玉兰盐胁迫下qRT-PCR分析中内参基因的筛选

选择合适的内参基因可以提高q RT-PCR分析相关基因表达的准确性。本研究以玉兰(Magnolia denudata)实生苗在盐胁迫下的根、茎、叶为材料,选取常用的13个内参基因:肌动蛋白(actin,ACTIN)、亲环蛋白(cyclophilin,CYP)、延伸因子1α蛋白(elongationfactors-1α,EF-1α)、甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphat dehydrogenase,GAPDH)、GTP结合蛋白(GTP binding protein,GBP)、NAC域蛋白(NAC domain protein,NAC)、异柠檬酸脱氢酶(NADP-isocitrate dehydrogenase,NADP)、翻译延伸因子(translation elongation factors,TEF)、泛素化酶基因(ubiquitin-conjugating enzyme,UBC)、多聚泛素蛋白(polyubiquitin protein,UBQ)、微管蛋白(α-tubulin alphaα,α-TUB)、β微管蛋白(tubulin beta,β-TUB)、18S核糖体RNA(18S ribosomal RNA,18S)作为候选内参基因,设计引物,通过普通PCR和溶解曲线验证引物特异性;结合ge Norm、Norm Finder和Best Keeper软件分析筛选最佳内参基因,进一步通过2个目的基因:纤维素合成酶类似蛋白D(cellulose synthase-like D,CSLD)和1,4-β-d-葡聚糖酶(endo-1,4-beta-d-glucanase,KOR)对筛选得到的内参基因进行验证。结果显示,13个内参基因PCR产物条带清晰单一,引物扩增效率均在95%到105%之间,且溶解曲线呈现明显的单一峰,表明引物特异性良好;3个内参软件ge Norm、Norm Finder和Best Keeper综合分析得到稳定性排名前3的内参基因为GBP、UBQ和UBC,而18S为最差的内参基因。进一步选取GBP、UBQ、UBC 3个基因的组合以及稳定性差的18S和GAPDH基因,对不同组织中的CSLD和KOR基因进行相对表达分析,结果表明,两个目的基因相对于3个稳定的内参基因及其组合显示出一致的相对表达量,而不稳定的内参基因18S和GAPDH没有对表达数据进行有效的标准化,结果存在偏差。由此可见,GBP、UBQ和UBC可以作为玉兰盐胁迫下不同组织器官中表达的稳定内参。本研究结果将为木兰属植物在逆境中相关目的基因的定量表达研究提供重要的参考依据。     

毛竹qRT-PCR分析中内参基因的选择

实时荧光定量PCR(quantitative Real-time PCR,qRT-PCR)是目前研究基因表达的常用方法,而在特定的实验材料及条件下选择合适的内参基因是准确分析目标基因相对表达量的首要条件。本研究以毛竹(Phyllostachys edulis)的根、茎、叶和笋等器官和组织为实验材料,通过qRT-PCR技术对5种常用内参基因:甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)、肌动蛋白(actin,ACT)、热休克蛋白(heat shock protein,HSP)、18S核糖体RNA(18S ribosomal RNA,18S r RNA)和真核起始因子4α(eukaryotic initiation factor 4α,e IF-4α)在毛竹不同器官和组织中的表达情况进行了分析。经Ge Norm、Norm Finder和Best Keeper 3个软件对比分析发现,对5种常用内参基因而言,在利用qRT-PCR分析比较毛竹不同叶片之间的基因表达差异时,可选取e IF-4α作为校正内参基因;比较笋不同部位之间的基因表达差异时,可选取18S r RNA或ACT作为校正内参基因;而比较毛竹根、茎、叶不同器官组织分化中的基因表达差异时,可选取18S r RNA作为校正内参基因。而上述发现与多数文献中把ACT作为毛竹唯一内参基因的研究不一致。本研究为在毛竹qRT-PCR分析中选择合适的内参基因提供了理论依据。     

