共查询到20条相似文献,搜索用时 23 毫秒
1.
Roest K Altinbas M Paulo PL Heilig HG Akkermans AD Smidt H de Vos WM Stams AJ 《Microbial ecology》2005,50(3):440-446
To gain insight into the microorganisms involved in direct and indirect methane formation from methanol in a laboratory-scale
thermophilic (55°C) methanogenic bioreactor, reactor sludge was disrupted and serial dilutions were incubated in specific
growth media containing methanol and possible intermediates of methanol degradation as substrates. With methanol, growth was
observed up to a dilution of 108. However, when Methanothermobacter thermoautotrophicus strain Z245 was added for H2 removal, growth was observed up to a 1010-fold dilution. With H2/CO2 and acetate, growth was observed up to dilutions of 109 and 104, respectively. Dominant microorganisms in the different dilutions were identified by 16S rRNA-gene diversity and sequence
analysis. Furthermore, dilution polymerase chain reaction (PCR) revealed a similar relative abundance of Archaea and Bacteria
in all investigated samples, except in enrichment with acetate, which contained 100 times less archaeal DNA than bacterial
DNA. The most abundant bacteria in the culture with methanol and strain Z245 were most closely related to Moorella glycerini. Thermodesulfovibrio relatives were found with high sequence similarity in the H2/CO2 enrichment, but also in the original laboratory-scale bioreactor sludge. Methanothermobacter thermoautotrophicus strains were the most abundant hydrogenotrophic archaea in the H2/CO2 enrichment. The dominant methanol-utilizing methanogen, which was present in the 108-dilution, was most closely related to Methanomethylovorans hollandica. Compared to direct methanogenesis, results of this study indicate that syntrophic, interspecies hydrogen transfer-dependent
methanol conversion is equally important in the thermophilic bioreactor, confirming previous findings with labeled substrates
and specific inhibitors. 相似文献
2.
Previous studies suggested that methanol and acetate were the likely methanogenic precursors in the cold Zoige wetland. In
this study, the contribution of the two substances to methanogenesis and the conversion in Zoige wetland were analyzed. It
was determined that methanol supported the highest CH4 formation rate in the enrichments of the soil grown with Eleocharis valleculosa, and even higher at 15°C than at 30°C; while hydrogenotrophic methanogenesis was higher at 30°C. Both methanol- and acetate-using
methanogens were counted at the highest (107 g−1) in the soil, whereas methanol-using acetogens (108 g−1) were ten times more abundant than either methanol- or acetate-using methanogens. Both methanol and acetate were detected
in the methanogenesis-inhibited soil samples, so that both could be the primary methanogenic precursors in E. valleculosa soil. However, the levels of methanol and acetate accumulated in 2-bromoethane-sulfonate (BES)- and CHCl3-treated soils were in reverse, i.e., higher methanol in CHCl3- and higher acetate in BES-treated soil, so that methanol-derived methanogenesis could be underestimated due to the consumption
by acetogens. Analysis of the soil 16S rRNA genes revealed Acetobacterum bakii and Trichococcus pasteurii to be the dominant methanol-using acetogens in the soil, and a strain of T. pasteurii was isolated, which showed the high conversion of methanol to acetate at 15°C. 相似文献
3.
Anaerobic degradation of benzaldehyde in methanogenic granular sludge: the influence of additional substrates 总被引:1,自引:0,他引:1
Summary The degradation of benzaldehyde in methanogenic granular sludge was investigated in batch and in upflow anaerobic sludge blanket (UASB) reactors. The effect due to the presence of co-substrates, such as H2, sodium butyrate and sucrose, was studied using formaldehyde as a reference compound. The additional substrates enhanced the activity of benzaldehyde- and formaldehyde-degrading microorganisms (ACTbdm and ACTfdm, respectiveky) and increased the transient production of benzyl alcohol and methanol. As a consequence, the concentrations of benzaldehyde and formaldehyde that caused 50% inhibition of the methanogenic activity (50% ICm) on sucrose were 3133 and 254 mg chemical oxygen demand (COD)/l respectively, three times higher than the literature data values on acetate. Experiments performed in UASB reactors on benzaldehyde showed that the replacement of volatile fatty acids with sucrose as co-substrate improved the treatment capacity of the system from 0.73 to 4.36 kg COD benzaldehyde·m–13·day–1.
