沙棘根瘤内生细菌中抑菌促生菌株的筛选和鉴定

【背景】植物内生细菌可产生具有抑菌和促生活性的物质,既能抑制植物病原菌对寄主植物的侵染,也能促进植物的生长。沙棘根瘤内生细菌是根瘤内除共生固氮的弗兰克氏菌外,与沙棘共生的一大类微生物。研究具有抑菌和促生活性的植物内生菌,可为微生物菌肥的研究提供理论基础。【目的】筛选具有优良抑菌和促生活性的沙棘根瘤内生细菌,初步研究其抑菌和促生活性,并对菌株进行鉴定。【方法】采用双层琼脂法、琼脂扩散法、双层平板对峙法、牛津杯法进行沙棘根瘤拮抗性内生细菌的筛选。选取抑菌活性较高的内生细菌,分别采用Salkowski比色法、ChromeAzurolS(CAS)平板检测法和钼锑抗比色法进行产吲哚乙酸、铁载体及溶磷能力的测定。采用发酵液灌根法测定沙棘根瘤内生细菌SR308对黄瓜促生作用的盆栽效果。通过形态和培养特征、生理生化试验及16S rRNA基因序列分析法对菌株TT201和SR308进行鉴定。【结果】从131株沙棘根瘤内生细菌中筛选出9株具有较强抑菌活性的内生细菌,其中菌株TT201抑菌性最佳、抑菌谱广;菌株SR308的促生活性最好,其发酵液对黄瓜的生长具有较强的促进作用。对具有较强抑菌和促生活性的菌株TT201和SR308进行鉴定的结果表明,菌株TT201为侧孢短芽孢杆菌(Brevibacilluslaterosporus),菌株SR308为蕈状芽孢杆菌(Bacillusmycoides)。【结论】获得2株具有优良抑菌和促生活性的沙棘根瘤内生细菌,为进一步开发微生物农药及菌肥提供了资源。     

2种药用阿魏植物内生细菌及促生属性比较

为深入了解2种新疆特有植物——新疆阿魏和准噶尔阿魏的内生细菌群落组成及促生属性,采用纯培养方法比较其内生细菌的群落组成和多样性,并评估内生细菌的固氮、溶磷等促生特性和潜在应用价值。从新疆阿魏中分离到125株内生细菌,属于3门、13目、23科、29属,优势度指数为0. 07,香农指数为2. 91;准噶尔阿魏分离到170株内生细菌,隶属于3门、14目、20科、27属,优势度指数为0. 08,香农指数为2. 83。2种阿魏的优势内生细菌均为芽胞杆菌属(Bacillus)和链霉菌属(Streptomyces)细菌。促生属性表明新疆阿魏内生细菌中Microbacterium活性最强,有24株具有固氮潜力,23株能够产生吲哚乙酸;准噶尔阿魏中共20株菌具有固氮潜力,10株为Bacillus,另外10株为Sphingomonas。此研究结果对于阿魏植物资源的保护及生态适应性等研究具有重要意义。     

地锦草内生细菌多样性、拮抗及促生特性测定

【背景】植物内生细菌既能抑制病原菌对植物的侵染,也具有促生作用。分离具有拮抗和促生活性的内生细菌可为开发微生物菌肥提供理论依据。【目的】筛选内生细菌中的优势拮抗、促生菌种资源。【方法】以地锦草为材料,采用4种分离培养基分离该植物内生细菌,通过形态特征以及16S r RNA基因序列分析,鉴定内生细菌的分类归属。采用平板对峙法,测定内生细菌对棉花立枯丝核菌(Rhizoctonia solani)、小麦赤霉病菌(Fusarium graminearum)、玉米小斑病菌(Bipolaris maydis)的拮抗活性。通过固氮、解磷、产吲哚乙酸(Indole Acetic Acid,IAA)、产铁载体能力等指标初步检测地锦草内生细菌的促生活性。【结果】共分离到133株内生细菌,分属于4门5纲8目13科25属,其中变形菌门(Proteobacteria)为优势门(52.63%),优势属为芽孢杆菌属(Bacillus),占15.79%。发现有8株菌相似性小于98.65%,可能为潜在新物种。拮抗活性结果表明,22株菌有不同程度的抑菌作用,其中菌株DHL56、DHN17、DHP3、DHP8对这3种病原菌都有抑制作用,均为芽孢杆菌属。菌株DHP8抑制作用最强,对棉花立枯丝核菌、小麦赤霉病菌抑制率分别为73.80%、71.25%,对玉米小斑病菌抑制率为61.70%。促生潜力结果表明,76株菌具有固氮能力;19株菌具有解磷能力;37株菌能产吲哚乙酸,菌株DHL55产吲哚乙酸的量达到105.67mg/L;7株菌能合成铁载体。其中有9株菌同时有固氮、解磷、产吲哚乙酸能力;菌株DHP8具有固氮、解磷、合成铁载体能力。DHP8不仅具有一定促生潜力,还对棉花立枯丝核菌、小麦赤霉病菌、玉米小斑病菌有明显的拮抗作用,需进一步研究。【结论】地锦草内生细菌种类丰富,获得多株具有优良拮抗和促生活性的菌株,为进一步开发微生物农药及菌肥资源提供新的菌株材料。     

