Plant microbe interactions
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Rescooped by Mitja Remus-Emsermann from The Plant Microbiome
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Antagonistic interactions between endophytic cultivable bacterial communities isolated from the medicinal plant Echinacea purpurea

Antagonistic interactions between endophytic cultivable bacterial communities isolated from the medicinal plant Echinacea purpurea | Plant microbe interactions | Scoop.it

In this work we have studied the antagonistic interactions existing among cultivable bacteria isolated from three ecological niches (rhizospheric soil, roots, and stem/leaves) of the traditional natural medicinal plant Echinacea purpurea. The three compartments harbored different taxonomic assemblages of strains, which were previously reported to display different antibiotic resistance patterns, suggesting the presence of differential selective pressure due to antagonistic molecules in the three compartments. Antagonistic interactions were assayed by the cross-streak method and interpreted using a network-based analysis. In particular “within-niche inhibition” and “cross-niche inhibition'’ were evaluated among isolates associated with each compartment as well as between isolates retrieved from the three different compartments, respectively. Data obtained indicated that bacteria isolated from the stem/leaves compartment were much more sensitive to the antagonistic activity than bacteria from roots and rhizospheric soil. Moreover, both the taxonomical position and the ecological niche might influence the antagonistic ability/sensitivity of different strains. Antagonism could play a significant role in contributing to the differentiation and structuring of plant-associated bacterial communities.


Via Kemen Lab, Nina Dombrowski, Stéphane Hacquard
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EM: Spatial distribution analyses of natural phyllosphere-colonizing bacteria on Arabidopsis thaliana revealed by fluorescence in situ

EM: Spatial distribution analyses of natural phyllosphere-colonizing bacteria on Arabidopsis thaliana revealed by fluorescence in situ | Plant microbe interactions | Scoop.it

Bacterial colonizers of the aerial parts of plants, or phyllosphere, have been identified on a number of different plants using cultivation-dependent and independent methods. However, the spatial distribution at the micrometer scale of different main phylogenetic lineages is not well documented and mostly based on fluorescence-tagged model strains. In this study we developed and applied a spatial explicit approach that allowed the use of fluorescence in situ hybridization (FISH) to study bacterial phylloplane communities of environmentally grown Arabidopsis thaliana. We found on average 5.4×106 bacteria per cm2 leaf surface and 1.5×108 bacteria per gram fresh weight. Furthermore we found that the total biomass in the phylloplane was normally distributed. About 31% of the bacteria found in the phylloplane did not hybridize to FISH probes but exhibited infrared autofluorescence indicative for aerobic anoxygenic phototrophs. Four sets of FISH probes targeting Alphaproteobacteria, Betaproteobacteria, Actinobacteria, and Bacteroidetes were sufficient to identify all other major contributors of the phylloplane community based on general bacterial probing. Spatial aggregation patterns were observed for all probe-targeted populations at distances up to 7 μm, with stronger tendencies to co-aggregate for members of the same phylogenetic group. Our findings contribute to a bottom-up description of leaf surface community composition.


Via Stéphane Hacquard
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Rescooped by Mitja Remus-Emsermann from Plant - Salmonella or E. coli Interactions
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Internalization and Fate of Escherichia coli O157:H7 in Leafy Green Phyllosphere Tissue Using Various Spray Conditions

In the past decade, leafy greens have been implicated in several outbreaks of foodborne illness, and research has focused on contamination during preharvest operations. Concerns have been raised that internalization of pathogens into the edible tissue occurs where postharvest chemical interventions would be ineffective. This study was initiated to measure the degree and fate ofEscherichia coli O157:H7 internalized in the phyllosphere tissue of leafy greens when spray conditions, inoculum level, and type of leafy green were varied. Two spraying treatments were applied: (i) spraying individual spinach or lettuce leaves on plants once with a high dose (7 to 8 log CFU/ml) of E. coli O157:H7 and (ii) spraying spinach, lettuce, or parsley plants repeatedly (once per minute) with a low dose (2.7 to 4.2 log CFU/ml) of E. coli O157:H7 over a 10- to 20-min period. With the high-dose spray protocol, no significant differences in the prevalence of internalization occurred between Shiga toxin–negative E. coli O157:H7 isolates and virulent isolates (P > 0.05), implying that the Shiga toxin virulence factors did not influence internalization or the subsequent fate of those populations under these test conditions. Significantly greater internalization of E. coli O157:H7 occurred in spinach leaves compared with lettuce leaves when leaves were sprayed once with the high-dose inoculum (P < 0.05), whereas internalization was not observed in lettuce leaves but continued to be observed in spinach and parsley leaves following repeated spraying of the low-dose inoculum. Based on these results, it is surmised that a moisture film was generated when spraying was repeated and this film assisted in the mobilization of pathogen cells to plant apertures, such as stomata. E. coli O157:H7 cells that were internalized into spinach tissue using a low-dose repeat-spray protocol were temporary residents because they were not detected 2 days later, suggesting that plant-microbe interactions may be responsible.


