α-Tomatine Suppresses Invasion and Migration of Human Non-Small Cell Lung Cancer NCI-H460 Cells Through Inactivating FAK/PI3K/Akt Signaling Pathway and Reducing Binding Activity of NF-κB

α-Tomatine, isolated from Lycopersicon esculentum Linn., is a naturally occurring steroidal glycoalkaloid in immature green tomatoes. Some reports demonstrated that α-tomatine had various anticarcinogenic properties. The purpose of this study is to investigate the anti-metastatic effect of α-tomatine in NCI-H460 human non-small cell lung cancer cells. First, the results showed that α-tomatine significantly suppressed the abilities of the adhesion, invasion, and migration of NCI-H460 cells under non-cytotoxic concentrations. Molecular data also showed α-tomatine could inhibit the activation of focal adhesion kinase (FAK) and phosphatidylinositol 3-kinase (PI3K)/Akt signal involve in the downregulation the enzyme activities, protein and messenger RNA levels of matrix metalloproteinase-7 (MMP-7). Next, α-tomatine also strongly inhibited the degradation of inhibitor of kappaBα (IκBα) and the nuclear levels of nuclear factor kappa B (NF-κB). Also, a dose-dependent inhibition on the binding ability of NF-κB by α-tomatine treatment was further observed. Furthermore, α-tomatine significantly decreased the levels of phospho-Akt and MMP-7 in Akt1-cDNA-transfected cells concomitantly with a marked reduction on cell invasion and migration. Presented results indicated α-tomatine might be further application for treating cancer metastasis.     

Culturable bacterial communities on leaf sheaths and panicles of rice plants in Japan

Culturable bacterial communities on rice plants were investigated from 2001 to 2003. In total, 1,394 bacterial isolates were obtained from the uppermost leaf sheaths at 1 month before heading time and from leaf sheaths and panicles at heading time. The average culturable bacterial population on the leaf sheaths was larger at heading time than at 1 month previously. Furthermore, the population was significantly larger on panicles than on leaf sheaths, suggesting that the bacterial population is influenced by the organs of rice plants. Larger proportions of bacteria were obtained from the macerates of leaf sheaths after washing with phosphate buffer, and most culturable bacteria were verified to inhabit the inside or inner surface, rather than the outer surface, of the tissues. Verification of the bacterial composition based on 16S rRNA gene sequences revealed that genera of Sphingomonas, Microbacterium, Methylobacterium, and Acidovorax tended to be dominant colonizers on leaf sheaths, whereas Pseudomonas and Pantoea were isolated mainly from the panicles, indicating that leaf sheaths and panicles harbor distinct communities. Furthermore, the richness of bacterial genera was less on both leaf sheaths and panicles at heading time compared with that observed 1 month before heading time. Phylogenetic analyses using bacterial isolates belonging to the four dominant genera inhabiting leaf sheaths at heading time revealed that particular bacterial groups in each genus colonized the leaf sheaths.     

Combined use of Alkane-Degrading and Plant Growth-Promoting Bacteria Enhanced Phytoremediation of Diesel Contaminated soil

Inoculation of plants with pollutant-degrading and plant growth-promoting microorganisms is a simple strategy to enhance phytoremediation activity. The objective of this study was to determine the effect of inoculation of different bacterial strains, possessing alkane-degradation and 1-amino-cyclopropane-1-carboxylic acid (ACC) deaminase activity, on plant growth and phytoremediation activity. Carpet grass (Axonopus affinis) was planted in soil spiked with diesel (1% w/w) for 90 days and inoculated with different bacterial strains, Pseudomonas sp. ITRH25, Pantoea sp. BTRH79 and Burkholderia sp. PsJN, individually and in combination. Generally, bacterial application increased total numbers of culturable hydrocarbon-degrading bacteria in the rhizosphere of carpet grass, plant biomass production, hydrocarbon degradation and reduced genotoxicity. Bacterial strains possessing different beneficial traits affect plant growth and phytoremediation activity in different ways. Maximum bacterial population, plant biomass production and hydrocarbon degradation were achieved when carpet grass was inoculated with a consortium of three strains. Enhanced plant biomass production and hydrocarbon degradation were associated with increased numbers of culturable hydrocarbon-degrading bacteria in the rhizosphere of carpet grass. The present study revealed that the combined use of different bacterial strains, exhibiting different beneficial traits, is a highly effective strategy to improve plant growth and phytoremediation activity.     

