The anaerobic biodegradation of diethanolamine by a nitrate reducing bacterium

The ability of bacterial cultures to degrade diethanolamine under anoxic conditions with nitrate as an electron acceptor was investigated. A mixed culture capable of anaerobic degradation of diethanolamine was obtained from river sediments by enrichment culture. From this a single bacterial strain was isolated which could use diethanolamine, monoethanolamine, triethanolamine and N-methyl diethanolamine as its sole carbon and energy sources either aerobically or anaerobically. Growth on diethanolamine was faster in the absence of oxygen. The accumulation of possible metabolites in the culture medium was determined as was the ability to grow on certain putative intermediates in the degradation of diethanolamine. A possible pathway for the degradation of ethanolamines by this organism is suggested.     

The anaerobic degradation of aromatic compounds by a denitrifying bacterium

Summary Six strains of Rhizobium, present as bacteroids, in Lotus nodules were studied by electron microscopy. Three inclusion bodies frequently detected are described and their distribution among the strains is given. Cytochemical techniques indicated that they have, as principal components, polyphosphate, lipid and neutral polysaccharide, probably glycogen, respectively.     

Degradation of methanol by a sulfate reducing bacterium

A sulfate reducing bacterium isolated from sewage sludge was capable of degrading methanol after growth on pyruvate, malate, or fumarate. ¹⁴C-Methanol was completely oxidized to carbon dioxide but not incorporated into the cellular material. The organism is a member of the genus Desulfovibrio.     

Enhanced anaerobic biodegradation of nonylphenol ethoxylates by introducing additional sulfate or nitrate as terminal electron acceptors

The potential to enhance the anaerobic biodegradation of nonylphenol ethoxylates (NPEOs) by introducing additional sulfate or nitrate as electron acceptor was investigated. The results showed that adding nitrate or sulfate could significantly enhance the anaerobic biodegradation of NPEOs and alleviate the accumulation of their estrogenic intermediates. However, these terminal electron acceptors had no influence on the component of the anaerobic biodegradation products of NPEOs. To the best of our knowledge, it is the first report of the enhancement of anaerobic biodegradation of NPEOs by introducing additional terminal electron acceptor with relatively high redox potential. These observations have significant environmental implications in terms of the environmental behavior of NPEO contaminants in natural environment.     

Aerobic biodegradation of 4-methylquinoline by a soil bacterium.

Methylquinolines and related N-heterocyclic aromatic compounds are common contaminants associated with the use of hydrocarbons in both coal gasification and wood treatment processes. These compounds have been found in groundwater, and many are known mutagens. A stable, five-member bacterial consortium able to degrade 4-methylquinoline was established by selective enrichment using soil collected from an abandoned coal gasification site. The consortium was maintained for 5 years by serial transfer in a medium containing 4-methylquinoline. A gram-negative soil bacterium, strain Lep1, was isolated from the consortium and shown to utilize 4-methylquinoline as a source of carbon and energy during growth in liquid medium. A time course experiment demonstrated that both the isolate Lep1 and the consortium containing Lep1 were able to degrade 4-methylquinoline under aerobic conditions. Complete degradation of 4-methylquinoline by either strain Lep1 alone or the consortium was characterized by the production and eventual disappearance of 2-hydroxy-4-methylquinoline, followed by the appearance and persistence of a second metabolite tentatively identified as a hydroxy-4-methylcoumarin. Currently, there is no indication that 4-methylquinoline degradation proceeds differently in the consortium culture compared with Lep1 alone. This is the first report of 4-methylquinoline biodegradation under aerobic conditions.     

Mechanism of anaerobic degradation of triethanolamine by a homoacetogenic bacterium

Triethanolamine (TEA) is converted into acetate and ammonia by a strictly anaerobic, gram-positive Acetobacterium strain LuTria3. Fermentation experiments with resting cell suspensions and specifically deuterated substrates indicate that in the acetate molecule the carboxylate and the methyl groups correspond to the alcoholic function and to its adjacent methylene group, respectively, of the 2-hydroxyethyl unit of TEA. A 1,2 shift of a hydrogen (deuterium) atom from -CH2-O- to =N-CH2- without exchange with the medium was observed. This fact gives evidence that a radical mechanism occurs involving the enzyme and/or coenzyme molecule as a hydrogen carrier. Such a biodegradation appears analogous to the conversion of 2-phenoxyethanol into acetate mediated by another strain of the anaerobic homoacetogenic bacterium Acetobacterium.     

