氯代苯胺类化合物微生物降解的研究进展*

对氯代苯胺类化合物(Chlovoanilines,CAS)好氧微生物降解的研究现状进行了系统的综述,内容包括具有降解氯代苯胺类化合物能力的微生物、氯代苯胺类化合物的代谢途径及相关代谢酶的分析、降解质粒和关键代谢酶的基因克隆和表达,并提出了氯代苯胺类化合物好氧微生物降解研究中存在的问题和尚需进一步研究的方面。     

填埋场氯代烃生物降解过程的机制转化与调控研究及展望

明晰氯代烃在复杂污染体系中的生物转化机制对强化污染物原位生物修复有重要意义。填埋场属典型复合污染场地,本文对不同地区填埋场填埋气中氯代烃种类、含量和其在覆盖层中的降解情况进行统计分析,发现填埋气中主要包括氯代烷烃和氯代烯烃两大类污染物,其浓度分别为0.20–32.45μg/m~3和0.50–32.45μg/m~3;覆盖土对氯代烃降解速率随着氯原子取代的增多而降低。基于覆盖层中微生物种类多、生长底物复杂多样和不同梯度氧气含量差异等特点,总结得出氯代烃在覆盖土中的降解途径主要是好氧共代谢、直接氧化和厌氧还原脱氯;并基于不同工况特点构建了氯代烃在填埋场覆盖层底部扩散至大气界面过程的生物转化机制模型。最后就复杂环境体系中氯代烃类污染物的去除进行了展望。     

氯代脂肪烃生物与非生物共促降解机制研究进展

氯代脂肪烃(Chlorinated aliphatic hydrocarbons,CAHs)具有高毒性、高富集性、高环境残留的特点和致癌、致畸、致突变效应,对人体健康和生态环境造成了严重危害。CAHs降解是生物和非生物过程共同作用的结果,存在多种交互作用,明晰CAHs的生物与非生物共促降解机制对于强化CAHs污染场地修复具有重要意义。文中首先对CAHs降解方式进行了分类介绍,按照还原脱氯、好氧共代谢和直接氧化三种方式总结了影响CAHs降解的典型生物与非生物降解因子。从共促降解的角度出发,系统分析并提出了诱导降解机制和协同降解机制,并对基于共促机制强化CAHs降解的工程应用与存在的技术局限进行了综述和分析,最后对未来的发展方向进行了展望。     

多氯联苯微生物脱氯研究进展

多氯联苯(polychlorinated biphenyls,PCBs)是环境中典型的氯代持久性有机污染物.微生物脱氯是一种氯代有机物自然降解模式,对全球PCBs特别是高氯代同系物消减起到至关重要的作用.厌氧条件下高氯代PCBs能够发生脱氯反应,使其毒性大大降低,脱氯后形成的低氯代化合物可以进一步好氧降解,直至完全矿化.本文综述了PCBs生物脱氯的研究进展,介绍了微生物脱氯反应的机理和特征、参与微生物脱氯过程的专性脱氯菌等,探讨了该微生物过程的影响因素及厌氧脱氯与好氧降解耦合的意义,并对脱氯微生物群落的复杂代谢网络研究、专性脱氯新菌种筛选及其污染地实际修复应用等未来研究方向进行了展望.     

宏基因组学分析揭示深古菌Bathyarchaeota B242的代谢特征

【背景】海洋沉积物中蕴含着丰富的微生物资源,估算约2.9×1029个细胞,与海水中的微生物总量相当。但是由于缺少可培养物,大部分的微生物缺乏生理特征、代谢方式以及生态功能的相关研究。深古菌(Bathyarchaeota)是一类典型的未培养微生物,在全球海洋沉积物中普遍存在,并且具有很高的丰度。【目的】对深古菌代谢潜能及其在海洋沉积物中发挥的生态功能进行更加深入的研究。【方法】应用宏基因组学的技术手段,对采集自瓜伊马斯盆地的深海热液沉积物样本进行了分析,获得了一个接近完整的深古菌基因组Bathyarchaeota B242。【结果】对Bathyarchaeota B242基因组的分析发现,其具有以降解蛋白质和多种碳水化合物为主的异养代谢途径,同时还具有通过还原型乙酰辅酶A途径实现的自养途径。【结论】同时具有自养和异养代谢途径对Bathyarchaeota B242适应低物质能量供给环境下的生存起到重要作用。     

