抗草甘膦转基因大豆对根际土壤细菌及根瘤菌的影响

转基因大豆是全球种植最广泛的转基因作物,抗除草剂是其最主要的转基因特性.微生物群落是土壤质量的监测指标之一,抗草甘膦转基因大豆及配施草甘膦是否影响大豆根际土壤细菌及根瘤菌群落尚不清楚.本研究基于大田试验,以非转基因亲本大豆‘中豆32’为对照(CK),分析转G10-epsps基因耐除草剂大豆SHZD32-01(GR)及配施草甘膦(GR+G)在大豆各生育时期对根际土壤细菌和根瘤菌的影响.结果表明: 与CK相比,GR、GR+G处理对苗期和成熟期根际土壤pH、总有机碳(TOC)、总氮(TN)、NH₄⁺-N含量等产生影响;GR处理显著增加结荚期根际土壤细菌群落丰度及多样性,GR+G处理显著增加结荚期根际土壤细菌群落多样性,但显著降低苗期和结荚期根际土壤细菌群落丰度;GR、GR+G处理改变了部分优势细菌类群的相对丰度,但不同生育期根际土壤优势细菌类群均为变形菌门、酸杆菌门、拟杆菌门、绿弯菌门、浮霉菌门和放线菌门;GR、GR+G处理改变了根瘤菌类群的相对丰度,但未影响慢生根瘤菌和中华根瘤菌两种主要大豆根瘤菌的相对丰度,且GR+G处理结荚期根际土壤根瘤菌相对丰度显著降低.环境因子分析显示,根际土壤放线菌和根瘤菌群落丰度主要受土壤pH影响.抗草甘膦转基因大豆或配施草甘膦显著影响结荚期根际土壤细菌和根瘤菌,但其影响随大豆的生长而消失.     

轮作和连作对胡萝卜根际和非根际细菌多样性的影响

细菌是土壤最重要的组成部分,土壤细菌的群落结构对土壤的健康至关重要,可以直接影响植物的生长。胡萝卜的长年连作导致其产量低、质量差等一系列问题的发生,连作问题已成为不可忽视的问题。本研究通过HiSeq PE250高通量测序和生物信息学方法获得了玉米胡萝卜轮作种植和胡萝卜连作种植中胡萝卜根际和非根际土壤细菌的组成结构。研究结果表明,相较于胡萝卜连作,玉米胡萝卜轮作种植改变了胡萝卜根际土壤细菌的组成和群落多样性。RM.M (玉米胡萝卜轮作根际土壤样品)样品中的优势菌门为放线菌门和厚壁菌门,RM.R (胡萝卜连作根际土壤样品)的优势菌门是变形菌门;有益菌如芽孢杆菌属和根瘤菌属在玉米胡萝卜轮作种植中的胡萝卜根际富集。RM.M与RM.R的细菌类群差异显著,群落多样性较低;NRM.M(玉米胡萝卜轮作非根际土壤样品)和NRM.R (胡萝卜连作非根际土壤样)的细菌类群差异不明显,群落多样性较高。与连作根际土壤相比,轮作根际土壤中有益菌的相对丰度较大,细菌相对丰度明显增加。本研究结果对通过调节根际土壤细菌组成来保证胡萝卜产量和质量的稳定,解决连作问题具有重要的意义。     

