共查询到20条相似文献,搜索用时 31 毫秒
1.
Methanosarcina sp. strain TM-1, an acetotrophic, thermophilic methanogen isolated from an anaerobic sludge digestor, was originally reported to require an anaerobic sludge supernatant for growth. It was found that the sludge supernatant could be replaced with yeast extract (1 g/liter), 6 mM bicarbonate-30% CO2, and trace metals, with a doubling time on methanol of 14 h. For growth on either methanol or acetate, yeast extract could be replaced with CaCl2 · 2H2O (13.6 μM minimum) and the vitamin p-aminobenzoic acid (PABA, ca. 3 nM minimum), with a doubling time on methanol of 8 to 9 h. Filter-sterilized folic acid at 0.3 μM could not replace PABA. The antimetabolite sulfanilamide (20 mM) inhibited growth of and methanogenesis by Methanosarcina sp. strain TM-1, and this inhibition was reversed by the addition of 0.3 μM PABA. When a defined medium buffered with 20 mM N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid was used, it was shown that Methanosarcina sp. strain TM-1 required 6 mM bicarbonate-30% CO2 for optimal growth and methanogenesis from methanol. Cells growing on acetate were less dependent on bicarbonate-CO2. When we used a defined medium in which the only organic compounds present were methanol or acetate, nitrilotriacetic acid (0.2 mM), and PABA, it was possible to limit batch cultures of Methanosarcina sp. strain TM-1 for nitrogen at NH4+ concentrations at or below 2.0 mM, in marked contrast with Methanosarcina barkeri 227, which fixes dinitrogen when grown under NH4+ limitation. 相似文献
2.
Anaerobic Degradation of Lactate by Syntrophic Associations of Methanosarcina barkeri and Desulfovibrio Species and Effect of H2 on Acetate Degradation 总被引:18,自引:13,他引:5
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
When grown in the absence of added sulfate, cocultures of Desulfovibrio desulfuricans or Desulfovibrio vulgaris with Methanobrevibacter smithii (Methanobacterium ruminantium), which uses H2 and CO2 for methanogenesis, degraded lactate, with the production of acetate and CH4. When D. desulfuricans or D. vulgaris was grown in the absence of added sulfate in coculture with Methanosarcina barkeri (type strain), which uses both H2-CO2 and acetate for methanogenesis, lactate was stoichiometrically degraded to CH4 and presumably to CO2. During the first 12 days of incubation of the D. desulfuricans-M. barkeri coculture, lactate was completely degraded, with almost stoichiometric production of acetate and CH4. Later, acetate was degraded to CH4 and presumably to CO2. In experiments in which 20 mM acetate and 0 to 20 mM lactate were added to D. desulfuricans-M. barkeri cocultures, no detectable degradation of acetate occurred until the lactate was catabolized. The ultimate rate of acetate utilization for methanogenesis was greater for those cocultures receiving the highest levels of lactate. A small amount of H2 was detected in cocultures which contained D. desulfuricans and M. barkeri until after all lactate was degraded. The addition of H2, but not of lactate, to the growth medium inhibited acetate degradation by pure cultures of M. barkeri. Pure cultures of M. barkeri produced CH4 from acetate at a rate equivalent to that observed for cocultures containing M. barkeri. Inocula of M. barkeri grown with H2-CO2 as the methanogenic substrate produced CH4 from acetate at a rate equivalent to that observed for acetate-grown inocula when grown in a rumen fluid-vitamin-based medium but not when grown in a yeast extract-based medium. The results suggest that H2 produced by the Desulfovibrio species during growth with lactate inhibited acetate degradation by M. barkeri. 相似文献
3.