果实红色与黄色番茄品种植株茎部内生细菌群落结构及代谢功能特征

[目的]比较果实颜色分别为红色和黄色的番茄植株茎部内生细菌群落组成及代谢功能特征,旨在探究番茄果色形成与植株内生细菌的关联,为构建番茄育种新型的评价体系,以及开发利用有益微生物功能提供理论依据和技术支撑.[方法]基于MiSeq高通量测序技术,分析果实颜色分别为红色和黄色番茄品种植株茎部内生细菌群落组成及相关代谢功能生物...     

Orchid-associated bacteria produce indole-3-acetic acid,promote seed germination,and increase their microbial yield in response to exogenous auxin

Germination of orchid seeds is a complex process. In this paper we focus on interactions between the host-plant and its bacterial partners via indole-3-acetic acid (IAA). Originally isolated from the roots of the epiphytic orchid Dendrobium moschatum, the strains of Rhizobium, Microbacterium, Sphingomonas, and Mycobacterium genera were among the most active IAA producers. Addition of exogenous tryptophan significantly enhanced auxin formation both in mineral and complex media. The presence of IAA and indole-3-acetaldehyde was confirmed by HPLC. Indole-3-pyruvic and indole-3-lactic acids were also detected in supernatants of culture filtrates of Sphingomonas sp., Rhizobium sp., and Microbacterium sp., while indole-3-acetamide was identified only in Mycobacterium sp. Some concentration- and strain-dependent effects of exogenous IAA on bacterial development were also established. Treatment of the cultures with 10 and 100 μg/ml of auxin resulted in an increase in microbial yield. None of the investigated strains was able to utilize IAA as a source of carbon and energy. Furthermore, inoculation of D. moschatum seeds with Sphingomonas sp. and Mycobacterium sp. resulted in considerable enhancement of orchid seeds germination. This growth-promoting activity was observed in the absence of any plant growth stimulators or mycorrhizal fungi, usually required for orchid germination.     

Characterization of plant-growth promoting diazotrophic bacteria isolated from field grown Chinese cabbage under different fertilization conditions

Diazotrophic bacteria isolated from the rhizosphere of Chinese cabbage were assessed for other plant growth promoting characteristics viz., production of IAA, ethylene, ACC deaminase, phosphate solubilization, and gnotobiotic root elongation. Their effect on inoculation to Chinese cabbage was also observed under growth chamber conditions. A total of 19 strains that showed higher nitrogenase activity identified by 16S rRNA gene sequence analysis were found to be the members of the genera Pseudomonas and Agrobacterium belonging to α- and γ-Proteobacteria groups. These strains were also efficient in producing IAA and ACC deaminase though they produced low levels of ethylene and no phosphate solubilization. In addition, inoculation of selected diazotrophic bacterial strains significantly increased seedling length, dry weight, and total nitrogen when compared to uninoculated control. The colonization of crop plants by diazotrophic bacteria can be affected by many biotic and abiotic factors, and further studies are oriented towards investigating the factors that could influence the establishment of a selected bacterial community.     

