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1.
Growth of Desulfovibrio in Lactate or Ethanol Media Low in Sulfate in Association with H2-Utilizing Methanogenic Bacteria 总被引:37,自引:29,他引:8
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In the analysis of an ethanol-CO2 enrichment of bacteria from an anaerobic sewage digestor, a strain tentatively identified as Desulfovibrio vulgaris and an H2-utilizing methanogen resembling Methanobacterium formicicum were isolated, and they were shown to represent a synergistic association of two bacterial species similar to that previously found between S organism and Methanobacterium strain MOH isolated from Methanobacillus omelianskii. In lowsulfate media, the desulfovibrio produced acetate and H2 from ethanol and acetate, H2, and, presumably, CO2 from lactate; but growth was slight and little of the energy source was catabolized unless the organism was combined with an H2-utilizing methanogenic bacterium. The type strains of D. vulgaris and Desulfovibrio desulfuricans carried out the same type of synergistic growth with methanogens. In mixtures of desulfovibrio and strain MOH growing on ethanol, lactate, or pyruvate, diminution of methane produced was stoichiometric with the moles of sulfate added, and the desulfovibrios grew better with sulfate addition. The energetics of the synergistic associations and of the competition between the methanogenic system and sulfate-reducing system as sinks for electrons generated in the oxidation of organic materials such as ethanol, lactate, and acetate are discussed. It is suggested that lack of availability of H2 for growth of methanogens is a major factor in suppression of methanogenesis by sulfate in natural ecosystems. The results with these known mixtures of bacteria suggest that hydrogenase-forming, sulfate-reducing bacteria could be active in some methanogenic ecosystems that are low in sulfate. 相似文献
2.
Energy-linked Sulfate Uptake by Corn Mitochondria via the Phosphate Transporter 总被引:3,自引:3,他引:0
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Corn shoot mitochondria possess an energy-linked transport system for sulfate uptake as demonstrated by osmotic swelling and [35S]SO42− accumulation. Maximum uptake is secured in the presence of Mg2+ and oligomycin with sucrose for osmotic support. Neither phosphate nor dicarboxylate anions are required. When added simultaneously, millimolar concentrations of phosphate block [35S]SO42− uptake after the initial minute. Mersalyl, N-ethylmaleimide, and 2,4-dinitrophenol are strong inhibitors of sulfate uptake; n-butylmalonate is a weak inhibitor. These inhibitors act in the same fashion on phosphate uptake. It is concluded that sulfate uptake in the absence of phosphate is by the phosphate transporter. 相似文献
3.
Cations were generally ineffective in stimulating succinate transport in a succinate dehydrogenase mutant of Bacillus subtilis unless accompanied by polyvalent anions; phosphate and sulfate being particularly active. The Km values for the phosphate or sulfate requirement were approx. 3 mM.Biphasic kinetics were characteristic of both the succinate (Km values 0.1 and 1 mM), and inorganic phosphate (Km values 0.1 and 3 mM) transport system(s). The phosphate transport system(s) was repressed by high inorganic phosphate and a coordinate increase in the transport of phosphate, arsenate, and phosphate-stimulated succinate transport accompanied growth in low phosphate media.A class of arsenate resistant mutants were simultaneously defective in the transport of arsenate, phosphate and succinate when cells were repressed for phosphate transport, however, the transport of these ions was regained in these mutants when grown in low phosphate media. Organic phosphate esters did not stimulate succinate transport in arsenate resistant mutants but were effective after growth in low phosphate media. Growth under phosphate limitation permitted the simultaneous regain of both phosphate and sulfate dependent succinate transport activities whereas sulfate limitation alone was ineffective.Succinate was not transported by an anion exchange diffusion mechanism since phosphate efflux was low or absent during succinate transport.The transport of C4-dicarboxylates in B. subtilis is strongly stimulated by intracellular polyvalent anions. The absence of an anion permeability mechanism precludes succinate transport but partial escape from this restriction is mediated by the derepression of a phosphate transport system. 相似文献
4.
