Microbial and Functional Diversity within the Phyllosphere of Espeletia Species in an Andean High-Mountain Ecosystem

Microbial populations residing in close contact with plants can be found in the rhizosphere, in the phyllosphere as epiphytes on the surface, or inside plants as endophytes. Here, we analyzed the microbiota associated with Espeletia plants, endemic to the Páramo environment of the Andes Mountains and a unique model for studying microbial populations and their adaptations to the adverse conditions of high-mountain neotropical ecosystems. Communities were analyzed using samples from the rhizosphere, necromass, and young and mature leaves, the last two analyzed separately as endophytes and epiphytes. The taxonomic composition determined by performing sequencing of the V5-V6 region of the 16S rRNA gene indicated differences among populations of the leaf phyllosphere, the necromass, and the rhizosphere, with predominance of some phyla but only few shared operational taxonomic units (OTUs). Functional profiles predicted on the basis of taxonomic affiliations differed from those obtained by GeoChip microarray analysis, which separated community functional capacities based on plant microenvironment. The identified metabolic pathways provided insight regarding microbial strategies for colonization and survival in these ecosystems. This study of novel plant phyllosphere microbiomes and their putative functional ecology is also the first step for future bioprospecting studies in search of enzymes, compounds, or microorganisms relevant to industry or for remediation efforts.     

Interactions of two endophytic fungi colonizing Atractylodes lancea and effects on the host’s essential oils

We investigated interactions between endophytic fungi infecting the same host; Gilmaniella sp. AL12 and Cunninghamella sp. AL4 are endophytes of Atractylodes lancea (Asteraceae). We studied the effect on the host’s essential oils of the single inoculation of one fungus and the mixed inoculation of both. We also observed the effects of these inoculations on endophytic fungal colonization and distribution. Single inoculation included two groups: single inoculation of AL12 (AL12 group), and single inoculation of AL4 (AL4 group). Mixed inoculation included three groups: AL4 inoculation first, followed by AL12 (AL4/AL12), simultaneous inoculation of AL4 and AL12 (AL4_VS_AL12), and AL12 inoculation first, followed by AL4 (AL12/AL4). The control (CK) did not include any fungi. AL4 was observed to prefer to colonize rhizomes, and AL12 to colonize blades of plants. The isolation rate of each fungus in the mixed inoculation group was lower than in the single inoculation group; this may have been due to niche competition. When we inoculated AL12 first and then AL4, the isolation rate of AL4 in stems, leaves, and roots decreased. Similarly, when we inoculated AL4 first and then AL12, the isolation rate of AL12 decreased in the stems and leaves. However, in the roots it appeared that the invasion of AL4 changed the volatile oil levels and that this helped the colonization of AL12; the colonization rate of AL12 following single inoculation was slightly lower than in the AL12/AL4 group and the AL4_VS_AL12 group. This may illustrate that these endophytes have a long history of mutual colonization of roots, and thus have synergies with each other. We used tissue staining to observe inoculated plant tissue. No hyphae were observed intruding into plant cells, and the hyphae of the two fungi were not observed intertwining; meaning that there was no physical interaction between them. However, we found hyphae colonizing the interspaces of leaf tissues and between root cortical cells. These hyphae were single bend fold and unbranched. These mycelia exhibited adaptive morphology compared with those in in vitro pure culture. Transmission electron microscopy (TEM) allowed us to more clearly observe endophytic colonization between root cortical cells. Gas chromatography showed that both single and mixed inoculation significantly increased levels of atractylone and atractylodin in the essential oils of A. lancea. In particular, the relative percentage of atractylodin in groups AL12/AL4 and AL4/AL12 was twice as much as in the control group, and the relative percentage of atractylone in AL4_VS_AL12 was more than three times that of the control. The gas chromatograph of the host’s essential oil was more complex following mixed inoculation than it was in the control.     

