Mechanism of Nitrification by Arthrobacter sp

Resting cells of Arthrobacter sp. excrete as much as 60 mug of hydroxylamine-nitrogen per ml when supplied with ammonium. An organic carbon source in abundant supply is necessary for the oxidation. Resting cells oxidize hydroxylamine to nitrite and 1-nitrosoethanol, the former accumulating only when an exogenous carbon source is available. Cell-free extracts contain an enzyme catalyzing the formation of hydroxylamine from acetohydroxamic acid, a hydroxylamine-nitrite oxido-reductase, and an enzyme producing nitrite and nitrate from various primary nitro compounds. Nitrite is not produced from hydroxylamine by the extracts, but 1-nitrosoethanol is formed from hydroxylamine in the presence of acetate. 1-Nitrosoethanol is also produced from acetohydroxamic acid by these preparations. Nitrite was formed from hydroxylamine, however, by extracellular enzymes excreted by the bacterium.     

异养硝化作用酶学研究进展

对异养硝化作用作了简单的概述,着重从异养硝化作用和好氧反硝化作用的偶联机理、其中涉及的关键酶和相关基因几方面综述了异养硝化作用的研究进展,最后还提出了研究展望。     

异养硝化细菌脱氮特性及研究进展

异养硝化细菌能够在利用有机碳源生长的同时将含氮化合物硝化生成羟胺、亚硝酸盐、硝酸盐等产物, 多数还能同时进行好氧反硝化作用, 直接将硝化产物转化为含氮气体。因此, 这类细菌已成为废水处理中生物脱氮新工艺的重要研究对象。本文综述了目前所分离出的一些异养硝化菌的脱氮特性, 分析了各种环境条件如温度、pH、溶解氧、碳源类型、C/N以及抑制剂等对异养硝化菌的影响, 并介绍了异养硝化菌的应用现状及前景。     

Heterotrophic nitrification by Arthrobacter sp. (strain 9006) as influenced by different cultural conditions,growth state and acetate metabolism

An Arthrobacter sp. (strain 9006), isolated from lake water, accumulated nitrite up to about 15 mg N/l, but no nitrate. In a mineral medium supplemented with tryptone, yeast extract, acetate and ammonium, the cells released nitrite into the medium parallel to growth or when growth had virtually ceased. The nitrite formed was proportional to the initial acetate concentration, indicating an involvement of acetate metabolism with nitrification. The organism grew with a wide variety of organic carbon sources, but washed cells formed nitrite from ammonium only in the presence of citrate, malate, acetate or ethanol. Magnesium ions were required for nitrification of ammonium and could not be replaced by other divalent metal ions. Analysis of the glyoxylate cycle key enzymes in washed suspensions incubated in a minimal medium revealed that isocitrate lyase and malate synthase were most active during the nitrification phase. Nitrite accumulation but not growth was inhibited by glucose, tryptone and yeast extract. A possible explanation for the different nitrification patterns during growth is based on the regulatory properties of glyoxylate cycle enzymes.Abbreviations IL Isocitrate lyase [threo-D_s-isocitrate glyoxylate-lase, E.C. 4.1.3.1.] - MS malate synthase [l-malate glyoxylate-lyase (CoA-acetylating), E.C. 4.1.3.2.]     

Uptake of Glyphosate by an Arthrobacter sp

The uptake of glyphosate (N-[phosphonomethyl]glycine) by an Arthrobacter sp. which can utilize this herbicide as its sole source of phosphorus was investigated. Orthophosphate suppressed the expression of the uptake system for glyphosate and also competed with glyphosate for uptake. The K_m for glyphosate uptake was 125 μM, and the K_i for orthophosphate was 24 μM. Organophosphonates as well as organophosphates inhibited glyphosate uptake, but only organophosphates and orthophosphate suppressed the uptake system. Glyphosate uptake was energy dependent, had a pH optimum of 6 to 7, and was differentially affected by divalent cations.     

