乙草胺降解菌株Rhodococcus sp.AC-1的分离及降解特性研究

为解决乙草胺残留问题,采用连续传代富集培养的方法,从长期生产乙草胺的农药厂污染土壤中分离筛选到1株乙草胺降解菌株AC-1。经过形态学特征、生理生化特征和16S rRNA基因序列系统发育分析,菌株AC-1被鉴定为红球菌属(Rhodococcus)。菌株AC-1在48h内能将0.2 m M的乙草胺完全降解,但不能矿化乙草胺。借助LC-MS,确定乙草胺降解终产物为2-氯-N-(2-乙基-6-甲基苯基)乙酰胺(CMEPA)。菌株AC-1降解乙草胺的最适温度为30℃,最适p H值为7.5。0.1 m M的Cu2+和Hg2+对菌株AC-1降解乙草胺具有很强的抑制作用,而0.1 m M的Fe2+则对菌株AC-1降解乙草胺具有微弱的促进作用。菌株AC-1对乙草胺的降解效果与起始接种量呈正相关。菌株AC-1对甲草胺和丁草胺表现出良好的降解效果,但对异丙甲草胺的降解能力非常微弱。土壤降解试验表明,投加菌株AC-1可以明显促进土壤中乙草胺的降解。本研究为乙草胺的有效降解提供了数据和技术支持。     

一株乙草胺降解菌株M-3的分离鉴定及其代谢途径的初步研究

乙草胺是一种广谱、高效的酰胺类除草剂,由于乙草胺具有较长的降解周期,还有不易挥发、不易光解、易残留的特点,如果过量、频繁使用,对人、动植物均有一定的毒害作用。为了探讨乙草胺的微生物降解机理,本研究从长期受乙草胺污染的土壤中分离到一株能降解乙草胺的菌株M-3,该菌株能以乙草胺为唯一碳源生长。通过菌落表型、生理生化特征和菌株16SrRNA基因序列的相似性分析,将其鉴定为寡养单胞菌属(Stenotrophomonas sp.)。在室内条件下,运用HPLC和HPLC-MS分析方法,研究了菌株M-3对乙草胺的降解特性,并对其代谢途径做了初步的研究。结果表明,菌株M-3在5d内对浓度为50mg/L的乙草胺的降解率可达76.6%。M-3降解乙草胺的最适温度和最适pH值分别为30℃和7.0。在对代谢产物结果进行分析的基础上推测了M-3降解乙草胺的途径,将产物鉴定为2-乙基-6-甲基-2-氯乙酰苯胺。该研究为乙草胺污染的生物修复提供了理论依据。     

邻苯二甲酸二丁酯DBP降解菌S-3的分离、鉴定及其代谢途径的初步研究

邻苯二甲酸二丁酯(DBP)是一种重要的增塑剂,广泛用于塑料、橡胶和涂料等的合成,但它并非与树脂共价连接,从而很容易扩散到环境中造成污染。为了获得一株DBP高效降解菌,本研究从长期受垃圾污染的土壤中分离到一株能以DBP为唯一碳源生长的菌株S-3。通过菌落表型、生理生化特征和菌株16S rRNA基因序列的相似性分析(测序后GenBank登录号:No.KF377815),将其鉴定为类芽胞杆菌属(Paenibacillus sp.)。在室内条件下,运用HPLC和HPLC-MS分析方法,研究了菌株S-3对DBP的降解特性,并对其代谢途径做了初步的研究。结果表明,菌株S-3在5 d内对浓度为100 mg/L DBP的降解率可达82.7%。S-3降解DBP的最适温度和最适pH值分别为30℃和7.0。在对代谢产物结果进行分析的基础上推测了S-3降解DBP的代谢途径,将产物鉴定为邻苯二甲酸。该研究为DBP污染的生物修复提供了理论依据。     