Effects of Switchgrass (Panicum virgatum) Rotations with Peanut (Arachis hypogaea L.) on Nematode Populations and Soil Microflora

A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut without nematicide application or peanut without nematicide following 2 years of cotton. Peanut yield did not differ among rotations in either sample year. Effects of crop rotation on the microbial community structure associated with peanut were examined using indices for diversity, richness, and similarity derived from culture-based analyses. Continuous peanut supported a distinctly different rhizosphere bacterial microflora compared to peanut following 1 year of switchgrass, or continuous switchgrass. Richness and diversity indices for continuous peanut rhizosphere and geocarposphere were not consistently different from peanut following switchgrass, but always differed in the specific genera present. These shifts in community structure were associated with changes in parasitic nematode populations.     

接种内生降解菌Stenotrophomonas pavanii DJL-M3对多菌灵胁迫下水稻根际微生态的影响

内生降解菌定殖可促进水稻中农药等有机污染物的降解代谢,研究功能内生菌对农药暴露下水稻根际微生态的影响,可为利用植物-微生物互作调控农作物农药残留及修复农田生态环境污染提供科学依据。以水稻根际土壤中的蚯蚓、土壤酶和微生物群落为研究对象,分析接种内生菌Stenotrophomonas pavanii DJL-M3对水稻根际微生态响应多菌灵胁迫的影响。结果表明：多菌灵暴露导致水稻根际土壤过氧化氢酶活性增强,脲酶和蔗糖酶活性被抑制;多菌灵污染可对水稻根际周围的蚯蚓造成氧化损伤,致使其体内丙二醛累积并诱导超氧化物歧化酶和乙酰胆碱酯酶过表达;多菌灵残留显著降低水稻根际土壤微生物群落的多样性与碳源代谢活性。接种内生降解菌S.pavanii DJL-M3促进了水稻根际残留多菌灵的降解,缓解根际土壤微生物与蚯蚓所受胁迫压力,显著提高了土壤脲酶、蔗糖酶活力以及蚯蚓的存活率,并有效提升了水稻根际微生物群落的代谢活性与多样性。因此,接种内生降解菌S.pavanii DJL-M3有助于多菌灵残留污染下稻田土壤生态环境的恢复。     

Cross-Talk Between Calcium–Calmodulin and Brassinolide for Fungal Endophyte-Induced Volatile Oil Accumulation of Atractylodes lancea Plantlets

Using pharmacological and biochemical approaches, the signalling pathways between calcium (Ca²⁺)–calmodulin (CaM), brassinolide (BL), and nitric oxide (NO) for fungal endophyte-induced volatile oil accumulation were investigated in Atractylodes lancea plantlets. Gilmaniella sp. AL12 inoculation elevated the concentrations of BL, CaM, and [Ca²⁺]_cyt, expression of the calmodulin 1 (CaM1) gene, and the levels of volatile oils. Treatment with AL12 or exogenous BL led to significant increases in the levels of cytosolic Ca²⁺ and CaM and CaM1 expression in plantlets. However, the upregulation of BL was almost completely blocked by pretreatments with CaM antagonists and Ca²⁺ channel blockers. Pretreatment with a BL inhibitor, brassinazole (BRz), did not influence the increase in levels of CaM induced by the endophyte. CaCl₂-induced increases in NO generation, CaM antagonists, and Ca²⁺ channel blockers were able to suppress NO production, and the NO-specific scavenger was not able to suppress the generation of [Ca²⁺]_cyt in plantlets. Exogenous BL was not able to induce NO generation, and BRz had no effect on NO generation. Our results suggest that Ca²⁺–CaM induced by this endophyte mediates NO generation and BL concentration, and also functions downstream of BL signalling, resulting in the upregulation of volatile oil accumulation in A. lancea plantlets.     