Via Jean-Michel Ané
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Internalization and Fate of Escherichia coli O1...

Internalization and Fate of Escherichia coli O1... | Plant microbe interactions | Scoop.it
In the past decade, leafy greens have been implicated in several outbreaks of foodborne illness, and research has focused on contamination during preharvest operations.
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Frontiers: Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria

Frontiers: Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria | Plant microbe interactions | Scoop.it

Plant pathogenic bacteria and rhizobia infect higher plants albeit the interactions with their hosts are principally distinct and lead to completely different phenotypic outcomes, either pathogenic or mutualistic, respectively. Bacterial protein delivery to plant host plays an essential role in determining the phenotypic outcome of plant-bacteria interactions. The involvement of type III secretion systems (T3SSs) in mediating animal- and plant-pathogen interactions was discovered in the mid-80’s and is now recognized as a multiprotein nanomachine dedicated to trans-kingdom movement of effector proteins. The discovery of T3SS in bacteria with symbiotic lifestyles broadened its role beyond virulence. In most T3SS-positive bacterial pathogens, virulence is largely dependent on functional T3SSs, while in rhizobia the system is dispensable for nodulation and can affect positively or negatively the mutualistic associations with their hosts. This review focuses on recent comparative genome analyses in plant pathogens and rhizobia that uncovered similarities and variations among T3SSs in their genetic organization, regulatory networks and type III secreted proteins and discusses the evolutionary adaptations of T3SSs and type III secreted proteins that might account for the distinguishable phenotypes and host range characteristics of plant pathogens and symbionts


Via Stéphane Hacquard
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Jean-Michel Ané's comment, March 12, 2014 12:00 PM
Ha ha ha.. I like your honesty!
Stéphane Hacquard's comment, March 12, 2014 12:44 PM
Although it correlates sometimes with the quality of some papers :-), the mention (null) is not related to that but is automatically added when I scoop something from my cellphone... very sorry for this misunderstanding.
Jean-Michel Ané's comment, March 12, 2014 4:15 PM
That's funny. Thanks for the clarification.
Rescooped by Mitja Remus-Emsermann from Plant-microbe interaction
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HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants

HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants | Plant microbe interactions | Scoop.it

The YopJ-family of type III effector (T3E) proteins is one of the largest and widely distributed families of effector proteins whose members are highly diversified in virulence functions. In the present study, HopZ4, a member of the YopJ-family of T3Es from the cucumber pathogen Pseudomonas syringae pv. lachrymans is described. HopZ4 shares high sequence similarity with the Xanthomonas T3E XopJ and a functional analysis suggests a conserved virulence function between these two T3Es. As has previously shown for XopJ, HopZ4 interacts with the proteasomal subunit RPT6 in yeast and in planta to inhibit proteasome activity during infection. The inhibitory effect on the proteasome is dependent on localization of HopZ4 to the plasma membrane as well as on an intact catalytic triad of the effector protein. Furthermore, HopZ4 is able to complement loss of XopJ in Xanthomonas as it prevents precocious host cell death during a compatible interaction of Xanthomonas with pepper. The data presented here suggest that different bacterial species employ inhibition of the proteasome as a virulence strategy by making use of conserved T3Es from the YopJ-family of bacterial effector proteins.