Sulfate-Dependent Interspecies H2 Transfer between Methanosarcina barkeri and Desulfovibrio vulgaris during Coculture Metabolism of Acetate or Methanol 总被引:7,自引:5,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We compared the metabolism of methanol and acetate when Methanosarcina barkeri was grown in the presence and absence of Desulfovibrio vulgaris. The sulfate reducer was not able to utilize methanol or acetate as the electron donor for energy metabolism in pure culture, but was able to grow in coculture. Pure cultures of M. barkeri produced up to 10 μmol of H2 per liter in the culture headspace during growth on acetate or methanol. In coculture with D. vulgaris, the gaseous H2 concentration was ≤2 μmol/liter. The fractions of 14CO2 produced from [14C]methanol and 2-[14C]acetate increased from 0.26 and 0.16, respectively, in pure culture to 0.59 and 0.33, respectively, in coculture. Under these conditions, approximately 42% of the available electron equivalents derived from methanol or acetate were transferred and were utilized by D. vulgaris to reduce approximately 33 μmol of sulfate per 100 μmol of substrate consumed. As a direct consequence, methane formation in cocultures was two-thirds that observed in pure cultures. The addition of 5.0 mM sodium molybdate or exogenous H2 decreased the effects of D. vulgaris on the metabolism of M. barkeri. An analysis of growth and carbon and electron flow patterns demonstrated that sulfate-dependent interspecies H2 transfer from M. barkeri to D. vulgaris resulted in less methane production, increased CO2 formation, and sulfide formation from substrates not directly utilized by the sulfate reducer as electron donors for energy metabolism and growth. 相似文献
4.
Control of Interspecies Electron Flow during Anaerobic Digestion: Significance of Formate Transfer versus Hydrogen Transfer during Syntrophic Methanogenesis in Flocs 总被引:18,自引:11,他引:7
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Microbial formate production and consumption during syntrophic conversion of ethanol or lactate to methane was examined in purified flocs and digestor contents obtained from a whey-processing digestor. Formate production by digestor contents or purified digestor flocs was dependent on CO2 and either ethanol or lactate but not H2 gas as an electron donor. During syntrophic methanogenesis, flocs were the primary site for formate production via ethanol-dependent CO2 reduction, with a formate production rate and methanogenic turnover constant of 660 μM/h and 0.044/min, respectively. Floc preparations accumulated fourfold-higher levels of formate (40 μM) than digestor contents, and the free flora was the primary site for formate cleavage to CO2 and H2 (90 μM formate per h). Inhibition of methanogenesis by CHCl3 resulted in formate accumulation and suppression of syntrophic ethanol oxidation. H2 gas was an insignificant intermediary metabolite of syntrophic ethanol conversion by flocs, and its exogenous addition neither stimulated methanogenesis nor inhibited the initial rate of ethanol oxidation. These results demonstrated that >90% of the syntrophic ethanol conversion to methane by mixed cultures containing primarily Desulfovibrio vulgaris and Methanobacterium formicicum was mediated via interspecies formate transfer and that <10% was mediated via interspecies H2 transfer. The results are discussed in relation to biochemical thermodynamics. A model is presented which describes the dynamics of a bicarbonate-formate electron shuttle mechanism for control of carbon and electron flow during syntrophic methanogenesis and provides a novel mechanism for energy conservation by syntrophic acetogens. 相似文献
5.
Relationship of Intracellular Coenzyme F420 Content to Growth and Metabolic Activity of Methanobacterium bryantii and Methanosarcina barkeri 总被引:3,自引:2,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The use of F420 as a parameter for growth or metabolic activity of methanogenic bacteria was investigated. Two representative species of methanogens were grown in batch culture: Methanobacterium bryantii (strain M.o.H.G.) on H2 and CO2, and Methanosarcina barkeri (strain Fusaro) on methanol or acetate. The total intracellular content of coenzyme F420 was followed by high-resolution fluorescence spectroscopy. F420 concentration in M. bryantii ranged from 1.84 to 3.65 μmol · g of protein−1; and in M. barkeri grown with methanol it ranged from 0.84 to 1.54 μmol · g−1 depending on growth conditions. The content of F420 in M. barkeri was influenced by a factor of 2 depending on the composition of the medium (minimal or complex) and by a factor of 3 to 4 depending on whether methanol or acetate was used as the carbon source. A comparison of F420 content with protein, cell dry weight, optical density, and specific methane production rate showed that the intracellular content of F420 approximately followed the increase in biomass in both strains. In contrast, no correlation was found between specific methane production rate and intracellular F420 content. However, qCH4(F420), calculated by dividing the methane production rate by the coenzyme F420 concentration, almost paralleled qCH4(protein). These results suggest that F420 may be used as a specific parameter for estimating the biomass, but not the metabolic activity, of methanogens; hence qCH4(F420) determined in mixed populations with complex carbon substrates must be considered as measure of the actual methanogenic activity and not as a measure of potential activity. 相似文献
6.