The kinetics of sulfate and acetate uptake was studied in the sulfate-reducing bacterium Desulfobacter postgatei (DSM 2034). Kinetic parameters (Km and Vmax) were estimated from substrate consumption curves by resting cell suspensions with [35S]sulfate and [14C]acetate. Both sulfate and acetate consumption followed Michaelis-Menten saturation kinetics. The half-saturation constant (Km) for acetate uptake was 70 μM with cells from either long-term sulfate- or long-term acetate-limited chemostat cultures. The average Km value for sulfate uptake by D. postgatei was about 200 μM. Km values for sulfate uptake did not differ significantly when determined with cells derived either from batch cultures or sulfate- or acetate-limited chemostat cultures. Acetate consumption was observed at acetate concentrations of ≤1 μM, whereas sulfate uptake usually ceased at 5 to 20 μM. The results show that D. postgatei is not freely permeable to sulfate ions and further indicate that sulfate uptake is an energy-requiring process. 相似文献
5.
Solubilization and partial purification of n,n'-dicyclohexylcarbodiimide-sensitive ATPase from pea cotyledon mitochondria
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The N,N′-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase of pea (Pisum sativum L.) cotyledon mitochondria was solubilized from submitochondrial particle membranes with sodium cholate and ammonium sulfate. Ammonium sulfate precipitation of the enzyme resulted in an increase in specific activity. At between 38% and 45% saturated ammonium sulfate, 20% of the ATPase activity was precipitated, with a specific activity 4 to 5 times higher than that of the crude enzyme. The precipitate was highly sensitive to DCCD.
The properties of the ammonium sulfate preparation were investigated. It contained levels of cytochrome and NADH dehydrogenase contamination comparable to those of the highly purified F0F1 preparations from animal tissue. The high degree of purification was corroborated by sodium dodecyl sulfate electrophoresis.
相似文献6.
Role of o-acetylserine in hydrogen sulfide emission from pumpkin leaves in response to sulfate 总被引:2,自引:0,他引:2
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Rennenberg H 《Plant physiology》1983,73(3):560-565
In the presence of excess sulfate, cysteine synthesis in pumpkin (Cucurbita pepo) leaves is not limited by sulfate reduction, but by the availability of O-acetylserine. Feeding of O-acetylserine or its metabolic precursors S-acetyl-coenzyme-A and coenzyme A to leaf discs enhanced the incorportion of [35S]sulfate into reduced sulfur compounds, mainly into cysteine, at the cost of lowered H2S emission; the uptake and reduction of sulfate is not affected by these treatments. β-Fluoropyruvate, an inhibitor of the generation of S-acetyl-coenzyme A via pyruvate dehydrogenase, stimulated H2S emission in response to sulfate. This stimulation is overcompensated by addition of O-acetylserine, S-acetyl-coenzyme A, or coenzyme A. These results indicate that, in the presence of high amounts of sulfate, excess sulfur is reduced and emitted as H2S into the atmosphere. The H2S emitted seems to be produced by liberation from a precursor of cysteine rather than by cysteine desulfhydration. 相似文献
7.
Bradfield G Somerfield P Meyn T Holby M Babcock D Bradley D Segel IH 《Plant physiology》1970,46(5):720-727
Inorganic sulfate enters the mycelia of Aspergillus nidulans, Penicillium chrysogenum, and Penicillium notatum by a temperature-, energy-, pH-, ionic strength-, and concentration-dependent transport system (“permease”). Transport is unidirectional. In the presence of excess external sulfate, ATP sulfurylase-negative mutants will accumulate inorganic sulfate intracellularly to a level of about 0.04 m. The intracellular sulfate can be retained against a concentration gradient. Retention is not energy-dependent, nor is there any exchange between intracellular (accumulated) and extracellular sulfate. The sulfate permease is under metabolic control. Sulfur starvation of high methionine-grown mycelia results in about a 1000-fold increase in the specific sulfate transport activity at low external sulfate concentrations. l-Methionine is a metabolic repressor of the sulfate permease, while intracellular sulfate and possibly l-cysteine (or a derivative of l-cysteine) are feedback inhibitors. Sulfate transport follows hyperbolic saturation kinetics with a Michaelis constant (Km) value of 6 × 10−5 to 10−4m and a Vmax (for maximally sulfurstarved mycelia) of about 5 micromoles per gram per minute. Refeeding sulfur-starved mycelia with sulfate or cysteine results in about a 10-fold decrease in the Vmax value with no marked change in the Km. Azide and dinitrophenol also reduce the Vmax. 相似文献
8.
