番茄根际微生物种群动态变化及多样性

采用盆栽试验的方法对番茄根际主要微生物种群在不同生育期的动态变化进行了跟踪研究.结果表明,在番茄整个生育期内,可培养细菌数量在初花期和初果期时最多;放线菌数量从苗期到末期逐渐减少;真菌数量逐渐增多.番茄对细菌根际效应明显.DGGE图谱显示不同生育期番茄根际均具有较高的细菌多样性.根际细菌种类和数量在初花期发生较为显著的变化,初果期根际群落多样性指数(H)和物种丰度(S)值都达到最高,微生物最丰富,是筛选拮抗菌的较好时期.     

施磷对干旱胁迫下箭竹根际土壤养分及微生物群落的影响

以箭竹及其根际土壤作为研究对象,采用两因素随机区组实验,设置2种水分处理（正常浇水和干旱胁迫）和2种施磷量处理（施磷和不施磷）,探究施磷对干旱胁迫下箭竹根际土壤养分及微生物群落结构和多样性的影响。结果表明：（1）干旱胁迫显著降低了箭竹根际土壤中微生物量碳、可溶性有机氮和有效磷的含量,虽对箭竹根际土壤微生物群落的多样性无显著影响,但显著降低了箭竹根际土壤中总PLFA（phospholipid fatty acid contents）的含量和真菌、细菌、革兰氏阳性菌与革兰氏阴性菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌的PLFA比值,显著改变了箭竹根际土壤微生物群落结构,结果显著降低了箭竹的生物量。（2）施磷显著增加了受旱箭竹根际土壤中微生物量碳和有效磷的含量,虽大体上对受旱箭竹根际土壤微生物群落的多样性无显著影响,但显著增加了受旱箭竹根际土壤中总PLFA和真菌PLFA的含量,并在一定程度上增加了细菌、革兰氏阳性菌、革兰氏阴性菌和放线菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌和真菌/细菌的PLFA比值,也在一定程度上改善了受旱箭竹根际土壤微生物群落结构,从而改善受旱箭竹的生长。（3）主成分分析表明,干旱对箭竹根际土壤微生物群落结构的影响显著,而施磷的影响不明显。（4）相关分析发现,箭竹根际土壤微生物群落结构与箭竹根际土壤微生物量碳、可溶性有机氮及箭竹生物量呈显著正相关。综上,干旱降低了箭竹根际土壤养分含量和微生物生物量,改变了箭竹根际土壤微生物群落结构,抑制了箭竹的生长;施磷能增加受旱箭竹根际土壤养分含量和微生物生物量,改善受旱箭竹根际土壤微生物群落结构,进而改善受旱箭竹的生长。     

Soil and plant effects on microbial community structure

We investigated the effects of two different plant species (corn and soybean) and three different soil types on microbial community structure in the rhizosphere. Our working hypothesis was that the rhizosphere effect would be strongest on fast-growing aerobic heterotrophs, while there would be little or no rhizosphere effect on oligotrophic and other slow-growing microorganisms. Culturable bacteria and fungi had larger population densities in the rhizosphere than in bulk soil. Communities were characterized by soil fatty acid analysis and by substrate utilization assays for bacteria and fungi. Fatty acid analysis revealed a very strong soil effect but little plant effect on the microbial community, indicating that the overall microbial community structure was not affected by the rhizosphere. There was a strong rhizosphere effect detected by the substrate utilization assay for fast-growing aerobic heterotrophic bacterial community structure, with soil controls and rhizosphere samples clearly distinguished from each other. There was a much weaker rhizosphere effect on fungal communities than on bacterial communities as measured by the substrate utilization assays. At this coarse level of community analysis, the rhizosphere microbial community was impacted most by soil effects, and the rhizosphere only affected a small portion of the total bacteria.     