十字花科作物根肿病对根际土壤微生物群落的影响

为探究根肿病对十字花科作物根际土壤微生物多样性的影响,以罹病大白菜和健康株根际土壤为研究对象,采用高通量测序技术对2组样本的细菌16S rDNA和真菌ITS基因进行序列测定,分析了样本间的微生物群落结构和组成差异,同时测定根际土壤理化性质,探讨根肿病、土壤微生物群落、土壤环境因子三者的相关性。研究表明:1)患病植株根际土壤pH和总磷、总钾、碱解氮、速效钾含量显著低于正常植株根际土,而交换性钙含量明显增加。2)根肿病的发生降低了根际土壤中细菌种群的丰富度和多样性程度,但对根际土壤中的真菌α-多样性无明显影响。3)变形菌门、拟杆菌门、放线菌门等是所测土壤样本的主要优势细菌种群,其中患病植株根际土壤中拟杆菌门丰度显著高于健康植株根际土壤,放线菌门丰度则显著降低(P<0.05)。优势细菌纲为γ-变形菌纲、拟杆菌纲、α-变形菌纲、放线菌纲、酸杆菌纲等,2组土壤样本间多种优势细菌纲相对丰度差异显著。4)根际土壤优势真菌类群为子囊菌门、被孢霉门、担子菌门和壶菌门,其相对丰度在患病和健康株根际土壤样本中均有明显差异。主要真菌纲为散囊菌纲、被孢霉纲、锤舌菌纲等,并且土壤样本间的多种优势真菌纲相对丰...     

土壤类型对花生根际土壤细菌群落多样性和产量的影响

为了解不同土壤类型花生根际土壤细菌菌群多样性差异与产量的关系,明确不同土壤类型花生生产特性的区域优势,以6个花生主产区代表性土壤为研究对象,采用盆栽实验利用高通量测序技术研究不同土类花生根际土与非根际土细菌群落结构和变化特征。对6个土壤样品细菌菌群丰富度和多样性分析显示,湖南邵阳红壤细菌丰富度和多样性均较低,河北滦县褐土细菌丰富度和多样性均较高。放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria)及芽单胞菌门(Gemmatimonadetes)等为共有优势菌门,但在不同土壤类型样本中的菌群丰度存在明显差异,其中湖南邵阳红壤中绿弯菌门优势最明显,其他土壤类型放线菌门和变形菌门优势较明显。根际土与非根际土细菌门丰度间有差异,湖南邵阳红壤根际土与非根际土各细菌门(包括放线菌门、变形菌门、绿弯菌门、酸杆菌门、芽单胞菌门以及厚壁菌门)丰度变化程度较其它地区大。冗余分析表明,土壤酸碱度(pH)、有机质(ORM)、碱解氮(N),速效磷(P)和速效钾(K)等土壤理化因子对细菌菌群组成和物种丰度均有...     

不同生境黑果枸杞根际与非根际土壤微生物群落多样性

研究典型生境黑果枸杞根际与非根际土壤微生物群落多样性及其与土壤理化性质间的关系,为进一步研究黑果枸杞抗逆性提供理论数据。采集新疆精河县艾比湖地区(EB)盐碱地、乌苏市(WS)路旁荒地、五家渠市(WQ)人工林带的黑果枸杞根际与非根际土壤,利用Illumina-MiSeq高通量测序技术分析细菌和真菌群落组成和多样性。结果表明:根际土壤细菌多样性高于非根际土壤(WQ除外),而根际真菌多样性低于非根际土壤。WQ非根际土壤细菌和真菌多样性均高于EB和WS;根际细菌多样性排序为EBWSWQ,根际真菌多样性排序为WSEBWQ。根际土壤优势细菌门依次是变形菌门、拟杆菌门、放线菌门、酸杆菌门,真菌优势门为子囊菌门、担子菌门。根际土壤细菌变形菌门、拟杆菌门、酸杆菌门的相对丰度高于非根际土壤,而厚壁菌在根际土壤中的丰度显著降低,真菌优势门丰度在根际土和非根际土中的变化趋势因地区而异; Haliea、Gp10、Pelagibius、Microbulbifer、假单胞菌属、Thioprofundum、Deferrisoma是根际土壤细菌优势属;多孢子菌属、支顶孢属、Corollospora、Cochlonema是根际真菌优势属。细菌、真菌优势类群(门、属)的组成以及丰富度存在地区间差异,厚壁菌门在EB地区的丰富度显著高于含盐量较低的WS、WQ;盐碱生境EB中根际土壤嗜盐细菌的丰度高于非盐碱生境(WQ、WS),如盐单胞菌属、动性球菌属、Geminicoccu、Pelagibius、Gracilimonas、Salinimicrobium等。小囊菌属是EB根际真菌的最优势属,Melanoleuca是WQ和WS的最优势属,地孔菌属、Xenobotrytis、Brachyconidiellopsis、多孢子菌属等在EB根际土壤中的丰度显著高于WQ和WS。非盐碱生境(WS和WQ)的微生物群落之间的相似性较高,并且高于与盐碱环境(EB)之间的相似性,表明土壤含盐量对微生物群落组成丰度具有重要的影响。     