非生物胁迫下多年生黑麦草qRT-PCR分析中内参基因的选择

提高实时荧光定量PCR(Real-time quantitative PCR,q RT-PCR)准确性的先决条件是选择表达稳定性较高的内参基因。本研究以多年生黑麦草(Lolium perenne L.)为材料,利用q RT-PCR技术检测翻译起始因子4A(eukaryotic initiation factor 4 alpha,e IF4A)、TNF结合蛋白Ⅰ(Tat binding protein-1,TBP-1)、泛素连接酶(ubiquitin-conjugating enzyme,E2)、多聚泛素酶基因(ubiquitin,UBQ)、生物钟受体蛋白(zeitlupe,ZTL)和甘油醛三磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)6个候选内参基因在不同非生物胁迫下的表达情况。运用ge Norm(ver.3.5)、Normfinder(ver.0.953)、Best Keeper(ver.1.0)、Delta Ct和Ref Finder软件综合分析表明,在干旱、盐、热胁迫及ABA处理下,e IF4A基因表达稳定性最高;在涝胁迫下,UBQ基因表达稳定性最高。因此,e IF4A和UBQ候选基因可作为不同胁迫下的内参基因,为进一步开展多年生黑麦草基因表达的定量研究了提供了一定的理论依据。     

大黄鱼microRNA荧光定量PCR中内参基因的选择与评价

为筛选适用于大黄鱼miRNA研究的内参基因,选取饥饿试验组(EG)中饥饿21d及正常投喂组(CG,对照)的大黄鱼肌肉组织进行miRNA高通量测序,初步筛选得到稳定表达的6个miRNA:miR-23a-3p,miR-4508,miR-1961,miR-1297,miR-1956-3p和Let-7。采用实时荧光定量PCR法检测这6个miRNA和3个传统的内参基因(U6,5S和18S)在大黄鱼6种组织(肌肉、肝脏、肾、脾、脑和心脏)以及不同饥饿时间段的肌肉组织中的表达,并利用Ge Norm,Best Keeper以及Norm Finder对数据进行分析。结果表明,miRNA的表达稳定性优于传统内参基因。在CG组大黄鱼不同组织中,最稳定单内参基因是miR-23a-3p,最佳内参基因组合为miR-23a-3p和Let-7。在不同饥饿时间的EG组大黄鱼肌肉组织中,最稳定单内参基因是miR-23a-3p,最佳内参基因组合为Let-7和miR-1961。本试验结果为研究大黄鱼miRNA时内参基因的选择提供了参考。     

牙鲆胚胎低温处理下内参基因筛选及CIRP和Hsp70基因表达分析

牙鲆(Paralichthys olivaceus)是我国主要的海水经济养殖鱼类,在胚胎冷冻保存方面已获得了超低温冷冻保存成功的案例,但在分子水平上对牙鲆胚胎在低温状态下相关基因的表达进行研究,至今还未见报导。本研究首先收集了牙鲆的3个胚胎时期(肌节期、尾芽期和心跳期),分别在0℃及16.5℃进行处理培养,使用实时荧光定量PCR技术检测4个内参基因18S rRNA、ACTB、GAPDH及EF1α的表达水平,并用Ge Norm和Norm Finder软件对其的稳定性进行排序分析。Ge Norm软件分析结果显示,18S rRNA和EF1α的稳定性最好,稳定性最差的为GAPDH;Norm Finder软件分析结果显示,18S rRNA的稳定性最好。综合两个软件的分析结果,在不同发育时期以及低温处理的牙鲆胚胎中,18S rRNA表达量相对稳定,较其他3个基因更适合作为内参基因。为探究牙鲆胚胎在低温处理下分子水平的变化,本研究选取了对温度适应性较强的尾芽期胚胎为实验材料,分别在低温0℃和正常培养温度16.5℃下进行培养,并选取与应激反应相关的热休克蛋白基因(heat shock protein,Hsp)70和冷诱导RNA结合蛋白基因(cold-inducible RNA-binding protein,CIRP)进行表达量分析。实时荧光定量PCR的结果表明,CIRP的表达量在0℃处理30 min之内逐渐下降,在30 min时达到最低值,30~120 min内上升,并在120 min时达到峰值,之后回落,在180 min时,其表达量回落到与对照组相似的水平。而Hsp70在低温处理的前30分钟表达量下降,后回升,120 min达到最大值后回落的现象,与对照组有显著性差异(P0.05)。研究结果说明低温会导致CIRP及Hsp70基因表达水平的改变,先下降后升高再回落的趋势也说明了机体内对低温应激产生了保护反应,为探索牙鲆胚胎在低温下调节和适应的分子机理提供了一定的依据。     