盐爪爪根部微生物分布特征及盐浓度对碳源代谢分析的影响

【背景】耐盐植物盐爪爪广泛分布于盐碱荒漠区域,其根际存在明显的盐离子富集,形成"盐岛效应",研究此过程中微生物如何演替和适应,对揭示盐爪爪根际微生物的分布及其耐盐特性、"盐岛"的形成具有重要科学意义。【目的】揭示盐爪爪根际、根区及其周围环境土壤中微生物分布特征,确定不同盐浓度处理对根际微生物Biolog Eco微平板碳源代谢多样性的影响。【方法】采用Biolog Eco微平板技术,对采自新疆和硕地区的盐爪爪根际、根区和环境土壤微生物碳源利用情况进行分析,并采用不同浓度NaCl溶液对盐爪爪根际土壤样品进行稀释加样,评估盐浓度对根际微生物活性及多样性分析的影响。【结果】样品微生物代谢活性总体呈现根际根区环境的趋势;随着与根部距离的增加,样品中利用氨基酸、胺类碳源微生物所占比例明显降低,而利用吐温和肝糖等多聚化合物类碳源微生物所占比例明显增加;多样性分析表明,随着与根部距离的增加,Shannon指数(H)随之降低且存在明显差异。不同浓度NaCl溶液对采用BiologEco微平板技术分析盐爪爪根际微生物的代谢活性和代谢多样性有着明显的影响,其中采用5%NaCl溶液作为稀释加样液的根际微生物活性最高。【结论】盐爪爪根部微生物组成和分布有着明显的演变规律,且采用Biolog Eco微平板技术分析微生物代谢多样性时需进行培养条件的优化。     

连作对麦冬根际土壤细菌群落的影响

以中草药麦冬为研究对象,采用变性梯度凝胶电泳(DGGE)方法,考察连作对麦冬根际土壤细菌群落的影响。结果表明,重茬麦冬根际细菌群落的Shannon-Wiener指数从苗期至快速生长期、再到块根膨大期分别为3.36-3.40-3.69,丰富度指数为55.0-61.5-63.5,均匀度指数为0.84-0.82-0.89;而同期正茬根际细菌群落的上述指数值分别为3.66-3.33-3.72、67.5-53.5-63.5和0.87-0.84-0.90。通过对土壤细菌群落的DGGE图谱进行主成分分析,结果显示,上述各个时期重茬与正茬样本均发生显著分离,表明连作改变了麦冬根际细菌群落的多样性变化趋势和结构组成。进一步比较麦冬块根膨大期根际主要功能菌群的数量变化,发现连作后氨化细菌和好气性纤维素分解菌数量增加,而硝化细菌和固氮菌的数量减少。对比发现重茬麦冬的产量仅为正茬的70.6%,表明麦冬连作减产与其根际土壤细菌群落的变化相关。     

Soil microbial diversity as affected by the rhizosphere of the hyperaccumulator Thlaspi caerulescens under natural conditions

It is hypothesized that metal hyperaccumulator plants have specific rhizosphere conditions, potentially modifying the bioavailability of soil metals. This article aims to further the knowledge about the rhizosphere of the hyperaccumulator Thlaspi caerulescens, focusing on its microflora isolated from metalliferous soils collected in situ where the plants grow naturally. We characterized the cultivable microbial communities isolated from the rhizosphere of one population of this Ni hyperaccumulator species grown on a serpentine soil. The rhizosphere soil harbored a wide variety of microorganisms, predominantly bacteria, confirming the stimulatory effect of the T. caerulescens rhizosphere on microbial growth and proliferation. We tested the hypothesis that the rhizosphere of T. caerulescens influences (1) the metabolic diversity of the bacterial community and (2) the bacterial resistance to metals. The principal component analysis of the Biolog plate's data confirmed a structural effect of the rhizosphere of T. caerulescens on bacterial communities. The percentage of Ni-resistant bacteria was higher in the rhizosphere than in the bulk soil, suggesting a direct effect of the rhizosphere on Ni tolerance, reflecting a greater bacterial tolerance to Ni in the rhizosphere.     