水稻种子内生泛菌(Pantoea spp.)系统发育多样性及其促生功能

【目的】Pantoea菌株是广泛分布在自然界中的一类功能多样的细菌。本研究对分离自水稻种子内生的Pantoea菌株进行系统发育分析及功能评价,从而确定分类地位、种类多样性、分布特征及功能特性。【方法】采用乙醇-次氯酸钠联合灭菌方法进行水稻种子的表面灭菌,进行内生细菌的分离与纯化;其次将纯化后的菌株进行16Sr RNA基因PCR扩增及序列分析,通过MEGA7软件构建系统发育树;将分离得到的菌株进行功能实验检测,如溶磷、产IAA、产铁载体、拮抗病原真菌等特性,最后检测菌株的溶血性;水稻分型采用SSR方法,并对水稻农学性状如分蘖数、株高、植株重及产量进行调查。【结果】本研究对分离自8个不同基因型水稻种子中的146株内生Pantoea菌株进行系统发育分析及功能评价,结果发现所分离到的泛菌菌株主要属于Pantoea dispersa、Pantoea agglomerans、Pantoea cypripedii以及Pantoea brenneri四个种,其中P. dispersa的菌株数量最多,分布最广,并且存在于所有的8个水稻种子样品中。对其中66株菌进行功能检测,发现86.3%和69.7%的菌株具有溶磷和产IAA能力,有7株菌具有产铁载体能力,未发现对真菌病害Fusarium moniliforme有拮抗作用的菌株,并发现3株菌具有溶血性;本实验未发现泛菌组成与水稻系统发育及农学性状存在明显的相关性。【结论】本研究首次对水稻种子中泛菌的多样性及其功能进行报道,发现不同基因型的水稻种子所含Pantoea种类及组成存在差异,种子选择性地积累了Pantoea类群,大部分菌株具有一定的促生特性。该研究结果有助于进一步探究微生物与植物的共进化、种子微生物的传播途径及作用方式。     

Endophytic bacterial diversity in grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) leaves described by 16S rRNA gene sequence analysis and length heterogeneity-PCR

Diversity of bacterial endophytes associated with grapevine leaf tissues was analyzed by cultivation and cultivation-independent methods. In order to identify bacterial endophytes directly from metagenome, a protocol for bacteria enrichment and DNA extraction was optimized. Sequence analysis of 16S rRNA gene libraries underscored five diverse Operational Taxonomic Units (OTUs), showing best sequence matches with γ-Proteobacteria, family Enterobacteriaceae, with a dominance of the genus Pantoea. Bacteria isolation through cultivation revealed the presence of six OTUs, showing best sequence matches with Actinobacteria, genus Curtobacterium, and with Firmicutes genera Bacillus and Enterococcus. Length Heterogeneity-PCR (LH-PCR) electrophoretic peaks from single bacterial clones were used to setup a database representing the bacterial endophytes identified in association with grapevine tissues. Analysis of healthy and phytoplasma-infected grapevine plants showed that LH-PCR could be a useful complementary tool for examining the diversity of bacterial endophytes especially for diversity survey on a large number of samples.     

Diversity of endophytic fungal and bacterial communities in <Emphasis Type="Italic">Ilex paraguariensis</Emphasis> grown under field conditions

The composition and diversity of the endophytic community associated with yerba mate (Ilex paraguariensis) was investigated using culture-depending methods. Fungi were identified based on their micromorphological characteristics and internal transcribed spacer rDNA sequence analysis; for bacteria 16S rDNA sequence analysis was used. Fungal and bacterial diversity did not show significant differences between organ age. The highest fungal diversity was registered during fall season and the lowest in winter. Bacterial diversity was higher in stems and increased from summer to winter, in contrast with leaves, which decreased. The most frequently isolated fungus was Fusarium, followed by Colletotrichum; they were both present in all the sampling seasons and organ types assayed. Actinobacteria represented 57.5 % of all bacterial isolates. The most dominant bacterial taxa were Curtobacterium and Microbacterium. Other bacteria frequently found were Methylobacterium, Sphingomonas, Herbiconiux and Bacillus. Nitrogen fixation and phosphate solubilization activity, ACC deaminase production and antagonism against plant fungal pathogens were assayed in endophytic bacterial strains. In the case of fungi, strains of Trichoderma, Penicillium and Aspergillus were assayed for antagonism against pathogenic Fusarium sp. All microbial isolates assayed showed at least one growth promoting activity. Strains of Bacillus, Pantoea, Curtobacterium, Methylobacterium, Brevundimonas and Paenibacillus had at least two growth-promoting activities, and Bacillus, Paenibacillus and the three endophytic fungi showed high antagonistic activity against Fusarium sp. In this work we have made a wide study of the culturable endophytic community within yerba mate plants and found that several microbial isolates could be considered as potential inoculants useful for improving yerba mate production.     

