根结线虫危害与健康黄瓜根际土壤微生物群落结构差异分析

为探明黄瓜根结线虫病与根际土壤微生物群落的关系,通过高通量测序分析对比了受根结线虫危害和健康黄瓜根系的根表土和根围土中微生物群落结构组成及丰富度的差异。结果表明,健康黄瓜根表土、健康黄瓜根围土、病害黄瓜根表土和病害黄瓜根围土4组土壤样品之间微生物Alpha多样性无显著差异,但Beta多样性在各组间差异显著。在门水平上,各组间细菌和真菌群落组成相似,但拟杆菌门（Bacteroidetes）和担子菌门（Basidiomycota）在各组的相对丰度存在显著差异,其中拟杆菌门在病害黄瓜根表土（13.58%）、担子菌门在健康黄瓜根表土（6.69%）中的相对丰度较高。在属水平上,各组间细菌和真菌的组成也基本一致,细菌中黄杆菌属（Flavobacterium）、假单胞菌属（Pseudomonas）、链霉菌属（Streptomyces）、根瘤菌属（Rhizobium）、德沃斯氏菌属（Devosia）、鞘氨醇杆菌属（Novosphingobium）、剑菌属（Ensifer）、纤维弧菌属（Cellvibrio）和噬几丁质菌属（Chitinophaga）在不同组中的相对丰度存在显著差异,且均在病害黄瓜根表土...     

Spatially tracking carbon through the root–rhizosphere–soil system using laser ablation‐IRMS

The intimate relationships between plant roots, rhizosphere, and soil are fostered by the release of organic compounds from the plant into soil through various forms of rhizodeposition and the simultaneous harvesting of nutrients from the soil to the plant. Here we present a method to spatially track and map the migration of plant‐derived carbon (C) through roots into the rhizosphere and surrounding soil using laser ablation‐isotope ratio mass spectrometry (LA‐IRMS). We used switchgrass microcosms containing soil from field plots at the Kellogg Biological Station (Hickory Corners, Michigan, USA) which have been cropped with switchgrass since 2008. We used a ¹³CO₂ tracer to isotopically label switchgrass plants for two diel cycles and tracked subsequent movement of labeled C using the spatially specific (< 100 µm resolution) δ¹³C analysis enabled by LA‐IRMS. This approach permitted assessment of variable C flow through different roots and enabled mapping of spatial variability of C allocation to the rhizosphere. Highly ¹³C‐enriched C (consistent with production during the ¹³CO₂ application period) extended ≈ 0.5–1 mm from the root into the soil, suggesting that the majority of recent plant‐derived C was within this distance of the root after 48 h. Tracking the physical extent of root exudation into the rhizosphere can help evaluate the localization of plant‐microbe interactions in highly variable subsurface environments, and the use of the isotopic label can differentiate freshly fixed C (presumably from root exudates) from other types of subsurface C (e.g., plant necromass and microbial turnover). The LA‐IRMS technique may also serve as a valuable screening technique to identify areas of high activity for additional microbial or geochemical assays.     

Modification of total and phosphorus mineralizing bacterial communities associated with Zea mays L. through plant development and fertilization regimes

Harnessing the rhizospheric microbiome, including phosphorus mineralizing bacteria (PMB), is a promising technique for maintaining sustainability and productivity in intensive agricultural systems. However, it is unclear as to which beneficial taxonomic group populations in the rhizosphere are potentially associated with the changes in soil microbiomes shifted by fertilization regimes. Herein, we analyzed the diversity and community structure of total bacteria and PMB in the rhizosphere of maize (Zea mays L.) grown in soils under 25 years of four fertilization regimes (compost, biocompost, chemical, or non-fertilized) via selective culture and Illumina sequencing of the 16S rRNA genes. Plant development explained more variations (29 and 13%, respectively) in the composition of total bacteria and PMB in the rhizosphere of maize than the different fertilization regimes. Among those genera enriched in the rhizosphere of maize, the relative abundances of Oceanobacillus, Bacillus, Achromobacter, Ensifer, Paracoccus, Ramlibacter, and Luteimonas were positively correlated with those in the bulk soil. The relative abundance of Paracoccus was significantly higher in soils fertilized by compost or biocompost than the other soils. Similar results were also observed for PMB affiliated with Ensifer, Bacillus, and Streptomyces. Although plant development was the major factor in shaping the rhizospheric microbiome of maize, fertilization regimes might have modified beneficial rhizospheric microbial taxa such as Bacillus and Ensifer.     

