Anaerobic and aerobic metabolism of diverse aromatic compounds by the photosynthetic bacterium Rhodopseudomonas palustris.

The purple nonsulfur photosynthetic bacterium Rhodopseudomonas palustris used diverse aromatic compounds for growth under anaerobic and aerobic conditions. Many phenolic, dihydroxylated, and methoxylated aromatic acids, as well as aromatic aldehydes and hydroaromatic acids, supported growth of strain CGA001 in both the presence and absence of oxygen. Some compounds were metabolized under only aerobic or under only anaerobic conditions. Two other strains, CGC023 and CGD052, had similar anaerobic substrate utilization patterns, but CGD052 was able to use a slightly larger number of compounds for growth. These results show that R. palustris is far more versatile in terms of aromatic degradation than had been previously demonstrated. A mutant (CGA033) blocked in aerobic aromatic metabolism remained wild type with respect to anaerobic degradative abilities, indicating that separate metabolic pathways mediate aerobic and anaerobic breakdown of diverse aromatics. Another mutant (CGA047) was unable to grow anaerobically on either benzoate or 4-hydroxybenzoate, and these compounds accumulated in growth media when cells were grown on more complex aromatic compounds. This indicates that R. palustris has two major anaerobic routes for aromatic ring fission, one that passes through benzoate and one that passes through 4-hydroxybenzoate.     

Detection of anaerobic processes and microorganisms in immobilized activated sludge of a wastewater treatment plant with intense aeration

Attached activated sludge from the Krasnaya Polyana (Sochi) wastewater treatment plant was studied after the reconstruction by increased aeration and water recycle, as well as by the installation of a bristle carrier for activated sludge immobilization. The activated sludge biofilms developing under conditions of intense aeration were shown to contain both aerobic and anaerobic microorganisms. Activity of a strictly anaerobic methanogenic community was revealed, which degraded organic compounds to methane, further oxidized by aerobic methanotrophs. Volatile fatty acids, the intermediates of anaerobic degradation of complex organic compounds, were used by both aerobic and anaerobic microorganisms. Anaerobic oxidation of ammonium with nitrite (anammox) and the presence of obligate anammox bacteria were revealed in attached activated sludge biofilms. Simultaneous aerobic and anaerobic degradation of organic contaminants by attached activated sludge provides for high rates of water treatment, stability of the activated sludge under variable environmental conditions, and decreased excess sludge formation.     

Study of Trichoderma viride metabolism under conditions of the restriction of oxidative processes

Trichoderma viride was capable of growth and conidiation in the presence of high concentrations of the uncoupler 3,3',4',5-tetrachlorosalicylanilide (up to 100 micromol x L(-1) and of the respiration inhibitor mucidin (up to 100 micromol x L(-1) ) in both submerged and surface cultivation. When vegetative mycelia were cultivated on the solid Czapek-Dox medium with yeast autolysate under an anaerobic and CO2-containing atmosphere, the growth was observed only rarely but the microorganism survived as long as 3 months under these conditions. Major products of metabolism of both aerobic and anaerobic submerged mycelia were identified by means of 1H-NMR measurements. Major products excreted to the medium under aerobic conditions were succinic and citric acids. Major metabolites present in the submerged mycelia were gamma-aminobutyric (and glutamic) acid and alanine. Under anaerobic conditions, citric acid was not excreted into the medium but ethanol appeared. Its production could not be increased upon increasing the sugar concentration. The appearance of secondary metabolites was found to be modified by oxygen availability during the mycelial growth. Results suggest that the vegetative form of T. viride is capable of fermentative metabolism characterized by the production of ethanol and succinate and that the excretion of carboxylic acids is developmentally regulated and modified by oxygen availability.     