小麦/玉米轮作田根际微生物多样性分析

【背景】小麦/玉米轮作是中国粮食作物主要种植模式之一,目前对小麦/玉米轮作田根际土壤微生物差异变化缺乏全面的了解。【目的】明确小麦/玉米根际土壤微生物差异变化并了解其潜在功能。【方法】以小麦/玉米根际土壤为材料,运用细菌16S rRNA基因和真菌rDNA ITS基因测序,分析小麦/玉米根际土壤微生物多样性。【结果】玉米季微生物丰富度高于小麦季,而多样性无明显差异。放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)和绿弯菌门(Chloroflexi)为小麦季和玉米季根际土壤的优势细菌门,优势真菌门为子囊菌门(Ascomycota)。小麦季和玉米季共有细菌和真菌分别是631个和261个,小麦季特有细菌和真菌分别是38个和58个,玉米季特有细菌和真菌分别是25个和39个。LEfSe分析(LDA阈值为2)细菌和真菌表明,放线菌纲(Actinobacteria)和微囊菌目(Microascales)在小麦季富集,鞘脂单胞菌目(Sphingomonadales)和银耳纲(Tremellomycetes)在玉米季富集。小麦季、玉...     

连作对地黄根际土壤细菌群落多样性的影响

采用末端限制性片段长度多态性(T-RFLP)技术研究地黄连作下根际土壤细菌群落的动态变化.结果表明:地黄根际土壤细菌群落的香农多样性指数、丰富度指数和相似性指数均为对照(CK)1年2年,地黄连作下细菌优势种群的比例显著下降,种植1年土壤中厚壁菌门的芽孢杆菌纲在整个细菌群落中处于主导地位,而种植2年土壤中变形菌门ε-变形菌纲处于主导地位.地黄连作使其根际土壤细菌种类大量减少,群落结构趋于简单.连作后细菌群落多样性水平的变化导致根际土壤微生物群落功能的失调,可能是引发连作障碍的原因之一.     

丹参内生拮抗细菌DS-R5对丹参根际和根表土壤细菌群落结构的影响CSCD

目的 探究生防细菌DS-R5施入丹参植株后根际和根表土壤细菌群落组成及多样性变化。方法 向丹参植株根部施入生防细菌DS-R5,以未施用细菌为对照组,分别采集根际和根表土壤样品提取总DNA,扩增样品总DNA的V3-V4区,采用Illumina MiSeq测序平台对PCR扩增产物进行双端测序分析,利用生物信息学分析解析丹参植株根际土壤和根表土壤细菌群落结构组成及多样性。结果 菌株DS-R5处理后增加了根际土壤细菌群落的多样性和丰度,降低了根表土壤细菌群落的多样性和丰度;高通量测序得到的根际和根表土壤的有效序列数量和OTU数量相比对照组均有所下降,根际土壤处理样品中微生物种类最丰富,根表土壤处理样品中微生物种类最少,根际土壤处理样品与根际土壤对照物种种类更接近;在门水平上,根际土壤处理样品相比对照变形菌门丰度下降,酸杆菌门丰度升高,根表土壤处理样品相比对照变形菌门和酸杆菌门丰度均升高,放线菌门丰度降低;在属水平上,根际土壤处理样品中鞘氨醇单胞菌属、芽胞杆菌属、慢生根瘤菌属相比根际土壤对照占比均有升高,根表土壤处理样品相比对照黄杆菌属和伯克菌属丰度下降,而土壤中的优势菌属根瘤菌属和芽胞杆菌属丰度升高。结论 丹参植株施用生防细菌DS-R5后,改变了根际土壤和根表土壤中微生物群落结构和多样性。     