Effects of Organic Acids on Heterotrophic Nitrification by Alcaligenes faecalis OKK17

Factors affecting heterotrophic nitrification by Alcaligenes faecalis OKK17, which was isolated from sewage sludge, were examined. Specific nitrifying activity increased as the pH increased up to 8.5. Most of the nitrogenous compounds (88%) in the culture supernatant were converted to hydroxylamine or nitrite at pH 9 but 87% of them remained as ammonium at pH 7. These results imply that the substrate for heterotrophic nitrification is ammonium and that the organism oxidizes ammonium to lower its toxic effect. Although the addition of acetate to a defined medium increased growth of the bacterium up to C/N = ca. 6, the accumulation of nitrification products almost paralleled the growth and the specific nitrifying activity decreased. Pyruvate and oxaloacetate increased the specific nitrifying activity six- to eightfold compared with the other organic acids examined, but the key enzyme activities in the glyoxylate cycle were not increased. Acetate, glyoxylate, and malonate did not increase the specific nitrifying activity, but they increased the enzyme activities. These results imply that the involvement of acetate metabolism in the heterotrophic nitrification is unlikely.     

Heterotrophic Nitrification in an Acid Forest Soil and by an Acid-Tolerant Fungus

Nitrate was formed from ammonium at pH 3.2 to 6.1 in suspensions of a naturally acid forest soil; the maximum rates of formation occurred at ca. pH 4 to 5. Nitrate was also formed from soil nitrogen in suspensions incubated at 50°C. Autotrophic nitrifying bacteria could not be isolated from this soil. Enrichment cultures produced nitrate in a medium with β-alanine if much soil was added to the medium, and nitrite but not nitrate was formed in the presence of small amounts of soil. Nitrification by these enrichments was abolished by eucaryotic but not procaryotic inhibitors. A strain of Absidia cylindrospora isolated from this soil was found to produce nitrate and nitrite in a medium with β-alanine at pH values ranging from 4.0 to 4.8. Nitrate production by A. cylindrospora required the presence of sterile soil. Free and bound hydroxylamine, hydroxamic acids, and primary aliphatic nitro compounds did not accumulate during the conversion of β-alanine to nitrite by the fungus. The organism also formed nitrite from ammonium in a medium containing acetate. We suggest that nitrification in this soil is a heterotrophic process catalyzed by acid-tolerant fungi and not by autotrophs or heterotrophs in nonacid microsites.     

Identification of Heterotrophic Nitrification in a Sierran Forest Soil

A potential for heterotrophic nitrification was identified in soil from a mature conifer forest and from a clear-cut site. Potential rates of NO₂⁻ production were determined separately from those of NO₃⁻ by using acetylene to block autotrophic NH₄⁺ oxidation and chlorate to block NO₂⁻ oxidation to NO₃⁻ in soil slurries. Rates of NO₂⁻ production were similar in soil from the forest and the clear-cut site and were strongly inhibited by acetylene. The rate of NO₃⁻ production was much greater than that of NO₂⁻ production, and NO₃⁻ production was not significantly affected by acetylene or chlorate. Nitrate production was partially inhibited by cycloheximide, but was not significantly reduced by streptomycin. Neither the addition of ammonium nor the addition of peptone stimulated NO₃⁻ production. ¹⁵N labeling of the NH₄⁺ pool demonstrated that NO₃⁻ was not coming from NH₄⁺. The potential for heterotrophic nitrification in these forest soils was greater than that for autotrophic nitrification.     

A Strain of Pseudomonas sp. Isolated from Piggery Wastewater Treatment Systems with Heterotrophic Nitrification Capability in Taiwan

A high concentration of NH₄⁺ in piggery wastewater is major problem in Taiwan. Therefore, in our study, we isolated native heterotrophic nitrifiers for piggery wastewater treatment. Heterotrophic nitrifier AS-1 was isolated and characterized from the activated sludge of a piggery wastewater system. Sets of triplicate crimp-sealed serum bottles were used to demonstrate the heterotrophic nitrifying capability of strain AS-1 in an incubator at 30°C. All serum bottles contained 80 mL medium, and the remainder of the bottle headspace was filled with pure oxygen. The experimental results showed that 2.5 ± 0.2 mmol L⁻¹ NH₄⁺ was removed by 58 hours, and, eventually, 1.5 ± 0.5 mmol L⁻¹ N₂ and 0.2 ± 0.0 mmol L⁻¹ N₂O were produced. The removal rate of NH₄⁺ by the strain AS-1 was 1.75 mmol NH₄⁺ g cell⁻¹ h⁻¹. This strain was then identified as Pseudomonas alcaligenes (97% identity) by sequencing its 16S rDNA and comparing it with other microorganisms. Thus, strain AS-1 displays high promise for future application for in situ NH₄⁺ removal from piggery wastewater.     