Diazotrophy and Nitrogenase Activity in the Archaebacterium Methanosarcina barkeri 227 总被引:4,自引:1,他引:3
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nitrogen fixation (diazotrophy) has recently been demonstrated in several methanogenic archaebacteria. To compare the process in an archaebacterium with that in eubacteria, we examined the properties of diazotrophic growth and nitrogenase activity in Methanosarcina barkeri 227. Growth yields with methanol or acetate as a growth substrate were significantly lower in N2-grown cultures than in NH4+-grown cultures, and the culture doubling times were increased, indicating that diazotrophy was energetically costly, as it is in eubacteria. Growth of nitrogen-fixing cells was inhibited when molybdenum was omitted from the medium; addition of 10 nM molybdate stimulated growth, while 1 μM molybdate restored maximum diazotrophic growth. Omission of molybdenum did not inhibit growth of ammonia-grown cells. Tungstate (100 μM) strongly inhibited growth of molybdenum-deficient diazotrophic cells, while ammonia-grown cells were unaffected. The addition of 100 nM vanadate or chromate did not stimulate diazotrophic growth of molybdenum-starved cells. These results are consistent with the presence of a molybdenum-containing nitrogenase in M. barkeri. Acetylene, the usual substrate for assaying nitrogenase activity, inhibited methanogenesis by M. barkeri and consequently needed to be used at a low partial pressure (0.3% of the headspace) when acetylene reduction by whole cells was assayed. Whole cells reduced 0.3% acetylene to ethylene at a very low rate (1 to 2 nmol h−1 mg of protein−1), and they “switched off” acetylene reduction in response to added ammonia or glutamine. Crude extracts from diazotrophic cells reduced 10% acetylene at a rate of 4 to 5 nmol of C2H4 formed h−1 mg of protein−1 when supplied with ATP and reducing power, while extracts of Klebsiella pneumoniae prepared by the same procedures had rates 100-fold higher. Acetylene reduction by extracts required ATP and was completely inhibited by 1 mM ADP in the presence of 5 mM ATP. The low rates of C2H2 reduction could be due to improper assay conditions, to switched-off enzyme, or to the nitrogenase's having lower activity towards acetylene than towards dinitrogen. 相似文献
7.
Acetate,methanol and carbon dioxide as substrates for growth of Methanosarcina barkeri 总被引:10,自引:0,他引:10
T. J. Hutten H. C. M. Bongaerts C. van der Drift G. D. Vogels 《Antonie van Leeuwenhoek》1980,46(6):601-610
Methanosarcina barkeri grows in defined media with acetate, methanol or carbon dioxide as carbon sources. Methanol is used for methanogenesis at a 5 times higher rate as compared with the other substrates. M. barkeri can use the substrates simultaneously, but due to acidification or alkalification of the medium during growth on methanol or acetate, respectively, growth and methanogenesis may stop before the substrates are exhausted. Growth and methanogenesis on methanol or acetate are inhibited by the presence of an excess of H2; the inhibition is abolished by the addition of carbon dioxide, which probably serves as an essential source of cell carbon, in the absence of which methano-genesis ceases. 相似文献
8.
After propagation of Rhizopus javanicus in defined media containing glucose, urea, and mineral salts in deionized distilled water, the ability of the nonliving biomass to sequester cupric ion was assayed. Growth, uptake capacity (saturation uptake at >1 mM Cu2+ concentration in solution), and biosorptive yield (biomass concentration × uptake capacity) were increased by augmentation of the growth medium with mineral salts once growth was under way. In the stationary phase, the uptake capacity of mycelia, which were normally a poor biosorbent, was improved within 4 h of trace metal addition to the growth medium. Growth of the culture was inhibited by excessive concentrations (0.04 to 40 μM) of metals in the medium in the following order: Cu > Co ≥ Ni > Mn > Mo; zinc was not inhibitory at 40 μM, and chromium was stimulatory at 0.53 μM but slightly inhibitory at higher levels. Iron and potassium phosphate stimulated growth at levels of 0.53 and 40 mM, respectively. When R. javanicus was propagated in a medium with a high salt concentration, exponential growth (0.23 h−1) to a biomass concentration of >3 g/liter and a biosorptive yield of >500 μmol/liter was achieved. It is evident that the powerful biosorbent characteristics of Rhizopus biomass led to depletion of available trace minerals in suspension culture, which in turn limited growth. 相似文献
9.