冬季覆盖作物秸秆还田对双季稻田根际土壤微生物群落功能多样性的影响

微生物群落功能多样性是土壤质量变化重要的指标,不同作物类型的秸秆还田措施对土壤微生物群落功能多样性具有明显的影响。以位于双季稻主产区不同冬季覆盖作物-双季稻种植模式大田定位试验田为研究对象,以冬闲-双季稻种植模式为对照(CK),应用Biolog-GN技术开展黑麦草-双季稻(Ry)、紫云英-双季稻(Mv)、油菜-双季稻(Ra)和马铃薯-双季稻(Po)种植模式条件下不同冬季覆盖作物秸秆还田后对双季稻田根际土壤微生物功能多样性影响的研究。研究结果表明,早稻和晚稻成熟期,与CK处理相比,冬季覆盖作物秸秆还田处理增加了稻田土壤碳源平均颜色变化率(AWCD),以Po处理AWCD均为最高,均显著高于Ry和CK处理。不同冬季覆盖作物秸秆还田处理土壤微生物代谢多样性指数表现出明显的差异,早稻成熟期,Po处理的Richness、Shannon和McIntosh指数均为最高,其次为Ry、Mv和Ra处理,CK处理最低;晚稻成熟期,各处理的Richness、Shannon和McIntosh指数大小顺序均表现为PoRaMvRyCK。土壤微生物碳源利用的主成分分析结果表明,各冬季覆盖作物秸秆还田处理根际土壤微生物利用的主要碳源为氨基酸类和糖类物质,不同处理间碳源利用类型有差异。冬季覆盖作物秸秆还田措施有利于提高双季稻田根际土壤微生物对碳源的利用能力、物种丰富度和均匀度。     

Diversity and metabolic potential of culturable root-associated bacteria from Origanum vulgare in sub-Himalayan region

Study of rhizospheric bacteria from important plants is very essential, as they are known to influence plant growth and productivity, and also produce industrially important metabolites. Origanum vulgare is a perennial medicinal aromatic plant rich in phenolic antioxidants. Present study investigates the diversity of culturable root-associated bacteria from this plant in Palampur, India, which constitutes a unique ecosystem due to high rain fall, wide temperature fluctuations and acidic soil. Both root endophytes and rhizospheric soil bacteria were isolated, which resulted in a total of 120 morphologically different isolates. They were found to group into 21 phylotypes based on restriction fragment length polymorphism analysis. Growth medium composition had significant effect on the diversity of the isolated bacterial populations. The isolates were characterized for various metabolic, plant growth promoting (PGP) and other biotechnologically useful activities, based on which they were clustered into groups by principal component analysis. Majority of the isolates belonged to ??-Proteobacteria and Firmicutes. Pseudomonas and Stenotrophomonas were the most dominant species and together constituted 27.5?% of the total isolates. Many isolates, especially ??-Proteobacteria, showed very high PGP activities. Few isolates exhibited very high antioxidant activity, which may find potential applications in food and health industries. Firmicutes were catabolically the most versatile group and produced several hydrolytic enzymes. To the best of our knowledge, it is the first study describing rhizospheric microbial community of O. vulgare.     

Specific influence of white clover on the rhizosphere microbial community in response to polycyclic aromatic hydrocarbon (PAH) contamination

Background and aims

Legumes respond to PAH-contamination in a systemic manner and influence the overall rhizosphere microbial community structure, but the effect on the functional microbial community is unknown. In this study, plant-mediated PAH effects on specific bacterial taxa and the PAH-degraders in the rhizosphere were examined.

Methods

White clover was cultivated using a split-root system, with one side exposed to phenanthrene or pyrene, and the other side uncontaminated. Rhizosphere microbial diversity and activity were assessed with DGGE and qPCR, and changes in the root exudation were analyzed with GC-MS and HPLC.

Results

PAH contamination of one side of the rhizosphere significantly influenced the community structure of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Verrucomicrobia in the uncontaminated side of the rhizosphere. This indirect PAH-effect also influenced the diversity of bacterial PAH dioxygenase genes present, though the expression levels of these genes was not affected. No significant difference in the root exudation of general metabolites (amino acids, organic acids, sugars and sugar alcohols) and a flavonoid was observed.

