitans’. Primary production parallels the variations of total solar radiations. It ranges from 0 in winter to 8 g O₂ m⁻² d⁻¹ in summer. In spring and summer, respiration variations parallel those of primary production (average value: 10 g O₂ m⁻² d⁻¹); in the dry autumn, decomposition of dying macrophytes considerably enhances the community respiration (15 g O₂ m⁻² d⁻¹). A P/R diagram is used to characterize the trophic state of the Viroin.     

The anode potential regulates bacterial activity in microbial fuel cells

The anode potential in microbial fuel cells controls both the theoretical energy gain for the microorganisms as the output of electrical energy. We operated three reactors fed with acetate continuously at a poised anode potential of 0 (R ₀), −200 (R ₋₂₀₀) and −400 (R ₋₄₀₀) mV versus Ag/AgCl and investigated the resulting bacterial activity. The anode potential had no influence on the start-up time of the three reactors. During a 31-day period, R ₋₂₀₀ produced 15% more charge compared to R ₀ and R ₋₄₀₀. In addition, R ₋₂₀₀ had the highest maximal power density (up to 199 W m⁻³ total anode compartment during polarization) but the three reactors evolved to the same power density at the end of the experimental period. During polarization, only the current of R ₋₄₀₀ levelled off at an anode potential of −300 mV versus Ag/AgCl. The maximum respiration rate of the bacteria during batch tests was also considerably lower for R ₋₄₀₀. The specific biomass activity however, was the highest for R ₋₄₀₀ (6.93 g chemical oxygen demand g⁻¹ biomass-volatile suspended solids (VSS) d⁻¹ on day 14). This lowered during the course of the experiment due to an increase of the biomass concentration to an average level of 578 ± 106 mg biomass-VSS L⁻¹ graphite granules for the three reactors. This research indicated that an optimal anode potential of −200 mV versus Ag/AgCl exists, regulating the activity and growth of bacteria to sustain an enhanced current and power generation.     

Genetic engineering of Oryza sativa by particle bombardment

Genetic engineering of rice (Oryza sativa L. cv. Pusa basmati 1) using synthetic Cry1Ac gene has been achieved by “particle bombardment”. Scutellar tissues excised after 5 – 6 d from mature seeds cultured on induction medium were bombarded using gold particles coated with a mixture of Cry1Ac and marker genes on medium with osmoticum. Bombarded tissues were subjected to 30 mg dm⁻³ hygromycin selection for two cycles. The selected calli after GUS assay were transferred to shoot regeneration medium. Regenerated shoots were rooted and plantlets (T₀) were grown to full maturity. Polymerase chain reaction (PCR) analysis of T₀ plants using Cry1Ac specific primers revealed the presence of Cry1Ac gene in 65 % plants. Phenotypic assay, β-glucuronidase assay and PCR during T₁ generation revealed the inheritance of the Cry1Ac and marker genes along with the native plant genes.     

Canopy photosynthetic production in a Japanese larch stand. I. Seasonal and vertical changes of leaf characteristics along the light gradient in a canopy

In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area growth curve was 0.155–0.175 day⁻¹, while that for the weight growth was 0.112–0.117 day⁻¹. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm² g⁻¹ and then decreased until it leveled off at about 140 cm²g⁻¹. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I ₀) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I ₀)+B andb=C/(I′/I ₀)+D. Leaf respiration rate was also increased with increasingI′/I ₀. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear regression on semilogarithmic co-ordinates.     

Differential growth response of <Emphasis Type="Italic">Ulva lactuca</Emphasis> to ammonium and nitrate assimilation

Controlled cultivation of marine macroalgal biomass such as Ulva species, notably Ulva lactuca, is currently studied for production of biofuels or functional food ingredients. In a eutrophic environment, this macrophyte is exposed to varying types of nutrient supply, including different and fluctuating levels of nitrogen sources. Our understanding of the influences of this varying condition on the uptake and growth responses of U. lactuca is limited. In this present work, we examined the growth response of U. lactuca exposed to different sources of nitrogen (NH₄⁺; NO₃⁻; and the combination NH₄NO₃) by using photo-scanning technology for monitoring the growth kinetics of U. lactuca. The images revealed differential increases of the surface area of U. lactuca disks with time in response to different N-nutrient enrichments. The results showed a favorable growth response to ammonium as the nitrogen source. The NH₄Cl and NaNO₃ rich media (50 μM of N) accelerated U. lactuca growth to a maximum specific growth rate of 16.4 ± 0.18% day⁻¹ and 9.4 ± 0.72% day⁻¹, respectively. The highest biomass production rate obtained was 22.5 ± 0.24 mg DW m⁻²·day⁻¹. The presence of ammonium apparently discriminated the nitrate uptake by U. lactuca when exposed to NH₄NO₃. Apart from showing the significant differential growth response of U. lactuca to different nitrogen sources, the work exhibits the applicability of a photo-scanning approach for acquiring precise quantitative growth data for U. lactuca as exemplified by assessment of the growth response to two different N-sources.     