Methanosarcina barkeri MS and 227 and Methanosarcina mazei S-6 produced acetate when grown on H2-CO2, methanol, or trimethylamine. Marked differences in acetate production by the two bacterial species were found, even though methane and cell yields were nearly the same. M. barkeri produced 30 to 75 μmol of acetate per mmol of CH4 formed, but M. mazei produced only 8 to 9 μmol of acetate per mmol of CH4. 相似文献
10.
Methane and Trichloroethylene Degradation by Methylosinus trichosporium OB3b Expressing Particulate Methane Monooxygenase
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Whole-cell assays of methane and trichloroethylene (TCE) consumption have been performed on Methylosinus trichosporium OB3b expressing particulate methane monooxygenase (pMMO). From these assays it is apparent that varying the growth concentration of copper causes a change in the kinetics of methane and TCE degradation. For M. trichosporium OB3b, increasing the copper growth concentration from 2.5 to 20 μM caused the maximal degradation rate of methane (Vmax) to decrease from 300 to 82 nmol of methane/min/mg of protein. The methane concentration at half the maximal degradation rate (Ks) also decreased from 62 to 8.3 μM. The pseudo-first-order rate constant for methane, Vmax/Ks, doubled from 4.9 × 10−3 to 9.9 × 10−3 liters/min/mg of protein, however, as the growth concentration of copper increased from 2.5 to 20 μM. TCE degradation by M. trichosporium OB3b was also examined with varying copper and formate concentrations. M. trichosporium OB3b grown with 2.5 μM copper was unable to degrade TCE in both the absence and presence of an exogenous source of reducing equivalents in the form of formate. Cells grown with 20 μM copper, however, were able to degrade TCE regardless of whether formate was provided. Without formate the Vmax for TCE was 2.5 nmol/min/mg of protein, while providing formate increased the Vmax to 4.1 nmol/min/mg of protein. The affinity for TCE also increased with increasing copper, as seen by a change in Ks from 36 to 7.9 μM. Vmax/Ks for TCE degradation by pMMO also increased from 6.9 × 10−5 to 5.2 × 10−4 liters/min/mg of protein with the addition of formate. From these whole-cell studies it is apparent that the amount of copper available is critical in determining the oxidation of substrates in methanotrophs that are expressing only pMMO. 相似文献
11.
Effects of Hydrogen Pressure during Growth and Effects of Pregrowth with Hydrogen on Acetate Degradation by Methanosarcina Species 总被引:2,自引:2,他引:0
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David R. Boone Jos A. G. F. Menaia Jane E. Boone Robert A. Mah 《Applied microbiology》1987,53(1):83-87
Methanosarcina barkeri 227 and Methanosarcina mazei S-6 grew with acetate as the substrate; we found little effect of H2 on the rate of aceticlastic growth in the presence of various H2 pressures between 2 and 810 Pa. We used physical (H2 addition or flushing the headspace to remove H2) and biological (H2-producing or -utilizing bacteria in cocultures) methods for controlling H2 pressure in Methanosarcina cultures growing on acetate. Added H2 (ca. 100 Pa) was removed rapidly (a few hours) by M. barkeri and slowly (within a day) by M. mazei. When the H2 produced by the aceticlastic methanogens was removed by coculturing with an H2-using Desulfovibrio sp., the H2 pressure was about 2.2 Pa. Under these conditions the stoichiometry of aceticlastic methanogenesis did not change. H2-grown inocula of M. barkeri grew with acetate as the sole catabolic substrate if the inoculum culture was transferred during logarithmic growth to acetate-containing medium or if the transfer was accomplished within 1 or 2 days after exhaustion of H2. H2-grown cultures incubated for 4 or more days after exhaustion of H2 were able to grow with H2 but not with acetate as the sole catabolic substrate. Addition of small quantities of H2 to acetate-containing medium permitted these cultures to initiate growth on acetate. 相似文献
12.
