鸡大肠杆菌质粒指纹图谱及某些生物学特性的研究

用广西分离的鸡大肠杆菌(E.coli)11种血清型的代表菌株进行研究。结果表明:鸡E.coli的致病性与血清型、菌毛及大肠杆菌素(colicin)的产生有关;与细菌的抗药性关系不大;鸡E.coli不产不耐热肠毒素(LT)及耐热肠毒素(ST);鸡E.coli的血凝特性及盐凝特性与其菌毛的产生有关;来源及血清型相同的菌株才具有完全相同或基本相同的质粒指纹图谱(PP)和酶切图谱;质粒分布与血清型及菌毛的产生无明显关系,与colicin的产生及抗约性有较密切的关系。结果还表明,鸡E.coil与其它人畜致病性E.coli有显著的区别。并对此作了进一步的讨论。     

禽大肠杆菌菌毛产生的特性及免疫原性研究

用电镜检查广西分离的鸡致病性大肠杆菌 O_(60),O_(7)和 O_(8)菌株,在37℃和43℃培养均可见到菌毛,低于28℃不产生菌毛。用营养肉汤,Minca 培养液或最低限量培养液培养,冰浴高速磁力搅拌和MgCl_2反复沉淀提取,可得到较纯的菌毛。经测定,O_(60),O_(7)和 O_(8)菌毛蛋白分子量分别是15500,17500和17800。1日龄雏鸡用 O_(60)菌毛亚单位油乳苗皮下注射和菌毛悬浮液气雾免疫,均可保护鸡免受大肠杆菌对气囊的攻击。O_(60),O_(7)和 O_(8)菌株菌毛之间缺乏显著的交互保护。雏鸡在1日龄和10日龄用 O_(60),O_(7)和 O_(8)多价菌毛油乳苗免疫,21日攻毒时,可抵抗3种菌株侵袭气囊造成的急性呼吸道感染。     

我国部分地区奶牛乳房炎源大肠杆菌生物学特性及耐药性分析

调查奶牛乳房炎源大肠杆菌的某些生物学特性及其耐药状况,以提高药物疗效,减少牛乳中药物的残留。本研究从国内7个省、市、自治区部分地区患乳房炎奶牛的乳样中分离纯化与鉴定出95株大肠杆菌(Escherichia coli),并对大肠杆菌分离株进行O血清型鉴定、小鼠(Mus musculus)致病性试验以及抗菌药物敏感性分析。研究结果显示,95株大肠杆菌共鉴定出37种血清型,覆盖了54株分离株,另有2株自凝,39株未鉴定出型,较常见血清型为093和09;大肠杆菌分离株接种小白鼠剖检可见明显病变;95株大肠杆菌对16种抗菌药物中的8种药物耐药率超过50%,青霉素的耐药率甚至达到100%,同一菌株最多耐药14种,最少耐药2种,耐药6种以上菌株占到51.58%。表明,奶牛乳房炎源大肠杆菌分离株血清型比较复杂,且对多种药物产生不同程度的耐药性,存在着严重的多重耐药情况。本研究为奶牛乳房炎疫苗的研制和乳房炎的临床治疗提供理论依据。     

鸡大肠杆菌菌苗免疫原性的研究

用不同的时间和温度培养鸡致病性Ｅ．ｃｌｏｉ，４１℃，４８ｈ和３７℃，７２ｈ均可见众多的菌毛，而在４１℃，４８ｈ的条件下，活菌数及菌毛产量均高于３７℃，７２ｈ的。用提取的菌毛、超声波灭活的Ｅ．ｃｏｌｉ制成油乳苗免疫鸡，用同型Ｏ５０菌株经后胸气囊攻毒后，免疫鸡无死亡，而氢氧化铝胶菌苗免疫组的死亡率为２０％，未免疫攻毒组死亡率为３３．３％。各免疫组幸存鸡平均病变级数均显著低于未免疫攻毒组（Ｐ＜０．０１）。Ｅ．ｃｏｌｉ的菌毛剂量为１２０μｇ／只和８０μｇ／只的油乳苗免疫组，在免疫后用同型Ｏ５０菌株攻击时，保护指数最高；当剂量为６０μｇ／只时，保护指数较高；而用３０μｇ／只的剂量免疫时，免疫无效。雏鸡经含菌毛、不含菌毛的Ｅ．ｃｏｌｉ超声波灭活油乳苗和福尔马林灭活油乳苗免疫后用同型Ｏ５０菌株攻毒，含菌毛菌苗的保护指数均高于相应的不含菌毛菌苗的；超声波灭活菌体的油乳苗免疫组幸存鸡平均病变级数低于福尔马林灭活菌体的油乳苗免疫组的；各免疫组与未免疫攻毒组幸存鸡平均病变级数差异极显著（Ｐ＜０．０１）。     