Correspondence to: O. Todini 相似文献
4.
青藏高原三个盐碱湖的产甲烷菌群和产甲烷代谢途径分析 总被引:1,自引:0,他引:1
【目的】分析青藏高原不同类型盐碱湖中的优势产甲烷菌群和优势产甲烷代谢途径。【方法】以不同盐度和植被类型的公珠错、昆仲错和无植被的兹格塘错的沉积物为研究对象,通过高通量测序和q PCR定量古菌16S r RNA多样性分析优势古菌类群;模拟原位盐浓度及p H,比较不同产甲烷底物(甲醇、三甲胺、乙酸和H_2/CO_2)富集沉积物的产甲烷速率,分析其优势产甲烷菌代谢类型。通过添加产甲烷抑制剂(2-溴乙烷磺酸盐),检测沉积物中产甲烷底物积累,确定不同盐碱湖中主要的产甲烷途径。【结果】昆仲错的优势菌群包括甲基/乙酸型的甲烷八叠球菌科(Methanosarcinaceae,11%),乙酸型的甲烷鬃菌科(Methanosaetaceae,7.9%)和氢型甲烷菌甲烷杆菌目(Methanomicrobiales,7.4%);公珠错和兹格塘错的优势菌群为甲烷鬃菌科(Methanosaetaceae)分别占15%和15.3%,及甲烷杆菌属(Methanobacterium)和甲基型的甲烷叶菌属(Methanolobus)。公珠错和昆仲错分别以乙酸和甲醇产甲烷速率最高,而兹格塘错从不同底物产甲烷速率无差异。抑制甲烷产生后,公珠错主要积累乙酸,昆仲错主要积累甲醇;兹格塘错不仅甲烷排放低,也无产甲烷物质显著积累。【结论】昆仲错沉积物中的甲烷主要来自甲醇,公珠错中的甲烷主要来自乙酸,而兹格塘错产甲烷和底物积累不活跃。因而推测高原盐碱湖主要的产甲烷途径和菌群可能与周围植被类型的相关性更高,而与盐度的直接相关性较低。 相似文献
5.
Desulfomonile tiedjei is the key dechlorinating organism in a three-tiered bacterial consortium that grows on the methanogenic degradation of 3-chlorobenzoate. 2,5-Dichlorobenzoate, however, is only converted to 2-chlorobenzoate and is not a methanogenic substrate for the consortium. The dechlorinator uses hydrogen produced from benzoate by the benzoate degrading member of consortium as its source of reducing equivalents for the dechlorination reaction. Incubation of 3-chlorobenzoate grown consortium cells with 2,5-dichlorobenzoate resulted in the consumption of acetate concurrent with the formation of 2-chlorobenzoate indicating that acetate can serve as an alternative source of reducing equivalents for reductive dechlorination. This interpretation was confirmed by the finding that the formation of 14CO2 from 2-14C-labeled acetate was stoichiometric. The addition of hydrogen to 2,5-dichlorobenzoate metabolizing cells resulted in (i) an 2.7-fold increase in the rate of dechlorination, and (ii) a drop in the amount of label recovered as CO2+CH4 from methyl
14C-labeled acetate, indicating that hydrogen was the preferred source of reducing equivalents for reductive dechlorination. Benzoate, an indirect source of H2 in the consortium, also inhibited the oxidation of acetate, while glucose, methanol, and butyrate did not affect labeled gas production and therefore were not suitable electron donors. Concomittant to dechlorination of 2,5-dichlorobenzoate 3- and 4-methoxybenzoate were converted to 3- and 4-hydroxybenzoate respectively. These conversions stimulated the rate of dechlorination 2-fold. Demethylation of 4-methoxybenzoate stimulated, but demethylation of 3-methoxybenzoate inhibited the oxidation of benzoate during the dechlorination of 2,5-dichlorobenzoate, suggesting that these isomers are metabolized through different pathways. Experiments with benzoate, 3-chlorobenzoate and 2,5-dichlorobenzoate metabolizing cells amended with 14CO2 showed that actively dechlorinating cells catalyzed an exchange reaction between CO2 and acetate. 相似文献
6.