The kinetics of ethanol inhibition on cell growth and ethanol production by Kluyveromyces marxianus UCD (FST) 55-82 were studied during batch growth. The liquid medium contained 10% (wt/vol) inulin-type sugars derived from an extract of Jerusalem artichoke (Helianthus tuberosus) tubers, supplemented with small amounts of Tween 80, oleic acid, and corn steep liquor. Initial ethanol concentrations ranging from 0 to 80 g/liter in the liquid medium were used to study the inhibitory effect of ethanol on the following parameters: maximum specific growth rate (μmax), cell and ethanol yields, and sugar utilization. It was found that as the initial ethanol concentration increased from 0 to 80 g/liter, and maximum specific growth rate of K. marxianus cells decreased from 0.42 to 0.09 h−1, whereas the ethanol and cell yields and sugar utilization remained almost constant. A simple kinetic model was used to correlate the μmax results and the rates of cell and ethanol production, and the appropriate constants were evaluated. 相似文献
13.
Microcystin Production by Microcystis aeruginosa in a Phosphorus-Limited Chemostat 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The production of microcystins (MC) from Microcystis aeruginosa UTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilized M. aeruginosa were extracted with 5% acetic acid, purified by a Sep-Pak C18 cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C18 reverse-phase column. The specific growth rate (μ) of M. aeruginosa was within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing μ. The MC-LR and MC-RR contents on a dry weight basis were highest at μ of 0.1/day at 339 and 774 μg g−1, respectively, while MC-YR was not detected. The MC content of M. aeruginosa was higher at a lower μ, whereas the MC-producing rate was linearly proportional to μ. The C fixation rate at an ambient irradiance (160 microeinsteins m−2 s−1) increased with μ. The ratios of the MC-producing rate to the C fixation rate were higher at a lower μ. Accordingly, the growth of M. aeruginosa was reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions. 相似文献
14.
Kinetics of Formate Metabolism in Methanobacterium formicicum and Methanospirillum hungatei 总被引:7,自引:6,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The kinetics of formate metabolism in Methanobacterium formicicum and Methanospirillum hungatei were studied with log-phase formate-grown cultures. The progress of formate degradation was followed by the formyltetrahydrofolate synthetase assay for formate and fitted to the integrated form of the Michaelis-Menten equation. The Km and Vmax values for Methanobacterium formicicum were 0.58 mM formate and 0.037 mol of formate h−1 g−1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanobacterium formicicum was 26 μM. The Km and Vmax values for Methanospirillum hungatei were 0.22 mM and 0.044 mol of formate h−1 g−1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanospirillum hungatei was 15 μM. The apparent Km for formate by formate dehydrogenase in cell-free extracts of Methanospirillum hungatei was 0.11 mM. The Km for H2 uptake by cultures of Methanobacterium formicicum was 6 μM dissolved H2. Formate and H2 were equivalent electron donors for methanogenesis when both substrates were above saturation; however, H2 uptake was severely depressed when formate was above saturation and the dissolved H2 was below 6 μM. Formate-grown cultures of Methanobacterium formicicum that were substrate limited for 57 h showed an immediate increase in growth and methanogenesis when formate was added to above saturation. 相似文献
15.
Energetics of Growth of a Defined Mixed Culture of Desulfovibrio vulgaris and Methanosarcina barkeri: Interspecies Hydrogen Transfer in Batch and Continuous Cultures 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alfred S. Traore Marie-Laure Fardeau Claude E. Hatchikian Jean Le Gall Jean-Pierre Belaich 《Applied microbiology》1983,46(5):1152-1156
Interspecies hydrogen transfer was studied in Desulfovibrio vulgaris-Methanosarcina barkeri mixed cultures. Experiments were performed under batch and continuous growth culture conditions. Lactate or pyruvate was used as an energy source. In batch culture and after 30 days of simultaneous incubation, these organisms were found to yield 1.5 mol of methane and 1.5 mol of carbon dioxide per mol of lactate fermented. When M. barkeri served as the hydrogen acceptor, growth yields of D. vulgaris were higher compared with those obtained on pyruvate without any electron acceptor other than protons. In continuous culture, all of the carbon derived from the oxidation of lactate was recovered as methane and carbon dioxide, provided the dilution rate was minimal. Increasing the dilution rate induced a gradual accumulation of acetate, causing acetate metabolism to cease at above μ = 0.05 h−1. Under these conditions all of the methane produced originated from carbon dioxide. The growth yields of D. vulgaris were measured when sulfate or M. barkeri was the electron acceptor. Two key observations resulted from the present study. First, although sulfate was substituted by M. barkeri, metabolism of D. vulgaris was only slightly modified. The coculture-fermented lactate produced equimolar quantities of carbon dioxide and methane. Second, acetogenesis and methane formation from acetate were completely separable. 相似文献
16.