玉米内生细菌资源研究进展

植物内生菌存在于植物的各个器官,种类繁多,对植物的生长发育具有重要作用。玉米是最重要粮食作物之一,通过研究玉米与其内生细菌的关系,对增产玉米以及生物防治有积极意义。本文归纳了玉米内生细菌资源的分离与收集,包括内生细菌的多样性及新种的鉴定;介绍了玉米内生细菌与宿主的相关性;总结了玉米内生细菌的生物学作用,包括抑菌性、耐受性、固氮作用和促生作用,以及内生细菌对玉米作用机制;并对玉米内生细菌研究趋势进行了前景展望,旨在为玉米内生细菌的研究提供参考。     

微生物共同作用下的铁皮石斛组培苗生长效应研究

植物体和植物根际均是复杂的微生态系统,其内栖息着关系复杂的共生微生物,共同影响植物的生长发育.为探讨混合接种真菌与细菌对兰科植物生长的影响,筛选出真菌与细菌的优势促生组合,本研究选取经分离、筛选获得的4株促生内生真菌(铁皮石斛内生真菌C22、C35,美花石斛内生真菌L12、L28)和3株促生内生细菌(铁皮石斛菌内生细菌TX-7、TX-16、TX-19),以"真菌+细菌"的方式混合接种于铁皮石斛无菌组培苗中,共培养120 d.结果获得了3组优势组合:C22+TX-19、L28+TX-16和L28+TX-19,它们对铁皮石斛组培苗的生长均表现出正效应,其中C22+TX-19和L28+TX-19对促进组培苗生物量的增长具有协同效应,L28+TX-19对提高组培苗的根分枝率具有协同效应,3个组合对增加组培苗的分蘖数和根尖数均表现为累加效应.研究结果表明,内生真菌与内生细菌的共同作用可显著促进铁皮石斛的生长,混合接种有可能更大地发挥微生物的效能.     

植物内生细菌的分离、分类、定殖与应用

植物内生细菌已成为国内外的研究热点,目前已从植物中分离得到许多不同种属的植物内生细菌,其中有的具有促生与防治病害等对宿主植物有利的作用,而一些则具有潜在的致病性。研究人员利用多种方法对植物内生细菌的内生定殖行为进行研究,发现了有意义的定殖规律,例如,某种植物内生细菌对其宿主的侵染能力明显强于另一种内生细菌。目前,尽管植物内生细菌还有不少问题有待解决,但它在农业上的巨大应用潜力业已彰显。     

达乌里胡枝子产铁载体根瘤内生细菌的鉴定及其促生抗逆效应

【背景】根瘤是植物-微生物共生的特殊结构，蕴含丰富的微生物资源。产铁载体根瘤内生细菌对促进结瘤固氮具有重要作用，但目前关于其是否对植物具有促生作用尚不明确。【目的】筛选鉴定达乌里胡枝子(Lespedeza daurica)根瘤产铁载体内生细菌，明确其促生作用，为丰富植物促生菌资源提供新的途径。【方法】利用铬天青(chrome azurol S, CAS)培养基初筛产铁载体根瘤内生细菌，对目的菌株进行鉴定；通过液体发酵试验确定其产铁载体能力；利用促生功能培养基测定其他促生特性；利用不同盐浓度(0.01%-9.00%)、不同pH值(3.0-12.0)的酵母甘露醇(yeast mannitol,YMA)液体培养基和不同培养温度(4-60℃)确定其抗逆特性；通过盆栽试验初步验证其对植物的促生作用。【结果】48株根瘤内生细菌可产铁载体，其中9株为高产铁载体细菌，分别为TG4、TG9、TG13、TG15、TG28、TG32、TG38、TG76和TG78，铁载体相对表达量为26%-93%；经鉴定，除了TG28为巨大普里斯特氏菌(Priestiamegaterium)，其余8株菌均为耐寒短杆菌(Bre...     