两种盐生植物根际土壤细菌多样性和群落结构

应用高通量测序技术对西北干旱区两种盐生植物黑果枸杞和里海盐爪爪根际土壤细菌的多样性和群落结构进行研究,旨在揭示两种耐盐植物根际土壤细菌之间以及根际与非根际细菌群落结构间的差异,为深入研究盐生植物根际土壤微生物与耐盐性之间的关系提供理论基础。结果表明:黑果枸杞、里海盐爪爪根际细菌多样性丰度高于非根际土,黑果枸杞根际土壤细菌多样性丰度高于里海盐爪爪。根际和非根际土壤细菌群落的组成和丰度存在差异,从黑果枸杞和里海盐爪爪根际土壤中分别检测出细菌21门289属和22门304属,而从非根际土壤中分别检测出28门285属和24门336属;在两种盐生植物根际土壤中,变形菌门和厚壁菌门均为优势门;拟杆菌门、放线菌门、蓝细菌门及浮霉菌门在根际土壤中的丰度显著高于非根际土壤,而厚壁菌门在根际土壤中的丰度低于非根际土壤。两种植物根际土壤中的细菌优势门和优势属的数量均高于非根际土壤,在黑果枸杞和里海盐爪爪的根际土壤中的细菌优势属分别有10个和9个,而二者非根际土壤中的细菌优势属各有4个,其中假单胞菌属是根际和非根际土壤中的共有优势属。黑果枸杞和里海盐爪爪根系细菌群落组成和丰度存在差异,只有假单胞菌属和盐单胞菌属是两种植物根际土壤中的共有优势属。Unifrac分析和聚类分析表明,两种盐生植物根际土壤细菌之间的相似性大于根际和非根际细菌群落间的相似性。细菌多样性与土壤有机碳、有机质、总氮正相关,与pH、电导率负相关,电导率和pH,有机碳和总氮分别是非根际土,根际土壤细菌群落物种组成的主要影响因素。     

广东省本地油茶和引种油茶根际土壤微生物群落特征

【背景】近年来,油茶低效林面积较大,根际土壤微生物影响林木抗性和生长,对林业可持续发展具有重要意义。【目的】了解广东省本地油茶和引种油茶根际土壤微生物群落特征。【方法】利用高通量测序分析油茶根际土壤微生物群落组成。【结果】油茶根际土壤细菌有26门77纲201目377科593属676种,真菌有14门50纲121目266科502属631种。油茶根际土壤中的优势细菌为酸杆菌门和变形菌门,优势真菌为子囊菌门和担子菌门。两种油茶根际土壤微生物组成差异显著,本地油茶根际土壤的细菌多样性显著高于引种油茶。在门水平上,脱硫杆菌门细菌和罗兹菌门、被孢霉门真菌的相对丰度在两种油茶间差异显著,Amorphotheca在本地油茶根际土壤中特异性富集。两种油茶根际土壤细菌碳代谢相对丰度差异显著,真菌以腐生营养型为主,其次为病理营养型和共生营养型。本地油茶根际土壤中显著富集土壤腐生菌,而共生营养型真菌(尤其是丛枝菌根真菌)相对丰度(6.43%)显著低于引种油茶中(21.83%)。此外,有机质和养分含量是影响油茶根际土壤微生物群落的关键因子。【结论】本地油茶和引种油茶根际土壤微生物群落组成和结构差异显著,Amorp...     

Bacterial communities associated with the rhizosphere of transgenic Bt 176 maize (Zea mays) and its non transgenic counterpart

The effect of transgenic Bt 176 maize on the rhizosphere bacterial community has been studied with a polyphasic approach by comparing the rhizosphere of Bt maize cultivated in greenhouse with that of its non transgenic counterpart grown in the same conditions. In the two plants the bacterial counts of the copiotrophic, oligotrophic and sporeforming bacteria, and the community level catabolic profiling, showed no significant differences; differences between the rhizosphere and bulk soil bacterial communities were evidenced. Automated ribosomal intergenic spacer analysis (ARISA) showed differences also in the rhizosphere communities at different plant ages, as well as between the two plant types. ARISA fingerprinting patterns of soil bacterial communities exposed to root growth solutions, collected from transgenic and non transgenic plants grown in hydroponic conditions, were grouped separately by principal component analysis suggesting that root exudates could determine the selection of different bacterial communities.     