Increased soil stable nitrogen isotopic ratio following phosphorus enrichment: historical patterns and tests of two hypotheses in a phosphorus-limited wetland

We used a P enrichment gradient in the Everglades to investigate patterns of the stable N isotopic ratio (δ¹⁵N) in peat profiles as an indicator of historic eutrophication of this wetland. We also tested two hypotheses to explain the effects of P on increased δ¹⁵N of organic matter including: (1) increased N mineralization/N loss, and (2) reduced isotopic discrimination during macrophyte N uptake. Spatial patterns of δ¹⁵N in surface litter and soil (0–10 cm) mimic those of the aboveground macrophytes (Typha domingensis Pers. and Cladium jamaicense Crantz). Peat profiles also show increased δ¹⁵N in the peat accumulated in areas near the historic P discharges since the early 1960s. The increased δ¹⁵N of bulk peat correlated well with both measured increases in soil total P and the historical beginning of nutrient discharges into this wetland. In 15-day bottle incubations of soil, added P had no effect on the δ¹⁵N of NH₄⁺ and significantly increased the δ¹⁵N of water-extractable organic N. Measurements of surface soils collected during a field mesocosm experiment also revealed no significant effect of P on δ¹⁵N even after 5 years of P addition. In contrast, δ¹⁵N of leaf and root tissues of hydroponically grown Typha and Cladium were shown to increase up to 12‰ when grown at elevated levels of P and fixed levels of N (as NH₄⁺). The magnitude of changes in δ¹⁵N resulting from altered discrimination during N uptake is significant compared with other mechanisms affecting plant δ¹⁵N, and suggests that this may be the dominant mechanism affecting δ¹⁵N of organic matter following P enrichment. The results of this study have implications for the interpretation of δ¹⁵N as an indicator of shifts in relative N limitation in wetland ecosystems, and also stress the importance of experimental validation in interpreting δ¹⁵N patterns.     

Hydrogen oxidation and nitrogen fixation in rhizobia,with special attention focused on strain ORS 571

In this survey we describe the influence of hydrogen oxidation on the physiology ofRhizobium ORS 571. The presence of hydrogen is required for the synthesis of hydrogenase. Carbon substrates do not repress the synthesis of hydrogenase. The respiratory system contains cytrochromes of theb- andc-type. Cytochromea ₆₀₀ is present after growth at high oxygen tensions. The nature of the terminal oxidases functioning at low oxygen tensions has not been established yet. → H⁺/O values with endogenous substrates are between 6 and 7. The results show the presence of two phosphorylation sites: site 1 (ATP/2e=1.0) and site 2(ATP/2e=1.33). By measuring molar growth yields it has been demonstrated that carbon-limited, nitrogen-fixing cultures obtain additional ATP from hydrogen oxidation, and that site 2 of oxidative phosphorylation is passed during hydrogen oxidation. A method is described to calculate ATP/N₂ values (the total amount of ATP used by nitrogenase during the fixation of 1 mol N₂) and H₂/N₂ ratios (mol hydrogen formed per mol N₂ fixed) in aerobic organisms. ForRhizobium ORS 571 the ATP/N₂ value is about 40 and the H₂/N₂ ratio is between 5 and 7.5. Cells obtained from oxygen-limited nitrogen-fixing cultures contain 30–40% poly-β-hydroxybutyrate, which explains the high molar growth yields found. Hydrogen has not been detected in the effluent gas of these cultures, which may point to reoxidation of the hydrogen formed at nitrogen fixation. Calculations show that the effect of hydrogen reoxidation on the efficiency of nitrogen fixation (g N fixed × mol⁻¹ substrate converted) is not very large and that the actual H₂/N₂ ratio is of much more importance. After addition of hydrogen to succinate-limited, ammonia-assimilating cultures, an initial increase of the Y_succinate value (g dry wt × mol⁻¹ succinate) is followed by a gradual decrease. This is accompanied by a large decrease of the value, and an increased permeability of the cytoplasmic membrane to protons. The results may be explained by a transition of the culture from an energy-limited state to a carbon-limited state.     