Isolation of soil Streptomyces strains capable of degrading humic acids and analysis of their peroxidase activity

Abstract Fifteen Streptomyces strains capable of decolorizing humic acids in presence of glucose were isolated from soil samples using the dilute suspension technique and spread on agar plates. Six strains, displaying a significant and stable activity, were selected for further characterization. Some features of these isolates (carbon source utilization, enzyme production, antibiotic resistance) were compared with those of the reference strain Streptomyces viridosporus ATCC 39115. Degradation properties studied in batch cultures at pH 7.0 showed that the catabolic activity on humic acids was generally stimulated by incubation with 100% oxygen and was cell surface-associated. Peroxidase activity from cell-free extracts was analysed by using the oxidation of N,N,N′,N′-tetramethyl-phenylene-diamine. PAGE analysis revealed the existence of two major types of peroxidases (molecular mass: about 39.2 and 61.6 kDa), dividing the strains into two groups. The role of cell surface-associated peroxidase activity in the breakdown of humic acids is discussed.     

Zn-Fe LDHs改性石英砂生物膜体系对BDE-47的去除效果与机理

文章以四溴联苯醚(BDE-47)为目标污染物, 利用共沉淀法制备Zn-Fe LDHs覆膜改性石英砂基质, 在好氧、厌氧及两者交替条件下, 研究腐败希瓦氏菌CN32(Shewanella putrefaciens CN32) 在LDHs改性基质上生物膜形成过程及其对培养液中BDE-47的去除效果; 通过监测反应体系中Fe2+和H₂O₂浓度变化探讨BDE-47的生物及非生物去除机制。结果表明, LDHs改性不影响石英砂基质表面生物膜的形成, 但在好氧条件下, Zn-Fe LDHs石英砂改性基质对CN32电子传递链活性存在一定抑制作用, 而在厌氧条件下, LDHs改性会影响基质生物膜胞外聚合物(EPS)组成特性, 使多糖占比升高。无论在好氧还是厌氧条件下, 基质生物膜反应体系中EPS总浓度均显著高于纯菌CN32体系; 且在好氧与交替条件下, 基质生物膜的形成均显著提高反应体系中BDE-47的去除效果(约25%)。在交替条件下, 前3次循环(72h内)BDE-47的去除以基质吸附为主; 72h后, 生物膜吸附与生物降解共同发挥作用, 且LDHs改性基质在后期上升潜力更大。研究报道了LDHs改性基质生物膜形成特性及其对水相中PBDEs去除的潜力, 为强化人工湿地中PBDEs生物降解提供新思路。     

Initiation of anaerobic growth of Saccharomyces cerevisiae by amino acids or nucleic acid bases: ergosterol and unsaturated fatty acids cannot replace oxygen in minimal media

Nine out of ten industrially important strains of Saccharomyces cerevisiae did not grow in minimal media under anaerobic conditions even when ergosterol and unsaturated fatty acids were provided. Anaerobiosis was maintained either by flushing the culture flasks with prepurified nitrogen or by incubating the flasks in an anaerobic chamber. Traces of oxygen present in ‘prepurified nitrogen gas’ were sufficient to initiate yeast growth and on removal of the oxygen by catalytic means the yeasts failed to grow. The yeast grew very well anaerobically if the medium was supplemented with a mixture of amino acids or with a mixture of purines and pyrimidines. The growth initiated by including a mixture of amino acids was further enhanced when the medium was supplemented with ergosterol and an unsaturated fatty acid. Since no oxygen requirement for the synthesis of amino acids or purines and pyrimidines has been demonstrated, growth promotion by these compounds under anaerobic conditions is most likely not by eliminating the need for oxygen for their synthesis. We suggest that the amino acids and the nucleic acid bases yielded, through some hitherto unknown reactions, small amounts of a molecular or usable form of oxygen which allowed key reactions essential for ‘anaerobic’ growth to proceed. Received 16 July 1998/ Accepted in revised form 8 October 1998     

The effect of oxygen on fatty acid composition of soil micromycetes

The aim of this work was to describe changes in fatty acid profiles of fungi growing under artificial conditions of oxygen depletion. In total, 133 fungal strains belonging to eight orders were isolated from cattle impacted soils and tested. The analysis of the ten most frequent fatty acids revealed significant shift in fatty acids composition as a result of decreasing oxygen level. Taxonomic- as well as aeration-dependent changes in the amounts of fungal biomarker fatty acids (18:1ω9 and 18:2ω6,9) were found. Therefore, the ratio of these two fatty acids could be considered as an indicator of anaerobic, microaerobic or aerobic conditions in soil. Moreover, fatty acid-based estimation of fungal biomass in soils should be performed as a sum of both biomarker fatty acids and with respect to the soil characteristics as well as to the composition of fungal community.     

Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds

The biodegradability of chlorinated methanes, chlorinated ethanes, chlorinated ethenes, chlorofluorocarbons (CFCs), chlorinated acetic acids, chlorinated propanoids and chlorinated butadienes was evaluated based on literature data. Evidence for the biodegradation of compounds in all of the compound categories evaluated has been reported. A broad range of chlorinated aliphatic structures are susceptible to biodegradation under a variety of physiological and redox conditions. Microbial biodegradation of a wide variety of chlorinated aliphatic compounds was shown to occur under five physiological conditions. However, any given physiological condition could only act upon a subset of the chlorinated compounds. Firstly, chlorinated compounds are used as an electron donor and carbon source under aerobic conditions. Secondly, chlorinated compounds are cometabolized under aerobic conditions while the microorganisms are growing (or otherwise already have grown) on another primary substrate. Thirdly, chlorinated compounds are also degraded under anaerobic conditions in which they are utilized as an electron donor and carbon source. Fourthly, chlorinated compounds can serve as an electron acceptor to support respiration of anaerobic microorganisms utilizing simple electron donating substrates. Lastly chlorinated compounds are subject to anaerobic cometabolism becoming biotransformed while the microorganisms grow on other primary substrate or electron acceptor. The literature survey demonstrates that, in many cases, chlorinated compounds are completely mineralised to benign end products. Additionally, biodegradation can occur rapidly. Growth rates exceeding 1 d^-1 were observed for many compounds. Most compound categories include chlorinated structures that are used to support microbial growth. Growth can be due to the use of the chlorinated compound as an electron donor or alternatively to the use of the chlorinated compound as an electron acceptor (halorespiration). Biodegradation linked to growth is important, since under such conditions, rates of degradation will increase as the microbial population (biocatalyst) increases. Combinations of redox conditions are favorable for the biodegradation of highly chlorinated structures that are recalcitrant to degradation under aerobic conditions. However, under anaerobic conditions, highly chlorinated structures are partially dehalogenated to lower chlorinated counterparts. The lower chlorinated compounds are subsequently more readily mineralized under aerobic conditions.     

Aerobic versus anaerobic metabolism of halogenated anilines by aParacoccus sp.

AParacoccus sp. which transforms aniline and different halogen-substituted derivatives under aerobic and anaerobic conditions was isolated from the soil. In experiments with¹⁴C-ring-labeled 4-chloroaniline, approximately 60% of the radioactive material disappeared from the growth medium after incubation under anaerobiosis within 48 hr, but under aerobic conditions no decrease of radioactivity in the growth medium was observed, although 4-chloroaniline was completely metabolized. Acetylation appears to constitute, especially under aerobic conditions, a major transformation mechanism by the bacterium, since almost 50% of the acetylated compound could be detected and identified if aniline, 2-, 3-, and 4-chloroaniline served as substrate. The formation of different metabolites under aerobic and anaerobic conditions clearly indicates the existence of two separate pathways in the metabolism of aniline compounds depending on the oxygen status of the environment.     

On humus formation

Summary A scheme on humus formation has been proposed. This is as follows: Lignin/carbohydrates, the chief sources of C for the microorganisms are first broken down by extracellular enzymes into smaller units. Soluble units are absorbed into the microbial cell where part of them are converted to phenols/quinones. These together with oxidising enzymes are discharged into the environment where they polymerise by a free radical mechanism. The formation of FA (fulvic acids) has also been explained and it has been concluded that the difference between FAs and HAs (humic acids) is merely in the degree of polymerisation and that FAs are not necessarily more aliphatic than HAs.     