High‐throughput sequencing reveals bacterial community composition in the rhizosphere of the invasive plant Flaveria bidentis

Bacteria are important soil components as both decomposers and plant symbionts and play a major role in plant–microbe interaction processes. However, little is known about the diversity of bacterial communities in the rhizosphere of the invasive plant Flaveria bidentis. In this study, we used high‐throughput sequencing to investigate bacterial communities in the rhizosphere of F. bidentis, compared with those of native crop maize and control plant Setaria viridis. We obtained >70 000 analysis reads from the three samples and used bioinformatics and multivariate statistics to analyse the results. An analysis of indicators showed that F. bidentis samples had lower richness but higher diversity than maize and S. viridis samples. Operational taxonomic unit (OTU)‐based bioinformatics and statistical analysis also demonstrated that F. bidentis significantly altered the bacterial rhizosphere community. Higher abundance of Actinobacteria and lower abundance of Firmicutes were observed in F. bidentis rhizosphere than those of maize and S. viridis. Redundancy analysis (RDA) revealed the correlations between soil bacteria communities, soil nutrients and the abundance of bacterial groups. Our results provide a starting point for investigations of the effects of F. bidentis on soil bacterial diversity and a theoretical basis for the microecological mechanism of F. bidentis invasion.     

枯草芽孢杆菌Bs916防治番茄青枯病

采用室内MS平板植物组培法、温室盆栽试验和微生物特异性平板分离检测技术,评估了枯草芽孢杆菌Bs916对番茄的促生、防治青枯病的作用,研究了菌株Bs916对番茄根表及茎内青枯菌种群数量的影响和对番茄根围可培养微生物含量的影响。在植物组培MS平板中,枯草芽孢杆菌Bs916对番茄植株鲜重具有促生作用,播种15 d后,其鲜重达79.8 mg,比未处理对照增加9.61%。盆栽试验显示,枯草芽孢杆菌Bs916灌根处理番茄后14 d,对番茄青枯病的防治效果达55.6%;菌株Bs916处理番茄后,番茄根表、茎内青枯菌含量和未处理对照的青枯菌含量变化趋势一致,均呈现随着时间的改变而逐渐下降的趋势,菌株Bs916处理的根表青枯菌含量约为未处理对照的1/100~1/10,而茎内青枯菌含量为未处理对照的1/50~1/2。此外,菌株Bs916的施用对番茄根围土壤中细菌种群具有先抑制后促进的作用,对真菌具有先促进后快速抑制的作用,而对根围放线菌则无显著性影响。以上结果表明,芽孢杆菌Bs916具有潜在的防治番茄青枯病的田间应用前景,也为其田间应用提供了理论基础。     

Evaluation of Extractants for Boron under the Influence of Organic Matter and Applied Boron in Rhizosphere and Nonrhizosphere Soils Growing Rape (Brassica campestris L.)

Field experiments during 2006–07 and 2007–08 were conducted in an Aeric Endoaquept to evaluate extractants suitable for boron (B) under the influence of organic matter and B in both rhizosphere (R) and nonrhizosphere (NR) soils with rape (Brassica campestris L.) as a test crop. The results reveal that the average B content in Mehlich 3 (MH-3) B was greatest (0.791 mg kg^?1) in NR soil, while that of the same in R soil was greatest (0.785 mg kg^?1) with Mannitol–calcium chloride (CaCl₂) (MCC) followed by hot -CaCl₂ (HCC, 0.750 mg kg^?1) in the treatment T₄ where NPK (80:40:40), B at 0.5 kg ha^?1, and farmyard manure (FYM) at 5 t ha^?1 were applied together. Based on linear regressions and correlations between different extractants and yield responses, the MH-3 extractant gave the greatest value of co-efficient of determination (R² = 0.36**, r = 0.598**) and has proved to be a superior extracting solution for B in NR in an Aeric Endoaquept. The results further suggested that the extractability of B with these three extractants did not have any control over rhizosphere soil zone.     