A combined experimental and computational study on the material properties of shape memory polyurethane

A type of shape memory polyurethane with 60 wt% hard segments (SMPU60) was prepared. Its material properties were tested by dynamic mechanical analysis (DMA) and Instron, and simulated using fully atomistic molecular dynamics (MD). The glass transition temperature (T _g) of SMPU60 determined by DMA is 316 K, which is slightly lower than that estimated through MD simulations (T _g = 328 K) , showing the calculated T _g is in good agreement with experimental data. A complex hydrogen bonding network was revealed with the calculation of radial distribution functions (RDFs). The C═O⋯H bond is the predominant hydrogen-bonding interaction. With increasing temperature, both the hydrogen bonding and the moduli decreased, and the dissociation of intermolecular hydrogen bonding induced the decrease of the moduli.     

Induction of H2-Uptake and Nitrogenase Activities in the Cyanobacterium Anabaena variabilis ATCC 29413: Effects of Hydrogen and Organic Substrate

A comparative study of the development of uptake hydrogenase and nitrogenase activities in cells of the cyanobacterium Anabaena variabilis was performed. The induction of heterocysts is followed by the induction of both in vivo hydrogen uptake and nitrogenase activities. Interestingly, a low but significant H₂-uptake [2–7 μmoles of H₂ · mg⁻¹ (Chl a) · h⁻¹] occurs in cultures with no heterocysts and with no nitrogenase activity. A slight stimulatory effect (30–40%) of H₂ on in vivo H₂-uptake was observed during the early stages of nitrogenase induction. However, exogenous H₂ does not further stimulate the induction of in vivo hydrogen uptake observed during heterocyst differentiation. Similarly, organic carbon (fructose) did not influence the induction of either in vivo hydrogen uptake or nitrogenase activities. Exogenous fructose supports higher in vivo hydrogen uptake and nitrogenase activities when the cells enter late exponential phase of growth. Received: 22 November 1995 / Accepted: 22 December 1995     

Decalactone Production by <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> under increased O<Subscript>2</Subscript> Transfer Rates

Yarrowia lipolytica converts methyl ricinoleate to γ-decalactone, a high-value fruity aroma compound. The highest amount of 3-hydroxy-γ-decalactone produced by the yeast (263 mg l^-1) occurred by increasing the k_La up to 120 h⁻¹ at atmospheric pressure; above it, its concentration decreased, suggesting a predominance of the activity of 3-hydroxyacyl-CoA dehydrogenase. Cultures were grown under high-pressure, i.e., under increased O₂ solubility, but, although growth was accelerated, γ-decalactone production decreased. However, by applying 0.5 MPa during growth and biotransformation gave increased concentrations of dec−2-en-4-olide and dec-3-en-4-olide (70 mg l⁻¹).     

Changes in fatty acids composition,hydrogen peroxide generation and lipid peroxidation of salt-stressed corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) roots

Comparative study about the salt-induced oxidative stress and lipid composition has been realised in primary root tissues for two varieties of maize (Zea mays L.) in order to evaluate their responses to salt stress. The root growth, root water content (WC), hydrogen peroxide (H₂O₂) generation, lipid peroxidation, membrane stability index and the changes in the profile of fatty acids composition were investigated. Salinity impacts in term of root growth, water content, H₂O₂ generation, lipid peroxidation and membrane destabilisation were more pronounced in primary roots of Aristo than in those of Arper indicating more sensitivity of the first variety. It was confirmed by gas chromatography that the composition of fatty acids in roots of both varieties was constituted mainly by 16:0 and 18:0 as major saturated fatty acids and 18:1ω9, 18:2ω6 and 18:3ω3 as major unsaturated fatty acids. Total lipid extracts from the roots of both varieties showed that the lipid saturation level increased under salt stress, notwithstanding the increased proportion of polyunsaturated fatty acids. The changes in lipid saturation being predominantly due to decreases in oleic acid (18:1ω9) and increases in palmitic acid (16:0). However, Arper root extracts contained a lower proportion of saturated lipids than Aristo. The enhanced proportion of highly polyunsaturated fatty acids especially linolenic and eicosapentaenoic acids was considered to be the characteristic of the relatively salt tolerance in Arper roots.     

Quasi steady state growth of <Emphasis Type="Italic">Lactococcus lactis</Emphasis> in glucose-limited acceleration stat (A-stat) cultures

Quasi steady state growth of Lactococcus lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h⁻² after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h⁻¹. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration rate 0.003 h⁻² the quasi steady state growth was observed until μ _crit = 0.59 h⁻¹, which is also the μ _max value for the culture. Lower values of μ _crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h⁻¹ was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h⁻². Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h⁻² (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption were higher if the medium contained S ₀ = 5 g L⁻¹ glucose instead of S ₀ = 10 g L⁻¹. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y _ATP), and biomass yields per glucose consumed (Y _XS) were less than 15%.     