The polysaccharide-chain fragments of rooster-comb dermatan sulfates (RC-20 and RC-30) were obtained by chondroitinase AC-II digestion and by periodate oxidation, followed by alkaline cleavage, and their structures analyzed both quantitatively and qualitatively. RC-20 having a lower d-glucuronic acid content (22.6%) is composed preponderantly of large clusters of N-acetyldermosine sulfate (Mr~17 600–41 000) at the nonreducing terminal, whereas RC-30, having a higher d-glucuronic acid content, (41.4%) is poor in this cluster. Both RC-20 and RC-30 have an N-acetyldermosine sulfate cluster (Mr 6500–7300) within the polysaccharide chains. Most N-acetylchondrosine sulfate units of RC-20 and RC-30 exist as clusters, the large clusters (Mr~17 600) being preponderant in RC-30; both RC-20 and RC-30 contain a large proportion of N-acetylchondrosine sulfate clusters (Mr 3500 and 9000) that corresponds to the uronic acid content. In RC-30, most N-acetyldermosine disulfate units (13.4%) are linked to N-acetylchondrosine sulfate units or clusters. 相似文献
9.
M. I. Kusaykin M. S. Pesentseva A. S. Sils’chenko S. A. Avilov V. V. Sova T. N. Zvyagintseva V. A. Stonik 《Russian Journal of Bioorganic Chemistry》2006,32(1):63-70
An aryl sulfatase of unusual specificity has been isolated from the liver of marine mollusk Littorina kurila. It hydrolyzes p-nitrophenyl sulfate, does not affect the natural fucoidan, and catalyzes splitting off the sulfate group in position C4 of xylose residues within the carbohydrate chains of holostane triterpene glycosides from sea cucumbers. The properties of the enzyme were studied at pH 5.4. The protein is homogeneous according to electrophoresis and has M 45 ± 1 kDa. The semiinactivation time of the enzyme at 60°C is 20 min, and its K m value for the hydrolysis of p-nitrophenyl sulfate is 8.7 ± 1 mM. It was shown that natural sulfated polyhydroxysteroids inhibit activity of the sulfatase; their I 50 values depend on their structures and are within the range from 10?3 to 10?5 M. 相似文献
10.
Biofilm Dynamics and Kinetics during High-Rate Sulfate Reduction under Anaerobic Conditions 总被引:7,自引:3,他引:4
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Per Halkjaer Nielsen 《Applied microbiology》1987,53(1):27-32
The sulfate kinetics in an anaerobic, sulfate-reducing biofilm were investigated with an annular biofilm reactor. Biofilm growth, sulfide production, and kinetic constants (Km and Vmax) for the bacterial sulfate uptake within the biofilm were determined. These parameters were used to model the biofilm kinetics, and the experimental results were in good agreement with the model predictions. Typical zero-order volume rate constants for sulfate reduction in a biofilm without substrate limitation ranged from 56 to 93 μmol of SO24-cm−3 h−1 at 20°C. The temperature dependence (Q10) of sulfate reduction was equivalent to 3.4 at between 9 and 20°C. The measured rates of sulfate reduction could explain the relatively high sulfide levels found in sewers and wastewater treatment systems. Furthermore, it has been shown that sulfate reduction in biofilms just a few hundred micrometers thick is limited by sulfate diffusion into biofilm at concentrations below 0.5 mM. This observation might, in some cases, be an explanation for the relatively poor capacity of the sulfate-reducing bacteria to compete with the methanogenic bacteria in anaerobic wastewater treatment in submerged filters. 相似文献
11.
Acyl-CoA oxidase from Candida tropicalis 总被引:3,自引:0,他引:3
S Shimizu K Yasui Y Tani H Yamada 《Biochemical and biophysical research communications》1979,91(1):108-113
The preparation of a highly purified acyl-CoA oxidase from the cell extract of an n-alkane-utilizing yeast, Candida tropicalis, is described. It can be crystallized from ammonium sulfate solutions without an increase in specific activity, and is homogeneous on ultracentrifuge and disc electrophoresis. The enzyme is an octamer with approximately a 600,000 molecular weight, and has an isoelectric point of 5.5. It exhibits a typical flavoprotein spectrum with absorption maxima at 277, 365 and 445 nm, and contains 8 mol of FAD per mol of enzyme. The enzyme catalyzes the stoichiometric conversion of palmitoyl-CoA and O2 into 2-hexadecenoyl-CoA and H2O2. It oxidizes acyl-CoAs with carbon chain lengths of 4 to 20, and is most active toward lauroyl-CoA, but acetyl- and succinyl-CoAs are not oxidized. The enzyme is sulfhydryl dependent and is inactivated by silver and mercury compounds. 相似文献
12.