小蓬竹根际土壤微生物及内生真菌多样性分析

为了解喀斯特典型物种-小蓬竹根际土壤微生物及不同部位内生真菌多样性,采用沿等高线等距离取样法采集小蓬竹根际土壤及健康植株,通过可培养对根际土微生物及内生菌进行分离,利用分子技术对其进行鉴定,根据鉴定结果构建系统发育树,并计算小蓬竹根际土壤微生物和根茎叶内生真菌多样性。结果如下：（1）共从根际土壤、根、茎、叶分离得到139个真菌菌株,隶属于27属,其中根际土壤分离得到34个真菌菌株隶属于12属,根部分离得到的63个内生真菌菌株隶属于17个属,茎部分离得到的14个内生真菌菌株隶属于8个属,叶部分离得到28个内生真菌菌株隶属于9个属;（2）根际土壤共分离得到41株细菌菌株,隶属于7个属26个种,20株放线菌菌株,隶属于1属15种;从Shannon-Wiener多样性指数、均匀度指数、Simpson指数排序来看,真菌主要表现为根 > 根际土壤 > 茎 > 叶,细菌和放线菌多样性均较低。（3）按层次聚类分析可分别将真菌、细菌、放线菌聚为3支。小蓬竹根际土壤、根、茎和叶具有丰富的微生物多样性,不同部位菌群组成存在差异性（P<0.05）,且存在以假单胞菌属、芽孢杆菌属等为优势属的抗盐耐旱菌群,这有助于揭示小蓬竹对喀斯特生境的适应性,以及为微生物-植物群落之间相互关系提供一定基础数据,为后期寻找小蓬竹相关耐性功能菌奠定基础。     

紫花苜蓿根际氢氧化细菌的分离及其对小麦种子促生作用的研究

从大豆植物根际分离的氢氧化细菌对植物的生长有促进作用,但是关于其他的豆科植物根际分离的氢氧化细菌是否也有促生作用的研究甚少。从紫花苜蓿根际土壤分离氢氧化细菌,并进行其对小麦种子促生实验的研究,判断氢氧化细菌是否有促生作用,从而丰富具有促生作用的根际微生物资源。采用MSA培养基,从铜川新区紫花苜蓿根际土壤中分离得到氢氧化细菌疑似菌株,对其进行TTC法检测菌株氢化酶活性和自养能力的特性,以获得氢氧化细菌;通过小麦种子的萌发进行促生实验验证。结果表明,16株菌株处理过的小麦根长分别增加25%～128%,芽长增长27%～73%,鲜重增加48%～103%。从苜蓿根际土壤分离出的氢氧化细菌均具有较明显的促生作用。     

间作绿肥对油菜根际土壤碳氮及根际微生物的影响

在我国西南紫色土地区,农田生态环境极为脆弱,绿肥应用也面临严峻问题。为改善农田土壤健康状况,探索绿肥的应用途径,通过紫云英与油菜间作,重点探讨了绿肥紫云英对油菜根际土壤碳氮及其微生物特征的影响,同时与秸秆覆盖的效应作了比较,其创新性在于将绿肥紫云英应用于西南旱地,并且为建立新的油菜种植模式作铺垫。结果表明:与秸秆覆盖相比,间作绿肥紫云英是影响油菜根际土壤环境的主要因素。间作紫云英减少了油菜根际土壤碳、氮含量,改变了油菜根际土壤碳氮比。间作紫云英也减少了油菜根际土壤微生物量,改变了油菜根际土壤微生物群落结构,改善了油菜根际土壤通气状况,抑制了厌氧细菌的生长。     

内蒙草原不同植物功能群及物种对土壤微生物组成的影响

为了分析不同植物群落组成对内蒙古典型草原土壤微生物群落组成的影响,本研究利用植物功能群剔除处理实验平台,采用荧光定量PCR(real-timePCR)和自动核糖体间隔区基因分析(automated ribosomal intergenic spacer analysis,ARISA)技术,对不同植物功能群组成的非根际土壤和常见物种的根际土壤中细菌和真菌的数量及群落结构进行了分析。结果表明,在非根际土壤中,不同植物功能群组成对细菌数量有显著影响,而对真菌数量及细菌和真菌的群落结构影响不明显;在根际土壤中,不同植物物种对细菌、真菌的数量都有显著影响。此外,聚类分析表明,不同物种的根际土中细菌和真菌的群落结构也有所不同,尤其以细菌的群落结构变化较为明显。研究结果表明不同植物物种可以通过根系影响土壤微生物群落组成。     

