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1、Deciphering the Rhizosphere Microbiomefor Disease-Suppressive Bacteria揭秘根际微生物中的抗病性细菌,Rodrigo Mendes,et al.27 MAY 2011 SCIENCE VOL 332,OUTLINE,Introduction&The Aim of This StudyMaterials&MethodsResultsDiscussion My gains and Thinking,Introduction&The Aim of This Study,Disease-suppressive soils are ex
2、ceptional eco-systems in which crop plants suffer less from specific soil-borne pathogens than expected owing to the activities of other soil microorganisms.抗病性土壤是一种特殊的生态系统，由于其他土壤微生物的活性，其比预期更好的减少作物因专性土传病原菌的带来的损失。,For most disease-suppressive soils,the microbes and mechanisms involved in pathogen con
3、trol are unknown.对于绝大多数的抗病性土壤而言，其调控病原菌的微生物种类及其机制还不清楚。,Similar to other eukaryotes（真核生物）,plants and their microbiomes can be viewed as“superorganisms”in which the plant relies,in part,on the soil microbiotic for specific functions and traits.与其它真核生物相似，植物与它们根际的微生物被称为“超个体”，由于植物的生长部分依赖于土壤微生物特殊的功能和特性。,In
4、 return,plants exude up to 21%of their photosynthetically fixed carbon in the root-soil interface,thereby feeding the microbial communities and influencing their activity and diversity.作为反馈，植物输出其光合作用固定的碳的21%进入根土界面，以此来供养微生物群落，并影响它们的活性和多样性。,For decades,studies about the interplay between plants and rh
5、izosphere microorganisms have focused on pathogens,symbiotic rhizobia,and mycorrhizal fungi,yet there is evidence that other groups of soil microorganisms can affect plant growth and health.过去的几十年间，关于植物与根际微生物相互作用的研究主要关注病原菌、共生根际细菌和菌根真菌，然而，有证据表明其它类群的土壤微生物也能影响植物的生长和健康。,It even has been postulated that
6、plants actively recruit beneficial soil microorganisms in their rhizospheres to counteract pathogen assault（袭击）.One well-known phenomenon is the occurrence of disease-suppressive soils,a property conferred by the resident microbiota via as yet unknown mechanisms.,The aim of this study is to decipher
7、 the rhizosphere microbiome to identify such disease-suppressive microbes and to unravel the mechanisms by which they protect plants against root diseases.本研究的目的在于鉴定根际微生物中的抗病性微生物，并阐明它们保护植物抵抗根部病害的机理。,Materials&Methods,The soil we investigated is suppressive to Rhizoctonia solani（立枯丝核菌）,an economicall
8、y important fungal pathogen of many crops including sugar beet,potato,and rice.In the years before its discovery,sugar beet plants grown in this field were severely affected by R.solani.,Disease suppressiveness was determined for various treatments:suppressive soil(S)conducive soil(C)conducive soil
9、amended with 10%(w/w)of suppressive soil(CS)suppressive soil heat-treated at 50 for 1 hour(S50)suppressive soil heat-treated at 80 for 1 hour(S80),I-Experimental design1 Sugar beet grown in the presence of R.solani(N=4).2 Sugar beet grown in the absence of R.solani(N=4).*Treatments selected for Phyl
10、oChip analysis.,III-Isolation of specific bacterial taxa targeted by PhyloChip analysis,1 Bacterial isolation from suppressive and conducive soils(1000 random isolates).General aerobic growth medium(TSA)Pseudomonadaceae（假单胞菌）semi-selective medium(PSA).2 Genetic and phenotypic characterization(107 is
11、olates).Screening for antagonistic traits(in vitro tests,PCR)BOX-PCR 16S rDNA sequencing in vivo bioassays.3 Alignments and BLAST searches in the GreenGenes database using 16S rDNA sequences of the functional bacterial groups.,IV-Genes and pathways involved in disease suppressionGenetic,bioinformati
12、c,and functional analysesMutagenesis（引发突变）Genome library constructions Sequencing Signature-sequence-based predictions in vivo bioassays.,Results,Fig.1.(A)Effect of R.solani infection on growth of sugar beet seedlings in disease-suppressive(S)and disease-conducive(C)soils.(B)Percentage(meanSEM,N=4)o