Effect of Fall Turnover on Terminal Carbon Metabolism in Lake Mendota Sediments 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 carbon and electron flow pathways and the bacterial populations responsible for the transformation of H2-CO2, formate, methanol, methylamine, acetate, ethanol, and lactate were examined in eutrophic sediments collected during summer stratification and fall turnover. The rate of methane formation averaged 1,130 μmol of CH4 per liter of sediment per day during late-summer stratification versus 433 μmol of CH4 per liter of sediment per day during the early portion of fall turnover, whereas the rate of sulfate reduction was 280 μmol of sulfate per liter of sediment per day versus 1,840 μmol of sulfate per liter of sediment per day during the same time periods, respectively. The sulfate-reducing population remained constant while the methanogenic population decreased by one to two orders of magnitude during turnover. The acetate concentration increased from 32 to 81 μmol per liter of sediment while the acetate transformation rate constant decreased from 3.22 to 0.70 per h, respectively, during stratification versus turnover. Acetate accounted for nearly 100% of total sedimentary methanogenesis during turnover versus 70% during stratification. The fraction of 14CO2 produced from all 14C-labeled substrates examined was 10 to 40% higher during fall turnover than during stratification. The addition of sulfate, thiosulfate, or sulfur to stratified sediments mimicked fall turnover in that more CO2 and CH4 were produced. The addition of Desulfovibrio vulgaris to sulfate-amended sediments greatly enhanced the amount of CO2 produced from either [14C]methanol or [2-14C]acetate, suggesting that H2 consumption by sulfate reducers can alter methanol or acetate transformation by sedimentary methanogens. These data imply that turnover dynamically altered carbon transformation in eutrophic sediments such that sulfate reduction dominated over methanogenesis principally as a consequence of altering hydrogen metabolism. 相似文献
7.
Vitamin E is localized in membranes and functions as an efficient inhibitor of lipid peroxidation in biological systems. In this study, we measured the reaction rates of vitamin E (α-, β-, γ-, δ-tocopherols, TocH) and tocol with aroxyl radical (ArO) as model lipid peroxyl radicals in membranes by stopped-flow spectrophotometry. Egg yolk phosphatidylcholine (EYPC) vesicles were used as a membrane model. EYPC vesicles were prepared in the aqueous methanol solution (MeOH:H2O = 7:3, v/v) that gave the lowest turbidity in samples. The second-order rate constants (ks) for α-TocH in MeOH/H2O solution with EYPC vesicles were apparently 3.45 × 105 M−1 s−1, which was about 8 times higher than that (4.50 × 104 M−1 s−1) in MeOH/H2O solution without EYPC vesicles. The corrected ks of α-TocH in vesicles, which was calculated assuming that the concentration of α-TocH was 133 times higher in membranes of 10 mM EYPC vesicles than in the bulk MeOH/H2O solution, was 2.60 × 103 M−1 s−1, which was one-seventeenth that in MeOH/H2O solution because of the lower mobility of α-TocH in membranes. Similar analyses were performed for other vitamin E analogues. The ks of vitamin E in membranes increased in the order of tocol < δ-TocH < γ-TocH ∼ β-TocH < α-TocH. There was not much difference in the ratios of reaction rates in vesicles and MeOH/H2O solution among vitamin E analogues [ks(vesicle)/ks (MeOH/H2O) = 7.7, 10.0, 9.5, 7.4, and 5.1 for α-, β-, γ-, δ-TocH, and tocol, respectively], but their reported ratios in solutions of micelles and ethanol were quite different [ks(micelle)/ks(EtOH) = 100, 47, 41, 15, and 6.3 for α-, β-, γ-, δ-TocH, and tocol, respectively]. These results indicate that the reaction sites of vitamin E analogues were similar in vesicle membranes but depended on hydrophobicity in micelle membranes, which increased in the order of tocol < δ-TocH < γ-TocH ∼ β-TocH < α-TocH. 相似文献
8.