近年来大肠杆菌K88ac菌毛的变异和生物学特性

2000~2005年，从猪大肠杆菌病 (colibacillosis)中分离到一些表达K88菌毛的大肠杆菌(Escherichia coli )，这些分离株只与K88 a因子单抗反应，而不与K88 b、c和d因子单抗反应。分离的菌株 (13/16)以O149为常见血清型，且全部拥有STb毒素基因，通过K88常规血清交叉吸收试验、SDS-PAGE和Western印迹，表明这些菌株不仅与K88ac参考菌株C83907制备的c因子血清反应，而且与以分离株SEC586制备且经K88ab、K88ac和K88ad参考菌株吸收后的血清也反应，表明这些分离株仍为K88ac大肠杆菌。对新近分离的SEC464、SEC525、SEC586、SEC799和EC910株及80年代我国分离的TM128株的K88主要亚单位结构基因faeG进行克隆、测序，发现新近分离株的faeG基因由846对核苷酸组成，编码菌毛主要亚单位的261个氨基酸及21个氨基酸的信号肽，比国内外报道的K88ac FaeG亚单位 (262个氨基酸)少了一个氨基酸，比K88ab、K88ad (264个氨基酸)少了3个氨基酸。TM128株的FaeG氨基酸序列与K88ac(M29375)的同源性为100.0%，SEC464、SEC525、SEC586、SEC799和SEC910株的FaeG亚单位氨基酸序列的同源性为97.7%~99.6%，它们与K88ac的同源性为94.6%~96.6%；与K88ab的同源性为90.0%~91.6%；与K88ad的同源性为87.0%~88.9%。 结果表明新分离的K88ac大肠杆菌黏附素主要亚单位已发生了部分变异。     

西瓜噬酸菌Ⅳ型菌毛相关基因pilO及pilQ的功能分析

瓜类细菌性果斑病是发生在葫芦科植物上的一种病害,其病原为噬酸菌属西瓜种(Acidovorax citrulli),自报道以来已给美国、澳大利亚、巴西、中国等众多国家的瓜类作物种植业造成了严重的损失。要从根本上防治瓜类细菌性果斑病,我们应弄清其致病机制。本实验对西瓜噬酸菌(A.citrulli)中部分Ⅳ型菌毛(pili)相关基因构建插入突变体,用浸种测定法筛选出两株致病力和发病率明显减弱的突变体,鉴定为pilO及pilQ基因突变体,并对这两株突变体的相关表型进行测定。在透射电子显微镜下观测发现,野生型及pilO基因突变体仍然能够形成Ⅳ型菌毛,而pilQ基因突变体丧失形成Ⅳ型菌毛的能力;光学显微镜下观测野生型、突变体及互补菌株的颤动能力发现,pilO及pilQ基因突变体与野生型相比,完全丧失颤动能力;同时pilO及pilQ基因突变体游动能力、生物膜形成能力也明显减弱。互补菌株中,颤动能力得到恢复,致病力、游动能力以及生物膜形成能力部分恢复。在MMX基本培养基中测定野生型与突变体的生长曲线发现,突变体菌株生长能力无明显改变;同时突变体也能激发非寄主植物烟草(Nicotiana tabacum)的过敏性反应。pilO基因突变体仍然能够形成Ⅳ型菌毛但丧失部分Ⅳ型菌毛介导的功能,由此表明,pilO基因并不直接参与西瓜噬酸菌Ⅳ型菌毛的合成,而是Ⅳ型菌毛的功能基因;pilQ基因突变体不能形成Ⅳ型菌毛且丧失其介导的部分功能表明,pilQ基因在西瓜噬酸菌中直接参与Ⅳ型菌毛的合成,是Ⅳ型菌毛的合成及功能基因。同时也进一步证明西瓜噬酸菌Ⅳ型菌毛与其颤动性、致病性、游动性及生物膜形成能力相关。     