Fermentative degradation of glyoxylate by a new strictly anaerobic bacterium

A new strictly anaerobic, gram-negative, nonsporeforming bacterium, Strain PerGlx1, was enriched and isolated from marine sediment samples with glyoxylate as sole carbon and energy source. The guanineplus-cytosine content of the DNA was 44.1±0.2 mol %. Glyoxylate was utilized as the only substrate and was stoichiometrically degraded to carbon dioxide, hydrogen, and glycolate. An acetyl-CoA and ADP-dependent glyoxylate converting enzyme activity, malic enzyme, and pyruvate synthase were found at activities sufficient for growth (0.25 U x mg protein^-1). These findings allow to design a new degradation pathway for glyoxylate: glyoxylate is condensed with acetyl-CoA to form malyl-CoA; the free energy of the thioester linkage in malyl-CoA is conserved by substrate level phosphorylation. Part of the electrons released during glyoxylate oxidation to CO₂ reduce a small fraction of glyoxylate to glycolate.     

Enhanced biodegradation of phenanthrene by a marine bacterium in presence of a synthetic surfactant

The biodegradation of phenanthrene by the marine strain Sphingomonas sp. 2MPII (DSMZ 11572) was enhanced by the solubilizating properties of the nonionic surfactant Tween 80. After 197 h of incubation, 85 +/- 4% of the initial amount of phenanthrene (0.4 g l-1) was biodegraded in presence of Tween 80 (0.5 g l-1) as opposed to 52 +/- 5% without this synthetic surfactant. These results confirm that the activity of the strain 2MPII is limited by the bioavailability of the polycyclic aromatic hydrocarbon (PAH) substrate in the aqueous phase. Tween 80 appears to be efficient in increasing the bioavailability of hydrophobic compounds such as PAHs.     

Enzymes involved in anaerobic degradation of acetone by a denitrifying bacterium

The pathway of anaerobic acetone degradation by the denitrifying bacterial strain BunN was studied by enzyme measurements in extracts of anaerobic acetone-grown cells. An ADP- and MgCl₂-dependent decarboxylation of acetoacetate was detected which could not be found in cell-free extracts of acetate-grown cells. It is concluded that free acetoacetate is formed by ATP-dependent carboxylation of acetone. Acetoacetate was converted into its coenzyme A ester by succinyl-CoA: acetoacetate CoA transferase, and cleaved by a thiolase into acetyl-CoA. The acetyl residue was completely oxidized in the citric acid cycle. The ADP-dependent decarboxylation of acetoacetate was inhibited by EDTA, but not by avidin. High myokinase activities led to equilibrium amounts of ATP, ADP, and AMP in the reaction mixtures, and prevented determination of the decarboxylase reaction stoichiometry, therefore.Abbreviations ADP adenosine diphosphate - AMP adenosine monophosphate - ATP adenosine triphosphate - BSA bovine serum albumine - MOPS 3-(N-morpholino)propanesulfonic acid - PIPES piperazine-N,N-bis-(2-ethanesulfonic acid) - PHB poly--hydroxybutyrate - Tris Tris-(hydroxymethyl-) aminomethane     

