一株植物促生菌的筛选、鉴定及其对花生的促生效应研究

从南京板桥镇自然条件下的潮土中,筛选出JX15菌株,具有较强分泌IAA的能力且性能稳定,20 h分泌IAA达到22.55μg/ml,并兼具解磷能力。经形态观察、部分生理生化特征测定及16S rRNA的保守序列鉴定,初步确定该菌株为巨大芽孢杆菌(Bacillus megaterium),GenBank登录号为JX424613。设置单因素试验对菌株生长和发酵条件进行初步研究,结果表明促进菌株JX15生长和增强分泌IAA的最佳培养条件基本一致,最佳培养条件是初始pH 7~8,装液量为50 ml/250 ml,30℃摇床培养24 h;最佳碳、氮源分别是甘露醇和酵母粉。在实验室条件下进行花生盆栽试验,结果表明接种JX15菌液的处理,花生植株较未接种菌液的处理其鲜重、株高、全氮、磷、钾及花生根系总长度、根平均直径、根表面积和根尖数均有显著增加。研究结果为该菌株的工程应用提供了理论依据。     

The survival of pathogenic bacteria and plant growth promoting bacteria during mesophilic anaerobic digestion in full‐scale biogas plants

The introduction of biogas plants is a promising way to recycle organic wastes with renewable energy production and reducing greenhouse gas. Application of anaerobic digestate as a fertilizer reduces the consumption of chemical fertilizers. In this study, the survival of pathogenic bacteria and plant growth promoting bacteria (PGPB) in two full‐scale biogas plants operated at mesophilic condition were investigated. Feedstock and anaerobic digestate samples were collected from biogas plants and bacteria load in samples were detected using standard dilution plate method. Pathogenic bacteria were reduced to not detected level through mesophilic digestion tank except for Campylobacter. However, it could be reduced by 98.7% through a sterilization tank. Bacillus was detected at 8.00 and 7.81 log₁₀ CFU/g dry matter in anaerobic digestates, and it was also resistant to sterilization tank. Bacillus spp. is considered to be the safe bacteria that hold remarkable abilities for promoting plant growth. The results showed that treatment at biogas plants is effective to reduce pathogenic bacteria in dairy manure, and sterilization could further reduce the sanitary risks of pathogenic bacteria relating to anaerobic digestate application. Anaerobic digestates could also be utilized as bio‐fertilizer as the high load of plant growth promoting bacteria.     

Restoration of giant cardon cacti in barren desert soil amended with common compost and inoculated with Azospirillum brasilense

Barren desert soil that otherwise could not support perennial plant growth was amended with six levels of common agricultural compost. Seedlings of the giant cardon cactus, one of the primary plant species responsible for soil stabilization in the southern Sonoran Desert, were inoculated with the plant-growth-promoting bacterium Azospirillum brasilense Cd, planted, and grown for 18 months under nursery conditions typical for slow-growth cacti. Control plants were grown without compost amendment, without inoculation (negative control), or in fertile, rare “resource island” soil preferred by cardon seedlings (positive control). During the prolonged growth period, the decisive factor in seedling growth in barren soil was the addition of small amounts of common compost; 6 to 25% of the growth substrate volume gave the best growth response and, to a lesser extent, so did inoculation with A. brasilense Cd. Although the bacteria significantly affects plant growth when amended with “resource island” soil and added to barren soil, its effect on plant growth was far smaller than when compost alone was added. Compost added to barren soil significantly increased the dry weight parameters of the plant to almost similar levels obtained by the “resource island” soil; however, the compost amendment supports a more voluminous and greener plant with elevated pigment levels. This study shows that barren soil supplemented with compost can replace the rare “resource island” soil for cardon nurseries destined to abate soil erosion in the desert.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