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
9.
The effect of temperature on granulation and microbial interaction of anaerobic sludges grown in thermophilic upflow anaerobic sludge bed (UASB) reactors was investigated at two different temperatures, 55°C (Run 1) and 65°C (Run 2). Each run consisted of two phases. Phase 1 was conducted by feeding acetate for a period of 200 days. In Phase 2, both reactors were fed a mixture of acetate and sucrose for a further 100 days. During Phase 1, no granulation occurred in the sludge of either run. Microscopic observation revealed that the predominant methanogen was Methanothrix in Run 1, whereas Methanobacterium-like bacteria existed to a significant extent in Run 2. The acetate-utilizing methanogenic activity of both sludges increased with increasing test temperature in the range 55–65°C. Since the acetate-grown sludges exhibited far higher H2-utilizing methanogenic activity than acetate-utilizing methanogenic activity, it is suggested that a syntrophic association of acetate-oxidizing bacteria with hydrogenotrophic methanogens was responsible for a considerable portion of the overall acetate elimination in thermophilic anaerobic sludge. During Phase 2, granules coated with either filamentous bacteria or cocci-type bacteria (both presumably acid-forming bacteria) were successfully established in Run 1 and Run 2, respectively. Since the acetate-utilizing methanogenic activities of the granular sludges were four to five times higher than those of the acetate-grown sludges (Phase 1), the co-existence of these coating bacteria appeared to contribute to the enclosing of acetate consumers inside granules.
Correspondence to: S. Uemura 相似文献
10.
In the presence of active hydrogenophilic sulfate-reducing bacteria, the homoacetogenic bacterium Sporomusa acidovorans did not produce acetate during methanol degradation. H2S and presumably CO2 were the only end products. Since the sulfate-reducer did not degrade methnol or acetate, the sulfidogenesis from methanol was related to a complete interspecific hydrogen transfer between both species.In coculture with hydrogenophilic methanogenic bacteria (Methanobacterium formicicum, Methanospirillum hungatei), the interspecific hydrogen transfer with S. acidovorans was incomplete. Beside CH4 and presumably CO2, acetate was produced. The results suggested that H2-production and H2-consumption were involved during anaerobic methanol degradation by S. acidovorans and the hydrogenophilic anaerobes play an important role during methanol degradation by homoacetogenic bacteria in anoxic environments. 相似文献
11.
Competition between Fe(III)-Reducing and Methanogenic Bacteria for Acetate in Iron-Rich Freshwater Sediments 总被引:3,自引:0,他引:3
The kinetics of acetate uptake and the depth distribution of [2-14C]acetate metabolism were examined in iron-rich sediments from a beaver impoundment in northcentral Alabama. The half-saturation constant (Km) determined for acetate uptake in slurries of Fe(III)-reducing sediment (0.8 µM) was more than 10-fold lower than that measured in methanogenic slurries (12 µM) which supported comparable rates of bulk organic carbon metabolism and Vmax values for acetate uptake. The endogenous acetate concentration (S n) was also substantially lower (1.7 µM) in Fe(III)-reducing vs methanogenic (9.0 µM) slurries. The proportion of [2-14C]acetate converted to 14CH4 increased with depth from ca 0.1 in the upper 0.5 cm to ca 0.8 below 2 cm and was inversely correlated (r2 = 0.99) to a decline in amorphous Fe(III) oxide concentration. The results of the acetate uptake kinetics experiments suggest that differences in the affinity of Fe(III)-reducing bacteria vs methanogens for acetate can account for the preferential conversion of [2-14C]acetate to 14CO2 in Fe(III) oxide-rich surface sediments, and that the downcore increase in conversion of [2-14C]acetate to 14CH4 can be attributed to progressive liberation of methanogens from competition with Fe(III) reducers as Fe(III) oxides are depleted with depth. 相似文献
12.