Via Suayib Üstün
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Rescooped by Mitja Remus-Emsermann from Plant - Salmonella or E. coli Interactions
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Response of Medicago truncatula Seedlings to Colonization by Salmonella enterica and Escherichia coli O157:H7

Response of Medicago truncatula Seedlings to Colonization by Salmonella enterica and Escherichia coli O157:H7 | Plant microbe interactions | Scoop.it
Disease outbreaks due to the consumption of legume seedlings contaminated with human enteric bacterial pathogens like Escherichia coli O157:H7 and Salmonella enterica are reported every year. Besides contaminations occurring during food processing, pathogens present on the surface or interior of plant tissues are also responsible for such outbreaks. In the present study, surface and internal colonization of Medicago truncatula, a close relative of alfalfa, bySalmonella enterica and Escherichia coli O157:H7 were observed even with inoculum levels as low as two bacteria per plant. Furthermore, expression analyses revealed that approximately 30% of Medicago truncatula genes were commonly regulated in response to both of these enteric pathogens. This study highlights that very low inoculum doses trigger responses from the host plant and that both of these human enteric pathogens may in part use similar mechanisms to colonize legume seedlings

Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, February 15, 2014 11:19 AM

A little bit of advertising... Who wants to eat alfalfa sprouts after reading this?

Jean-Michel Ané's curator insight, February 15, 2014 11:20 AM

A little bit of advertising... Who wants to eat alfalfa sprouts after reading this?

Rescooped by Mitja Remus-Emsermann from Plant-Microbe Interaction
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Getting the ecology into interactions between plants and the plant growth-promoting bacterium Pseudomonas fluorescens

Getting the ecology into interactions between plants and the plant growth-promoting bacterium Pseudomonas fluorescens | Plant microbe interactions | Scoop.it

Plant growth-promoting rhizobacteria (PGPR) are increasingly appreciated for their contributions to primary productivity through promotion of growth and triggering of induced systemic resistance in plants. Here we focus on the beneficial effects of one particular species of PGPR (Pseudomonas fluorescens) on plants through induced plant defense. This model organism has provided much understanding of the underlying molecular mechanisms of PGPR-induced plant defense. However, this knowledge can only be appreciated at full value once we know to what extent these mechanisms also occur under more realistic, species-diverse conditions as are occurring in the plant rhizosphere. To provide the necessary ecological context, we review the literature to compare the effect of P. fluorescens on induced plant defense when it is present as a single species or in combination with other soil dwelling species. Specifically, we discuss combinations with other plant mutualists (bacterial or fungal), plant pathogens (bacterial or fungal), bacterivores (nematode or protozoa), and decomposers. Synergistic interactions between P. fluorescens and other plant mutualists are much more commonly reported than antagonistic interactions. Recent developments have enabled screenings of P. fluorescens genomes for defense traits and this could help with selection of strains with likely positive interactions on biocontrol. However, studies that examine the effects of multiple herbivores, pathogens, or herbivores and pathogens together on the effectiveness of PGPR to induce plant defenses are underrepresented and we are not aware of any study that has examined interactions between P. fluorescens and bacterivores or decomposers. As co-occurring soil organisms can enhance but also reduce the effectiveness of PGPR, a better understanding of the biotic factors modulating P. fluorescens–plant interactions will improve the effectiveness of introducing P. fluorescens to enhance plant production and defense.

 

 


Via Stijn Spaepen, Jean-Michel Ané, Guogen Yang
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Ascending Migration of Endophytic Rhizobia, from Roots to Leaves, inside Rice Plants and Assessment of Benefits to Rice Growth Physiology

Ascending Migration of Endophytic Rhizobia, from Roots to Leaves, inside Rice Plants and Assessment of Benefits to Rice Growth Physiology | Plant microbe interactions | Scoop.it

Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. We examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. The results indicated a dynamic infection process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. In situ CMEIAS image analysis indicated local endophytic population densities reaching as high as 9 × 1010 rhizobia per cm3 of infected host tissues, whereas plating experiments indicated rapid, transient or persistent growth depending on the rhizobial strain and rice tissue examined. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growth-regulating phytohormones. Considered collectively, the results indicate that this endophytic plant-bacterium association is far more inclusive, invasive, and dynamic than previously thought, including dissemination in both below-ground and above-ground tissues and enhancement of growth physiology by several rhizobial species, therefore heightening its interest and potential value as a biofertilizer strategy for sustainable agriculture to produce the world's most important cereal crops.


Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, December 6, 2013 12:32 PM

Not new but I found it very interesting.

Rescooped by Mitja Remus-Emsermann from The Plant Microbiome
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The ISME Journal: Fitness and stability of obligate cross-feeding interactions that emerge upon gene loss in bacteria

Cross-feeding interactions, in which bacterial cells exchange costly metabolites to the benefit of both interacting partners, are very common in the microbial world. However, it generally remains unclear what maintains this type of interaction in the presence of non-cooperating types. We investigate this problem using synthetic cross-feeding interactions: by simply deleting two metabolic genes from the genome of Escherichia coli, we generated genotypes that require amino acids to grow and release other amino acids into the environment. Surprisingly, in a vast majority of cases, cocultures of two cross-feeding strains showed an increased Darwinian fitness (that is, rate of growth) relative to prototrophic wild type cells—even in direct competition. This unexpected growth advantage was due to a division of metabolic labour: the fitness cost of overproducing amino acids was less than the benefit of not having to produce others when they were provided by their partner. Moreover, frequency-dependent selection maintained cross-feeding consortia and limited exploitation by non-cooperating competitors. Together, our synthetic study approach reveals ecological principles that can help explain the widespread occurrence of obligate metabolic cross-feeding interactions in nature.


Via Stéphane Hacquard
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New insights into the structure and function of phyllosphere microbiota through high-throughput molecular approaches - Rastogi - 2013 - FEMS Microbiology Letters - Wiley Online Library

New insights into the structure and function of phyllosphere microbiota through high-throughput molecular approaches - Rastogi - 2013 - FEMS Microbiology Letters - Wiley Online Library | Plant microbe interactions | Scoop.it

The phyllosphere is an ecologically and economically important ecosystem that hosts a large and diverse microbial community. Phyllosphere microbiota play a critical role in protecting plants from diseases as well as promoting their growth by various mechanisms. There are serious gaps in our understanding of how and why microbiota composition varies across spatial and temporal scales, the ecology of leaf surface colonizers and their interactions with their host, and the genetic adaptations that enable phyllosphere survival of microorganisms. These gaps are due in large part to past technical limitations, as earlier studies were restricted to the study of culturable bacteria only and used low-throughput molecular techniques to describe community structure and function. The availability of high-throughput and cost-effective molecular technologies is changing the field of phyllosphere microbiology, enabling researchers to begin to address the dynamics and composition of the phyllosphere microbiota across a large number of samples with high, in-depth coverage. Here, we discuss and connect the most recent studies that have used next-generation molecular techniques such as metagenomics, proteogenomics, genome sequencing, and transcriptomics to gain new insights into the structure and function of phyllosphere microbiota and highlight important challenges for future research.


Via Stijn Spaepen
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Genome of an arbuscular mycorrhizal fungus provides insight into the oldest plant symbiosis

Genome of an arbuscular mycorrhizal fungus provides insight into the oldest plant symbiosis | Plant microbe interactions | Scoop.it

The arbuscular mycorrhizal symbiosis between fungi of the Glomeromycota phylum and plants involves more than two-thirds of all known plant species, including important crop species. This mutualistic symbiosis, involving one of the oldest fungal lineages, is arguably the most ecologically and agriculturally important symbiosis in terrestrial ecosystems. The Glomeromycota are unique in that their spores and coenocytic hyphae contain hundreds of nuclei in a common cytoplasm, which raises important questions about the natural selection, population genetics, and gene expression of these highly unusual organisms. Study of the genome of Rhizophagus irregularis provides insight into genes involved in obligate biotrophy and mycorrhizal symbioses and the evolution of an ancient asexual organism, and thus is of fundamental importance to the field of genome evolution.


Via Francis Martin
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Rhizosphere microbiome assemblage is affected by plant development

Rhizosphere microbiome assemblage is affected by plant development | Plant microbe interactions | Scoop.it
There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (P<0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.

 

Chaparro, J. M., Badri, D. V., Vivancio, J. M. (2013). ISME Journal , advance online publication, Nov 7.


