Soil dwelling bacteria able to colonize plant roots and closely associated soil are referred to as rhizobacteria. A wide range of rhizobacteria has the ability to promote plant growth directly by producing phytohormone and nutrients; and indirectly by controlling plant pathogen. These beneficial bacteria are known as plant growth promoting rhizobacteria (PGPR). PGPR control phytopathogens by producing chemicals that could damage pathogen cells, removing pathogen specific nutrients from the environment, or inducing resistance against pathogen in plant body. Antagonistic bacteria specifically damage pathogens by producing lytic enzymes, antibiotics and bacteriocins; and excluding pathogen from plant environment by siderophores oriented iron chelation. This review highlights the antagonistic feature of PGPR. Application of antagonistic bacteria as biopesticides is an attractive alternate of chemical pesticides. Chemical pesticides are non-targeted and cause pollution during its synthesis as well as at the site of application. Antagonistic bacteria could be used as biopesticides and biofertilizers for better plant health and growth improvement.

Endophytism is the phenomenon of mutualistic association of a plant with a microorganism wherein the microbe lives within the tissues of the plant without causing any symptoms of disease. In addition to being a treasured biological resource, endophytes play diverse indispensable functions in nature for plant growth, development, stress tolerance, and adaptation. Our understanding of endophytism and its ecological aspects are overtly limited, and we have only recently started to appreciate its essence. Endophytes may impact plant biology through the production of diverse chemical entities including, but not limited to, plant growth hormones and by modulating the gene expression of defense and other secondary metabolic pathways of the host. Studies have shown differential recruitment of endophytes in endophytic populations of plants growing in the same locations, indicating host specificity and that endophytes evolve in a coordinated fashion with the host plants. Endophytic technology can be employed for the efficient production of agricultural and economically important plants and plant products. The rational application of endophytes to manipulate the microbiota, intimately associated with plants, can help in enhancement of production of agricultural produce, increased production of key metabolites in medicinal and aromatic plants, as well as adaption to new bio-geographic regions through tolerance to various biotic and abiotic conditions. However, the potential of endophytic biology can be judiciously harnessed only when we obtain insight into the molecular mechanism of this unique mutualistic relationship. In this paper, we present a discussion on endophytes, endophytism, their significance, and diverse functions in nature as unraveled by the latest research to understand this universal natural phenomenon.

Studies of allelopathy in terrestrial systems have experienced tremendous growth as interest has risen in describing biochemical mechanisms responsible for structuring plant communities, determining agricultural and forest productivity, and explaining invasive behaviors in introduced organisms. While early criticisms of allelopathy involved issues with allelochemical production, stability, and degradation in soils, an understanding of the chemical ecology of soils and its microbial inhabitants has been increasingly incorporated in studies of allelopathy, and recognized as an essential predictor of the outcome of allelopathic interactions between plants. Microbes can mediate interactions in a number of ways with both positive and negative outcomes for surrounding plants and plant communities. In this review, we examine cases where soil microbes are the target of allelopathic plants leading to indirect effects on competing plants, provide examples where microbes play either a protective effect on plants against allelopathic competitors or enhance allelopathic effects, and we provide examples where soil microbial communities have changed through time in response to allelopathic plants with known or potential effects on plant communities. We focus primarily on interactions involving wild plants in natural systems, using case studies of some of the world's most notorious invasive plants, but we also provide selected examples from agriculturally managed systems. Allelopathic interactions between plants cannot be fully understood without considering microbial participants, and we conclude with suggestions for future research.

为了鉴定从红壤中分离得到的一株自生固氮菌,并探讨其固氮能力。采用形态观察、生理生化测定和16S rDNA基因序列分析的方法研究了菌株的分类地位,采用乙炔还原法测定其固氮酶活性,并在室内培养条件下,通过花生、玉米的幼苗盆栽试验研究菌株对土壤MBN、矿化氮和植株氮素积累量的影响。结果表明：从种植于红壤的玉米根际,筛选出15株自生固氮菌,以菌株CM12固氮能力最强,初步鉴定CM12为伯霍尔德杆菌属(Burkholderia sp.),固氮酶活性达C₂H₄ 39.1 nmol/(h·mL)。室内培养试验结果表明,接种CM12菌株的处理,花生和玉米土壤MBN含量较CK处理分别提高了2.38和2.37倍,其中种植花生体系中,接菌处理与施用化学氮肥处理土壤MBN含量无显著差异。接种固氮菌影响了旱地红壤NO₃^--N和NH₄⁺-N比例,降低了土壤中NO₃^--N含量,且种植玉米体系中土壤NO₃^--N含量降低较明显。固氮菌短期接种增加了花生根系和玉米地上植株的氮素积累量。研究结果为该菌株在红壤旱地实际生产中的应用提供了理论基础。