A continuous-stirred, hydrogen-based, hollow-fiber membrane biofilm reactor (HFMBfR) that was active in nitrate and sulfate reductions was shown to be effective for degradation or detoxification of para-chloronitrobenzene (p-CNB) in water by biotransforming it first to para-chloroaniline (nitro-reduction) and then to aniline (reductive dechlorination) with hydrogen (H2) as an electron donor. A series of short-term experiments examined the effects of nitrate and sulfate on p-CNB bioreduction. The results obtained showed both higher nitrate and sulfate concentration declined the p-CNB bioreduction in the biofilm, and this suggests the competition for H2 caused less H2 available for the p-CNB bioreduction when the H2 demand for the reductions was larger. Denitrification and sulfate reduction intermediates were thought to be potential factors inhibiting the p-CNB bioreduction. Analysis of electron-equivalent fluxes and reaction orders in the biofilm further demonstrated both denitrification and sulfate reduction competed more strongly for H2 availability than p-CNB bioreduction. These findings have significant implications for the HFMBfR used for degrading p-CNB under denitrifying and/or sulfate reducing conditions. 相似文献
13.
Sulfhydrolase Activity in Sediments of Wintergreen Lake, Kalamazoo County, Michigan 总被引:9,自引:5,他引:4
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The hydrolysis of p-nitrophenyl sulfate, p-nitrocatechol sulfate, and [35S]sodium dodecyl sulfate was examined in anoxic sediments of Wintergreen Lake, Michigan. Significant levels of sulfhydrolase activity were observed in littoral, transition, and profundal sediment samples. Rates of sulfate formation suggest that the sulfhydrolase system would represent a major source of sulfate within these sediments. Sulfate formed by ester sulfate hydrolysis can support dissimilatory sulfate reduction as shown by the incorporation of 35S from labeled sodium dodecyl sulfate into H235S. Sulfhydrolase activity varied with sediment depth, was greatest in the littoral zone, and was sensitive to the presence of oxygen. Estimations of ester sulfate concentrations in sediments revealed large quantities of ester sulfate (~30% of total sulfur). Both total sulfur and ester sulfate concentrations varied with the sediment type and were two to three orders of magnitude greater than the inorganic sulfur concentration. 相似文献
14.
Periplasmic Cytochrome c3 of Desulfovibrio vulgaris Is Directly Involved in H2-Mediated Metal but Not Sulfate Reduction
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Dwayne A. Elias Joseph M. Suflita Michael J. McInerney Lee R. Krumholz 《Applied microbiology》2004,70(1):413-420
Kinetic parameters and the role of cytochrome c3 in sulfate, Fe(III), and U(VI) reduction were investigated in Desulfovibrio vulgaris Hildenborough. While sulfate reduction followed Michaelis-Menten kinetics (Km = 220 μM), loss of Fe(III) and U(VI) was first-order at all concentrations tested. Initial reduction rates of all electron acceptors were similar for cells grown with H2 and sulfate, while cultures grown using lactate and sulfate had similar rates of metal loss but lower sulfate reduction activities. The similarities in metal, but not sulfate, reduction with H2 and lactate suggest divergent pathways. Respiration assays and reduced minus oxidized spectra were carried out to determine c-type cytochrome involvement in electron acceptor reduction. c-type cytochrome oxidation was immediate with Fe(III) and U(VI) in the presence of H2, lactate, or pyruvate. Sulfidogenesis occurred with all three electron donors and effectively oxidized the c-type cytochrome in lactate- or pyruvate-reduced, but not H2-reduced cells. Correspondingly, electron acceptor competition assays with lactate or pyruvate as electron donors showed that Fe(III) inhibited U(VI) reduction, and U(VI) inhibited sulfate loss. However, sulfate reduction was slowed but not halted when H2 was the electron donor in the presence of Fe(III) or U(VI). U(VI) loss was still impeded by Fe(III) when H2 was used. Hence, we propose a modified pathway for the reduction of sulfate, Fe(III), and U(VI) which helps explain why these bacteria cannot grow using these metals. We further propose that cytochrome c3 is an electron carrier involved in lactate and pyruvate oxidation and is the reductase for alternate electron acceptors with higher redox potentials than sulfate. 相似文献
15.