益生菌肥料在桉树人工林可持续发展中的应用

为促进林木生长,减少化学肥料使用,保护环境,维护地力,本研究从林木根际分离植物益生菌,经系统试验,筛选出一批对桉树生长具有明显促进作用的优良菌株。其中的 DU07菌株兼具固氮、解磷、解钾功能,被研制成菌剂、有机菌肥、益生菌复合肥。菌剂接种桉树苗木的育苗和造林试验覆盖广西桉树大部分栽培区。在广西高峰林场建立的146.2 hm2示范林,18月龄林木平均树高达11.16 m,胸径7.38 cm,均分别高于对照,起到了良好的示范作用。不含无机氮素的有机菌肥在试验初期的肥效较慢,但半年后,菌肥处理的林木胸径、树高均超过对照,其肥效显示长效缓释作用;施用菌肥的桉树根区土壤微生物、尤其是固氮菌数量明显增多,土壤酶活性均有不同程度的提高。无机有机益生菌复合肥总养分≥15%,比总养分≥30.0%的对照肥减少一半,然而1.5年生试验林的树高和胸径均分别高于对照,土壤的速效氮、磷、钾也均高于对照。表明益生菌肥有利于土壤中各种物质的分解和转化,在改善土壤状况和维护地力上具独特作用。这对于在生产中减少无机化肥的使用,保护土壤环境具有重要的现实意义。     

PGPB菌剂对5种红树小苗的野外接菌效应1）

在湛江雷州附城镇红树林苗圃进行试验,研究了PGPB菌剂对5种红树小苗的野外接菌效应。接菌后1 a,对供试小苗进行了生长指标及叶片氮、磷质量分数的测定。结果表明：固氮菌（ NGWB－y1）和溶磷菌（ P7）以（1∶1）混合并按1∶10兑水的比例对苗床进行接菌后明显促进了5种红树小苗的苗高、地径、叶片数、生物量的生长;与对照相比,5种红树叶片的氮、磷质量分数明显升高。综合看,PGPB对桐花（ Aegiceras corniculatum）和秋茄（ Kandelia candel）的促生作用明显大于拉关木（ Laguncularia racemosa）、红海榄（ Rhizophora stylosa）和白骨壤（ Avi-cennia marina）,对桐花的促进作用主要表现在苗高、地径、生物量的增加,对秋茄的促进作用主要表现在叶片数、叶片全氮、全磷质量分数的增加。 PGPB接种5种红树小苗后,其土壤化学性质的变化无规律。     

Plant growth promoting bacteria increases biomass,effective constituent,and modifies rhizosphere bacterial communities of Panax ginseng

Purpose: The main aim of this study was to introduce and explore plant growth-promoting bacteria (PGPB) indigenous to ginseng, and to evaluate their ability to improve production and quality, and effect on rhizosphere niche in ginseng.

Materials and methods: Endophytic bacteria were isolated from root, stem, and leaf of ginseng from different sites and genotype in China and Korea, screened based on their beneficial properties as PGPB. Nine bacterial isolates were selected according to their plant growth properties including soluble phosphate and potassium, ammonia, auxin and siderophore producing, ACC deaminase, and antagonistic pathogen as well. Changes in ginseng after PGPB inoculation were evaluated with respect to the non-inoculated control.

Results and Conclusions: The PGPB isolates were identified as genera Bacillus, Lysinibacillus, Rhizobium, Stenotrophomonas, Erwinia, Ochrobactrum, Enterobacter and Pantoea based on 16S rRNA sequences. Inoculation of G209 and G119 increased not only plant height, root length, fresh weight, and dry weight, but also root activity and the amount of ginsenosides significantly. In particular, using the Illumina Miseq platform, the native bacterial community of rhizospheric soil maintained high community diversity and increased abundance of specific bacteria. Therefore, they may be play a crucial role in sustainable ginseng cultivating in farmland.     