Response of fluoranthene-degrading bacteria to surfactants

A prerequisite for surfactant-enhanced biodegradation is that the microorganisms survive, take up substrate and degrade it in the presence of the surfactant. Two Mycobacterium and two Sphingomonas strains, degrading fluoranthene, were investigated for their sensitivity towards non-ionic chemical surfactants. The effect of Triton X-100 and Tween 80 above their critical micelle concentration on mineralization of [¹⁴C]-glucose and [¹⁴C]-fluoranthene was measured in shaker cultures. Tween 80 had no toxic effect on any of the tested strains. The surfactant inhibited fluoranthene mineralization by the hydrophobic Mycobacterium spp. slightly, but more than doubled that by the two less hydrophobic Sphingomonas strains. Triton X-100 inhibited fluoranthene mineralization by all strains, yet this was more pronounced for the Sphingomonas spp. Both surfactants caused cell wall permeabilization, as shown by transient colouring of surfactant-containing media. Inhibition of glucose mineralization, indicating non-specific toxic effects of Triton X-100, was observed only for the Sphingomonas strains and the toxicity was caused by micelle-to-cell interactions. These strains, however, appeared to recover from initial Triton X-100 toxicity within 50–500 h of exposure. The ratio of surfactant concentration to initial cell density was found to determine critically the bacterial response to surfactants. For both Sphingomonas and Mycobacterium strains, this work indicates that fluoranthene solubilized in surfactant micelles is only partially available for mineralization by the bacteria tested. However, our results suggest that optimal conditions for polycyclic aromatic hydrocarbon mineralization can be developed by selection of the proper surfactant, bacterial strains, cell density and incubation conditions. Received: 6 February 1998 / Received revision: 19 June 1998 / Accepted: 19 June 1998     

Ultraviolet Radiation (UVR) Sensitivity Analysis and UVR Survival Strategies of a Bacterial Community from the Phyllosphere of Field-Grown Peanut (Arachis hypogeae L.)

Abstract The short-term population dynamics of the culturable bacterial community from field-grown peanut (Arachis hypogeae L.) was analyzed over three 2-day periods. As in other phyllosphere studies, significant numbers of pigmented organisms were detected, suggesting the importance of pigmentation in the colonization of this habitat. Isolates were grouped according to pigmentation (orange, pink, yellow, nonpigmented), and the sensitivity of each isolate in the collection (n= 617) to ultraviolet radiation (UVR) was determined as the minimal inhibitory dose (MID_C) of UVR that resulted in an inhibition of growth compared to an unirradiated control. The majority of isolates recovered (56.1%) had an MID_C equal to or exceeding that of Pseudomonas syringae 8B48, a known UV-tolerant strain. Among pigmentation groups, the mean MID_C of pink- and orange-pigmented isolates was significantly greater than that of yellow- or nonpigmented isolates at each sampling time of day. Identification of 213 of the isolates using fatty acid methyl ester analysis indicated that a large proportion of the isolates were gram-positive, with Bacillus spp. alone accounting for 35.7% of the total. The genus Curtobacterium contained the largest percentage of highly UVR-tolerant strains. Nonpigmented mutants of four Curtobacterium strains were selected following ethyl methane sulfonate mutagenesis; these nonpigmented mutants were significantly altered in survival following irradiation with UV-A wavelengths. The strategy of avoidance of UVR through colonization of the abaxial leaf surface was evaluated on three separate occasions by leaf imprint sampling. Only 3 of 120 leaves (2.5%) contained larger bacterial populations on the adaxial surface, indicating that colonization of the abaxial leaf surface is important to phyllosphere survival. Our results indicate that tolerance to UVR is a common phenotype among phyllosphere bacteria, suggesting that solar radiation has a strong influence on the microbial ecology of the phyllosphere. Received: 30 November 1998; Accepted: 9 March 1999     

Isolation,partial characterization,and the effect of plant growth-promoting bacteria (PGPB) on micro-propagated sugarcane in vitro

We report the isolation of nitrogen fixing, phytohormone producing bacteria from sugarcane and their beneficial effects on the growth of micropropagated sugarcane plantlets. Detection of the nitrogen fixing bacteria by ARA-based MPN (acetylene reduction assay-based most probable number) method indicated the presence of up to 10⁶ bacteria per gram dry weight of stem and 10⁷ bacteria per gram dry weight of root of field-grown sugarcane. Two nitrogen fixing bacterial isolates were obtained from stem (SC11, SC20) and two from the roots (SR12, SR13) of field-grown plants. These isolates were identified as Enterobacter sp. strains on the basis of their morphological characteristics and biochemical tests. The isolate SC20 was further characterized by 16S rRNA sequence analysis, which showed high sequence similarity to the sequence of Enterobacter cloacae and Klebsiella oxytoca. All the isolates produced the phytohormone indoleacetic acid (IAA) in pure culture and this IAA production was enhanced in growth medium containing tryptophan. The bacterial isolates were used to inoculate micro-propagated sugarcane in vitro where maximum increase in the root and shoot weight over control was observed in the plantlets inoculated with strain SC20. By using the¹⁵N isotope dilution technique, maximum nitrogen fixation contribution (28% of total plant nitrogen) was detected in plantlets inoculated with isolate SC20.     