Helmut Mucha Franz Lingens Walter Trösch 《Applied microbiology and biotechnology》1988,27(5-6):581-586
Summary The anaerobic degradation of propionate to acetate and methane by a defined sulfidogenic syntrophic co-culture consisting of Syntrophobacter wolinii and Desulfovibrio G11, and a new thermophilic, methanogenic consortium T13 was studied. Tracer experiments using (14C) propionate produced evidence for the generally accepted biochemical pathway involving methylmalonyl-CoA as an intermediate in the degradation of propionate. The degradation of (1-14C) propionate led exclusively to the formation of 14CO2 by S. wolinii/D. G11 and to the formation of 14CH4 by the methanogenic consortium T13. The conversion of either (2-14) or (3-14) propionate by S. wolinii/D. G11 resulted in uniform labelled acetate as the endproduct. The methanogenic consortium formed (U-14C) acetate from (2-14) and (3-14) propionate as an intermediary product followed by aceticlastic splitting to yield equivalent amounts of 14CO2 and 14CH4. 相似文献
13.
The community structure of methanogenic Archaea on anoxically incubated rice roots was investigated by amplification, sequencing, and phylogenetic analysis of 16S rRNA and methyl-coenzyme M reductase (mcrA) genes. Both genes demonstrated the presence of Methanomicrobiaceae, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Rice cluster I, an uncultured methanogenic lineage. The pathway of CH4 formation was determined from the 13C-isotopic signatures of the produced CH4, CO2 and acetate. Conditions and duration of incubation clearly affected the methanogenic community structure and the pathway of CH4 formation. Methane was initially produced from reduction of CO2 exclusively, resulting in accumulation of millimolar concentrations of acetate. Simultaneously, the relative abundance of the acetoclastic methanogens (Methanosarcinaceae, Methanosaetaceae), as determined by T-RFLP analysis of 16S rRNA genes, was low during the initial phase of CH4 production. Later on, however, acetate was converted to CH4 so that about 40% of the produced CH4 originated from acetate. Most striking was the observed relative increase of a population of Methanosarcina spp. (but not of Methanosaeta spp.) briefly before acetate concentrations started to decrease. Both acetoclastic methanogenesis and Methanosarcina populations were suppressed by high phosphate concentrations, as observed under application of different buffer systems. Our results demonstrate the parallel change of microbial community structure and function in a complex environment, i.e., the increase of acetoclastic Methanosarcina spp. when high acetate concentrations become available. 相似文献
14.
The activities of formylmethanofuran dehydrogenase, methylenetetrahydromethanopterin dehydrogenase, methylenetetrahydromethanopterin
reductase, and heterodisulfide reductase were tested in cell extracts of 10 different methanogenic bacteria grown on H2/CO2 or on other methanogenic substrates. The four activities were found in all the organisms investigated: Methanobacterium thermoautotrophicum,M. wolfei, Methanobrevibacter arboriphilus, Methanosphaera stadtmanae, Methanosarcina
barkeri (strains Fusaro and MS), Methanothrix soehngenii, Methanospirillum hungatei, Methanogenium organophilum, and Methanococcus voltae. Cell extracts of H2/CO2 grown M. barkeri and of methanol grown M. barkeri showed the same specific activities suggesting that the four enzymes are of equal importance in CO2 reduction to methane and in methanol disproportionation to CO2 and CH4. In contrast, cell extracts of acetate grown M. barkeri exhibited much lower activities of formylmethanofuran dehydrogenase and methylenetetrahydromethanopterin dehydrogenase suggesting
that these two enzymes are not involved in methanogenesis from acetate. In M. stadtmanae, which grows on H2 and methanol, only heterodisulfide reductase was detected in activities sufficient to account for the in vivo methane formation rate. This finding is consistent with the view that the three other oxidoreductases are not required for
methanol reduction to methane with H2. 相似文献
15.
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
16.