Via Jean-Michel Ané, IvanOresnik
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Frontiers | Pivotal roles of phyllosphere microorganisms at the interface between plant functioning and atmospheric trace gas dynamics

Frontiers | Pivotal roles of phyllosphere microorganisms at the interface between plant functioning and atmospheric trace gas dynamics | Plant microbe interactions | Scoop.it

The phyllosphere, which lato sensu consists of the aerial parts of plants, and therefore primarily, of the set of photosynthetic leaves, is one of the most prevalent microbial habitats on earth. Phyllosphere microbiota are related to original and specific processes at the interface between plants, microorganisms and the atmosphere. Recent –omics studies have opened fascinating opportunities for characterizing the spatio-temporal structure of phyllosphere microbial communities in relation with structural, functional, and ecological properties of host plants, and with physico-chemical properties of the environment, such as climate dynamics and trace gas composition of the surrounding atmosphere. This review will analyze recent advances, especially those resulting from environmental genomics, and how this novel knowledge has revealed the extent of the ecosystemic impact of the phyllosphere at the interface between plants and atmosphere.


Via Stéphane Hacquard
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Bacterial quorum sensing compounds are importan...

Bacterial quorum sensing compounds are importan... | Plant microbe interactions | Scoop.it
Higher organisms evolved in the omnipresence of microbes, which could be of pathogenic or symbiotic nature. A framework of response patterns evolved which is known as innate immunity.
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Populus trichocarpa and Populus deltoides Exhib...

Populus trichocarpa and Populus deltoides Exhib... | Plant microbe interactions | Scoop.it
Within boreal and temperate forest ecosystems, the majority of trees and shrubs form beneficial relationships with mutualistic ectomycorrhizal (ECM) fungi that support plant health through increased access to nutrients as well as aiding in stress...
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MPMI: Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA (2014)

MPMI: Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA (2014) | Plant microbe interactions | Scoop.it

Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogenPseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacterial species. In addition we investigated the role of AprA in virulence of the bacterial plant pathogen Pseudomonas syringae pv. tomato DC3000 (Pst). The AprA-deficient Pst ∆aprA knockout mutant was significantly less virulent on both tomato and A. thaliana. Moreover, infiltration of A. thaliana Col-0 leaves with Pst ∆aprA evoked a significantly higher level of expression of the defense-related genes FRK1 and PR-1 than did wild-type Pst. In the flagellin receptor mutant fls2, pathogen virulence and defense-related gene activation did not differ between Pst and Pst ∆aprA. Together, these results suggest that AprA of Pst is important for evasion of recognition by the FLS2 receptor, allowing wild-type Pst to be more virulent on its host plant than AprA-deficient Pst ∆aprA. To provide further evidence for the role of Pst AprA in host immune evasion, we overexpressed the AprA inhibitory peptide AprI of Pst in A. thaliana to counteract the immune evasive capacity of Pst AprA. Ectopic expression of aprI in A. thaliana resulted in an enhanced level of resistance against wild-type Pst, while the already elevated level of resistance against Pst ∆aprA remained unchanged. Together, these results indicate that evasion of host immunity by the alkaline protease AprA is important for full virulence of Pst and likely acts by preventing flagellin monomers from being recognized by its cognate immune receptor.


Via Kamoun Lab @ TSL
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Plant–microbe interactions as drivers of ecosystem functions relevant for the biodegradation of organic contaminants

Plant–microbe interactions as drivers of ecosystem functions relevant for the biodegradation of organic contaminants | Plant microbe interactions | Scoop.it

Highlights• Biotransformation is an ecosystem property.• Microbes are the main drivers in biotransformation.• Dispersal of chemicals and bacteria drives degradation effectiveness.• Ecosystem stability is increased by plant–microbe interactions


Via Francis Martin
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MPMI: Metabolic Environments and Genomic Features Associated with Pathogenic and Mutualistic Interactions between Bacteria and Plants

MPMI: Metabolic Environments and Genomic Features Associated with Pathogenic and Mutualistic Interactions between Bacteria and Plants | Plant microbe interactions | Scoop.it