Influence of Manganese on Growth of a Sheathless Strain of Leptothrix discophora 总被引:7,自引:3,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mn2+ exerted various effects on the growth of Leptothrix discophora strain SS-1 in batch cultures depending on the concentration added to the medium. Concentrations of 0.55 to 5.5 μM Mn2+, comparable to those in the environment from which strain SS-1 was isolated, decreased cell yield and prolonged stationary-phase survival, but did not affect growth rate. Elevated concentrations of 55 to 910 μM Mn2+ also decreased cell yield and prolonged survival, but growth rate was decreased as well. The addition of 1,820 μM Mn2+ caused a decline in cell numbers followed by an exponential rise after 80 h of incubation, indicating the development of a population of cells resistant to Mn2+ toxicity. When 360 μM Mn2+ or less was added to growth flasks, Mn2+ was oxidized to manganese oxide (MnOx, where x is ~2), which appeared as brown particles in the medium. Quantification of Mn oxidation during growth of cultures to which 55 μM Mn2+ was added showed that nearly all of the Mn2+ was oxidized by the beginning of the stationary phase of growth (15 to 25 h). This result suggested that the decrease in cell yield observed at low and moderate concentrations of Mn2+ was related to the formation of MnOx, which may have bound cationic nutrients essential to the growth of SS-1. The addition of excess Fe3+ to cultures containing 55 μM Mn2+ increased cell yield to levels near those found in cultures with no added Mn2+, indicating that iron deprivation by MnOx was at least partly responsible for the decreased cell yield. 相似文献
17.
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
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
18.
Kinetics of Butyrate, Acetate, and Hydrogen Metabolism in a Thermophilic, Anaerobic, Butyrate-Degrading Triculture 总被引:7,自引:4,他引:3
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kinetics of butyrate, acetate, and hydrogen metabolism were determined with butyrate-limited, chemostat-grown tricultures of a thermophilic butyrate-utilizing bacterium together with Methanobacterium thermoautotrophicum and the TAM organism, a thermophilic acetate-utilizing methanogenic rod. Kinetic parameters were determined from progress curves fitted to the integrated form of the Michaelis-Menten equation. The apparent half-saturation constants, Km, for butyrate, acetate, and dissolved hydrogen were 76 μM, 0.4 mM, and 8.5 μM, respectively. Butyrate and hydrogen were metabolized to a concentration of less than 1 μM, whereas acetate uptake usually ceased at a concentration of 25 to 75 μM, indicating a threshold level for acetate uptake. No significant differences in Km values for butyrate degradation were found between chemostat- and batch-grown tricultures, although the maximum growth rate was somewhat higher in the batch cultures in which the medium was supplemented with yeast extract. Acetate utilization was found to be the rate-limiting reaction for complete degradation of butyrate to methane and carbon dioxide in continuous culture. Increasing the dilution rate resulted in a gradual accumulation of acetate. The results explain the low concentrations of butyrate and hydrogen normally found during anaerobic digestion and the observation that acetate is the first volatile fatty acid to accumulate upon a decrease in retention time or increase in organic loading of a digestor. 相似文献
19.
Pyruvate — a novel substrate for growth and methane formation in Methanosarcina barkeri 总被引:1,自引:0,他引:1
Methanosarcina barkeri strain Fusaro was found to grow on pyruvate as sole carbon and energy source after an incubation period of 10–12 weeks in the presence of high pyruvate concentrations (100 mM). Growth studies, cell suspension experiments and enzymatic investigations were performed with pyruvate-utilizing M. barkeri. For comparison acetate-adapted cells of M. barkeri were analyzed.