拮抗微生物对茄根腐病菌的抑制作用

从上海5个不同地区的茄果类蔬菜田中,采集土壤样品112份,经稀释平板法分离获得对茄根腐病菌桔抗作用较强的菌株5个,其编号为9-16,8-13,8-8,7-5,3-4。经鉴定,菌株9-16、8-8为假单胞杆菌属,菌株8-13、7-5、3-4为芽孢杆菌属。通过对根腐病菌菌丝的抑制实验表明,这类拮抗菌能显著抑制病菌菌丝生长并使菌丝变细扭曲,菌丝细胞畸形等。在活体条件下,试验表明5个菌株对茄根腐病菌有较好的防治作用,其中9-16菌株和5个菌株混合防治效果最好达80％以上,其拮抗能力与防治效果之间呈正相关,与50％多菌灵处理比较差异不显著。     

花生根际土壤细菌群落对干旱和盐胁迫的响应

为明确旱、盐及旱盐双重胁迫对花生根际土壤细菌群落的影响,本研究采用盆栽试验,通过16S rRNA基 因测序技术,研究了花生开花期干旱、盐胁迫及旱盐双重胁迫下花生根际土壤细菌群落结构的变化。结果表明,花 生根际土壤细菌群落均以放线菌纲（Actinobacteria）、α-变形菌纲（Alphaproteobacteria）、未分类菌目（norank_p__Sac⁃ charibacteria）、蓝藻纲（Cyanobacteria）、酸杆菌纲（Acidobacteria）、芽单胞菌纲（Gemmatimonadetes）和β-变形菌纲 （Betaproteobacteria）7个优势菌纲为主。干旱和盐胁迫处理均不同程度提高了α-变形菌纲和蓝藻纲的含量,且对蓝 藻纲的诱导效果较显著,推测蓝藻纲在提高花生胁迫耐受性方面具有重要功能。非生物胁迫影响根际土壤微域环 境,对花生根际土壤细菌群落结构具有调控作用。调节微生物群落结构,改良土壤微域环境,是提高植物胁迫耐受 性的有效途径。     

极端微生物对极端环境的适应机理及应用研究进展

极端微生物在极端环境中生长繁殖,其必然有适应恶劣环境下的特殊细胞结构、生理机制、遗传基因等。对近几年的六大类极端微生物在分类、生存机制和应用方面的最新研究进展进行综述,为极端微生物菌种资源利用及代谢产物开发提供了一些理论依据。     

单施和配施有机物料对沙化土壤微生物群落功能多样性的短期影响

为探讨施用有机物料对宁夏沙化土壤的改良效果,以当地易得的杨树枝条、玉米秸秆、牛粪为原料在2015年4~10月期间进行桶栽试验,采用Biolog技术研究了有机物料单施和配施对宁夏沙化土壤微生物群落功能多样性的短期影响。结果显示:(1)施用有机物料使土壤微生物利用碳源总量增加,微生物代谢活性增强。其利用比例较高的碳源类型为氨基酸类、胺类和碳水化合物类。(2)单施有机物料比配施有机物料对微生物代谢的促进作用强;单施杨树枝条粉碎物的土壤微生物平均颜色变化率在所有处理中最大,而且微生物各种多样性指数也有明显提高。(3)对各类碳源的利用强度与土壤易氧化有机碳、全氮含量和碳氮比之间表现出了密切的关系,微生物多样性指数则与土壤易氧化有机碳和无机氮存在紧密联系。本研究表明,土壤施入杨树枝条粉碎物后微生物代谢活性增强、土壤质量提高,对土壤改良有积极作用。