铜胁迫下天蓝苜蓿根组织实时定量PCR内参基因的选择

豆科植物-根瘤菌共生体系因固氮能力卓越,肥土效应明显,常被作为先锋植物进行环境修复。利用qRT-PCR分析铜胁迫下天蓝苜蓿(Medicago lupulina L.)与根瘤菌(Sinorhizobium meliloti,CCNWSX0020)共生固氮过程中差异基因时,由于环境中铜离子差异可能使持家基因表达不稳定,因此需要筛选合适的持家基因作为内参。本研究选取8个天蓝苜蓿的持家基因(肌动蛋白(beta actin,ACT)、组蛋白(histone H2A,H2A)、核糖体蛋白18S(ribosomal 18S,18S)、微管蛋白(tubulin beta,TUB)、泛素连接酶(ubiquitin,UBI)、延伸因子1(elongation factor 1,EF1)、甘油醛-3-磷酸脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)和亲环蛋白(cyclophilin,CYP))作为候选内参基因,人工模拟不同水平铜(浓度分别为50、100、150和200 mg/kg)污染,以接种根瘤菌后30 d的天蓝苜蓿根为材料,筛选最佳内参基因。经引物特异性及PCR扩增效率检测,各候选内参基因引物均符合稳定性筛选要求。荧光定量PCR分析结果表明,8个候选内参基因的表达水平和稳定性随铜离子浓度不同而呈现差异。在线评估所有样品中候选内参基因表达稳定性,结合geNorm软件分析最佳内参基因组合数目,结果发现,最适内参基因组合为GAPDH和EF1;分别在线评估不同铜浓度处理下候选内参基因表达稳定性,结果表明,低浓度铜(≤50 mg/kg)处理下最佳内参基因为GAPDH,中高浓度铜(≥100 mg/kg)处理时最佳内参基因为UBI。本研究结果为铜胁迫下天蓝苜蓿共生结瘤过程中差异基因的表达分析提供了基础资料,同时为其他重金属胁迫下内参基因的筛选提供了参考和借鉴。     

柳枝稷根组织实时定量PCR分析中内参基因的选择

选择表达稳定性高的内参基因是提高实时荧光定量PCR分析(qRT-PCR)准确性的重要条件。本研究以能源植物柳枝稷(Panicum virgatum L.)根组织为材料,通过不同非生物条件胁迫,利用qRT-PCR技术检测UBQ1(泛素基因)、ACT2(肌动蛋白基因)、UBQ2(泛素基因)、TUB(β微管蛋白基因)、GAPDH(甘油醛-3-磷酸-脱氢酶基因)、CBP20(类胡萝卜素结合蛋白基因)、UCE2(泛素接合酶基因)、18S rRNA1(18S核糖体RNA基因)、NAC(NAC域蛋白基因)和CYP2(亲环蛋白基因)10个内参基因的mRNA的表达情况,并运用Delta-Ct method,Genorm(ver.3.5)、Bestkeeper(ver.1.0)和NormFinder(ver.0.953)软件综合分析10个内参基因的表达稳定性。结果显示,在不同的非生物环境胁迫条件下,最适合作为柳枝稷根组织研究的内参基因各不相同。10个内参基因平均表达稳定由高到低排序为:ACT2,TUB,UCE2,CBP20,CYP2,UBQ2,18S rRNA1,NAC,UBQ1,GAPDH。在干旱胁迫条件下,ACT2基因表达稳定性最高;在盐胁迫和热胁迫条件下,18S rRNA1基因表达稳定性最高;在冷胁迫和涝胁迫条件下,ACT2基因表达稳定性最高。经软件综合分析显示,ACT2、TUB和UCE2基因最适合作为柳枝稷非生物胁迫研究的内参基因;UBQ1和GAPDH基因最不合适作为内参基因。该研究结果可用于柳枝稷非生物胁迫下各种基因表达的进一步研究。     