Conclusions

In response to PAH-stress, white clover specifically influenced the diversity of the PAH-degrading community in its rhizosphere, but the abundance and activity of these PAH-degraders was not enhanced by the indirect PAH-effect. The plant-mediated response therefore does not appear to be directed towards enhanced removal of PAH for plant protection.

     

异裂菊属根际微生物群落结构及功能多样性

异裂菊属是广西喀斯特石山区典型的特有属,根际微生物是其能否有效吸收、有效利用土壤养分和适应石山恶劣土壤环境的最直接表征之一。该研究采用DGGE和Biolog两种方法对异裂菊属植物根际和非根际微生物多样性进行了研究。结果表明:(1)异裂菊属5个种根际pH、碱解氮等9个养分含量都高于非根际。(2)5个种的根际、非根际存在2个共有细菌类群,但在数量上存在差异,3个种的根际条带小于非根际;5个种的根际、非根际微生物群落较为相似,较易聚在一起。(3)绢叶异裂菊根际微生物对碳源利用能力最强,凹脉异裂菊非根际最弱,其他对碳源的利用能力较接近;异裂菊属种根际微生物利用碳源的能力都高于非根际,根际微生物多样性指数均高于非根际,优势度指数与非根际基本相同或略高于非根际,丰富度和均匀度指数与优势度指数规律相似;异裂菊属根际、非根际微生物利用的碳源主要是糖类、羧酸类和氨基酸类化合物,4个种根际微生物利用碳源的能力高于非根际。(4)阳离子交换量、黏粒含量百分率和碱解氮是影响异裂菊属根际微生物碳源利用模式的最重要因子。总体来说,土壤理化性质对异裂菊属植物根际微生物群落多样性具有重要影响,异裂菊属通过分泌羧酸、糖等多类化合物提高了根际微生物的活性,进而有效地提高了根际肥力水平。     

北京龙形水系三种沉水植物根际及叶际微生物群落特征

水生植物及植物表面附着微生物在人工湿地水体净化过程中发挥着重要的作用。以北京奥林匹克公园龙形水系为研究对象,通过高通量测序技术,对其底泥、水体及3种沉水植物——苦草Vallisneria natans、狐尾藻Myriophyllum verticillatum、龙须眼子菜Potamogeton pectinatus——的根际及叶际微生物群落的结构及功能进行了研究。结果表明,微生物多样性从高到低分别为底泥样品、植物根际样品、植物叶际样品和水体样品,植物叶际微生物种类要显著高于水体中微生物种类。LEfSe分析结果显示不同生境富集不同的微生物类群,其中底泥主要富集厌氧微生物类群,水体及植物叶际主要富集好氧微生物类群,植物根际则两者兼具。功能预测结果显示植物叶际样品的反硝化标志基因丰度要高于根际样品及底泥和水体样品,且狐尾藻和龙须眼子菜叶际样品反硝化标志基因丰度要高于苦草叶际样品。本研究可以为人工湿地构建时对沉水植物及功能微生物的选择提供指导意义。     

Chemical characterization of root exudates from rice (Oryza sativa) and their effects on the chemotactic response of endophytic bacteria

Root exudates represent an important source of nutrients for microorganisms in the rhizosphere and seem to participate in early colonization inducing chemotactic responses of rhizospheric bacteria. We characterized the root exudates collected from rice plantlets cultured under hydroponic conditions and assessed their effects on the chemotaxis of two strains of endophytic bacteria, Corynebacterium flavescens and Bacillus pumilus, collected from the rice rhizosphere. We compared these chemotactic effects on endophytic bacteria with those on two strains of plant-growth-promoting bacteria, Azospirillum brasilense (isolated from the corn rhizosphere) and Bacillus sp. (from the rice rhizosphere). The root exudates were collected at different time intervals. The highest concentration and diversity of amino acids and carbohydrates were found during the first 2 weeks after seeding. Histidine, proline, valine, alanine, and glycine were the main amino acid residues identified during the 4 weeks of culture. The main carbohydrates identified were glucose, arabinose, mannose, galactose, and glucuronic acid. The chemotactic responses of the analyzed endophytic bacteria to root exudates were 3.9 to 5.1 times higher than those of A. brasilense and 2.2 to 2.8 times higher than Bacillus sp. Our results indicate that rice exudates may induce a higher chemotactic response for endophytic bacteria than for other bacterial strains present in the rice rhizosphere.     