乙草胺降解菌Y-4的分离鉴定及降解特性研究

从长期经乙草胺污染的污泥中分离到一株能以乙草胺为唯一碳源和能源生长的菌株Y-4,通过生理生化实验和16S rDNA同源性序列分析,鉴定为申氏杆菌属（Shinella sp.）。采用室内培养方法,研究了Y-4对乙草胺的降解特性。结果表明,Y-4能有效地降解浓度为5～200 mg.L-1的乙草胺,在48 h内对50 mg.L-1乙草胺的降解率达到83.3%。菌株Y-4降解乙草胺的最适pH值为8.0,最适温度为30℃,其对丙草胺和丁草胺等农药也有良好的降解效果。     

三种农用抗生素降解真菌的筛选及其降解性能

为了从重金属污染的土壤中分离筛选出能降解土霉素、诺氟沙星、磺胺二甲嘧啶的真菌菌株,利用抗生素作为唯一碳源进行抗生素降解真菌富集驯化培养,分离纯化耐受真菌,将纯化后的菌株回接到以抗生素作为唯一碳源的液体培养基中,运用高效液相色谱法(HPLC)及紫外分光光度法对各菌株抗生素降解能力进行检测,并通过菌落形态学特征、ITS序列和系统发育树对菌株进行分子鉴定。筛选到4株抗生素降解真菌KS248、KS256、KS257、KS272,分别鉴定为轮状镰刀菌(Fusarium verticillioides)、腐皮镰刀菌(Fusarium solani)、聚多曲霉(Aspergillus sydowii)、微紫青霉(Penicillium janthinellum)。其中,菌株KS248、KS256、KS257具有土霉素、诺氟沙星、磺胺二甲嘧啶降解能力;菌株KS272具有土霉素、诺氟沙星降解能力。在抗生素初始浓度1500μg·L~(-1)、30℃、150 r·min~(-1)条件下避光培养7 d后,菌株KS272降解土霉素、诺氟沙星能力最强,降解率分别达到40.29%、10.59%,菌株KS256降解磺胺二甲嘧啶能力最强,降解率达到18.53%。筛选出的菌株均具有2种及以上抗生素降解能力,对抗生素的降解率从高到低依次为土霉素、诺氟沙星、磺胺二甲嘧啶,且随着抗生素浓度增加,菌株对各抗生素降解能力有不同程度的削弱。     

Cry1Ac蛋白降解菌株FJSB3的分离鉴定及降解特性

从转Cry1Ac基因水稻种植田土壤中,分离纯化得到1株能高效降解Cry1Ac蛋白的细菌FJSB3。通过表型特征、16S rDNA扩增和电镜观察,初步鉴定FJSB3为寡养单胞菌（Stenotrophomonas sp.）。FJSB3发酵液能降解粗Bt蛋白。通过单因素试验确定FJSB3降解水稻秸秆中Cry1Ac蛋白的最适条...     

一株红霉素降解菌红圆酵母的选育及其降解特性

选取长期堆放红霉素药渣的土壤,经驯化富集后筛选到1株能高效降解红霉素的菌株,根据表型特征、生理生化特性及18S rDNA序列同源性分析,鉴定为红酵母属的粘性红圆酵母（Rhodotorula mucilaginosa）。该菌的18S rDNA序列片段长度为1 562 bp,在GenBank登录号为EU294522。该菌可以利用红霉素作为碳源生长,适用碳源与氮源分别为蔗糖和NH4Cl。该菌降解红霉素的最适温度为30 ℃,最适pH 5.0～5.5,最适接菌量6%,降解率与通气量成正相关。在最适反应条件下培养48 h, 该菌株对红霉素的降解率可达100%。     