A new genus of methanogenic bacteria is described, which was isolated from a mesophilic sewage digester. It is most probably the filamentous bacterium, earlier referred to asMethanobacterium soehngenii, fat rod or acetate organism. The single non-motile, non-sporeforming cells are rod-shaped (0.8×2 m) and are normally combined end to end in long filaments, surrounded by a sheath-like structure. The filaments form characteristic bundles.Methanothrix soehngenii decarboxylates acetate, yielding methane and carbon dioxide. Other methanogenic substrates (H2–CO2, formate, methanol, methylamines) are not used for growth or methane formation. Formate is split into hydrogen and carbon dioxide. The temperature optimum for growth and methane formation is 37°C and the optimal pH range is 7.4–7.8. Sulfide and ammonia serve as sulfur and nitrogen source respectively. Oxygen completely inhibits growth and methane formation, but the bacteria do not loose their viability when exposed to high oxygen concentrations. 100 mg/l vancomycin showed no inhibition of growth and methanogenesis. No growth and methane formation was observed in the presence of: 2-bromoethanesulfonic acid, viologen dyes, chloroform, and KCN. The bacterium has a growth yield on acetate of 1.1–1.4 g biomass per mol acetate. The apparent K
S
of the acetate conversion system to methane and carbon dioxide is 0.7 mmol/l. The DNA base composition is 51.9 mol% guanine plus cytosine. The nameMethanothrix is proposed for this new genus of filamentous methane bacterium. The type species,Methanothrix soehngenii sp. nov., is named in honor of N. L. Söhngen. 相似文献
17.
Effect of Temperature on Carbon and Electron Flow and on the Archaeal Community in Methanogenic Rice Field Soil 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)
Temperature is an important factor controlling CH4 production in anoxic rice soils. Soil slurries, prepared from Italian rice field soil, were incubated anaerobically in the dark at six temperatures of between 10 to 37°C or in a temperature gradient block covering the same temperature range at intervals of 1°C. Methane production reached quasi-steady state after 60 to 90 days. Steady-state CH4 production rates increased with temperature, with an apparent activation energy of 61 kJ mol−1. Steady-state partial pressures of the methanogenic precursor H2 also increased with increasing temperature from <0.5 to 3.5 Pa, so that the Gibbs free energy change of H2 plus CO2-dependent methanogenesis was kept at −20 to −25 kJ mol of CH4−1 over the whole temperature range. Steady-state concentrations of the methanogenic precursor acetate, on the other hand, increased with decreasing temperature from <5 to 50 μM. Simultaneously, the relative contribution of H2 as methanogenic precursor decreased, as determined by the conversion of radioactive bicarbonate to 14CH4, so that the carbon and electron flow to CH4 was increasingly dominated by acetate, indicating that psychrotolerant homoacetogenesis was important. The relative composition of the archaeal community was determined by terminal restriction fragment length polymorphism (T-RFLP) analysis of the 16S rRNA genes (16S rDNA). T-RFLP analysis differentiated the archaeal Methanobacteriaceae, Methanomicrobiaceae, Methanosaetaceae, Methanosarcinaceae, and Rice clusters I, III, IV, V, and VI, which were all present in the rice field soil incubated at different temperatures. The 16S rRNA genes of Rice cluster I and Methanosaetaceae were the most frequent methanogenic groups. The relative abundance of Rice cluster I decreased with temperature. The substrates used by this microbial cluster, and thus its function in the microbial community, are unknown. The relative abundance of acetoclastic methanogens, on the other hand, was consistent with their physiology and the acetate concentrations observed at the different temperatures, i.e., the high-acetate-requiring Methanosarcinaceae decreased and the more modest Methanosaetaceae increased with increasing temperature. Our results demonstrate that temperature not only affected the activity but also changed the structure and the function (carbon and electron flow) of a complex methanogenic system. 相似文献
18.