一株水稻根内生拮抗细菌SM13的分离及鉴定

【背景】作物根内生细菌具有固氮、分泌激素、产生病原真菌抗性物质等特性,根系内生菌的分离及应用成为环境友好型防控技术研究的热点之一。近年来盐碱地水稻种植面积逐年增加,而关于盐碱地水稻根内生菌的分离与应用鲜有报道。【目的】从大庆盐碱地水稻根中分离内生细菌,筛选对植物真菌病害有拮抗作用的促生菌株,初步探讨其抑菌和促生功效,为进一步研究其抑菌和促生机理提供菌种资源。【方法】对水稻根表面灭菌后研磨涂布分离内生细菌,采用对峙培养法和改良Salkowski比色法筛选具有广谱抑菌效果并有分泌吲哚-3-乙酸(Indole-3-acetic acid,IAA)能力的菌株,通过形态鉴定、革兰氏染色、生理生化测定、16S rRNA结构基因以及srfA、ituA、fenB功能基因序列系统进化分析,确定细菌的分类地位。【结果】从水稻根部分离到一株内生细菌SM13,该菌株具有广谱性抑菌作用,对玉米新月弯孢菌、大豆菌核病菌、稻瘟病菌、禾谷镰刀菌的抑菌率分别为59.38%、78.13%、53.12%、37.50%,分泌IAA的能力为5.56±0.41μg/mL (n=6)。经形态学、生理生化试验结合系统进化分析初步鉴定SM13菌株属于枯草芽孢杆菌(Bacillus subtilis),该菌株在pH 11.0、盐浓度10%的NA培养基中生长良好,具有较高的耐盐碱性。【结论】水稻根内生菌SM13菌株具有耐盐碱性、促生和生防性能,可作为微生物农药及菌肥的材料。     

植物内生细菌生物学作用研究进展

内生细菌是植物内生微生物群的主要成员 ,对寄主植物有促生、防病、固氮等多方面的有益生物学作用 ,还可以作为受体 ,将外源基因携带入植物体内 ;但是有的内生细菌对寄主植物的生长发育等也有不利的影响。由于它们生存在植物体内 ,是生物农药和生物肥料等方面的天然资源菌物 ,具有广泛的研究和应用价值     

东乡野生稻内生细菌Fse32拮抗作物病害真菌及对水稻的促生活性

【背景】植物种子是植物内生菌筛选的重要原料,从中能够分离得到具有巨大应用价值的内生菌株。【目的】为发掘优良的种子内生细菌资源,对分离自东乡野生稻种子的内生细菌Fse32进行鉴定并研究其抗病原真菌和促生活性。【方法】通过形态学观察、生理生化特征和16SrRNA基因序列分析进行菌种鉴定,采用拮抗试验检测抑制病原真菌的活性,通过促生能力测定试验、水稻种子萌发及盆栽试验评价该菌株的促生效果。【结果】内生细菌Fse32鉴定为唐菖蒲伯克霍尔德氏菌,命名为Burkholderia gladioli Fse32。拮抗试验结果显示,菌株Fse32对禾谷镰孢菌(Fusarium graminearum)、水稻纹枯病菌(Rhizoctoniasolani)、核盘菌(Sclerotiniasclerotiorum)、大豆核盘菌(Sclerotinialibertiana)、尖孢镰刀菌(Fusariumoxysporum)和辣椒疫霉病菌(Phytophthoracapsici)均有较好的抑制作用,吲哚乙酸(indole-3-aceticacid,IAA)产率为17.95mg/L,能产铁载体,其A/Ar比值为0....     