Effect of volatile substances released fromOriganum majorana andOcimum basilicum on the rhizosphere and phyllosphere fungi ofPhaseolus vulgaris

Differences were found in the counts and occurrence of fungi in the phyllosphere and thizosphere of two representatives of the Lamiacea family,Origanum majorana andOcimum basilicum, and in the phyllosphere and rhizosphere ofPhaseolus vulgaris growing separately or in coenosis withO. majorana orO. basilicum. Both the volatile substances released from ground leaves of the two latter pantl species and the root exudates affected considerably spore germination of isolated phylospheric and rhizospheric fungi. The results indicated a possible role of root exudates and volatile substances released from leaves in colonization of rhizosphere and/or phyllosphere by fungi, especially in associations of various plants.     

宁南山区典型植物根际与非根际土壤微生物功能多样性

选择宁南山区9种典型植物的根际与非根际土壤为研究对象,采用Biolog方法对土壤微生物功能多样性进行了研究。结果表明:9种不同植物根际土壤与非根际土壤的微生物活性(AWCD)、微生物多样性指数和微生物均匀度指数均存在明显差异;除冰草外,其他各种植物的根际土壤的微生物活性AWCD、微生物多样性指数和微生物均匀度指数均比非根际土壤的高;9种典型植物根际土壤微生物主要碳源利用类型是羧酸类和氨基酸类,非根际土壤微生物主要碳源利用类型是羧酸类、胺类、氨基酸类;微生物活性、微生物多样性指数和微生物均匀度指数两两之间均达到了极显著相关,与土壤化学性质各指标之间均未达到显著相关水平。     

蒙古沙冬青根际土壤细菌群落组成及多样性与生态因子相关性研究

蒙古沙冬青（Ammopiptanthus mongolicus）是中国西北荒漠唯一的常绿阔叶灌木,耐干旱、抗逆性强,在水土和荒漠化防治方面发挥着重要作用。为了探究蒙古沙冬青根际微生物多样性与生态因子互作机制,采用高通量测序技术测定了26个自然种群根际土壤细菌多样性;利用冗余分析（Redundancy analysis,RDA）探讨了根际细菌群落组成和多样性与生态因子之间的关系。结果表明：蒙古沙冬青根际土壤细菌隶属于15门、43纲、68目、123科、185属;主要优势细菌群为蓝菌门（Cyanobacteria）65.74%、变形菌门（Proteobacteria）21.72%、放线菌门（Actinobacteria）6.28%（相对丰度>2%）;优势菌纲为α-变形菌纲（Alphaproteobacteria）17.48%、放线菌纲（Actinobacteria）4.76%、γ-变形菌纲（Gammaproteobacteria）3.28%。RDA分析显示：生态因子能够解释蒙古沙冬青根际土壤细菌群落多样性52.69%的方差,其中年均降雨量（F=12.8,P=0.002）、纬度（F=5.1,P=0.016）、太阳辐射（F=5,P=0.02）是影响土壤细菌多样性的主要因素。研究结果可为深入认识荒漠生态系统中根际土壤细菌的群落结构和影响因素提供理论依据。     

Comparison of Survival of Campylobacter jejuni in the Phyllosphere with That in the Rhizosphere of Spinach and Radish Plants