Di Alcuni Caratteri Differenziali Nelle Plantule di “ Cuscuta Epithymum „ Mürr. e di “ Cuscuta Pentagona „ Eng.

Endophytes are micro-organisms that colonize the internal tissues of plants without inducing signs of negative effects and that can provide benefits to plant health and yield. In the present work, the culturable bacterial endophyte community, colonizing vegetative organs of grapevine, was isolated from surface-sterilized plant tissues and characterized by molecular methods. From roots, shoots and leaves of Vitis vinifera “Glera”, located in six different vineyards throughout the Conegliano-Valdobbiadene DOCG area (Veneto, Italy), 381 culturable strains were successfully isolated; amplified ribosomal DNA restriction analysis and nucleotide sequencing showed that approximately 30% of the endophyte community belonged to the genus Bacillus, which was the most represented; other genera such as Staphylococcus, Microbacterium, Paenibacillus, Curtobacterium, Stenotrophomonas, Variovorax, Micrococcus and Agrococcus were identified. Endophyte community composition within each vine was different in respect to other endophyte populations living in grapevine plants coming from different vineyards; moreover, the bacterial composition changed depending on the season of sampling. The above data highlight the great diversity of culturable bacterial species inhabiting Glera grapevines and open the way for a characterization and selection of strains that could potentially be used to improve the vineyard management for plant growth and yield, plant responses to stresses, biocontrol and biofertilization.     

基于高通量测序的3种淫羊藿叶片内生细菌群落结构研究

了解3种淫羊藿内生细菌群落的结构和组成,为淫羊藿内生菌资源的开发及利用提供参考.采用Illumina Miseq高通量测序技术,分析了粗毛淫羊藿、箭叶淫羊藿及巫山淫羊藿新叶和老叶内生细菌群落的结构和组成.3种淫羊藿叶片内生细菌群落组成结果显示,门水平的优势菌群主要包括变形菌门、厚壁菌门和放线菌门,优势菌属主要为甲基杆菌...     

西藏扎布耶盐碱湖细菌的多样性与分离菌株的生长特性

【背景】扎布耶湖位于青藏高原地区,是以水体中富含高浓度CO₃²⁻、HCO₃⁻和Na⁺为显著特性的盐碱湖,因其地理位置高寒、高海拔,人迹罕至,涉及该盐湖微生物的研究相对较少。【目的】系统探究湖水中细菌多样性和菌种资源等,发掘可利用的潜在菌种。【方法】采用Illumina测序16S rRNA基因V3−V4区分析扎布耶湖细菌的群落结构组成、物种多样性特征;采用纯培养筛选分离可培养细菌,明确分离菌株分类学地位、生长特性及产酸能力,同时测定分离菌株四氢嘧啶(ectoine)、吲哚乙酸(3-indoleacetic acid, IAA)和胞外聚合物(extracellular polymeric substances, EPS)的积聚量。【结果】Illumina测序明确分类地位的细菌有21门44纲86目583属,其中优势门类群是变形菌门(Proteobacteria, 25.11%−67.60%)、拟杆菌门(Bacteroidetes, 4.84%−35.02%)和厚壁菌门(Firmicutes, 1.24%−11.01%),优势属类群是克雷伯氏菌属(Klebsiella, 0.01%−9.53%)、盐单胞菌属(Halomonas, 0.54%−8.75%)、芽单胞菌属(Gemmatimonas, 2.39%−6.00%)和腈基降解菌属(Nitriliruptor, 1.27%−6.26%)。纯培养法筛选获得嗜盐碱菌38株,其中芽孢杆菌属(Bacillus) 23株(60.53%)和盐单胞菌属(Halomonas) 10株(26.32%),菌株均具有耐盐碱和产酸能力(19.80%−29.68%)。大多数菌株能积聚四氢嘧啶、IAA和EPS,产量范围分别为1.36−175.59、0.27−8.69和0.02−0.22 g/g。【结论】扎布耶湖细菌群落结构与其他地区盐碱湖相似,但存在大量未明确分类学地位的细菌,分离菌株多具有耐盐碱及产酸特性。此外,还发现4株高效生产四氢嘧啶、3株生产吲哚乙酸和3株生产胞外聚合物的潜力菌株,为扎布耶盐湖微生物资源的开发利用奠定了基础。     