Suppression of damping-off in maize seedlings by Pseudomonas corrugata

Two strains of Pseudomonas corrugata, (1 and 7), isolated from subtropical and temperate soils in Sikkim Himalaya, respectively, were subjected to Petri-dish as well as plant-based bioassay to examine their potential for disease suppression against three major pathogens of maize. A mixture of Pythium ultimum, P. arrhenomanes and Fusarium graminearum was introduced in the soil; maize seed inoculated with one of the two strains of Pseudomonas corrugata (1 or 7) were sown in pots containing such soil. The bacterial inoculation resulted in significant disease suppression as well as growth promotion of seedlings. The bacterial strains were also evaluated for their intrinsic antibiotic resistance against a range of concentrations of ten antibiotics. While the bacteria were found to be sensitive to gentamycin and rifampicin, they exhibited resistance against ampicillin, carbenicillin and penicillin, even at high concentrations.     

马铃薯内生细菌的分离及其对环腐病菌的拮抗作用检测（简报）

马铃薯是世界四大作物之一,我国是世界上马铃薯种植面积最大的国家,种植面积达6000万亩。近年来,在马铃薯经济良好发展的带动下,马铃薯生产在种植面积和单产水平上有了大幅度提高。然而各种病害随之表现出逐年上升的趋势。     

马铃薯内生细菌的分离及其对环腐病菌的拮抗作用检测(简报)

马铃薯是世界四大作物之一,我国是世界上马铃薯种植面积最大的国家,种植面积达6000万亩。近年来,在马铃薯经济良好发展的带动下,马铃薯生产在种植面积和单产水平上有了大幅度提高。然而各种病害随之表现出逐年上升的趋势。环腐病、黑胫病、干腐病是造成北方马铃薯田间和窖存烂薯的主要病害,一般经济损失达20%—30%,严重年份可达50%。马铃薯环腐病害难以防治是因为病菌侵染部     

Host and geographical factors influence the thermal niche of enteric bacteria isolated from native Australian mammals

The thermal profiles of 118 bacterial strains, representing six species of the family Enterobacteriaceae, isolated from a variety of native Australian mammals were determined under in vitro conditions. Each of the bacterial species had a unique thermal profile and differed in their minimum or maximum temperature for growth and in their response to changing temperatures. The taxonomic classification of the host from which the bacterial strains were isolated explained a significant amount of the variation in thermal profile among strains of a species. Host effects were detected at all taxonomic levels: order, family, genus, and species. The locality (State or Territory) or climate zone from which the strain was collected explained a significant amount of the variation in the thermal profile of Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae strains. Genetically similar strains, as determined by allozyme profiles, had similar thermal profiles for the bacterial species Hafnia alvei and Escherichia coli. The results of this study indicate that there are potentially many aspects of host biology that may determine the thermal profile of these bacteria.     

Plant beneficial effect of two strains of Proteus vulgaris isolated from tea plantations

Two strains of Proteus isolated from tea plantation soil were tested for their ability to colonise the roots of gram (Cicer arietinum), bean (Phaseolus radiatus) and mung (Phaseolus mungo) using a gnotobiotic system. Seeds bacterized with the two strains grew faster and showed significant increase in root and shoot enlargement of the plants tested. The bioactive fractions obtained from the culture filtrates and separated through HPLC showed that the plant growth promoting fractions were not always fungicidal and that the insecticidal fraction which was found only in RRLJ 16 was not plant growth promoting. These results suggest that the plant growth promotion effect of the plant beneficial bacteria may not always be due to disease suppression.     

Screening rhizobacteria for biological control of Ralstonia solanacearum in Ethiopia

Bacterial wilt caused by Ralstonia solanacearum (Smith) has become a severe problem mainly on potato and tomato in Ethiopia and no effective control measure is available yet. To explore possibilities for the development of biological control for the disease, 118 rhizobacteria, most of them collected from Ethiopia, were screened against an Ethiopian R. solanacearum strain. On the basis of in vitro screening, six strains (RP87, B2G, APF1, APF2, APF3, and APF4) with good inhibitory effect were selected for in planta testing in a greenhouse. In the greenhouse, soil and tomato seedlings were treated with the antagonists and their effects studied. The study showed that APF1 and B2G strains significantly reduced disease incidence and increased weight of tomato plants. Area under disease progress curves (AUDPC) was reduced by 60% and 56% in plants inoculated with APF1 and B2G strains, respectively. Plant dry weight increase in plants inoculated with APF1 and B2G strains was 96% and 75%, respectively. APF1 was found to be the most beneficial strain in disease suppression and also growth promotion resulting in 63% dry weight increase compared to untreated control. The study revealed that APF1 and B2G strains are promising strains whose effectiveness under field conditions and their mode of action should be investigated.     