禽多杀性巴氏杆菌和大肠杆菌二联灭活油乳剂疫苗免疫保护试验

用禽多杀性巴氏杆菌和大肠杆菌本地分离菌株,分别液体培养、灭活,按一定比例混合,加入油佐剂制成二联灭活油乳剂疫苗。以0．5mL／只、1．0mL／只两个剂量分别肌肉注射免疫2月龄非免鸡30只,同条件设非免疫对照组8只,免疫后21d用两种分离菌株分别攻毒及两种菌混合攻毒。试验结果显示,对禽多杀性巴氏杆菌的保护率为80％,对大肠杆菌病的保护率为100％,对两种菌混合攻毒的保护率为80％。本试验结果说明研制的二联灭活油乳剂疫苗安全有效。     

水稻种子相关细菌的系统发育分析与促生能力评价

对15株分离自水稻冀粳14号(90-3)的种子表面及其内生细菌进行了多功能筛选评价和16S rRNA系统发育分析.结果表明,供试菌株都能够溶解无机磷,不能分解有机磷;筛选获得6株具有明显分泌植物生长素吲哚-3-乙酸(IAA)能力的菌株;12株菌株明显产生铁载体,占所测菌株总数的80％,其中7株铁载体产量达到中等水平,通...     

鸡源沙门氏菌的血清型、耐药性和耐药机制调查

沙门氏菌(Salmonella)是一种重要的食源性致病菌,为了解不同地区鸡源沙门氏菌的血清型、耐药性和耐药机制,本研究对从北京和陕西地区分离的110株鸡(Gallus domesticus)源沙门氏菌进行了分析。血清型结果表明,沙门氏菌流行株为肠炎沙门氏菌(S.enteritidis),占76.58%。微量肉汤稀释法检测110株沙门氏菌对13种抗菌药物的耐药性,结果显示对多粘菌素E的耐药性最强,耐药率为41.82%,其次依次为磺胺异噁唑(31.82%)、氨苄西林(29.09%)和多西环素(20.91%),对其余9种药物的耐药率均低于20%。耐药机制研究结果表明,相关耐药基因在耐药菌株中的携带率较高,Ⅰ类整合子主要携带氨基糖苷类、磺胺类、林可胺类等药物的耐药基因,该整合子在沙门氏菌耐药性的传播方面具有重要作用,本研究为鸡源沙门氏菌的流行性分析以及兽医临床沙门氏菌感染的科学用药提供了基础资料。     

百色市鸭疫里默氏杆菌病的流行病学及其病原的分离与鉴定

2006年5月~2007年3月间,对百色市所辖12个县(区)的86个养鸭场(户)多个品种的鸭群进行鸭疫里默氏杆菌(R iem erella ana tip estif er,RA)病发生和流行情况的调查。结果从186羽具有浆膜炎病变的死鸭及其同群病鸭的肝和脑中分离到62株RA可疑菌株,通过生化试验证明它们基本符合RA的特征;应用建立的PCR技术均可从这些菌株扩增到RA的特异性基因片断;通过与阳性血清所做的玻片凝集试验证明,分离出的RA菌株全部属于血清1型;在鸭疫里默氏杆菌阳性病料中,RA单一感染的占25.81%(16/62)、RA与大肠杆菌混合感染率56.45%(35/62)、RA与沙门氏杆菌混合感染率17.74%(11/62);病例中大肠杆菌单独感染占6.99%(13/186);2~5周龄雏鸭最易感染,北京鸭最易感染;药敏试验表明,大多数RA分离株对头孢类药物表现高敏,但总体上耐药性比较严重;分离株的致病性试验结果显示,RA的致病力比较强,与大肠杆菌的混合感染的致病力更强。本研究证明鸭疫里默氏杆菌病已成为百色肉鸭养殖业最常见的、危害最大的传染病之一。     

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.