Genomic characteristics discriminating parasitic and mutualistic relationship of bacterial symbionts with plants are poorly understood. This study comparatively analysed the genomes of 54 mutualists and pathogens to discover genomic markers associated with the different phenotypes. Using metabolic network models we predict external environments associated with free living and symbiotic lifestyles and quantify dependences of symbionts on the host in terms of the consumed metabolites. We show that specific differences between the phenotypes are pronounced at the levels of metabolic enzymes, especially carbohydrate active, and protein functions. Overall, biosynthetic functions are enriched and more diverse in plant mutualists while processes and functions involved in degradation and host invasion are enriched and more diverse in pathogens. A distinctive characteristic of plant pathogens is a putative novel secretion system with a circadian rhythm regulator. A specific marker of plant mutualists is the co-residence of genes encoding nitrogenase and Ribulose Bisphosphate Carboxylase/Oxygenase (RuBisCO). We predict that RuBisCO is likely used in a putative metabolic pathway to supplement carbon obtained heterotrophically with low-cost assimilation of carbon from CO2. We validate results of the comparative analysis by predicting correct phenotype, pathogenic or mutualistic, for 20 symbionts in an independent set of 30 pathogens, mutualists, and commensals.


Via Stéphane Hacquard
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Simultaneous profiling of seed-associated bacteria and fungi reveals antagonistic interactions between microorganisms within a shared epiphytic microbiome on Triticum and Brassica seeds

Simultaneous profiling of seed-associated bacteria and fungi reveals antagonistic interactions between microorganisms within a shared epiphytic microbiome on Triticum and Brassica seeds | Plant microbe interactions | Scoop.it

In order to address the hypothesis that seeds from ecologically and geographically diverse plants harbor characteristic epiphytic microbiota, we characterized the bacterial and fungal microbiota associated with Triticum and Brassica seed surfaces.The total microbial complement was determined by amplification and sequencing of a fragment of chaperonin 60 (cpn60). Specific microorganisms were quantified by qPCR. Bacteria and fungi corresponding to operational taxonomic units (OTU) that were identified in the sequencing study were isolated and their interactions examined.A total of 5477 OTU were observed from seed washes. Neither total epiphytic bacterial load nor community richness/evenness was significantly different between the seed types; 578 OTU were shared among all samples at a variety of abundances. Hierarchical clustering revealed that 203 were significantly different in abundance on Triticum seeds compared with Brassica. Microorganisms isolated from seeds showed 99–100% identity between the cpn60 sequences of the isolates and the OTU sequences from this shared microbiome. Bacterial strains identified as Pantoea agglomerans had antagonistic properties toward one of the fungal isolates (Alternaria sp.), providing a possible explanation for their reciprocal abundances on both Triticum and Brassica seeds.cpn60 enabled the simultaneous profiling of bacterial and fungal microbiota and revealed a core seed-associated microbiota shared between diverse plant genera.


Via Jean-Michel Ané
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Competition and facilitation in synthetic communities of arbuscular mycorrhizal fungi

Interactions between arbuscular mycorrhizal fungal (AMF) species co-colonizing the same host plant are still little understood in spite of major ecological significance of mycorrhizal symbiosis and widespread occurrence of these fungi in communities rather than alone. Furthermore, shifting the composition of AMF communities has demonstrated consequences for provision of symbiotic benefits to the host as well as for the qualities of ecosystem services. Therefore, here we addressed the nature and strength of interactions between three different AMF species in all possible two-species combinations on a gradient of inoculation densities. Fungal communities were established in pots with Medicago truncatula plants and their composition was assessed with taxon-specific real-time PCR markers. Nature of interactions between the fungi was varying from competition to facilitation and was influenced by both the identity and relative abundance of the co-inoculated fungi. Plants co-inoculated with Claroideoglomus and Rhizophagus grew bigger and contained more phosphorus than with any of these two fungi separately, although these fungi obviously competed for root colonization. On the other hand, plants co-inoculated with Gigaspora and Rhizophagus, which facilitated each other's root colonization, grew smaller than with any of these fungi separately. Our results point to as yet little understood complexity of interactions in plant-associated symbiotic fungal communities, which, depending on their composition, can induce significant changes in plant host growth and/or phosphorus acquisition in either direction.