Functional Potential of Soil Microbial Communities in the Maize Rhizosphere

Microbial communities in the rhizosphere make significant contributions to crop health and nutrient cycling. However, their ability to perform important biogeochemical processes remains uncharacterized. Here, we identified important functional genes that characterize the rhizosphere microbial community to understand metabolic capabilities in the maize rhizosphere using the GeoChip-based functional gene array method. Significant differences in functional gene structure were apparent between rhizosphere and bulk soil microbial communities. Approximately half of the detected gene families were significantly (p<0.05) increased in the rhizosphere. Based on the detected gyrB genes, Gammaproteobacteria, Betaproteobacteria, Firmicutes, Bacteroidetes and Cyanobacteria were most enriched in the rhizosphere compared to those in the bulk soil. The rhizosphere niche also supported greater functional diversity in catabolic pathways. The maize rhizosphere had significantly enriched genes involved in carbon fixation and degradation (especially for hemicelluloses, aromatics and lignin), nitrogen fixation, ammonification, denitrification, polyphosphate biosynthesis and degradation, sulfur reduction and oxidation. This research demonstrates that the maize rhizosphere is a hotspot of genes, mostly originating from dominant soil microbial groups such as Proteobacteria, providing functional capacity for the transformation of labile and recalcitrant organic C, N, P and S compounds.     

Comparison of the Rhizosphere Bacterial Communities of Zigongdongdou Soybean and a High-Methionine Transgenic Line of This Cultivar

Previous studies have shown that methionine from root exudates affects the rhizosphere bacterial population involved in soil nitrogen fixation. A transgenic line of Zigongdongdou soybean cultivar (ZD91) that expresses Arabidopsis cystathionine γ-synthase resulting in an increased methionine production was examined for its influence to the rhizosphere bacterial population. Using 16S rRNA gene-based pyrosequencing analysis of the V4 region and DNA extracted from bacterial consortia collected from the rhizosphere of soybean plants grown in an agricultural field at the pod-setting stage, we characterized the populational structure of the bacterial community involved. In total, 87,267 sequences (approximately 10,908 per sample) were analyzed. We found that Acidobacteria, Proteobacteria, Bacteroidetes, Actinobacteria, Chloroflexi, Planctomycetes, Gemmatimonadetes, Firmicutes, and Verrucomicrobia constitute the dominant taxonomic groups in either the ZD91 transgenic line or parental cultivar ZD, and that there was no statistically significant difference in the rhizosphere bacterial community structure between the two cultivars.     

Effects of transgenic fructan-producing potatoes on the community structure of rhizosphere and phyllosphere bacteria

The rhizosphere and phyllosphere microbial communities of transgenic potatoes producing fructan were studied in comparison with isogenic controls and conventional varieties in a field release experiment over a period of 3 years. Population densities and 16S rRNA gene-based terminal restriction fragment length polymorphism (T-RFLP) analysis of the rhizosphere bacterial community only displayed the influence of annual and seasonal effects and the influence of field heterogeneity. In contrast, the T-RFLP analysis of the phyllosphere bacteria revealed in two of the 3 years significant differences in the community structure between the transgenic lines producing inulin and the other variants. This effect was studied in more detail through the analysis of bacterial isolates and a 16S rRNA gene clone library obtained from a transgenic line and the control. Both methods revealed a lower genetic diversity in the transgenic line and changes in the abundance of several bacterial groups. The isolates of the transgenic line were dominated by Bacilli, whereas most of the control isolates represented Actinobacteria. The clones were dominated by Proteobacteria, with main differences between both variants in Deltaproteobacteria, Bacilli and Bacteroidetes. However, all in all, the impact of the transgenic lines did not exceed the natural variability of the phyllosphere community structure on potato plants.     