沼灌土壤17β-雌二醇专性降解菌的分离筛选及降解特性

集约化畜禽养殖场产生的沼液通常就地回用,在循环利用有机物的同时也会带来类固醇雌激素（Steroid Estrogens,SEs）的累积及污染。为降低沼灌后SEs对水土环境的污染风险,该研究采用富集和纯化培养法,对西南地区某奶牛养殖场沼灌区土壤中雌激素降解菌进行分离及筛选,获得一株利用17β-雌二醇（17β-E2）为唯一碳源生长繁殖的降解菌。通过16S rDNA 基因序列进行同源性比对以确定种属,并研究其降解特性。分别研究了菌株在不同温度、pH值、底物浓度三种单因素条件下的降解特性,然后利用三因素三水平正交试验继续优化菌株最适降解条件。结果表明：分离出的优势菌为生丝微菌属（Hyphomicrobium sp.）,命名为Hyphomicrobium sp.SS-1,该菌株在10～40 ℃、pH值为5～9、底物浓度为1～10 mg/L的条件下,均能不同程度降解17β-E2。其中菌株在温度为30 ℃、pH值为7、底物浓度5 mg/L的条件下,培养7 d对17β-E2的降解率可达71%,并伴随毒性低于E2的降解产物E1和E3生成,总雌激素去除率为56.8%。正交试验结果显示,各因素对菌株降解能力的影响顺序从小到大为：底物浓度、温度、pH值,且都为显著影响（P<0.05）;菌株最适降解条件为温度35 ℃、pH值为7、底物浓度5 mg/L,该条件下培养7 d,菌株对17β-E2的降解率可达97.09%。研究结果可为复杂基质环境中微生物降解SEs提供优质菌种资源,并为沼液灌溉区土壤的雌激素污染修复提供有效途径。     

耐镉邻苯二甲酸二辛酯降解菌的筛选及特性研究

为获得既耐受重金属镉又能高效降解邻苯二甲酸二辛酯(DOP)的微生物菌株,利用选择培养基从污染土壤中分离高效降解微生物,并对其菌种分类和降解特性进行分析。共筛选获得5株耐镉的DOP降解菌株,其中PD-2对DOP的降解效率最高,120 h后降解率可达93.1%。结合形态学特征和16S rDNA序列分析,鉴定该菌为生丝微菌属(Hyphomicrobium sp.)。菌株PD-2对液体培养基中DOP的降解依赖于其生物量的增加,其对DOP的作用浓度和耐镉浓度范围广,可高效降解100～800 mg·L~(-1)范围的DOP(降解率大于80%),并在镉浓度0～600 mg·L~(-1)的培养基中生长良好。PD-2可利用邻苯二甲酸二甲酯(DMP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二(2-乙基己基)酯(DEHP)、邻苯二甲酸二辛酯(DOP)和邻苯二甲酸(PA)作为底物生长,底物种类范围广。添加PD-2到镉和DOP复合污染土壤中,其对DOP具有显著的降解作用,PD-2在镉和DOP复合污染土壤的修复方面具有潜在的应用价值。     

一株阿苯达唑降解菌株ZS-1的分离鉴定与降解特性研究

阿苯达唑(albendazole)类药物是一种广谱抗蠕虫药物,在水产养殖上有重要作用,但大量使用直接进入水体,并通过食物链富集影响人体健康.为了获得一株阿苯达唑高效降解菌,本研究从长期施用阿苯达唑药物的水体中分离到一株能以阿苯达唑为唯一碳源生长的菌株ZS-1,通过菌落表型、生理生化特征和菌株16S rRNA基因序列的相似性分析(测序后GenBank登录号:No.KC763472),将其鉴定为红球菌属(Rhodococcus sp.).ZS-1对阿苯达唑的降解特性表明,在以阿苯达唑为唯一碳源的无机盐培养基中,该菌株能有效地降解100 mg/L的阿苯达唑,3d内对50 mg/L阿苯达唑的降解率高达90.6％.菌株ZS-1降解阿苯达唑的最适pH值和温度分别为7.0和30℃,Cu2+对ZS-1降解阿苯达唑有一定的抑制作用.该研究为阿苯达唑污染水体的生物修复提供了理论依据.     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.