A. Kotyk J. Horák A. Knotková 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,698(3):243-251
Addition of a metabolizable substrate (glucose, ethanol and, to a degree, trehalose) to non-growing baker's yeast cells causes a boost of protein synthesis, reaching maximum rate 20 min after addition of glucose and 40–50 min after ethanol or trehalose addition. The synthesis involves that of transport proteins for various solutes which appear in the following sequence: H+, l-proline, sulfate, l-leucine, phosphate, α-methyl-d-glucoside, 2-aminoisobutyrate. With the exception of the phosphate transport system, the Kt of the synthesized systems is the same as before stimulation. Glucose is usually the best stimulant, but ethanol matches it in the case of sulfate and exceeds it in the case of proline. This may be connected with ethanol's stimulating the synthesis of transport proteins both in mitochondria and in the cytosol while glucose acts on cytosolic synthesis alone. The stimulation is often repressed by ammonium ions (leucine, proline, sulfate, H+), by antimycin (proline, trehalose, sulfate, H+), by iodoacetamide (all systems tested), and by anaerobic preincubation (leucine, proline, trehalose, sulfate). It is practically absent in a respiration-deficient petite mutant, only little depressed in the op1 mutant lacking ADP/ATP exchange in mitochondria, but totally suppressed (with the exception of transport of phosphate) in a low-phosphorus strain. The addition of glucose causes a drop in intracellular inorganic monophosphate by 30%, diphosphate by 45%, ATP by 70%, in total amino acids by nearly 50%, in transmembrane potential (absolute value) by about 50%, an increase of high-molecular-weight polyphosphate by 65%, of total cAMP by more than 100%, in the endogenous respiration rate by more than 100%, and a change of intracellular pH from 6.80 to 7.05. Ethanol caused practically no change in ATP, total amino acids, endogenous respiration, intracellular pH or transmembrane potential; a slight decrease in inorganic monophosphate and diphosphate and a sizeable increase in high-molecular-weight polyphosphate. The synthesis of the various transport proteins thus appears to draw its energy from different sources and with different susceptibility to inhibitors. It is much more stimulated in facultatively aerobic species (Saccharomyces cerevisiae, Endomyces magnusii) than in strictly aerobic ones (Rhodotorula glutinis, Candida parapsilosis) where an inhibition of transport activity is often observed after preincubation with metabolizable substrates. 相似文献
16.
Enzymatic sulfation of a large molecular weight glycoprotein associated with pig brain membranes 总被引:6,自引:0,他引:6
Pig brain membranes catalyze the transfer of [35S]sulfate from 3′-phosphoadenosine 5′-phospho[35S]sulfate into two macromolecular endogenous acceptors. Several operational enzymatic properties of the sulfotransferase activity have been defined. An apparent Km = 0.65 μm for 3′-phosphoadenosine 5′-phosphosulfate has been determined for the pig brain in vitro sulfotransferase system. Direct proof for the absolute requirement of the 3′-phosphate moiety of 3′-phosphoadenosine 5′-phosphosulfate is presented. The nucleotide end product, 3′,5′-ADP, is a potent competitive inhibitor of the pig brain sulfotransferase activity. One of the major products enzymatically labeled during incubation with 3′-phosphoadenosine 5′-phospho[35S]sulfate is a membrane-bound glycoprotein of high molecular weight. The sulfated glycoprotein appears to be an integral membrane glycoprotein, requiring 1% Triton X-100 for extraction. An 35S-labeled oligosaccharide, released by mild base treatment, contains O-sulfate ester groups and at least one N-acetylneuraminic acid residue. The sulfated glycoprotein has an apparent molecular weight of 198,000. Under the same in vitro conditions [35S]sulfate is also incorporated into a membrane-associated 35S-labeled proteoglycan having the properties of heparan sulfate. The 35S-labeled proteoglycan is electrostatically bound to the pig brain membranes, and can be readily extracted with 1 m NaCl. 相似文献
17.