Contrasting Soil Ciliate Species Richness and Abundance between Two Tropical Plant Species: A Test of the Plant Effect

We still have a rudimentary understanding about the mechanism by which plant roots may stimulate soil microbial interactions. A biochemical model involving plant-derived biochemical fractions, such as exudates, has been used to explain this “rhizosphere effect” on bacteria. However, the variable response of other soil microbial groups, such as protozoa, to the rhizosphere suggests that other factors could be involved in shaping their communities. Thus, two experiments were designed to: (1) determine whether stimulatory and/or inhibiting factors associated with particular plant species regulate ciliate diversity and abundance and (2) obtain a better understanding about the mechanism by which these plant factors operate in the rhizosphere. Bacterial and chemical slurries were reciprocally exchanged between two plant species known to differ in terms of ciliate species richness and abundance (i.e., Canella winterana and plantation Tectona grandis). Analysis of variance showed that the bacteria plus nutrients and the nutrients only treatment had no significant effect on overall ciliate species richness and abundance when compared to the control treatment. However, the use of only colpodean species increased the taxonomic resolution of treatment effects revealing that bacterial slurries had a significant effect on colpodean ciliate species richness. Thus, for particular rhizosphere ciliates, biological properties, such as bacterial diversity or abundance, may have a strong influence on their diversity and possibly abundance. These results are consistent with a model of soil bacteria-mediated mutualisms between plants and protozoa.     

Dissecting the Rhizosphere complexity: The truffle-ground study case

The word Rhizosphere describes the part of the soil which is immediately adjacent to and affected by plant roots. This is a very dynamic environment where plants, soil and microorganisms interact. The plant releases, in addition to biologically active substances, nutritive substances (exudates), which create a privileged habitat for many microbial populations. The same microbes that live in the rhizosphere may be useful for the plant. Interest in this fascinating environment has increased over the years. However, our knowledge of the biology and diversity of microbial populations in the rhizosphere is still limited, because it has always been linked to traditional culture-based techniques. These methods, which only allow the study of cultured microorganisms, do not allow the majority of the organisms existing in nature to be characterized. Over the last few years, this limitation has been overcome through the introduction of methodologies that are independent of culture techniques. This different approach, which has revolutionized scientific research, is known as metagenomics. In this review, the rhizosphere environment is considered with particular attention to the fungal and symbiotic organisms, which populate it. The new environmental genomic techniques and how these have been applied to the study of the various environments and the rhizosphere are described. Finally, a specific rhizosphere, a truffle-ground, is described as our study case.      

Rhizosphere soil microorganism populations and community structures of different watermelon cultivars with differing resistance to Fusarium oxysporum f. sp. niveum

Fusarium wilt is an increasingly serious disease of watermelon that reduces crop productivity. Changes in microorganism populations and bacterial and fungal community structures in rhizosphere soil of watermelon cultivars resistant or susceptible to Fusarium oxysporum f. sp. niveum were investigated using a plate culture method and PCR-DGGE analysis. Plate culture showed that populations of culturable bacteria and actinomycetes were more abundant in the rhizosphere of the resistant watermelon cultivar than the susceptible cultivar, but the fungi population had the opposite pattern. Populations of Penicillium , Fusarium , and Aspergillus were significantly lower in the resistant cultivar than the susceptible cultivar at the fruiting and uprooting stages (p?< 0.05). Pattern matching analysis generated the dendrogram of the DGGE results indicating the relatedness of the different resistant watermelon cultivars and their corresponding rhizosphere microbial communities. Further sequencing analysis of specific bands from DGGE profiles indicated that different groups of bacteria and fungi occurred in the rhizosphere of different watermelon cultivars. Our results demonstrated that plant genotype had a significant impact on soil microbial community structure, and the differences in the rhizosphere microbial community may contribute to the differences in resistance to F. oxysporum f. sp. niveum.     