Maize rhizosphere modulates the microbiome diversity and community structure to enhance plant health

Metagenomic has been explored in investigating microbiome diversity. However, there is limited available information on its application towards securing plant health. Hence, this study adopts the metagenomic approach to unravel the microbiome diversity associated with healthy (LI and MA) and Northern corn leaf blight (NCLB) infected (LID and MAD) maize rhizosphere in the maize growing field at Lichtenburg and Mafikeng, North-West province of South Africa. The extraction of whole DNA from the respective healthy and diseased rhizosphere soils was conducted and sequenced using shotgun metagenomics. A total of 12 bacteria, 4 archaea and 2 fungal phyla were found as predominant across the fields with the use of the SEED subsystem database. The most predominant bacteria phyla included Proteobacteria, Dienococcus-Thermus, Gemmatimonadetes, Chlorobi, Cyanobacteria, Planctomycetes, Verrucomicrobia, Acidobacteria, Firmicutes, Chloroflexi and Bacteroidetes. Archaea consisted of Euryarchaeota, Thaumarchaeota, Crenarchaeota and Korachaeota, while Ascomycota and Basidiomycota were the dominant fungal phyla. Microbial abundance and diversity were higher in the rhizosphere of healthy maize (LI and MA) rhizosphere as compared to the NCLB diseased (LID and MAD), in the order LI > MA > LID > MAD. At phylum and genus level, alpha diversity index showed no significant (p > 0.05) difference in the abundance of the microbial community of healthy and NCLB infected maize rhizosphere, while beta analysis produced a significant (p = 0.01) difference in the microbial diversity in the soil. Taken together, the study revealed that the abundance of microbial diversity in the maize rhizosphere influences the efficacy of the rhizosphere microbiome to modulate microbial functions towards managing and sustaining plant health.     

Potential of a 16S rRNA-based taxonomic microarray for analyzing the rhizosphere effects of maize on Agrobacterium spp. and bacterial communities

Bacterial diversity is central to ecosystem sustainability and soil biological function, for which the role of roots is important. The high-throughput analysis potential of taxonomic microarray should match the breadth of bacterial diversity. Here, the power of this technology was evidenced through methodological verifications and analysis of maize rhizosphere effect based on a 16S rRNA-based microarray developed from the prototype of H. Sanguin et al. (Environ. Microbiol. 8:289-307, 2006). The current probe set was composed of 170 probes (41 new probes in this work) that targeted essentially the Proteobacteria. Cloning and sequencing of 16S rRNA amplicons were carried out on maize rhizosphere and bulk soil DNA. All tested clones that had a perfect match with corresponding probes were positive in the hybridization experiment. The hierarchically nested probes were reliable, but the level of taxonomic identification was variable, depending on the probe set specificity. The comparison of experimental and theoretical hybridizations revealed 0.91% false positives and 0.81% false negatives. The microarray detection threshold was estimated at 0.03% of a given DNA type based on DNA spiking experiments. A comparison of the maize rhizosphere and bulk soil hybridization results showed a significant rhizosphere effect, with a higher predominance of Agrobacterium spp. in the rhizosphere, as well as a lower prevalence of Acidobacteria, Bacteroidetes, Verrucomicrobia, and Planctomycetes, a new taxon of interest in soil. In addition, well-known taxonomic groups such as Sphingomonas spp., Rhizobiaceae, and Actinobacteria were identified in both microbial habitats with strong hybridization signals. The taxonomic microarray developed in the present study was able to discriminate and characterize bacterial community composition in related biological samples, offering extensive possibilities for systematic exploration of bacterial diversity in ecosystems.     