- Pyruvate-utilizing M. barkeri grew on pyruvate (100 mM) with an initial doubling time of about 25 h (37 °C, pH 6.5) up to cell densities of about 0.8 g cell dry weight/l. The specific growth rate was linearily dependent on the pyruvate concentration up to 100 mM indicating that pyruvate was taken up by passive diffusion. Only CO2 and CH4 were detected as fermentation products. As calculated from fermentation balances pyruvate was converted to CH4 and CO2 according to following equation: Pyruvate-+H++0.5 H2O » 1.25 CH4+1.75 CO2. The molar growth yield (Ych 4) was about 14 g dry weight cells/mol CH4. In contrast the growth yield (Ych 4) of M. barkeri during growth on acctate (Acetate-+H+ » CH4+CO2) was about 3 g/mol CH4.
- Cell suspensions of pyruvate-grown M. barkeri catalyzed the conversion of pyruvate to CH4, CO2 and H2 (5–15 nmol pyruvate consumed/min x mg protein). At low cell concentrations (0.5 mg protein/ml) 1 mol pyruvate was converted to 1 mol CH4, 2 mol CO2 and 1 mol H2. At higher cell concentration less H2 and CO2 and more CH4 were formed due to CH4 formation from H2/CO2. The rate of pyruvate conversion was linearily dependent on the pyruvate concentration up to about 30 mM. Cell suspensions of acetate-grown M. barkeri also catalyzed the conversion of 1 mol pyruvate to 1 mol CH4, 2 mol CO2 and 1 mol H2 at similar rates and with similar affinity for pyruvate as pyruvate-grown cells.
- Cell extracts of both pyruvate-grown and acetate-grown M. barkeri contained pyruvate: ferredoxin oxidoreductase. The specific activity in pyruvate-grown cells (0.8 U/mg) was 8-fold higher than in acetate-grown cells (0.1 U/mg). Coenzyme F420 was excluded as primary electron acceptor of pyruvate oxidoreductase. Cell extracts of pyruvate-grown M. barkeri contained carbon monoxide dehydrogenase activity and hydrogenase activity catalyzing the reduction by carbon monoxide and hydrogen of both methylviologen and ferredoxin (from Clostridium).
20.
Effect of Tungstate on Nitrate Reduction by the Hyperthermophilic Archaeon Pyrobaculum aerophilum
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sepideh Afshar Christopher Kim Harold G. Monbouquette Imke Schrder 《Applied microbiology》1998,64(8):3004-3008
Pyrobaculum aerophilum, a hyperthermophilic archaeon, can respire either with low amounts of oxygen or anaerobically with nitrate as the electron acceptor. Under anaerobic growth conditions, nitrate is reduced via the denitrification pathway to molecular nitrogen. This study demonstrates that P. aerophilum requires the metal oxyanion WO42− for its anaerobic growth on yeast extract, peptone, and nitrate as carbon and energy sources. The addition of 1 μM MoO42− did not replace WO42− for the growth of P. aerophilum. However, cell growth was completely inhibited by the addition of 100 μM MoO42− to the culture medium. At lower tungstate concentrations (0.3 μM and less), nitrite was accumulated in the culture medium. The accumulation of nitrite was abolished at higher WO42− concentrations (<0.7 μM). High-temperature enzyme assays for the nitrate, nitrite, and nitric oxide reductases were performed. The majority of all three denitrification pathway enzyme activities was localized to the cytoplasmic membrane, suggesting their involvement in the energy metabolism of the cell. While nitrite and nitric oxide specific activities were relatively constant at different tungstate concentrations, the activity of nitrate reductase was decreased fourfold at WO42− levels of 0.7 μM or higher. The high specific activity of the nitrate reductase enzyme observed at low WO42− levels (0.3 μM or less) coincided with the accumulation of nitrite in the culture medium. This study documents the first example of the effect of tungstate on the denitrification process of an extremely thermophilic archaeon. We demonstrate here that nitrate reductase synthesis in P. aerophilum occurs in the presence of high concentrations of tungstate. 相似文献