13、f seedlings with damping-off symptoms.,These results indicated that disease suppressiveness toward R.solani was microbiological in nature.,Fig.S2.Effect of-irradiation on soil disease suppressiveness.Suppressive soil(S)and-irradiated(60 kGray,Isotron,The Netherlands)suppressive soil(SG)were cultivat
14、ed with sugarbeet.,PhyloChip analysis A total of 33,346 bacterial and archaeal（古细菌）operational taxonomic units(OTUs)were detected in the rhizosphere microbiome.,The relative abundance of several bacterial taxa is a more important indicator of disease suppression than the exclusive presence of specif
15、ic bacterial taxa.,The-and-Proteobacteria(变形菌门）and the Firmicutes（厚壁菌门）were identified as the most dynamic taxa associated with disease suppression.These were all more abundant in suppressive soil than in conducive soil;more abundant in the transplantation soil than in the conducive soil;and more ab
16、undant in the suppressive soil when R.solani was present.SC CS C Sr S,The Actinobacteria too were more abundant in suppressive than in conducive soil and were the most dynamic taxa in the suppressive soil amended with the fungal pathogen.,Isolation of specific bacterial taxa targeted by PhyloChip an
17、alysisCulture-based approaches for identifying functional groups involved in disease suppressiveness of soils have focused on bacterial taxa that are easy to grow and amenable to genetic and genomic analyses.Most of the antagonistic bacterial isolates from the suppressive soil were obtained from the
18、 growth medium that is semiselective for the Pseudomonadaceae.,Haplotypes SH-A(38 isolates),SH-B(21 isolates),and SH-C(37 isolates)constituted 90%of the antagonistic bacterial isolates from the disease-suppressive soil and were selected for further functional analyses.O33、KO26:Random transposon muta
19、genesis generated two mutants of strain SH-C52.,Plant bioassays with representative isolates of each of these three haplotypes showed that only strain SH-C52 protected sugar beet seedlings from infection by R.solani.,Subsequent genetic analyses revealed that the putative biosynthetic pathway consist
20、ed of two gene clusters,designated thaAB and thaC1C2D,which were predicted to encode a nineamino acid chlorinated lipopeptide.,小结,1、土壤的抗病性是由于一些特殊的微生物类群所赋予的。2、假单胞菌科、伯克氏菌科、黄色单胞菌目、乳酸杆菌科被发现与土壤的抗病性有关。3、遗传分析结果表明，可能是由于thaAB 和 thaC1C2D两个基因簇编码氯化九氨基酸脂肽保护了甜菜籽苗免受真菌病原菌的侵染。,The multifaceted approach adopted in th
21、is study,linking culture-independent and culture-dependent analyses,shows that plants,like mammals and insects,can rely on specific constituents of the microbial community for protection against pathogen infections.在本研究中采用了多种方法，结合了纯培养和免培养的方法研究根际微生物，结果显示，植物与哺乳动物和昆虫一样，依赖微生物群落中的特殊组分以保护自己抵御病原菌的侵染。,Discu
22、ssion,The findings suggest that the complex phenomenon of disease suppressiveness of soils cannot simply be ascribed to a single bacterial taxon or group,but is most likely governed by microbial consortia.研究结果表明，土壤的抗病性是一个复杂的现象，不能单一的归因于一个单一的细菌分类单元或种群，而极可能是被微生物联盟所支配。,The bacteria and biosynthetic path
23、way identified here provide a set of microbial and genetic markers to elucidate whether and how plants recruit beneficial soil micro-organisms for protection against infections.土壤细菌及其生物合成路径在研究中被鉴定，提供了一系列的微生物的和遗传标记以阐明植物是否会以及如何补充有益土壤微生物以保护其抵御病原菌侵染。,1、看SCIENCE的几点体会。2、只有多种方法结合才能全面、客观、系统的反应根际微生物对植物病害的影响。3、对于根际微生物是如何影响植物的病害的机理目前还存在很多争论，个人认为根际微生物活动产生的一些酶类也是使土壤获得抗病性的直接原因。,My gains and Thinking,Thank You for Time!Question and Advise!,