Kinetics of anaerobic biodegradation of glycerol by sulfate-reducing bacteria

A kinetic model has been developed and kinetic parameters of anaerobic degradation of glycerol, an abundant by-product of biofuel manufacturing, by a consortium of sulfate reducing bacteria (SRB) in a closed system have been determined. The following main species of SRB has been identified in the consortium: Desulfovibrio baarsii, Desulfomicrobium sp., and Desufatomaculum sp. The proposed model included processes of glycerol degradation, sulfate reduction, and inhibition by metabolic products, as well as effects of pH and temperature. The suggested equation for the anaerobic glycerol degradation was based on Edward and Andrew’s equation. The following kinetic parameters of the anaerobic glycerol degradation were obtained for the initial glycerol concentration from 0.15 to 4 ml/l and sulfate concentration of 2760 mg/l at 22°C: maximum specific growth rate of SRB μ_max = 0.56 day⁻¹, economic coefficient of ashless biomass from glycerol of 0.08 mol SRB/mol COC, and yield of ashless biomass from sulfate of 0.020 mol SRB/mol SO₄. It was shown that the optimum molar ratio of $ {{C_{Gl} } \mathord{\left/ {\vphantom {{C_{Gl} } {C_{SO_4 } }}} \right. \kern-\nulldelimiterspace} {C_{SO_4 } }} $ {{C_{Gl} } \mathord{\left/ {\vphantom {{C_{Gl} } {C_{SO_4 } }}} \right. \kern-\nulldelimiterspace} {C_{SO_4 } }} for SRB growth was 0.8. Initial boundary concentration of inhibition by undissociated hydrogen sulfide was 70 mg/l. Dependence of the specific growth rate of bacteria on the temperature was approximated by the Arrhenius equation in the temperature range of 20–30°C with the goodness of fit R² = 0.99.     

Aerobic and anaerobic catabolism of phthalic acid by a nitrate-respiring bacterium

A Bacillus sp., isolated by anaerobic enrichment on a o-phthalic acid-nitrate medium, grew either aerobically or anaerobically on phthalic acid. Cells grown anaerobically on phthalate immediately oxidized phthalate and benzoate with nitrate, whereas aerobic oxidation only occurred after a lag period and was inhibited by chloramphenicol. 2-Fluoro-and 3-fluorobenzoate were formed from 3-fluorophthalate by cells grown anaerobically on phthalate. Aerobically grown cells immediately oxidized phthalate, benzoate, 3-hydroxybenzoate and gentisate with oxygen. The aerobic and anaerobic route of catabolism of phthalate may thus share an initial decarboxylation to benzoate. This is the first report of the anaerobic dissimilation of phthalic acid by a pure bacterial culture.     

N-alkane biodegradation by a marine bacterium in the presence of an oleophilic nutriment

Summary Hexadecane biodegradation by a marine bacterium has been investigated in the presence of an oleophilic nutriment (INIPOL EAP 22). Hydrocarbon attack was only observed after metabolism of the fatty acids present in the fertilizer. The bacterium used up 95 % fatty acids in the first 24 hours. Hexadecane biodegradation took place after 50 h incubation and reached 40 % after 360 h.     

一株油藏嗜热厌氧杆菌的分离鉴定和代谢特征的分析

摘要：【目的】从高温油藏中发掘新的微生物种质资源。【方法】采用 Hungate 厌氧操作技术从大港油田采出水中分离到一株厌氧杆菌 HL-3。通过生理生化特征比较和16S rRNA序列比对,确定HL-3的分类地位。【结果】菌株HL-3为严格厌氧的革兰氏阴性杆菌。生长温度范围 40℃－75℃（最适温度 60℃）;pH 范围 5.0－8.0（最适 pH 6.5）;NaCl 浓度范围 0%－3.2%（最适NaCl浓度0.25%）。能够利用葡萄糖、核糖、甘露糖、木糖、纤维二糖等多种碳水化合物,发酵葡萄糖的产物是乙醇、乙酸、CO2及少量丙酸和丁醇。菌株HL-3的（G+C）mol%含量为 33.9%,与Thermoanaerobacter（嗜热厌氧杆菌属）中模式菌株T.uzonensis DSM18761T (EF530067)的16SrRNA 序列相似性为98.8%,与T.sulfurigignens DSM17917T (AF234164)的相似度次之为98.1％。菌株能够耐受浓度较高的亚硫酸根（0.1 mol/L）离子和浓度极高的硫代硫酸根（0.8 mol/L）。当硫代硫酸根浓度高于0.075 mol/L时,菌体内产生硫单质颗粒;同时,在培养血清瓶顶空中检测到硫化氢气体。菌株 HL-3与T.uzonensis DSM18761T对硫代硫酸根和亚硫酸根的耐受程度有很大不同。菌株HL-3对硫代硫酸根和亚硫酸根耐受程度及对硫代硫酸根的代谢机制与T.sulfurigignens DSM17917T(AF234164)极为相似,但二者代谢葡萄糖的产物却极不相同。【结论】所以菌株HL-3可能是Thermoanaerobacter属中的一个新种,其确切分类地位还有待用DNA分子杂交[1]的技术手段做进一步的鉴定。     