微生物降解对氯苯胺的一条新代谢途径

迄今为止的研究报道表明,对氯苯胺的生物降解只能以邻位途径或修饰邻位途径进行。采用HPLC、液相色谱质谱联用技术(LC/MS)对Diaphorobacter PCA039菌株降解对氯苯胺的中间代谢产物进行了分析和鉴定,结果表明,对氯苯胺经PCA039菌株的降解形成了氯代邻苯二酚,5-氯-4草酰巴豆酸,5-氯-2-氧戊烯酸,5-氯-2-氧-4-羟戊酸,氯代乙酸等中间代谢产物,这些都是典型的间位代谢途径(meta-pathway)的中间物质,说明Diaphorobacter PCA039菌株以间位裂解途径对对氯苯胺进行降解。这对于对氯代胺的生物降解代谢研究、代谢机理及其遗传表达调控研究具有意义。     

专一营养与兼性甲烷氧化菌降解氯代烃的研究现状、动力学分析及展望

生物修复技术被认为是氯代烃类污染物处理处置的最有效途径之一,而甲烷氧化菌在该领域表现出较大的应用潜力。近期研究发现,突破了仅能利用单碳化合物的局限,兼性甲烷氧化菌能够利用多种底物降解氯代烃,这一独特的新陈代谢特性,使其在污染物生物处置领域逐渐受到关注。结合本课题组研究成果,对甲烷氧化菌降解氯代烃进行了全面总结,主要包括:分析了不同菌株(纯菌株和混合菌株)对不同氯代烃的降解效果;比较了不同类型甲烷单加氧酶在不同底物体系中的活性表达和催化特性;总结了模型菌株甲基弯菌Methylosinus trichosporium OB3b降解氯代烃的动力学特性;概述了兼性甲烷氧化菌株降解氯代烃的特性及其应用潜力;最后讨论了甲烷氧化菌降解氯代烃存在的问题及未来发展方向。     

异养硝化机理的研究进展

硝化作用是自然界氮素循环的一个重要环节。除了传统上的自养硝化细菌以外,至今为止已发现许多异养微生物可以进行硝化作用。异养硝化已成为环境领域的热点问题。简要的介绍了自然界中的异养硝化微生物的分布以及针对其生物多样性而建立的探测和分离方法。着重从异养硝化的关键酶,相关基因,电子传递及代谢途径这几个方面综述了异养硝化机理的研究进展。最后总结了目前在研究异养硝化机理过程中存在的问题,并对其今后进一步的研究方向做出了展望。     

东钱湖水体异养细菌的时空分布及其与环境影响因素和有机质的关系

为探究宁波东钱湖表层水体中异养细菌丰度的时空分布特征及其环境影响因素对可溶性有机质转化的影响, 实验采用主成分分析及多元逐步回归分析方法研究了三者之间的关系, 结果表明: 调查期间东钱湖表层水体中异养细菌丰度的季节分布特征为夏季>春季>冬季, 支流汇入口、码头或水上乐园区域水体中异养细菌丰度较高, 近岸人类活动带来的陆源污染是造成此分布特征的主要原因; 多元统计分析结果表明ST、DO、COD、Chla、DOM是制约宁波东钱湖表层水体中异养细菌分布的主要环境因素, 且ST、Chla、COD、DOM中的类芳香族蛋白质Ⅰ及类溶解性微生物代谢产物IV与异养细菌丰度呈显著正相关(p<0.05), DO与异养细菌丰度呈极显著负相关(p<0.01); 异养细菌等微生物的代谢转化活动和陆源输入共同决定DOM的来源和转化, 但异养细菌对DOM具体的驱动转化机制有待于进一步的研究。     