GC-MS SPME profiling of rhizobacterial volatiles reveals prospective inducers of growth promotion and induced systemic resistance in plants

Chemical and plant growth studies of Bacilli strains GB03 and IN937a revealed that the volatile components 2,3-butanediol and acetoin trigger plant growth promotion in Arabidopsis. Differences in growth promotion when cytokinin-signaling mutants are exposed to GB03 versus IN937a volatiles suggest a divergence in chemical signaling for these two bacterial strains. To provide a comprehensive chemical profile of bacterial volatiles emitted from these biologically active strains, headspace solid phase microextraction (SPME) coupled with software extraction of overlapping GC-separated components was employed. Ten volatile metabolites already reported from GB03 and IN937a were identified as well as 28 compounds not previously characterized. Most of the newly identified compounds were branched-chain alcohols released from IN937a, at much higher levels than in GB03. Principal component analysis clearly separated GB03 from IN937a, with GB03 producing higher amounts of 3-methyl-1-butanol, 2-methyl-1-butanol and butane-1-methoxy-3-methyl. The branched-chain alcohols share a similar functional motif to that of 2,3-butanediol and may afford alternative structural patterns for elicitors from bacterial sources.     

Comparison of the bacterial community and characterization of plant growth-promoting rhizobacteria from different genotypes of <Emphasis Type="Italic">Chrysopogon zizanioides</Emphasis> (L.) Roberty (Vetiver) rhizospheres

Molecular approaches [PCR-denaturing gradient gel electrophoresis (DGGE)] were used to determine whether three different vetiver (Chrysopogon zizanioides) genotypes, commercially used in Brazil and considered economically important over the world, select specific bacterial populations to coexist in their rhizospheres. DGGE profiles revealed that the predominant rhizospheric bacterial community hardly varies regarding the vetiver genotype. Moreover, using traditional cultivation methods, bacterial strains were isolated from the different rhizospheres. Colonies presenting different morphologies (83) were selected for determining their potential for plant growth promotion. More than half of the strains tested (57.8%) were amplified by PCR using nifH-based primers, specific for the enzyme nitrogenase reductase. The production of siderophores was observed in 88% of the strains, while the production of antimicrobial substances was detected in only 14.5% of the isolates when Micrococcus sp. was used as the indicator strain. Production of indole-3-acetic acid and the solubilization of phosphate were observed in 55.4% and 59% of the isolates, respectively. In total, 44 strains (53%) presented at least three characteristics of plant growth promotion and were submitted to amplified ribosomal DNA restriction analysis. Twenty-four genetic groups were formed at 100% similarity and one representative of each group was selected for their identification by partial 16S rRNA gene sequencing. They were affiliated with the genera Acinetobacter, Comamonas, Chryseobacterium, Klebsiella, Enterobacter, Pantoea, Dyella, Burkholderia, or Pseudomonas. These strains can be considered of great importance as possible biofertilizers in vetiver.     

Pharmacodynamic parameters and hydrophobicity changes induced by meropenem in Acinetobacter baumannii.

The suppression of bacterial growth of four Acinetobacter baumannii strains after 60 min exposure to meropenem at supra-inhibitory concentrations (postantibiotic effect; PAE) or at supra-subinhibitory concentrations (postantibiotic-sub-MIC effect; PA SME) was studied. The duration of the PAE was dependent on antibiotic concentration and on the strain. Meropenem at 2x or 4x the minimum inhibitory concentration (MIC), with the exception of one strain treated with 4x MIC, did not provoke suppression of bacterial growth compared with untreated controls. The highest concentration of meropenem (8x MIC) induced PAE for the strains tested in the range of 0.6-6.9 h. The effect of supra-subinhibitory concentrations of meropenem (2x, 4x or 8x MIC + 0.2x MIC) on bacterial growth was more efficient compared with supra-inhibitory concentrations alone. Two out of the four strains treated did not renew their growth. Bacterial suspensions exposed to meropenem showed reduced surface hydrophobicity. Decreases in hydrophobicity were associated with longer PAE and PA SME depending on the strain.