Monitoring of two-stage anaerobic biodegradation using a BOD biosensor

A previously developed biosensor for fast estimation of short-term biochemical oxygen demand (BOD_st) was used for off-line monitoring of intermediate products from the initial step of an anaerobic process in laboratory scale. Good agreement was generally achieved between the results from the biosensor method and the conventional 5-day test except for samples with high content of organic polymers. During the period of agreement between the measurement principles, good correlation was achieved between the biogas production rate and the organic loading rate. The results from this study demonstrate that BOD_st can be a successful monitoring parameter to achieve a better process control.     

Thermophilic biodegradation of BTEX by two consortia of anaerobic bacteria

Two thermophilic anaerobic bacterial consortia (ALK-1 and LLNL-1), capable of degrading the aromatic fuel hydrocarbons, benzene, toluene, ethylbenzene, and the xylenes (BTEX compounds), were developed at 60 °C from the produced water of ARCO'S Kuparuk oil field at Alaska and the subsurface water at the Lawrence Livermore National Laboratory gasoline-spill site, respectively. Both consortia were found to grow at 45–75 °C on BTEX compounds as their sole carbon and energy sources with 50 °C being the optimal temperature. With 3.5 mg total BTEX added to sealed 50-ml serum bottles, which contained 30 ml mineral salts medium and the consortium, benzene, toluene, ethylbenze, m-xylene, and an unresolved mixture of o- and p-xylenes were biodegraded by 22%, 38%, 42%, 40%, and 38%, respectively, by ALK-1 after 14 days of incubation at 50 °C. Somewhat lower, but significant, percentages of the BTEX compounds also were biodegraded at 60 °C and 70 °C. The extent of biodegradation of these BTEX compounds by LLNL-1 at each of these three temperatures was slightly less than that achieved by ALK-1. Use of [ring-¹⁴C]toluene in the BTEX mixture incubated at 50 °C verified that 41% and 31% of the biodegraded toluene was metabolized within 14 days to water-soluble products by ALK-1 and LLNL-1, respectively. A small fraction of it was mineralized to ¹⁴CO₂. The use of [U-¹⁴C]benzene revealed that 2.6%–4.3% of the biodegraded benzene was metabolized at 50 °C to water-soluble products by the two consortia; however, no mineralization of the degraded [U-¹⁴C]benzene to ¹⁴CO₂ was observed. The biodegradation of BTEX at all three temperatures by both consortia was tightly coupled to sulfate reduction as well as H₂S generation. None was observed when sulfate was omitted from the serum bottles. This suggests that sulfate-reducing bacteria are most likely responsible for the observed thermophilic biodegradation of BTEX in both consortial cultures. Received: 12 July 1996 / Received revision: 31 December 1996 / Accepted: 31 January 1997     

Changes in iso- and n-alkane distribution during biodegradation of crude oil under nitrate and sulphate reducing conditions

Crude oil consists of a large number of hydrocarbons with different susceptibility to microbial degradation. The influence of hydrocarbon structure and molecular weight on hydrocarbon biodegradation under anaerobic conditions is not fully explored. In this study oxygen, nitrate and sulphate served as terminal electron acceptors (TEAs) for the microbial degradation of a paraffin-rich crude oil in a freshly contaminated soil. During 185 days of incubation, alkanes from n-C11 to n-C39, three n- to iso-alkane ratios commonly used as weathering indicators and the unresolved complex mixture (UCM) were quantified and statistically analyzed. The use of different TEAs for hydrocarbon degradation resulted in dissimilar degradative patterns for n- and iso-alkanes. While n-alkane biodegradation followed well-established patterns under aerobic conditions, lower molecular weight alkanes were found to be more recalcitrant than mid- to high-molecular weight alkanes under nitrate-reducing conditions. Biodegradation with sulphate as the TEA was most pronounced for long-chain (n-C32 to n-C39) alkanes. The observation of increasing ratios of n-C17 to pristane and of n-C18 to phytane provides first evidence of the preferential degradation of branched over normal alkanes under sulphate reducing conditions. The formation of distinctly different n- and iso-alkane biodegradation fingerprints under different electron accepting conditions may be used to assess the occurrence of specific degradation processes at a contaminated site. The use of n- to iso-alkane ratios for this purpose may require adjustment if applied for anaerobic sites.     