Via Christophe Jacquet, Jean-Michel Ané
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The rhizosphere microbial community in a multiple parallel mineralization system suppresses the pathogenic fungus Fusarium oxysporum

The rhizosphere microbial community in a multiple parallel mineralization system suppresses the pathogenic fungus Fusarium oxysporum | Plant microbe interactions | Scoop.it

The rhizosphere microbial community in a hydroponics system with multiple parallel mineralization (MPM) can potentially suppress root-borne diseases. This study focused on revealing the biological nature of the suppression against Fusarium wilt disease, which is caused by the fungus Fusarium oxysporum, and describing the factors that may influence the fungal pathogen in the MPM system. We demonstrated that the rhizosphere microbiota that developed in the MPM system could suppress Fusarium wilt disease under in vitro and greenhouse conditions. The microbiological characteristics of the MPM system were able to control the population dynamics of F. oxysporum, but did not eradicate the fungal pathogen. The roles of the microbiological agents underlying the disease suppression and the magnitude of the disease suppression in the MPM system appear to depend on the microbial density. F. oxysporum that survived in the MPM system formed chlamydospores when exposed to the rhizosphere microbiota. These results suggest that the microbiota suppresses proliferation of F. oxysporum by controlling the pathogen's morphogenesis and by developing an ecosystem that permits coexistence with F. oxysporum.


Via Nina Dombrowski
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Environmental Microbiology: Synthetic microbial ecosystems: an exciting tool to understand and apply microbial communities

Environmental Microbiology: Synthetic microbial ecosystems: an exciting tool to understand and apply microbial communities | Plant microbe interactions | Scoop.it

Many microbial ecologists have described the composition of microbial communities in a plenitude of environments, which has greatly improved our basic understanding of microorganisms and ecosystems. However, the factors and processes that influence the behaviour and functionality of an ecosystem largely remain black boxes when using conventional approaches. Therefore, synthetic microbial ecology has gained a lot of interest in the last few years. Because of their reduced complexity and increased controllability, synthetic communities are often preferred over complex communities to examine ecological theories. They limit the factors that influence the microbial community to a minimum, allowing their management and identifying specific community responses. However, besides their use for basic research, synthetic ecosystems also found their way towards different applications, like industrial fermentation and bioremediation. Here we review why and how synthetic microbial communities are applied for research purposes and for which applications they have been and could be successfully used.


Via Jean-Michel Ané, Stéphane Hacquard, Nina Dombrowski
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Inside the root microbiome: Bacterial root endophytes and plant growth promotion

Bacterial root endophytes reside in a vast number of plant species as part of their root microbiome, with some being shown to positively influence plant growth. Endophyte community structure (species diversity: richness and relative abundances) within the plant is dynamic and is influenced by abiotic and biotic factors such as soil conditions, biogeography, plant species, microbe–microbe interactions and plant–microbe interactions, both at local and larger scales. Plant-growth-promoting bacterial endophytes (PGPBEs) have been identified, but the predictive success at positively influencing plant growth in field conditions has been limited. Concurrent to the development of modern molecular techniques, the goal of predicting an organism’s ability to promote plant growth can perhaps be realized by more thorough examination of endophyte community dynamics. This paper reviews the drivers of endophyte community structure relating to plant growth promotion, the mechanisms of plant growth promotion, and the current and future use of molecular techniques to study these communities.


Via Stijn Spaepen
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Rescooped by Mitja Remus-Emsermann from Rhizobium Research
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Time-lapse film of the infection of clover root hairs by rhizobia

Time-lapse film of the infection of clover root hairs by rhizobia | Plant microbe interactions | Scoop.it
Note that the root hair is curled, one of the first visible steps of the compatible nodulation reaction. The arrows point to the end of the growing infection thread during the infection process. The tubular infection thread is the means by which the rhizobia gain entry into the root. Once the thread exits the root hair, it ramifies into the root cortex, finally ending at a cortical cell that will become infected. Time lapse film kindly provided by Drs. S. Higashi and M. Abe, Kagoshima University, Japan.

Via Jean-Michel Ané, IvanOresnik
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Jean-Michel Ané's curator insight, November 2, 2013 6:46 PM

Cool video but a bit slow to load... I'll probably use it for teaching.

IvanOresnik's curator insight, November 6, 2013 1:08 PM

Even though I have seen many infection threads, I still find it fascinating to watch this video.