含ACC脱氨酶的植物促生菌对荷花耐镉性及镉富集的影响

为研究含ACC脱氨酶的植物促生菌（PGPB）对改善荷花耐Cd性及植物修复效率的作用,以观赏荷花品种“秣陵秋色”（Nelumbo nucifera ‘Molingqiuse’）为材料,通过盆栽试验探讨了Cd胁迫条件下,接种含ACC脱氨酶的PGPB （Pantoea vagans So23和Pseudomonas veronii E02）对荷花的生长、生理代谢及Cd吸收积累能力的影响。结果显示：接种So23和E02能够有效缓解Cd胁迫对荷花生长的抑制作用,使得株高、叶面积及立叶数与未接菌Cd处理相比均有不同程度的增加,叶片中丙二醛含量分别降低38.39%和31.21%,抗坏血酸含量分别升高54.85%和36.64%。接种So23和E02显著改变了Cd在荷花不同器官间的分配模式,能够通过限制Cd从地下部向地上部叶片的转移来抵抗Cd胁迫;此外,接种So23能明显增强荷花对底泥中Cd的富集,使底泥中Cd含量下降56.47%,改善了底泥环境。研究表明,接种So23和E02在一定程度上能够通过提高抗氧化剂含量增强荷花对Cd胁迫的耐受性,同时改变荷花对Cd的转运及富集能力。     

Inhibitory effect of ACC deaminase‐producing bacteria on crown gall formation in tomato plants infected by Agrobacterium tumefaciens or A. vitis

This study showed that various rhizosphere bacteria producing the enzyme 1‐aminocyclopropane‐1‐carboxylate (ACC) deaminase (ACCD), which can degrade ACC, the immediate precursor of ethylene in plants, and thereby lower plant ethylene levels, can act as promising biocontrol agents of pathogenic strains of Agrobacterium tumefaciens and A. vitis. Soaking the roots of tomato (Solanum lycopersicum) seedlings in a suspension of the ACCD‐producing Pseudomonas putida UW4, Burkholderia phytofirmans PsJN or Azospirillum brasilense Cd1843 transformed by plasmid pRKTACC carrying the ACCD‐encoding gene acdS from UW4, significantly reduced the development of tumours on tomato plants injected 4–5 days later with pathogenic Agrobacterium strains via wounds on the plant stem. The fresh mass of tumours formed by plants pretreated with ACCD‐producing strains was typically four‐ to fivefold less than that of tumours formed on control plants inoculated only with a pathogenic Agrobacterium strain. Simultaneously, the level of ethylene evolution per amount of tumour mass on plants pretreated with ACCD‐producing bacteria decreased four to eight times compared with that from tumours formed on control plants or plants pretreated with bacteria deficient in ACCD production. Moreover, transgenic tomato plants expressing a bacterial ACCD were found to be highly resistant to crown gall formation relative to the parental, non‐transformed tomato plants. The results support the hypothesis that ethylene is a crucial factor in Agrobacterium tumour formation, and that ACCD‐produced rhizosphere bacteria may protect plants infected by pathogenic Agrobacteria from crown gall disease.     

Tilapia recirculating aquaculture systems as a source of plant growth promoting bacteria

A recirculating aquaculture system with farmed tilapia is the most popular combination in aquaponics, an integration of aquaculture and hydroponics. Despite nutrient‐rich fish‐rearing water being regarded as a valuable resource for aquaponics, the quality and value of inhabitant microorganisms are certainly understudied. Our present research illustrates the feasibility of the tilapia‐rearing water as a valuable source of beneficial microorganisms called plant growth promoting bacteria (PGPB). Microbial communities were examined with a combination of culture‐independent high‐throughput 16S rRNA gene sequencing and cultivation methods. Microbial communities determined using high‐throughput sequencing indicated the usefulness of Bacteroidetes and Alphaproteobacteria as beneficial microbial indicators to assess the health condition of recirculating aquaculture systems. Siderophore production, ammonia production and phosphate solubilization assays were used for screening and 41% of isolates were identified as plant growth promoting bacteria. These bacteria were classified as Actinobacteria (eight strains [32% in total], Dietzia, Gordonia, Microbacterium, Mycobacterium and Rhodococcus), Bacilli (six strains [24%], Bacillus and Paenibacillus), Flavobacteriia (one strain [4%], Myroides), Betaproteobacteria (two strains [8%], Acidovorax and Chromobacterium) and Gammaproteobacteria (eight strains [32%], Aeromonas, Plesiomonas and Pseudomonas). We found that the tilapia‐rearing water naturally contained various lineages of PGPB and could be esteemed as a worthy seed bank of PGPB. Because aquaponics is a difficult system to use pesticides and herbicides, the role of PGPB to prevent plant pathogens and maintain healthy root system may be more important than traditional agricultural settings.