节杆菌(Arthrobacter sp.)降解阿魏酸的效能

[背景]蓄积在土壤中的阿魏酸类化感自毒物质对农作物生长产生危害,利用有益微生物分解该类物质是一项有效的治理措施.[目的]从自然界土壤分离获得能高效降解阿魏酸的菌株,并评估典型环境因子对降解效能的影响,以期为该菌在阿魏酸类自毒物质降解领域中的应用提供理论依据.[方法]采用一次性投加高浓度化合物的驯化方法分离筛选得到能有效...     

Degradation of 4-Chlorobenzoic Acid by Arthrobacter sp

A mixed population, enriched and established in a defined medium, from a sewage sludge inoculum was capable of complete mineralization of 4-chlorobenzoate. An organism, identified as Arthrobacter sp., was isolated from the consortium and shown to be capable of utilizing 4-chlorobenzoate as the sole carbon and energy source in pure culture. This organism (strain TM-1), dehalogenated 4-chlorobenzoate as the initial step in the degradative pathway. The product, 4-hydroxybenzoate, was further metabolized via protocatechuate. The ability of strain TM-1 to degrade 4-chlorobenzoate in liquid medium at 25°C was improved by the use of continuous culture and repeated sequential subculturing. Other chlorinated benzoates and the parent compound benzoate did not support growth of strain TM-1. An active cell extract was prepared and shown to dehalogenate 4-chloro-, 4-fluoro-, and 4-bromobenzoate. Dehalogenase activity had an optimum pH of 6.8 and an optimum temperature of 20°C and was inhibited by dissolved oxygen and stimulated by manganese (Mn²⁺). Strain improvement resulted in an increase in the specific activity of the cell extract from 0.09 to 0.85 nmol of 4-hydroxybenzoate per min per mg of protein and a decrease in the doubling time of the organism from 50 to 1.6 h.     

trans-Stilbene degradation by Arthrobacter sp. SL3 cells

trans-Stilbene degradation was examined by the reaction using resting cells of microorganisms isolated through the enrichment culture using trans-stilbene. The strain SL3, showing the highest trans-stilbene-degrading activity, was identified as Arthrobacter sp. One of the reaction products was identified to be cis,cis-muconic acid. Arthrobacter sp. SL3 cells also transformed benzaldehyde, benzoic acid and catechol into cis,cis-muconic acid, suggesting that one benzene ring of trans-stilbene was converted into cis,cis-muconic acid via benzaldehyde formed by its C_α=C_β bond cleavage.     

The catabolism of L-tyrosine by an Arthrobacter sp.

An Arthrobacter sp. metabolizes L-tyrosine by a pathway involving 3,4-dihydroxyphenylacetate as a key intermediate. p-Hydroxyphenylpyruvate is formed from tyrosine by an amino-transferase specifically requiring alpha-ketoglutarate for activity, and is then converted to p-hydroxyphenylacetate by an oxidative decarboxylation. p-Hydroxyphenylacetaldehyde is not an intermediate in the formation of p-hydroxyphenylacetate. Extracts of the bacterium oxidize 3,4-dihydroxyphenylacetate to delta-carboxymethyl-alpha-hydroxymuconic acid which, when supplemented with 2 mol of diphosphopyridine dinucleotide, results in the production of stoichiometric amounts of succinate and pyruvate.     

A Hydroxylamine-Cytochrome c Reductase Occurs in the Heterotrophic Nitrifier Arthrobacter globiformis

A partially purified cell-free extract of Arthrobacter globiformisshowed hydroxylamine-cytochrome c reductase activity. The enzymedid not seem to contain cytochrome, it was activated by ferrousions and inhibited by EDTA, and had an optimal pH of 9. ¹ On leave from Suido Kiko Kaisha, Ltd., Tokyo.     

Initial reactions of xanthone biodegradation by an Arthrobacter sp.