甲烷单加氧酶的催化性能和活性中心结构

甲烷单加氧酶是甲烷利用细菌代谢甲烷过程中的重要酶系,它能够催化烷烃羟基化和烯烃环氧化反应;还能催化降解氯代烃类,可用于环境中氯代烃类化合物污染的治理,是具有广泛应用前景的生物催化剂．甲烷单加氧酶是含有μ－氧桥双核铁催化活性中心的蛋白,它的研究对分子氧的活化、化学催化剂的设计具有重要意义．文章介绍了甲烷单加氧酶催化性能和机理的最新研究进展．     

Use of heterotrophic CO2 assimilation as a measure of metabolic activity in planktonic and sessile bacteria

We have examined whether assimilation of CO2 can be used as a measure of metabolic activity in planktonic and sessile heterotrophic bacteria. CO2 assimilation by environmental samples and pure cultures of heterotrophic bacteria was studied using 14CO2 and 13CO2 as tracers. Heterotrophic growth on complex organic substrates resulted in assimilation of CO2 into cell biomass by activated sludge, drinking water biofilm, and pure cultures of Escherichia coli ATCC 25922, Es. coli ATCC 13706, Rhodococcus ruber, Burkholderia sp., Bacillus circulans, Pseudomonas putida, Pseudomonas stutzeri, and Pseudomonas aeruginosa. Analysis of 13C-labelled phospholipid fatty acids (PLFAs) confirmed that heterotrophic bacteria may assimilate 13CO2 into cell macromolecules such as membrane lipids. All major PLFAs extracted from activated sludge and drinking water biofilm samples were enriched in 13C after incubation with CO2. Between 1.4% and 6.5% of the biomass produced by cultures of P. putida and a drinking water biofilm during growth in complex media was apparently derived from assimilation of CO2. Resting cells assimilated less CO2 compared to actively growing cells, and CO2 assimilation activity correlated with the amount of biomass produced during heterotrophic growth. The 14CO2 assimilation assay was evaluated as a tool to examine inhibitory effects of biocides on planktonic and sessile heterotrophs (biofilms). On the basis of 14CO2 assimilation activity, the minimum inhibitory concentration (MIC) of benzalkonium chloride was estimated to 21.1 and 127.2 mg l(-1) for planktonic and biofilm samples, respectively. The results indicate that assimilation of isotopically labelled CO2 can be used as a relatively simple measure of metabolic activity in heterotrophic bacteria. CO2 assimilation assays may be used to study the effects of antimicrobial agents on growth and survival of planktonic and sessile heterotrophic organisms.     

Growth of Chlorinated Solvent‐Degrading Consortia in Fed‐Batch Bioreactors and Development of a Double‐Substrate High‐Performing Microbial Inoculum

The long‐term growth process of two microbial consortia effective in the aerobic cometabolic biodegradation of a mixture of 6‐chlorinated aliphatic hydrocarbons (CAHs), the effectiveness of these consortia as inocula for the bio‐augmentation of different types of microcosms and the development of a double‐substrate, high‐performing consortium is presented. The propane‐utilizing consortium generally proved to be the most effective one, being able to biodegrade vinyl chloride, cis‐ and trans‐1,2‐dichloroethylene, trichloroethylene, 1,1,2‐trichloroethane and 1,1,2,2‐tetrachloroethane at all the CAH concentrations tested (0–4 μM). Both consortia maintained unaltered CAH degradation capacities over a 300‐day growth period in the absence of the CAHs and were effective in inducing the rapid onset of CAH depletion upon inoculation in slurry microcosms set up with five types of aquifer materials. A consortium supplied with both methane and propane combined the best degradation capacities of the two single‐substrate consortia, and maintained stable performances for 150 days under slurry conditions. The degree of conversion of the organic Cl to chloride ions was equal to 90 %.     