小麦条锈菌实时荧光定量PCR分析中内参基因的选择

选择合适的内参基因是利用实时荧光定量PCR准确分析基因相对表达量的先决条件.基于现有对内参基因的研究,本研究挑选出10个基因作为小麦条锈菌(Puccinia striiformis f.sp.tritici)的候选内参基因.经过PCR扩增效率筛选,8个基因符合要求可用于稳定度的筛选,这些基因包括泛素连接酶(UBC、泛素连接酶E2(UBCE2)、核糖体蛋白SS(RPS5)、α微管蛋白(TUBA)、β肌动蛋白(ACTB)、β微管蛋白(TUBB)、延伸因子1(EF1)和延伸因子3(EF3).本研究以两种小麦条锈菌(CYR32和Pst78)的夏孢子、萌发芽管分别接种两个小麦(Triticum aestivam)品种(CYR32/XZ9104和Pst78/AvS)后0.5、3和14 d的样品为材料,利用实时荧光定量PCR技术,检测了这8个持家基因在不同发育阶段的小麦条锈菌中的表达情况.经geNorm软件分析发现,3个持家基因在样品中的表达趋势与小麦条锈菌的侵染过程相符合.ACTB、TUBB和TUBA的组合可作为检测小麦条锈菌基因表达的内参基因.     

冬瓜实时荧光定量PCR内参基因的筛选与评价

为筛选适合冬瓜稳定表达的内参基因,以黑皮冬瓜低温、高温、干旱胁迫处理不同时间的叶片和正常处理不同组织为试验材料,利用RT-qPCR技术,结合GeNorm、NormFinder和BestKeeper软件评价7个候选内参基因(28SrRNA、UBQ、RP Ⅱ、GAPDH、EF-1α、UBC21和TUA)稳定性。结果表明,7个候选内参基因在不同组织和不同胁迫处理下表达丰度及稳定性存在差异; EF-1α在低温胁迫处理下表达稳定性最好;UBQ和TUA在高温和干旱胁迫处理下表达稳定性最好; EF-1α 在不同组织中表达稳定性最好。本研究结果为冬瓜内参基因的选择提供了一定的理论参考。     

丝瓜18S rRNA基因克隆及其作为内参基因的应用

选择合适的内参基因是提高实时荧光定量PCR分析(q RT-PCR)准确性的重要条件。18S r RNA基因表达范围广、表达量恒定,常作为内参基因应用于实时荧光定量PCR中。为了获得丝瓜18S r RNA基因,并设计合适的荧光定量PCR内参引物,解决丝瓜实时荧光定量PCR检测中无内参基因的现状,通过PCR和序列测定,首次克隆到了丝瓜的18S r RNA基因序列,其长度为1 862 bp,Gen Bank登录号为KM656452。在此基础上设计1对荧光定量PCR引物,该引物特异性强,扩增效率高,在丝瓜各生长发育阶段及各种非生物胁迫条件下均能稳定表达,适合在丝瓜基因表达研究中作为内参基因。该研究结果可为开展丝瓜重要功能基因的表达模式和调控机制的研究奠定基础。     

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.