Campylobacter jejuni has been isolated previously from market produce and has caused gastroenteritis outbreaks linked to produce. We have tested the ability of this human pathogen to utilize organic compounds that are present in leaf and root exudates and to survive in the plant environment under various conditions. Carbon utilization profiles revealed that C. jejuni can utilize many organic acids and amino acids available on leaves and roots. Despite the presence of suitable substrates in the phyllosphere and the rhizosphere, C. jejuni was unable to grow on lettuce and spinach leaves and on spinach and radish roots of plants incubated at 33°C, a temperature that is conducive to its growth in vitro. However, C. jejuni was cultured from radish roots and from the spinach rhizosphere for at least 23 and 28 days, respectively, at 10°C. This enteric pathogen also persisted in the rhizosphere of spinach for prolonged periods of time at 16°C, a temperature at which many cool-season crops are grown. The decline rate constants of C. jejuni populations in the spinach and radish rhizosphere were 10- and 6-fold lower, respectively, than on healthy spinach leaves at 10°C. The enhanced survival of C. jejuni in soil and in the rhizosphere may be a significant factor in its contamination cycle in the environment and may be associated with the sporadic C. jejuni incidence and campylobacteriosis outbreaks linked to produce.     

桐花树内生和根际细菌多样性及抗血栓活性研究

红树植物内生菌在红树共生体的物质循环、能量传递和健康维护等方面起着重要作用。为探究红树植物内生菌的多样性,进一步揭示内生菌在红树共生体的功能多样性提供菌种资源,该研究选择6种分离培养基和采用传统稀释涂布法对从广西北海滩涂上采集的桐花树组织和根际土壤样品进行分离,对获得的可培养细菌进行多样性分析,并通过体外溶栓实验筛选出具有抗血栓活性的菌株。结果表明:(1)基于16S rRNA基因序列系统进化分析,从桐花树组织和根际土壤中共获得125株细菌;分布于变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和厚壁菌门(Firmicutes) 3个门27个科39个属74个种中,芽孢杆菌属为优势菌属,菌株数量占13.5%。(2)抗血栓活性实验表明,初筛获得18株具有抗血栓活性细菌,总阳性率为24.32%;将初筛有活性的菌株进行复筛和重复验证实验,进一步验证其活性,结果复筛出3株细菌B1850、B1989和B2632具有很强抗血栓活性。综上所述,广西北海滩涂上红树植物桐花树中存在丰富的可培养细菌资源,具有从中挖掘新的纤溶酶和开发溶血栓药物的潜力。     

Taxus associated fungal endophytes: anticancerous to other biological activities

Endophytes are the plant microorganisms that flourish inside plants (endosphere) and support the growth under normal and challenging environmental circumstances. Besides biological activities, microbial endophytes are important for their contribution in adaptation and survival of the host plants under stressed environments. While various species of Taxus have been globally recognized mainly due to their anticancer property, emphasis has also been on isolation of taxol producing endophytes in view of the taxonomic (endangered) status of the species. Furthermore, Taxus associated endophytes are also being recognized for the biological activities other than taxol production. The present study reviews the diversity of Taxus associated endophytes along with their biological activities. Available literature on Taxus associated endophytes revealed that T. chinensis has received maximum attention (19.5 %), followed by T. wallichiana (18.5 %), T. baccata (16.4 %), T. cuspidata (11.3 %), and T. mairei (10.3 %); with a minimum number of reports accounted for T. globose (1.0 %), and T. celebica (2.0 %). Most fungal endophytes have been identified as ascomycetes. Basidiomycetous endophytes have been reported in a limited number of studies. No endophytes have yet been identified from three species, namely T. controta (West Himalayan yew), T. floridana (Florida yew), and T. canadensis (Canadian yew). A total of 70 diverse endophytic species have been reported from different Taxus species. Fusarium sp. (25.2 %), Aspergillus sp. (17.6 %), Alternaria sp. (11.3 %), Penicillium sp. and Cladosporium sp. (10.0 %) are the five dominant genera. Furthermore, 59.6 % of studies from the reported literature are related to taxol production by fungal endophytes, 9.6 % related to antimicrobial activity, and a combined 15.3 % related to other biological activities, i.e., antifeeding, antimitogenic, antioxidant and cytotoxic activities. Additionally, 3.8 % of fungal endophytes were not studied for any of their biological activities. Only three bacterial endophytes namely Burkholderia sp., Enterobacter sp., and Pseudomonas sp., have been recorded from Taxus along with their contribution in plant growth, antagonistic, and antioxidant activities. Isolation and characterization of microbial endophytes from Taxus plant parts is important for the associated ecology and medicinally important biological activities. It will support the much-required conservation strategy of Taxus species. Further, isolation of plant growth promoting microorganisms from Taxus will help in propagation of the species.     