广西蚕沙细菌组成多样性解析和VBNC菌群的发掘

【目的】解析广西蚕沙中细菌群落组成与多样性,为蚕沙中菌种资源发掘和蚕沙的综合利用提供科学依据。【方法】通过高通量测序技术研究细菌群落组成特征,同时利用常规稀释涂布平板法和基于复苏促进因子(Rpf)的MPN培养系统解析并筛选蚕沙中可培养和活的非可培养(VBNC)状态的优势菌群,并经16SrRNA基因测序对筛选得到的菌株作初步分类鉴定。【结果】高通量测序表明,广西蚕沙样品中细菌归属于10个门、18个纲、27个目、57个科、96个属,其中4个属的丰度达1%以上,优势菌群为变形菌门(Proteobacteria)肠杆菌属(Enterobacter);通过稀释涂布平板法共获得14个属的33株可培养细菌,其中4个属(Citrobacter、Weissella、Chitinophaga、Pseudoclavibacter)在高通量测序中未被检测到;而在MPN培养系统中,基于复苏促进因子的处理组细菌总数最大检出丰度提高了100倍,并从中共检出21株对Rpf敏感的VBNC菌株,其中6个属(Paenibacillus、Caulobacter、Roseomonas、Pantoea、Erwinia、Acine...     

Ability of Moderately Halophilic Bacteria to Control Grey Mould Disease on Tomato Fruits

Tomato is one of the leading crops in Tunisia in terms of weight consumed (20 kg/per person/year). Preserving the quality of the fruit from field to consumer is essential to successful marketing. Grey mould rot induced by Botrytis cinerea is an important cause of postharvest loss depending on season and handling practices. We describe here the ability of halotolerant to moderately halophilic bacteria isolated from different Tunisian Sebkhas (hypersaline soils) to protect fresh‐market tomato fruits from B. cinerea. The tomatoes tested were at two different stages of ripening, (i) mature‐green and (ii) red. Six strains significantly reduced growth of the pathogens from 67% to 87%. The effectiveness of these antagonists was also confirmed on green tomatoes; in which the fruit rot protection rate ranged from 74% to 100%. The antagonists were characterized by morphological, biochemical and physiological tests as well as 16S rDNA sequencing. The halotolerant effective isolates were identified as belonging to one of the species Bacillus subtilis (M1‐20, J9) or B. licheniformis (J24). One effective moderately halophilic isolate (M2‐26) was identified as Planococcus rifietoensis. These strains are a source of hydrolytic enzymes such as chitinases, proteases, laminarinases, amylases, lipases and cellulases. For comparison, 12 halotolerant or moderately halophilic strains obtained from DSM culture collection were also evaluated for their antifungal activity against B. cinerea on tomato fruits. The most effective strains were Halomonas subglaciescola, Halobacillus litoralis, Marinococcus halophilus, Salinococcus roseus, Halovibrio variabilis and Halobacillus halophilus with a percentage of grey mould rot reduction ranging from 71% to 97%. Inoculation of mature‐green tomatoes by the bacterial antagonist of Halobacillus trueperi resulted in no disease development. Our results indicate that the use of halotolerant to halophilic micro‐organisms should be helpful in reducing grey mould disease of stored tomatoes.     