Microbial community in the rhizosphere of young maize seedlings is susceptible to the impact of introduced pseudomonads as indicated by FAME analysis

Two species of Pseudomonas (i.e. P. chlororaphis or P. putida) derived from a maize rhizosphere were studied for their impact on the structure of the microbial community in the rhizosphere of young maize seedlings after inoculation. The culturable bacteria and total microbial communities were analyzed based on profiles of whole-cell fatty acid methyl esters (MIDI-FAME). The introduction of Pseudomonas species resulted in the shift from the Gram-positive dominated culturable community in the rhizosphere of uninoculated maize to more Gram-negative populations in the rhizospheres of the inoculated plants. For the total rhizosphere communities, 43, 47 and 42 FAMEs were detected in the uninoculated maize and the samples inoculated with P. chlororaphis or P. putida, respectively. In contrast to the culturable communities, low concentrations of marker FAMEs for Gram-positives (i15:0, a15:0, i16:0) were found in the profiles of the total rhizosphere communities. The maize inoculations resulted in an enrichment of some Gram-negative isolates; however, Gram-positive bacteria, Cytophaga/Flavobacterium and saprophytic fungi were found in the uninoculated rhizosphere.     

Phenotypic characterization of microbes in the rhizosphere of Alyssum murale

Metal hyperaccumulator plants like Alyssum murale are used for phytoremediation of Ni contaminated soils. Soil microorganisms are known to play an important role in nutrient acquisition for plants, however, little is known about the rhizosphere microorganisms of hyperaccumulators. Fresh and dry weight, and Ni and Fe concentrations in plant shoots were higher when A. murale was grown in non-sterilized compared to sterilized soils. The analysis of microbial populations in the rhizosphere of A. murale and in bulk soils demonstrated that microbial numbers were affected by the presence of the plant. Significantly higher numbers of culturable actinomycetes, bacteria and fungi were found in the rhizosphere compared to bulk soil. A higher percent of Ni-resistant bacteria were also found in the rhizosphere compared to bulk soil. Percentage of acid producing bacteria was higher among the rhizosphere isolates compared to isolates from bulk soil. However, proportions of siderophore producing and phosphate solubilizing bacteria were not affected by the presence of the plant. We hypothesize that microbes in the rhizosphere of A. murale were capable of reducing soil pH leading to an increase in metal uptake by this hyperaccumulator.     

青稞根腐病对根际土壤微生物及酶活性的影响

选取甘肃省卓尼县青稞种植区为研究地点,调查青稞根腐病的发病情况,并分别采集其健康植株和发病株根际的土壤,对比分析其土壤微生物生物量(碳、氮、磷)、微生物数量(细菌、真菌、放线菌)以及过氧化氢酶、蔗糖酶、脲酶、碱性磷酸酶、纤维素酶5种酶活性。结果发现,研究区10个采样点均有青稞根腐病的发生,发病率在5%—20%之间,不同地点发病率不同。根腐病的发生,会显著影响青稞根际微生物生物量,导致微生物生物量碳、氮、磷的含量发生变化,其中微生物生物量氮和磷含量整体降低,且不同采样点微生物量不同。土壤微生物数量总体呈现细菌放线菌真菌的趋势,但不同微生物对根腐病发病的响应不同,细菌和放线菌数量因根腐病的发生而减少,真菌的数量则增多;不同采样点土壤微生物数量不相同,细菌和真菌呈现区域性特征,放线菌的数量不呈现地域性。根腐病的发生还造成土壤酶活性的改变,其中蔗糖酶、脲酶、磷酸酶的含量因根腐病的发生而降低,而纤维素酶则升高,过氧化氢酶的变化没有规律。总而言之,根腐病的发生会使青稞根际土壤微生物组成发生改变,碳、氮、磷等物质代谢受到抑制,而能量代谢发生紊乱。因此,研究和防治青稞根腐病就必须重视土壤微生物及土壤酶的作用。     