Kinetic and inhibition studies for the aerobic cometabolism of 1,1,1-trichloroethane, 1,1-dichloroethylene,and 1,1-dichloroethane by a butane-grown mixed culture

Batch kinetic and inhibition studies were performed for the aerobic cometabolism of 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethylene (1,1-DCE), and 1,1-dichloroethane (1,1-DCA) by a butane-grown mixed culture. These chlorinated aliphatic hydrocarbons (CAHs) are often found together as cocontaminants in groundwater. The maximum degradation rates (k(max)) and half-saturation coefficients (K(s)) were determined in single compound kinetic tests. The highest k(max) was obtained for butane (2.6 micromol/mg TSS/h) followed by 1,1-DCE (1.3 micromol/mg TSS/h), 1,1-DCA (0.49 micromol/mg TSS/h), and 1,1,1-TCA (0.19 micromol/mg TSS/h), while the order of K(s) from the highest to lowest was 1,1-DCA (19 microM), butane (19 microM), 1,1,1-TCA (12 microM) and 1,1-DCE (1.5 microM). The inhibition types were determined using direct linear plots, while inhibition coefficients (K(ic) and K(iu)) were estimated by nonlinear least squares regression (NLSR) fits to the kinetic model of the identified inhibition type. Two different inhibition types were observed among the compounds. Competitive inhibition among CAHs was indicated from direct linear plots, and the CAHs also competitively inhibited butane utilization. 1,1-DCE was a stronger inhibitor than the other CAHs. Mixed inhibition of 1,1,1-TCA, 1,1-DCA, and 1,1-DCE transformations by butane was observed. Thus, both competitive and mixed inhibitions are important in cometabolism of CAHs by this butane culture. For competitive inhibition between CAHs, the ratio of the K(s) values was a reasonable indicator of competitive inhibition observed. Butane was a strong inhibitor of CAH transformation, having a much lower inhibition coefficient than the K(s) value of butane, while the CAHs were weak inhibitors of butane utilization. Model simulations of reactor systems where both the growth substrate and the CAHs are present indicate that reactor performance is significantly affected by inhibition type and inhibition coefficients. Thus, determining inhibition type and measuring inhibition coefficients is important in designing CAH treatment systems.     

Differences of heterotrophic 13CO2 assimilation by Pseudomonas knackmussii strain B13 and Rhodococcus opacus 1CP and potential impact on biomarker stable isotope probing

Motivated by the finding that Pseudomonas knackmussii B13 but not Rhodococcus opacus 1CP grows in the absence of externally provided CO(2), we investigated the assimilation of (13)CO(2) into active cells cultivated with non-labelled glucose as sole energy substrate. (13)C found in the bulk biomass indicated a substantial but different CO(2) assimilation by Pseudomonas and Rhodococcus, respectively (3500 per thousand and 2600 per thousand). Cellular fatty acids were labelled from -15 per thousand to 470 per thousand and amino acids from 500 per thousand to 24,000 per thousand demonstrating clear differences between various compound classes. 'You are what you eat plus 1 per thousand' is therefore only valid for the average bulk C without specific isotope signature deviation of the external CO(2) or carbonates. Odd-numbered and 10-methyl fatty acids, which are much more abundant in Rhodococcus or other Gram-positive bacteria, were up to fivefold higher enriched in (13)C relative to the Pseudomonas fatty acids. A high-level growth-phase-independent, labelling of the oxaloacetate-derived amino acids indicated heterotrophic CO(2) fixation by anaplerotic reactions known to replenish the tricarboxylic acid cycle. Although both strains assimilate CO(2) via similar general pathways, Rhodococcus depends to a much higher extent on carboxylations reactions with external CO(2) owing to the formation of odd-numbered fatty acids. As a general consequence, heterotrophic fixation of CO(2) should be taken into account in investigations of degradation experiments using isotope tracer compounds.     