This study examined the catabolism of xanthone by an Arthrobacter sp. (strain GFB100) capable of growth on xanthone as its main source of carbon and energy. An early catabolic intermediate was 3,4-dihydroxyxanthone. This compound was isolated from the growth medium of a mutant strain of the Arthrobacter sp. which lacked the xanthone-inducible dihydroxyxanthone ring-fission dioxygenase of the wild-type strain. Cell extracts from wild-type xanthone-grown cells oxidized 3,4-dihydroxyxanthone to a yellow ring-fission metabolite. The same yellow compound accumulated in xanthone-grown cultures of a spontaneous mutant which lacked an active, xanthone-inducible, NADPH-linked ring-fission metabolite reductase. The yellow ring-fission metabolite appears to be 4-hydroxy-3-(2'-oxo-3-trans-butenoate)-coumarin, based on its nuclear magnetic resonance spectrum and mass spectral fragmentation pattern, indicating that ring cleavage of 3,4-dihydroxyxanthone was by an extra-diol (meta-fission) mechanism. Enzymatic analyses indicated that growth on xanthone induced a complete gentisate pathway: dioxygenase-catalyzed cleavage of gentisate to maleylpyruvate, isomerization of maleylpyruvate to fumarylpyruvate, and hydrolysis of fumarylpyruvate to fumarate and pyruvate. 4-Hydroxycoumarin was thought to be a likely pathway intermediate linking the early xanthone catabolic steps to the gentisate pathway, since 2-hydroxyacetophenone, a byproduct of 4-hydroxycoumarin hydrolysis, was formed when wild-type cells were cultured with xanthone. Chlorinated 2-hydroxyacetophenones were also obtained from specific chloro-substituted xanthones.     

Degradation of a Sodium Acrylate Oligomer by an Arthrobacter sp

Arthrobacter sp. strain NO-18 was first isolated from soil as a bacterium which could degrade the sodium acrylate oligomer and utilize it as the sole source of carbon. When 0.2% (wt/wt) oligomer was added to the culture medium, the acrylate oligomer was found to be degraded by 70 to 80% in 2 weeks, using gel permeation chromatography. To determine the maximum molecular weight for biodegradation, the degradation test was done with the hexamer, heptamer, and octamer, which were separated from the oligomer mixture by fractional gel permeation chromatography. The hexamer and heptamer were consumed to the extents of 58 and 36%, respectively, in 2 weeks, but the octamer was not degraded. Oligomers with three different terminal groups were synthesized to examine the effect of the different terminal groups on biodegradation, but few differences were found. Arthrobacter sp. NO-18 assimilated acrylic acid, propionic acid, glutaric acid, 2-methylglutaric acid, and 1,3,5-pentanetricarboxylic acid. Degradation of the acrylic unit structure by this strain is discussed.     

异养硝化⁃好氧反硝化复合菌剂在垃圾渗滤液处理中的应用

垃圾渗滤液中往往含有高浓度的有机物、氨氮等污染物。异养硝化-好氧反硝化型微生物能在脱氮的同时去除部分有机物,但目前对于相关混合菌剂直接应用于垃圾渗滤液处理的研究较少。从垃圾渗滤液中筛选出6株异养硝化-好氧反硝化菌株并组配成复合菌剂F6,探究菌剂在垃圾渗滤液中的脱氮效果。分别以单一菌株和复合菌剂F6为投放原料;以不同碳氮比、活性炭浓度、转速以及微量元素浓度为影响因素,研究复合菌剂对于垃圾渗滤液中氨氮(NH{}_{\mathrm{4}}^{+}-N)、总氮(total nitrogen, TN)、化学需氧量(chemical oxygen demand, COD)的去除性能。结果表明,提高碳氮比和微量元素浓度能够促进复合菌剂F6的降解效果;当接种量为10%、碳氮比为15%时,F6对NH{}_{\mathrm{4}}^{+}-N、TN、COD的去除率分别为74.69%、89.23%和83.50%,与不添加活性炭的处理相比,分别提高了约18.46%、20.97%和7.98%。复合异养硝化-好氧反硝化菌剂F6对高氨氮垃圾渗滤液去除NH{}_{\mathrm{4}}^{+}-N、TN、COD等方面具有良好的应用前景。     

Biodegradation of p-nitrophenol via 1,2,4-benzenetriol by an Arthrobacter sp.

The degradation of p-nitrophenol (PNP) by Moraxella and Pseudomonas spp. involves an initial monooxygenase-catalyzed removal of the nitro group. The resultant hydroquinone is subject to ring fission catalyzed by a dioxygenase enzyme. We have isolated a strain of an Arthrobacter sp., JS443, capable of degrading PNP with stoichiometric release of nitrite. During induction of the enzymes required for growth on PNP, 1,2,4-benzenetriol was identified as an intermediate by gas chromatography-mass spectroscopy (GC-MS) and radiotracer studies. 1,2,4-Benzenetriol was converted to maleylacetic acid, which was further degraded by the beta-ketoadipate pathway. Conversion of PNP to 1,2,4-benzenetriol is catalyzed by a monooxygenase system in strain JS443 through the formation of 4-nitrocatechol, 4-nitroresorcinol, or both. Our results clearly indicate the existence of an alternative pathway for the biodegradation of PNP.