小麦-蚕豆间作条件下氮肥施用量对根际微生物区系的影响

通过田间小区试验,研究了小麦/蚕豆间作条件下4种施氮水平(0、90、180和270 kg·hm^-2)对根际微生物区系和多样性的影响.结果表明：在整个生育期,微生物数量有一定的波动,但均以开花期数量最高.与单作相比,间作显著增加了小麦和蚕豆根际的细菌、真菌、放线菌数量和微生物总量,而显著降低了开花期和成熟期蚕豆根际的微生物多样性.在不施氮（N₀）和低氮（N₉₀）水平下,间作与单作在微生物数量上的差异较大.间作对土壤微生物数量的促进效应在分蘖期和开花期最大,成熟期显著降低.小麦根际的微生物数量随施氮量的增加先增加后降低,以常规施氮处理（N₁₈₀）的微生物数量最多,氮肥用量对单作小麦的影响大于间作小麦. 施氮量对蚕豆根际细菌、真菌、放线菌数量和微生物多样性无显著影响,但降低了间作蚕豆根际微生物总量.适量施用氮肥能有效调节根际微生物区系,间作系统地上部植物多样性与地下部微生物区系间存在紧密联系.     

转HrpN的工程菌E4对水稻根际细菌群落结构的影响

采用单一碳源回收菌群的方法与ERIC-PCR方法相结合,检测水稻(Oryza sativa L.)根际施用转基因微生物E4(Enterobacteria cloacae E4)后,其根际微生物的群落结构和多样性的变化,进而推测转基因微生物E4在田间施用的安全性。结果表明：转基因微生物E4施用到水稻根际后,水稻根际的代谢指纹图谱和。DNA指纹图谱都发生了改变,采用Sollthelxi blotting检测显示：E4成为根际的优势菌,这对植物生长有利,应该不会造成不利的影响。     

内蒙古草原典型植物对土壤微生物群落的影响

为了分析内蒙古草原不同植物物种对土壤微生物群落的影响, 采用实时荧光定量PCR (real-time PCR)以及末端限制性片段长度多态性分析(terminal restriction fragment length polymorphism, T-RFLP)等分子生物学技术, 测定了退化-恢复样地上几种典型植物的根际土壤和非根际土壤中细菌和真菌的数量及群落结构。结果表明, 不同植物物种对根际和非根际细菌及根际真菌数量均有显著影响。根际土壤中的细菌和真菌数量普遍高于非根际土壤, 尤其以真菌更为明显。对T-RFLP数据进行多响应置换过程(multi-response permutation procedures, MRPP)分析和主成分分析(principal component analysis, PCA), 结果表明, 大多数物种的根际细菌及真菌的群落结构与非根际有明显差异, 并且所有物种的真菌群落可以按根际和非根际明显分为两大类群。此外, 细菌和真菌群落结构在一定程度上存在按物种聚类的现象, 以细菌较为明显。这些结果揭示了不同植物对土壤微生物群落的影响特征, 对理解内蒙古草原地区退化及恢复过程中植被演替引起的土壤性质和功能的变化有一定的帮助。     

The alternative oxidase from Euglena gracilis

We still have a rudimentary understanding about the mechanism by which plant roots may stimulate soil microbial interactions. A biochemical model involving plant-derived biochemical fractions, such as exudates, has been used to explain this "rhizosphere effect" on bacteria. However, the variable response of other soil microbial groups, such as protozoa, to the rhizosphere suggests that other factors could be involved in shaping their communities. Thus, two experiments were designed to (a) obtain a better understanding of the mechanism by which ciliate species richness and abundance differ among plant species and (b) to determine whether this mechanism is maintained via stimulatory and/or inhibiting factors associated with particular plant species. Bacterial and chemical slurries were reciprocally exchanged between two plant species known to differ in terms of ciliate species richness and abundance (i.e., Canella winterana and plantation Tectona grandis ). The ANOVA showed that the bacteria plus nutrients, and the nutrients-only treatment have no significant effect on the overall ciliate species richness and abundance when compared to the control treatment. However, the use of only colpodean species to increase the taxonomic resolution of treatment effects showed that bacterial slurries have a significant effect on colpodean ciliate species richness. These results suggest that for particular rhizosphere ciliates, biological properties, such as bacterial diversity or abundance, may have a strong influence on their diversity and possibly abundance. These results are consistent with a model of soil bacteria-mediated mutualism between plants and protozoa.