Illumina-based analysis of the rhizosphere microbial communities associated with healthy and wilted Lanzhou lily (<Emphasis Type="Italic">Lilium davidii</Emphasis> var. <Emphasis Type="Italic">unicolor</Emphasis>) plants grown in the field

Lanzhou lily (Liliumdavidii var. unicolor) is the best edible lily as well as a traditional medicinal plant in China. The microbes associated with plant roots play crucial roles in plant growth and health. However, little is known about the differences of rhizosphere microbes between healthy and wilted Lanzhou lily (Lilium davidii var. unicolor) plants. The objective of this study was to compare the rhizosphere microbial community and functional diversity of healthy and wilted plants, and to identify potential biocontrol agents with significant effect. Paired end Illumina Mi-Seq sequencing of 16S rRNA and ITS gene amplicons was employed to study the bacterial and fungal communities in the rhizosphere soil of Lanzhou lily plants. BIOLOG technology was adopted to investigate the microbial functional diversity. Our results indicated that there were major differences in the rhizosphere microbial composition and functional diversity of wilted samples compared with healthy samples. Healthy Lanzhou lily plants exhibited lower rhizosphere-associated bacterial diversity than diseased plants, whereas fungi exhibited the opposite trend. The dominant phyla in both the healthy and wilted samples were Proteobacteria and Ascomycota, i.e., 34.45 and 64.01 %, respectively. The microbial functional diversity was suppressed in wilted soil samples. Besides Fusarium, the higher relative abundances of Rhizoctonia, Verticillium, Penicillium, and Ilyonectria (Neonectria) in the wilted samples suggest they may pathogenetic root rot fungi. The high relative abundances of Bacillus in Firmicutes in healthy samples may have significant roles as biological control agents against soilborne pathogens. This is the first study to find evidence of major differences between the microbial communities in the rhizospheric soil of healthy and wilted Lanzhou lily, which may be linked to the health status of plants.     

Analogous wheat root rhizosphere microbial successions in field and greenhouse trials in the presence of biocontrol agents Paenibacillus peoriae SP9 and Streptomyces fulvissimus FU14

Two Pythium-infested soils were used to compare the wheat root and rhizosphere soil microbial communities from plants grown in the field or in greenhouse trials and their stability in the presence of biocontrol agents. Bacteria showed the highest diversity at early stages of wheat growth in both field and greenhouse trials, while fungal diversity increased later on, at 12 weeks of the crop cycle. The microbial communities were stable in roots and rhizosphere samples across both soil types used in this study. Such stability was also observed irrespective of the cultivation system (field or greenhouse) or addition of biocontrol coatings to wheat seeds to control Pythium disease (in this study soil infected with Pythium sp. clade F was tested). In greenhouse plant roots, Archaeorhizomyces, Debaryomyces, Delftia, and unclassified Pseudeurotiaceae were significantly reduced when compared to plant roots obtained from the field trials. Some operational taxonomic units (OTUs) represented genetic determinants clearly transmitted vertically by seed endophytes (specific OTUs were found in plant roots) and the plant microbiota was enriched over time by OTUs from the rhizosphere soil. This study provided key information regarding the microbial communities associated with wheat roots and rhizosphere soils at different stages of plant growth and the role that Paenibacillus and Streptomyces strains play as biocontrol agents in supporting plant growth in infested soils.