目的】内生真菌能够促进植物生长，提高植物抵御外界不良环境的能力。本文旨在对棉花内生真菌的群落结构和多样性进行系统分析，明确内生真菌资源分布，同时探讨生长环境与内生真菌群落结构和多样性的关系。【方法】在山东省19个地区采集棉花叶片，运用马铃薯葡萄糖（Potato dextrose agar）培养基进行内生真菌的分离、纯化、保存, 采用内转录间隔区（Internal transcribed spacer）序列分析技术进行种属鉴定，并对分离得到的内生真菌进行群落结构和生物多样性分析。【结果】19个地区的棉花取样中，共分离得到134个菌株归属于15个属（包括Alternaria、Fusarium、Diaporthe、Penicillium、Stemphylium、Bipolaris、Epicoccum、Curvularia、Nigrospora、Botryosphaeria、Lichtheimia、Gibellulopsis、Phaeosphaeria、Cladosporium、Setosphaeria）。依据相对分离率，山东省的棉花内生真菌优势属为Alternaria（77.12%）。具体分析，滨州市滨城区和桓台的优势属为Fusarium（66.67%、100.00%），曹县的优势属为Alternaria（50.00%）、Fusarium（50.00%），济阳的优势属为Alternaria（37.50%）和Setosphaeria（37.50%）。不同地区内生真菌定植率差异显著，其中最高的是垦利（85%），其次为茌平（70%）、无棣（60%），而惠民、邹城的最低（5%）。根据Shannon-Weaver指数，济阳棉花内生真菌生物多样性最高（1.26），其后依次为茌平（1.15）、滨州市滨城区（0.87）、曹县（0.69）、郓城（0.64）、无棣（0.59）、垦利（0.57）、金乡（0.51）、商河（0.35），成武、东阿、高唐、惠民、聊城市东昌府区、夏津、阳谷、鱼台、邹城、桓台仅鉴定出1种棉花内生真菌，生物多样性最低。19个地区内生真菌聚成2个类群，一类是茌平、无棣、垦利，此类内生真菌定植率高，鉴定出的菌属数目多，其他地区聚为一类，内生真菌种类少，定植率低。【结论】山东省棉花内生真菌具有丰富的多样性。地域对内生真菌的分布具有一定的影响。

为丰富油茶根腐病生防资源并探究其抗病机理，采用平板对峙法和比色法等从油茶根系内生菌中筛选出拮抗促生细菌，并测定其对油茶根系防御酶活性及防御基因的影响。结果表明：结合拮抗效果、产IAA、溶有机磷、无机磷及产铁载体能力，从油茶根系筛选到两株高效内生拮抗促生菌AF9和AH6，经鉴定均为芽孢杆菌；二者均可以诱导油茶根系防御酶活性提高，超氧化物歧化酶（SOD）、苯丙氨酸解氨酶（PAL）、多酚氧化酶（PPO）以及过氧化物酶（POD）活性分别在8 h、10 h、12 h和24 h达到峰值；PAL、RBOHC和POD基因分别在处理10 h、12 h 及24 h时高度表达，对照组基因无明显表达。表明拮抗促生菌AF9和AH6可以诱导油茶产生系统抗性，为后期菌剂的研制以及油茶根腐病的生物防治奠定基础。

紫罗兰是一种极具观赏和经济价值的植物。基因组DNA的提取是紫罗兰分子育种的基础,但常用的十六烷基三甲基溴化铵法(CTAB法)存在操作繁琐、试剂毒性大等缺点,不利于在大规模育种实践中的应用。因此,建立一种简单、快速、安全的紫罗兰基因组DNA提取方法是十分必要的。本研究建立了一种适合紫罗兰基因组DNA快速提取的方法,约30 min即可获得能够用于PCR反应的DNA。该方法提取时间短、操作步骤简单,是一种简单、安全、高通量和低成本DNA提取方法,为紫罗兰分子育种奠定了基础。

Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seedborne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endophytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.