Atypical polyphosphate accumulation by the denitrifying bacterium Paracoccus denitrificans

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-beta-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of these findings to those with polyphosphate-accumulating organisms thought to be responsible for phosphate removal in activated sludge systems, it is concluded that P. denitrificans is capable of combined phosphate and nitrate removal without the need for alternating anaerobic/aerobic or anaerobic/anoxic switches. Studies on additional denitrifying isolates from a denitrifying fluidized bed reactor suggested that polyphosphate accumulation is widespread among denitrifiers.     

Phosphorus Retention at the Redox Interface of Peatlands Adjacent to Surface Waters in Northeast Germany

It is demanded currently in public discussions to rewet peatlands and re-establish their function as nutrient sinks. But due to high phosphorus (P) concentrations in the pore water of rewetted peatlands (40–420 μM) it is hypothesized that they can act as a surplus P source for adjacent surface waters and consequently support the eutrophication of such waters. Our detailed investigations of processes at the redox interface in four fens with different geochemical character show the dependence of P retention from the chemistry of the pore water. The precipitation of Fe(III) oxyhydroxide led to high retention of phosphorus and other substances such as DOC and sulphate in the eutrophic fens. When molar Fe/P ratios were larger than about 3 the initially high P concentrations in the anaerobic pore water (20–210 μM) decreased to concentrations below 1 μM under aerobic conditions. Thus, after rewetting high pore water concentrations of P do not automatically result in an increased P load to adjacent surface waters compared to pre-rewetting conditions. An enhanced P export to adjacent surface waters from eutrophic fens can be expected when the Fe/P ratio is smaller than 3 in the anaerobic pore water. In our investigations of natural, oligotrophic to mesotrophic fens the precipitation of Fe(III) oxyhydroxide was inhibited by the formation of stable dissolved Fe ∼ humic complexes. P retention in these fens was only related to the DOC concentrations at the redox interface, so that lower DOC concentrations concurred with higher P retention. The P equilibrium concentrations in an aerobic environment can be higher than that of eutrophic fens with Fe/P ratios larger than about 3 in the anaerobic pore water.     

Heathland restoration in The Netherlands: Effects of turf cutting depth on germination of Arnica montana

Abstract. Germination experiments were conducted in a heathland after turf cutting and in a climate chamber to investigate the effects of turf cutting depth, aluminium toxicity and aluminium detoxification by humic acids and base cations on the germination and establishment of Arnica montana. Turfs were cut at three different depths, creating a gradient from organic to mineral soils. Germination and establishment of A. montana were negatively correlated with turf cutting depth. The removal of organic matter resulted in a major decrease in organic fraction of the soil and its nutrients. It also resulted in a considerable decrease in moisture content and humic acids. Additional liming after turf cutting increased germination and establishment in all plots and at all depths. Germination experiments under controlled conditions in a climate chamber revealed a significantly higher germination at low aluminium/calcium (Al:Ca) ratios. High Al:Ca ratios resulted in poor germination, suggesting Al toxicity. Addition of humic acids increased germination, even at high Al:Ca ratios, suggesting immobilization of Al by humic acids. It is concluded that turf cutting can have a marked effect on the success of heathland restoration. It results in the intended removal of the eutrophic layer but also in the unintentional removal of much of the buffering mechanisms and/or Al immobilizing compounds. Additional buffering and/or less deep turf cutting may be necessary to allow germination and establishment of rare herbaceous species such as A. montana.     

Atypical Polyphosphate Accumulation by the Denitrifying Bacterium Paracoccus denitrificans

Polyphosphate accumulation by Paracoccus denitrificans was examined under aerobic, anoxic, and anaerobic conditions. Polyphosphate synthesis by this denitrifier took place with either oxygen or nitrate as the electron acceptor and in the presence of an external carbon source. Cells were capable of poly-β-hydroxybutyrate (PHB) synthesis, but no polyphosphate was produced when PHB-rich cells were incubated under anoxic conditions in the absence of an external carbon source. By comparison of these findings to those with polyphosphate-accumulating organisms thought to be responsible for phosphate removal in activated sludge systems, it is concluded that P. denitrificans is capable of combined phosphate and nitrate removal without the need for alternating anaerobic/aerobic or anaerobic/anoxic switches. Studies on additional denitrifying isolates from a denitrifying fluidized bed reactor suggested that polyphosphate accumulation is widespread among denitrifiers.     