Production of nitrate spikes in a model of ammonium biodegradation

Nitrification at the site of a contaminant ammonium plume from a former coal carbonisation plant can be modelled with three competing bacterial populations of Nitrosomonas, Nitrobacter, and Brocadia anammoxidans. Oscillations of chemical species at the site can be explained by a reduced model of ammonium competition between Nitrosomonas and B. anammoxidans which effectively acts as an activator-inhibitor system. Stable oscillations occur in conditions of low nutrient (ammonium) supply and this causes a spatial travelling wave in a borehole profile when diffusion is introduced.     

一株高效丙烯腈降解细菌Rhodococus rhodochrous BX2的丙烯腈降解条件优化

【目的】以丙烯腈为目标污染物,利用实验室已筛选获得的一株高效腈降解菌Rhodococus rhodochrous BX2,研究其对丙烯腈的降解特性,优化降解条件以提高菌株对丙烯腈的降解能力。【方法】通过单因素试验和响应面分析相结合的方法优化Rhodococus rhodochrous BX2对丙烯腈的降解条件。考察外加碳、氮源对BX2的生长及丙烯腈降解的影响,并确定其在丙烯腈合成废水中对丙烯腈的处理效果。【结果】菌株BX2优化后的最佳降解条件为:底物浓度403.51 mg/L、p H 7.44、温度34.46°C,在此条件下丙烯腈的降解率为95.1%。外加碳源为葡萄糖,或外加氮源为氯化铵对菌株生长及丙烯腈降解有明显的促进作用。菌株Rhodococus rhodochrous BX2能够高效降解合成废水中的丙烯腈,在30 h时其丙烯腈降解率可达89.4%。【结论】降解条件优化以及外源物质的添加强化了菌株对丙烯腈合成废水的处理效果,为生物法处理丙烯腈废水新方法的开发提供技术支持。     

Genome sequence of the anaerobic bacterium Bacillus sp. strain ZYK,a selenite and nitrate reducer from paddy soil

Bacillus sp. strain ZYK, a member of the phylum Firmicutes, is of interest for its ability to reduce nitrate and selenite and for its resistance to arsenic under anaerobic conditions. Here we describe some key features of this organism, together with the complete genome sequence and annotation. The 3,575,797 bp long chromosome with its 3,454 protein-coding and 70 RNA genes, and the information gained from its sequence will be relevant to the elucidation of microbially-mediated transformations of nitrogen, selenium and arsenic in paddy soil.     

Selenate-dependent anaerobic arsenite oxidation by a bacterium from Mono Lake, California

Arsenate was produced when anoxic Mono Lake water samples were amended with arsenite and either selenate or nitrate. Arsenite oxidation did not occur in killed control samples or live samples with no added terminal electron acceptor. Potential rates of anaerobic arsenite oxidation with selenate were comparable to those with nitrate ( approximately 12 to 15 mumol.liter(-1) h(-1)). A pure culture capable of selenate-dependent anaerobic arsenite oxidation (strain ML-SRAO) was isolated from Mono Lake water into a defined salts medium with selenate, arsenite, and yeast extract. This strain does not grow chemoautotrophically, but it catalyzes the oxidation of arsenite during growth on an organic carbon source with selenate. No arsenate was produced in pure cultures amended with arsenite and nitrate or oxygen, indicating that the process is selenate dependent. Experiments with washed cells in mineral medium demonstrated that the oxidation of arsenite is tightly coupled to the reduction of selenate. Strain ML-SRAO grows optimally on lactate with selenate or arsenate as the electron acceptor. The amino acid sequences deduced from the respiratory arsenate reductase gene (arrA) from strain ML-SRAO are highly similar (89 to 94%) to those from two previously isolated Mono Lake arsenate reducers. The 16S rRNA gene sequence of strain ML-SRAO places it within the Bacillus RNA group 6 of gram-positive bacteria having low G+C content.