Microbes are the unseen majority in soil and comprise a large portion of life's genetic diversity. Despite their abundance, the impact of soil microbes on ecosystem processes is still poorly understood. Here we explore the various roles that soil microbes play in terrestrial ecosystems with special emphasis on their contribution to plant productivity and diversity. Soil microbes are important regulators of plant productivity, especially in nutrient poor ecosystems where plant symbionts are responsible for the acquisition of limiting nutrients. Mycorrhizal fungi and nitrogen-fixing bacteria are responsible for c. 5-20% (grassland and savannah) to 80% (temperate and boreal forests) of all nitrogen, and up to 75% of phosphorus, that is acquired by plants annually. Free-living microbes also strongly regulate plant productivity, through the mineralization of, and competition for, nutrients that sustain plant productivity. Soil microbes, including microbial pathogens, are also important regulators of plant community dynamics and plant diversity, determining plant abundance and, in some cases, facilitating invasion by exotic plants. Conservative estimates suggest that c. 20 000 plant species are completely dependent on microbial symbionts for growth and survival pointing to the importance of soil microbes as regulators of plant species richness on Earth. Overall, this review shows that soil microbes must be considered as important drivers of plant diversity and productivity in terrestrial ecosystems.

Phytoremediation is an emerging technology that uses plants and their associated microbes to clean up pollutants from the soil, water and air. In recent years, phytoremediation assisted by bacterial endophytes has been highly recommended for cleaning up of metal polluted soils since endophytic bacteria can alleviate metal toxicity in plant through their own metal resistance system and facilitate plant growth under metal stress. Endophytic bacteria improve plant growth in metal polluted soils in two different ways: 1) directly by producing plant growth beneficial substances including solubilization/transformation of mineral nutrients (phosphate, nitrogen and potassium), production of phytohormones, siderophores and specific enzymes; and 2) indirectly through controlling plant pathogens or by inducing a systemic resistance of plants against pathogens. Besides, they also alter metal accumulation capacity in plants by excreting metal immobilizing extracellular polymeric substances, as well as metal mobilizing organic acids and biosurfactants. The present work aims to review the progress of recent research on the isolation, identification and diversity of metal resistant endophytic bacteria and illustrate various mechanisms responsible for plant growth promotion and heavy metal detoxification/phytoaccumulation/translocation in plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

摘  要：本研究从多年种植辣椒的田间采集了长势优良的植株根系，表面消毒后从中分离到1株内生细菌PEB40。该菌株能在铬天青（CAS）平板上产生较大的噬铁圈，还具有较好的产吲哚-3-乙酸（IAA）和溶解有机磷的能力，显示了很好的植物促生长潜能。盆栽试验显示，PEB40菌株对辣椒具有显著的促生长效果，施用该菌剂后，辣椒的结果数、产量、株高、展幅与空白组相比均存在显著的优势（P＜0.05），其中株高增加了18.9%，展幅增加了20.7%，产量增加了35.3%，表明内生菌PEB40对辣椒具有明显的促生长效果。根据其16S rDNA序列、进化树及形态特征分析，该菌为假单胞菌属（Pseudomonas）新种的可能性大。本研究结果表明，CAS平板可用于高通量快速筛选促生菌，所得菌株PEB40亦为进一步开发新型微生物肥料奠定了基础。

从健康多花黄精根部分离筛选对黄精种子萌发具促生作用的内生细菌，以期为解决黄精资源短缺问题奠定理论基础。采用传统组织培养法分离纯化内生菌，沙尔科夫斯基反应（Salkowski法）筛选产IAA能力的促生菌；通过形态学观察、生理生化特征检测及16S rDNA序列分析确定目标菌株的分类地位；温室纸床实验验证目标菌株对黄精种子发芽的促生效果。从多花黄精中共分离纯化得到34株内生菌，其中细菌25株，真菌9株；从中筛选出两株具有稳定高产IAA的内生细菌HNC2和HPB1，其产IAA能力分别高达4.833 mg/L、4.608 mg/L；菌种鉴定结果表明菌株HNC2和HPB1分别为芽孢杆菌（Bacillus sp.）和葡萄球菌（Staphylococcus sp.）；菌种对种子萌发影响的实验结果显示，与无菌水和培养基对照组比，促生菌Bacillus sp. HNC2和Staphylococcus sp. HPB1均显著提高黄精种子的发芽势与发芽率，且对萌发幼苗的生长具有不同程度的促生功效。多花黄精具有丰富的内生菌资源，Bacillus sp. HNC2和Staphylococcus sp. HPB1有望进一步开发为微生物菌肥以提高黄精种子的繁殖率。