轮作模式对冬小麦土壤氨氧化微生物群落多样性和组成的影响

农田温室气体减排已成为农业绿色发展的重要内容,驱动温室气体氧化亚氮(N₂O)产生的氨氧化微生物受到了研究者们的广泛关注。为探究轮作模式对土壤氨氧化微生物群落的影响,基于田间定位试验,研究了夏红小豆-冬小麦、夏绿豆-冬小麦、夏花生-冬小麦、夏大豆-冬小麦和夏玉米-冬小麦5种轮作模式中冬小麦根际和非根际土壤氨氧化古菌(AOA)和氨氧化细菌(AOB)的群落组成和多样性变化特征。结果表明:与夏玉米-冬小麦模式相比,豆禾轮作模式增加了根际土中有机碳和硝态氮含量,以及非根际土中全氮和铵态氮含量。豆禾轮作模式降低了非根际土壤中AOA群落的ACE指数和Chao1指数,并显著降低根际土中AOB群落的ACE指数和Chao1指数(P<0.05)。豆禾轮作显著增加AOA群落中泉古菌门(Crenarchaeota)和AOB群落中变形菌门(Proteobacteria)某些类群的相对丰度(P<0.05)。根际土中豆禾轮作模式与麦玉模式的AOA群落结构发生明显分离,而非根际土中豆禾轮作模式与麦玉模式的AOB群落发生分离(P<0.05)。研究结果表明:豆禾轮作种植改变了AOA和AOB的群落结构和多样性,土壤pH值和速效氮含量是驱动AOA和AOB群落结构变化的重要因子,且根际与非根际土壤中氨氧化微生物存在生态位分离。     

Isolation and diversity of culturable rhizobacteria associated with economically important crops and uncultivated plants in Québec,Canada

Plants are chronically associated with microorganisms, residing all tissues. Holonomic analysis of diversity of established rhizobacteria in uncultivated plants is scarce. Thus, the present study was conducted to access the root-associated bacterial diversity of 6 crops (maize, canola, soybean, reed canarygrass, alfafa, and miscanthus) and 20 uncultivated plant species in the region of Sainte-Anne-de-Bellevue, Québec, Canada, using pure-culture methods. Based on 16S rRNA gene sequence analysis, 446 bacterial isolates were distributed onto four phyla (Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes), 32 families and 90 genera. Proteobacteria constituted the largest group of isolates (240), 40% of ectophytic and 61% of endophytic bacteria. Representatives of the genera Bacillus and Pseudomonas dominated in rhizosphere soil; Microbacterium and Pseudomonas were the predominant endophytes. Some genera were associated with specific plant species, such as Stenotrophomonas, Yersinia, Labrys and Luteibacter. Several endophytes were occasionally observed in the rhizosphere, and vice versa. This is the first survey of culturable endophytic bacteria associated with uncultivated plants in Québec. The culturable bacterial community studied herein are assumed to represent a portion of the entire phytomicrobiome of the evaluated plants. Results confirmed that the crops and uncultivated plants of Québec represent an extremely rich reservoir of diverse rhizobacteria.     

污染条件下VAM玉米元素积累和分布与根际重金属形态变化的关系

为了了解重金属Cu、Zn、Pb、Cd在土壤－根际－植物系统中的行为,揭示VAM植物减弱土壤中过量重金属对植物生理毒的抗性机理,采用原子吸收光谱测定Cu、Zn、Pb、Cd在污灌土壤中生长的VA菌根玉米和无菌根玉米中的积累和分布,并用连接形态分析技术分析了菌根际中Cu、Zn、Pb、Cd的形态分布和变化趋势,结果表明,Cu、Zn、Pb、Cd在菌根玉米中的积累量比非攻根中积累量分别减少10％、18％和29％,Cd积累量没有改变,生长7周后,菌根玉米是非菌根玉米生物量的1．5倍,与对照土壤相比,根际中除Cu交换态显著增加外,Zn、Pb、Cd各形态相对改变量显著大于非菌根,且菌根根际上中Cu、Zn、Pb有机结合态增加量显著大于非根际土,说明菌根际金属向稳定状态转移的程度显著大于非菌根际,同时,讨论了根际金属形态对金属有效性的影响,及其与菌根植物金属抗性机理的关系。