Plasmid maintenance and gene expression of a recombinant culture under aerobic and anaerobic conditions

Summary The stability and gene expression of a batch culture ofEscherichia coli, strain C600, carrying the plasmid pKN401 under both aerobic and anaerobic conditions were studied. It was observed that the plasmid was stable under both conditions and during a step change in the environment in which oxygen and nitrogen were supplied alternately. In addition, the -lactamase specific activity was sensitive to the availability of oxygen, with higher activities and a strong dependence on optical density observed under anaerobic conditions.     

Oxygen requirements of the food spoilage yeast Zygosaccharomyces bailii in synthetic and complex media

Most yeast species can ferment sugars to ethanol, but only a few can grow in the complete absence of oxygen. Oxygen availability might, therefore, be a key parameter in spoilage of food caused by fermentative yeasts. In this study, the oxygen requirement and regulation of alcoholic fermentation were studied in batch cultures of the spoilage yeast Zygosaccharomyces bailii at a constant pH, pH 3.0. In aerobic, glucose-grown cultures, Z. bailii exhibited aerobic alcoholic fermentation similar to that of Saccharomyces cerevisiae and other Crabtree-positive yeasts. In anaerobic fermentor cultures grown on a synthetic medium supplemented with glucose, Tween 80, and ergosterol, S. cerevisiae exhibited rapid exponential growth. Growth of Z. bailii under these conditions was extremely slow and linear. These linear growth kinetics indicate that cell proliferation of Z. bailii in the anaerobic fermentors was limited by a constant, low rate of oxygen leakage into the system. Similar results were obtained with the facultatively fermentative yeast Candida utilis. When the same experimental setup was used for anaerobic cultivation, in complex YPD medium, Z. bailii exhibited exponential growth and vigorous fermentation, indicating that a nutritional requirement for anaerobic growth was met by complex-medium components. Our results demonstrate that restriction of oxygen entry into foods and beverages, which are rich in nutrients, is not a promising strategy for preventing growth and gas formation by Z. bailii. In contrast to the growth of Z. bailii, anaerobic growth of S. cerevisiae on complex YPD medium was much slower than growth in synthetic medium, which probably reflected the superior tolerance of the former yeast to organic acids at low pH.     

水体腐殖酸对甲氰菊酯的生物可利用性与急性毒性的影响

本文在实验室淡水试验系统中,研究了天然水体腐殖酸对甲氰菊酯对草鱼（Ｃｔｅｎｏｐｈａｒｙｎｇｏｄｏｎｉｄｅｌｌｕｓ）的生物积累和急性毒性的影响。研究结果表明：当水体中腐殖酸浓度为５和１０ｍｇ／Ｌ时,甲氰菊酯对草鱼的生物可利用性以及它对草鱼的急性毒性均呈有意义地减少趋势,而且这种影响的程度随着水体腐殖酸浓度的增加而增大。     

The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment

Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.A contribution to the GRIL (Groupe de Recherche Interuniversitaire de Limnologie)     

L-丙氨酸厌氧发酵关键技术及产业化

传统氨基酸制造主要是通过化学合成或好氧发酵实现。相对于化学合成,微生物发酵可以实现以可再生资源为原料直接生产氨基酸,减少了对石油基原料的依赖,解决了化学合成高污染、高能耗等问题。好氧发酵具有生长快、产量高等特点,但好氧发酵中大量碳源用于细胞生长容易造成糖酸转化率低、能耗高等问题。厌氧发酵是近年来新出现的氨基酸生产模式,具有操作简单、无需通氧、糖酸转化率高容易接近理论最大值等优势。L-丙氨酸是国际上首个实现厌氧发酵产业化生产的氨基酸。本文以L-丙氨酸为例,综述了氨基酸厌氧发酵过程中的关键问题及其在产业化实施中的应用。未来,随着厌氧发酵关键技术在更多化合物生物制造技术中的突破,这种低成本、高效、低碳环保型发酵方式将会带来更大的经济价值和社会效益。