不同栽培方式的铁皮石斛根、茎中内生细菌多样性及其抑菌活性研究

【目的】分析树干仿生栽培和大棚种植的铁皮石斛根、茎中内生细菌的组成与分布,并挖掘潜在的微生物资源及功能。【方法】利用Illumina MiSeq高通量测序技术,对不同栽培方式铁皮石斛根、茎中免培养内生细菌丰富度及多样性进行比较分析;通过传统的内生菌分离法以及16S rRNA基因测序技术对可培养内生细菌进行分离鉴定;采用滤纸片法筛选拮抗石斛病原菌的内生菌株。【结果】高通量测序分析中内生细菌以Pseudomonas(30.52%)为主,其次是Mycobacterium(10.22%)以及Brachybacterium(8.32%),树干仿生栽培石斛内生细菌组成丰富度及多样性高于大棚种植,石斛根中内生细菌组成丰富度及多样性高于石斛茎。可培养内生细菌中Bacillus(18.37%)所占比例最高,其次是Curtobacterium (8.16%),同时筛选得到8株具有抑制石斛病原菌活性的菌株。【结论】铁皮石斛中蕴含着丰富的内生细菌资源,菌群组成和分布受其不同栽培方式和组织部位的影响。此外,筛选得到8株具有抑制病原菌活性的菌株,表明铁皮石斛内生细菌代谢产物具有抗菌活性。本试验对铁皮石斛内生细菌多...     

Leaf microbiota in an agroecosystem: spatiotemporal variation in bacterial community composition on field-grown lettuce

The presence, size and importance of bacterial communities on plant leaf surfaces are widely appreciated. However, information is scarce regarding their composition and how it changes along geographical and seasonal scales. We collected 106 samples of field-grown Romaine lettuce from commercial production regions in California and Arizona during the 2009–2010 crop cycle. Total bacterial populations averaged between 10⁵ and 10⁶ per gram of tissue, whereas counts of culturable bacteria were on average one (summer season) or two (winter season) orders of magnitude lower. Pyrosequencing of 16S rRNA gene amplicons from 88 samples revealed that Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were the most abundantly represented phyla. At the genus level, Pseudomonas, Bacillus, Massilia, Arthrobacter and Pantoea were the most consistently found across samples, suggesting that they form the bacterial ‘core'' phyllosphere microbiota on lettuce. The foliar presence of Xanthomonas campestris pv. vitians, which is the causal agent of bacterial leaf spot of lettuce, correlated positively with the relative representation of bacteria from the genus Alkanindiges, but negatively with Bacillus, Erwinia and Pantoea. Summer samples showed an overrepresentation of Enterobacteriaceae sequences and culturable coliforms compared with winter samples. The distance between fields or the timing of a dust storm, but not Romaine cultivar, explained differences in bacterial community composition between several of the fields sampled. As one of the largest surveys of leaf surface microbiology, this study offers new insights into the extent and underlying causes of variability in bacterial community composition on plant leaves as a function of time, space and environment.     

Diversity and functional traits of culturable microbiome members,including cyanobacteria in the rice phyllosphere

The diversity and abundance of culturable microbiome members of the rice phyllosphere was investigated using cv. Pusa Punjab Basmati 1509. Both diversity and species richness of bacteria were significantly higher in plants in pots in a semi‐controlled environment than those in fields. Application of fertilisers reduced both diversity and species richness in field‐grown plants under a conventional flooded system of rice intensification (SRI) and in dry‐seeded rice (DSR) modes. Sequence analyses of 16S rDNA of culturable bacteria, those selected after amplified ribosomal DNA restriction analysis (ARDRA), showed the dominance of α‐proteobacteria (35%) and actinobacteria (38%); Pantoea, Exiguobacterium and Bacillus were common among the culturable phyllospheric bacteria. About 34% of 83 culturable bacterial isolates had higher potential (>2 μg·ml^?1) for indole acetic acid production in the absence of tryptophan. Interestingly, the phyllosphere bacterial isolates from the pot experiment had significantly higher potential for nitrogen fixation than isolates from the field experiment. Enrichment for cyanobacteria showed both unicellular forms and non‐heterocystous filaments under aerobic as well as anaerobic conditions. PCR‐DGGE analysis of these showed that aerobic and anaerobic conditions as well as the three modes of cultivation of rice in the field strongly influenced the number and abundance of phylotypes. The adaptability and functional traits of these culturable microbiome members suggest enormous diversity in the phyllosphere, including potential for plant growth promotion, which was also significantly influenced by the different methods of growing rice.