Interactions between photoautotrophic and heterotrophic metabolism in photoheterotrophic cultures of Euglena gracilis

Interactions between photoautotrophic and heterotrophic metabolism in photoheterotrophic culture of Euglena gracilis were studied. Under a low light supply coefficient, these two metabolic activities seem to proceed independently. The cell growth rate in photoheterotrophic culture was about the sum of the growth rates in pure photoautotrophic and heterotrophic cultures. However under a high light supply coefficient, both photoautotrophic and heterotrophic (glucose assimilation) metabolic activities were inhibited, resulting in a low photoheterotrophic growth rate. The photoheterotrophic culture was more sensitive to photoinhibition compared to the pure photoautotrophic culture. Inhibition of glucose assimilation in the photoheterotrophic culture was due to both direct and indirect (through photosynthesis) effects of high light intensity. Cell growth, glucose assimilation and alpha-tocopherol content of the cells were higher when ambient air was used for aeration than when a mixture of carbon dioxide and air was used. Even when photosynthesis was inhibited by addition of 3-(3,4-dichlorophenyl)- 1,1-dimethylurea to photoheterotrophic culture, light stimulated alpha-tocopherol synthesis by E. gracilis.     

Synthèse et dégradation des composés glucidiques au sein de la communauté planctonique en zone marine eutrophe

A general study on the relations between “phytoplanktonic excretion” and “heterotrophic assimilation” has been carried out in eutrophic systems, natural or artificial. In the complex systems of these relations, two types of heterotrophic responses were obtained according to prevailing algal species. High heterotrophic potentials in NW African upwelling show the role of microorganisms in the disappearance of freshly excreted organic substances and in the composition of the remaining organic matter.     

Theoretical evaluation of necessity of carbon dioxide assimilation by microorganisms during growth on various substrates

The biological role of exogenous carbon dioxide during substrate assimilation with a various degree of reductivity is evaluated. The investigation of metabolic pathways of carbon dioxide incorporation into the metabolic processes of methaneoxidizing bacteria shows that the HCO3- ion assimilation is catalyzed by phosphoenolpyruvate carboxylase and in certain strains also by the key enzyme of autotrophic pathway of the carbon dioxide assimilation, ribulose-1,5-diphosphate carboxylase. The theoretical calculations and experimental studies indicate that exogenous carbon dioxide is a necessary participant of the metabolic processes of methane or methanol assimilation. It is also an acceptor of the excess electrons of these compounds. It is the degree of reductivity of the substrate metabolized that determines the activity of the exogenous carbon dioxide fixation by microorganisms. The carbon dioxide fixation by heterotrophic microorganisms must be considered, therefore, as a process which is mostly due to the elementary composition of the source of carbon under conversion.     

Number of bacteria and features of their activity in hypersaline reservoirs of the Crimea

The incidence of bacteria, their biomass production, and heterotrophic assimilation of CO2 by bacterioplankton were studied in the Crimean hypersaline water reservoirs from May to October of 1974. The total incidence of bacteria in the natural brine of these reservoirs varied from 20 to 70 x 10(6) cells per 1 ml. Such a high bacterial number may be caused by the combined action of water evaporation which increased the concentration of bacterial cells and active growth of microflora. Low values of bacterial production and heterotrophic CO2 assimilation should be attributed to weak activity of microflora in the reservoirs.     

Utilization of light for the assimilation of organic matter in Chlorella sp. VJ79

Chlorella sp. strain VJ79 was isolated from a total heterotrophic count of a wastewater collector. It grows autotrophically, heterotrophically, and mixotrophically on a variety of organic substrates. Glucose and serine promote a mixotrophic growth from which the yield is higher than the sum of autotrophic and heterotrophic yields, but serine assimilation requires light. The interaction of glucose and light was studied in proliferating and nonproliferating cells by respirometry (IRGA and Warburg) and growth experiments. Glucose inhibits the photosynthetic CO(2) fixation ten-fold and modifies the pigmentary system as it does in heterotrophic cultures. Light inhibits glucose uptake and assimilation, but under mixotrophic conditions maximal utilization of glucose is obtained. Mutants defective in autotrophic growth were isolated by mutagenesis with nitrosoguanidine. They show a degenerated pigmentary system and a mixotrophic growth yield equal to that of the heterotrophic growth. The analysis of the mixotrophic system shows that light energy, dissipated during autotrophic growth, is used under mixotrophic conditions. From the increase in growth, the increase in photosynthetic efficiency can be calculated as ca. sixfold.