An atomic absorption method for cation measurements in Kjeldahl digests of biological materials 总被引:1,自引:0,他引:1
Sulfate ion produced little or no interference in absorption by sodium, potassium, and magnesium, but produced a large depression in calcium absorbance in the atomic absorption spectrophotometric measurement of these cations in an acetylene-air flame. Nearly maximal depression of calcium absorbance by 2 mM sulfate was followed by a plateau region of only slight depression from 2 mM to 1 M sulfate concentration. Presence of 25 mM lanthanum in the samples resulted in no depression of calcium absorbance up to 2 mM sulfate, a sharp decrease to about 30 mM sulfate and a plateau from 30 mM up to 1 M sulfate. From these observations, it was determined that the addition of H2SO4 to provide approximately 40 mM added sulfate in standards and samples permitted accurate measurement of calcium even though the original sample contained relatively high and variable sulfate. 相似文献
18.
Hashem AM Van Domselaar G Li C Wang J She YM Cyr TD Sui J He R Marasco WA Li X 《Biochemical and biophysical research communications》2010,402(2):247-251
Dialysis related amyloidosis (DRA) is a serious complication to long-term hemodialysis treatment which causes clinical symptoms such as carpal tunnel syndrome and destructive arthropathies. The disease is characterized by the assembly and deposition of β2-microglobulin (β2m) predominantly in the musculoskeletal system, but the initiating events leading to β2m amyloidogenesis and the molecular mechanisms underlying amyloid fibril formation are still unclear. Glycosaminoglycans (GAGs) and metal ions have been shown to be related to the onset of protein aggregation and to promote de novo fiber formation. In this study, we show that fibrillogenesis of a cleavage variant of β2m, ΔK58-β2m, which can be found in the circulation of hemodialysis patients and is able to fibrillate at near-physiological pH in vitro, is affected by the presence of copper ions and heparan sulfate. It is found that the fibrils generated when heparan sulfate is present have increased length and diameter, and possess enhanced stability and seeding properties. However, when copper ions are present the fibrils are short, thin and less stable, and form at a slower rate. We suggest that heparan sulfate stabilizes the cleaved monomers in the early aggregates, hereby promoting the assembly of these into fibrils, whereas the copper ions appear to have a destabilizing effect on the monomers. This keeps them in a structure forming amorphous aggregates for a longer period of time, leading to the formation of spherical bodies followed by the assembly of fibrils. Hence, the in vivo formation of amyloid fibrils in DRA could be initiated by the generation of ΔK58-β2m which spontaneously aggregate and form fibrils. The fibrillogenesis is enhanced by the involvement of GAGs and/or metal ions, and results in amyloid-like fibrils able to promote the de novo formation of β2m amyloid by a scaffold mechanism. 相似文献
19.
20.
Nitrate Reduction in a Sulfate-Reducing Bacterium, Desulfovibrio desulfuricans, Isolated from Rice Paddy Soil: Sulfide Inhibition, Kinetics, and Regulation 总被引:7,自引:2,他引:5
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From the second-highest dilution in a most-probable-number dilution series with lactate and sulfate as substrates and rice paddy soil as the inoculum, a strain of Desulfovibrio desulfuricans was isolated. In addition to reducing sulfate, sulfite, and thiosulfate, the strain also reduced nitrate to ammonia. The latter process was studied in detail, since the ability to reduce nitrate was strongly influenced by the presence of sulfide. Sulfide inhibited both growth on nitrate and nitrate reduction. A 70% inhibition of the nitrate reduction rate was obtained at 127 μM sulfide, and growth was inhibited by 50% at approximately 320 μM sulfide and was not detectable above 700 μM sulfide. In contrast, sulfate reduction was not affected at concentrations of up to 5 mM. After growth with sulfate, an induction period of 2 to 4 days was needed before nitrate reduction started. When nitrate and sulfate were present simultaneously, only sulfate was reduced, except when sulfate was present at very low concentrations (4 μM). At higher sulfate concentrations (500 μM), nitrate reduction was temporarily halted. The affinity for nitrate uptake was extremely high (Km = 0.05 μM) compared with that for sulfate uptake (Km = 5 μM). Thus, at low nitrate concentrations this bacterium is favored relative to denitrifiers (Km = 1.8 to 13.7 μM) or other nitrate ammonifiers (e.g., Clostridium spp. [Km = 500 μM]). 相似文献