Stable isotopes (δD and δ13C) are geographic indicators of natal origins of monarch butterflies in eastern North America

Wing membranes of laboratory and field-reared monarch butterflies (Danaus plexippus) were analyzed for their stable-hydrogen (δD) and carbon (δ¹³C) isotope ratios to determine whether this technique could be used to identify their natal origins. We hypothesized that the hydrogen isotopic composition of monarch butterfly wing keratin would reflect the hydrogen isotope patterns of rainfall in areas of natal origin where wings were formed. Monarchs were reared in the laboratory on milkweed plants (Asclepias sp.) grown with water of known deuterium content, and, with the assistance of volunteers, on native milkweeds throughout eastern North America. The results show that the stable hydrogen isotopic composition of monarch butterflies is highly correlated with the isotopic composition of the milkweed host plants, which in turn corresponds closely with the long-term geographic patterns of deuterium in rainfall. Stable-carbon isotope values in milkweed host plants were similarly correlated with those values in monarch butterflies and showed a general pattern of enrichment along a southwest to northeast gradient bisecting the Great Lakes. These findings indicate that natal origins of migratory and wintering monarchs in Mexico can be inferred from the combined δD and δ¹³C isotopic signatures in their wings. This relationship establishes that analysis of hydrogen and carbon isotopes can be used to answer questions concerning the biology of migratory monarch butterflies and provides a new approach to tracking similar migratory movements of other organisms. Received: 1 July 1998 / Accepted: 11 November 1998     

Effects of heavy ions on rabbit tissues: Induction of DNA strand breaks in retinal photoreceptor cells by high doses of radiation

Excised retinas from New Zealand white (NZW) rabbits were irradiated at 0° C with 9–260 Gy (depending on the type of radiation) of 300 kVp X-rays, or the first 5 cm (range: 14 cm in water) of 365 MeV/u Ne ions or 530 MeV/u Ar ions (LET's : 1, 35 ± 3 and 90 ± 5 keV/µm, respectively). Other positions (LET's) in the Ne-ion beam (Bragg curve) were employed in more limited experiments. The retinas were frozen and stored in liquid nitrogen until analysis.Total strand breakage in the DNA of retinal photoreceptor (sensory) cells was determined from sedimentation profiles obtained by velocity sedimentation through reoriented alkaline sucrose gradients under conditions free from anomalies related to rotor speed. For the radiation doses employed: the reciprocal of the number average molecular weight,M _n , was related linearly to dose for each radiation quality and extrapolation to zero dose in each case gave positive intercepts for which the mean unitradiated molecular weight,M ₀, was 6.1 ± 1.0 × 10⁸ daltons; the efficiencies of total strand breakage for the different radiations were 50 ± 3, 110 ± 2 and 240±6 eV/strand break, respectively. For the heavy ions, accurate analogous calculations for other positions in the Bragg curves were precluded by beam degeneration due to fragmentation of the primary particles, etc.Overall, the experimental results support the concept that ionizing radiations damage cellular DNA by two general processes. One process causes localized damage, which under our experimental conditions is revealed as strand breaks and/or alkali-labile bonds in regions between molecules of sizecirca 10⁹ daltons (subunits); the other causes essentially random damage. Base damage caused by either process would not have been delineated in our experiments.     

Inhibition of hydrogen uptake in <Emphasis Type="Italic">Escherichia coli</Emphasis> by expressing the hydrogenase from the cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis>sp. PCC 6803

Background  

Molecular hydrogen is an environmentally-clean fuel and the reversible (bi-directional) hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 as well as the native Escherichia coli hydrogenase 3 hold great promise for hydrogen generation. These enzymes perform the simple reaction 2H⁺ + 2e^- ↔ H₂ (g).     

H<Subscript>2</Subscript> enrichment from synthesis gas by <Emphasis Type="Italic">Desulfotomaculum</Emphasis><Emphasis Type="Italic">carboxydivorans</Emphasis> for potential applications in synthesis gas purification and biodesulfurization

Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism grows rapidly at 200 kPa CO, pH 7.0, and 55°C, with a generation time of 100 min, producing nearly equimolar amounts of H₂ and CO₂ from CO and H₂O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)⁻¹ h⁻¹, makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic water–gas shift reaction to purify synthesis gas (contains mainly H₂, CO, and CO₂). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)⁻¹ h⁻¹) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and pH 6.5, respectively.