Jiang B Henstra AM Paulo PL Balk M van Doesburg W Stams AJ 《Archives of microbiology》2009,191(2):123-131
A thermophilic spore-forming bacterium (strain AMP) was isolated from a thermophilic methanogenic bioreactor that was fed
with cobalt-deprived synthetic medium containing methanol as substrate. 16S rRNA gene analysis revealed that strain AMP was
closely related to the acetogenic bacterium Moorella thermoacetica DSM 521T (98.3% sequence similarity). DNA–DNA hybridization showed 75.2 ± 4.7% similarity to M. thermoacetica DSM 521T, suggesting that strain AMP is a M. thermoacetica strain. Strain AMP has a unique one-carbon metabolism compared to other Moorella species. In media without cobalt growth of strain AMP on methanol was only sustained in coculture with a hydrogen-consuming
methanogen, while in media with cobalt it grew acetogenically in the absence of the methanogen. Addition of thiosulfate led
to sulfide formation and less acetate formation. Growth of strain AMP with CO resulted in the formation of hydrogen as the
main product, while other CO-utilizing Moorella strains produce acetate as product. Formate supported growth only in the presence of thiosulfate or in coculture with the
methanogen. Strain AMP did not grow with H2/CO2, unlike M. thermoacetica (DSM 521T). The lack of growth with H2/CO2 likely is due to the absence of cytochrome b in strain AMP. 相似文献
19.
Miguel Angel Marín Muñoz Leobardo Serrano Carreón Norma Angélica Chávez Vela 《Preparative biochemistry & biotechnology》2013,43(6):606-615
AbstractMost of the reported bioprocesses carried out by the methylotrophic yeast Pichia pastoris have been performed at laboratory scale using high power inputs and pure oxygen, such conditions are not feasible for industrial large-scale processes. In this study, volumetric mass transfer (kLa) and volumetric gassed power input (Pg/V) were evaluated within values attainable in large-scale production as scale-up criteria for recombinant dextranase production by MutS P. pastoris strain. Cultures were oxygen limited when the volumetric gassed power supply was limited to 2?kW m?3. Specific growth rate, and then dextranase production, increased as kLa and Pg/V did. Meanwhile, specific production and methanol consumption rates were constant, due to the limited methanol condition also achieved at 2?L bioprocesses. The specific dextranase production rate was two times higher than the values previously reported for a Mut+ strain. After a scale-up process, at constant kLa, the specific growth rate was kept at 30?L bioprocess, whereas dextranase production decreased, due to the effect of methanol accumulation. Results obtained at 30?L bioprocesses suggest that even under oxygen-limited conditions, methanol saturated conditions are not adequate to express dextranase with the promoter alcohol oxidase. Bioprocesses developed within feasible and scalable operational conditions are of high interest for the commercial production of recombinant proteins from Pichia pastoris. 相似文献
20.
An anaerobic, motile, gram-negative, rod-shaped bacterium is described which degrades benzoate in coculture with an H2-utilizing organism and in the absence of exogenous electron acceptors such as O2, SO
4
=
or NO
3
-
. The bacterium was isolated from a municipal primary, anaerobic sewage digestor using anaerobic roll-tube medium with benzoate as the main energy source and in syntrophic association with an H2-utilizing sulfate-reducing Desulfovibrio sp. which cannot utilize benzoate or fatty acids apart from formate as energy source. The benzoate utilizer produced acetate (3 mol/mol of substrate degraded) and presumably CO2 and H2, or formate from benzoate. In media without sulfate and with Methanospirillum hungatei (a methanogen that utilizes only H2–CO2 or formate as the energy source) added, 3 mol of acetate and 0.7 mol of methane were produced per mol of benzoate and CO2 was probably formed. Low numbers of Desulfovibrio sp. were present in the methanogenic coculture and a pure coculture of the benzoate utilizer with M. hungatei was not obtained. The generation times for growth of the sulfate-reducing and methanogenic cocultures were 132 and 166h, respectively. The benzoate utilizer did not utilize other common aromatic compounds, C
3
-
–C7 monocarboxylic acids, or C4-C6 dicarboxylic acids for growth, nor did it appear to use SO
4
=
, NO
3
-
or fumarate as alternative electron acceptors. Addition of H2 inhibited growth and benzoate degradation. 相似文献