Littérature scientifique sur le sujet « Microbial exudated »
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Articles de revues sur le sujet "Microbial exudated"
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Rieusset, Laura, Marjolaine Rey, Florence Gerin, Florence Wisniewski-Dyé, Claire Prigent-Combaret et Gilles Comte. « A Cross-Metabolomic Approach Shows that Wheat Interferes with Fluorescent Pseudomonas Physiology through Its Root Metabolites ». Metabolites 11, no 2 (31 janvier 2021) : 84. http://dx.doi.org/10.3390/metabo11020084.
Texte intégralRésumé :
Roots contain a wide variety of secondary metabolites. Some of them are exudated in the rhizosphere, where they are able to attract and/or control a large diversity of microbial species. In return, the rhizomicrobiota can promote plant health and development. Some rhizobacteria belonging to the Pseudomonas genus are known to produce a wide diversity of secondary metabolites that can exert a biological activity on the host plant and on other soil microorganisms. Nevertheless, the impact of the host plant on the production of bioactive metabolites by Pseudomonas is still poorly understood. To characterize the impact of plants on the secondary metabolism of Pseudomonas, a cross-metabolomic approach has been developed. Five different fluorescent Pseudomonas strains were thus cultivated in the presence of a low concentration of wheat root extracts recovered from three wheat genotypes. Analysis of our metabolomic workflow revealed that the production of several Pseudomonas secondary metabolites was significantly modulated when bacteria were cultivated with root extracts, including metabolites involved in plant-beneficial properties.
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Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips et A. C. Finzi. « Stoichiometry constrains microbial response to root exudation- insights from a model and a field experiment in a temperate forest ». Biogeosciences 10, no 2 (7 février 2013) : 821–38. http://dx.doi.org/10.5194/bg-10-821-2013.
Texte intégralRésumé :
Abstract. Plant roots release a wide range of chemicals into soils. This process, termed root exudation, is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates ("exudate mimics") containing C alone or C in combination with N (C : N ratio of 10) through microlysimeter "root simulators" into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was, under most circumstances, in excess of the N in the exudate pulse, suggesting that the exudation of N-containing compounds can be a viable strategy for plant-N acquisition via a priming effect. The experimental and modeling results were consistent with our hypothesis that N-containing compounds in root exudates affect rhizosphere processes by providing substrates for the synthesis of N-rich microbial biomass and exoenzymes. This study suggests that exudate stoichiometry is an important and underappreciated driver of microbial activity in rhizosphere soils.
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Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips et A. C. Finzi. « Stoichiometry constrains microbial response to root exudation – insights from a model and a field experiment in a temperate forest ». Biogeosciences Discussions 9, no 6 (13 juin 2012) : 6899–945. http://dx.doi.org/10.5194/bgd-9-6899-2012.
Texte intégralRésumé :
Abstract. Healthy plant roots release a wide range of chemicals into soils. This process, termed root exudation, is thought to increase the activity of microbes and the exo-enzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The causal role of exudation, however, is difficult to isolate with in-situ observations, given the complex nature of the rhizosphere environment. We investigated the potential effects of root exudation on microbial and exo-enzyme activity using a theoretical model of decomposition and a field experiment, with a specific focus on the stoichiometric constraint of nitrogen (N) availability. The field experiment isolated the effect of exudation by pumping solutions of exudate mimics through microlysimeter "root simulators" into intact forest soils over two 50-day periods. Using a combined model-experiment approach, we tested two hypotheses: (1) exudation alone is sufficient to stimulate microbial and exo-enzyme activity in rhizosphere soils, and (2) microbial response to C-exudates (carbohydrates and organic acids) is constrained by N-limitation. Experimental delivery of exudate mimics containing C and N significantly increased microbial respiration, microbial biomass, and the activity of exo-enzymes that decompose labile components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exo-enzymes that degrade recalcitrant SOM (e.g., polyphenols, lignin). However, delivery of C-only exudates had no effect on microbial biomass or overall exo-enzyme activity, and only increased microbial respiration. The theoretical decomposition model produced complementary results; the modeled microbial response to C-only exudates was constrained by limited N supply to support the synthesis of N-rich microbial biomass and exo-enzymes, while exuding C and N together elicited an increase in modeled microbial biomass, exo-enzyme activity, and decomposition. Thus, hypothesis (2) was supported, while hypothesis (1) was only supported when C and N compounds were exuded together. This study supports a cause-and-effect relationship between root exudation and enhanced microbial activity, and suggests that exudate stoichiometry is an important and underappreciated driver of microbial activity in rhizosphere soils.
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Wang, Haining, Xiaohe Yang, Songhong Wei et Yan Wang. « Proteomic Analysis of Mycelial Exudates of Ustilaginoidea virens ». Pathogens 10, no 3 (18 mars 2021) : 364. http://dx.doi.org/10.3390/pathogens10030364.
Texte intégralRésumé :
Rice false smut (RFS) disease, which is caused by Ustilaginoidea virens, has been widespread all over the world in recent years, causing irreversible losses. Under artificial culture conditions, exudates will appear on colonies of U. virens during the growth of the hyphae. Exudation of droplets is a common feature in many fungi, but the functions of exudates are undetermined. As the executors of life functions, proteins can intuitively reflect the functions of exudates. Shotgun proteomics were used in this study. A total of 650 proteins were identified in the exudate of U. virens, and the raw data were made available via ProteomeXchange with the identifier PXD019861. There were 57 subcategories and 167 pathways annotated with Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, respectively. Through protein–protein interaction (PPI) network analysis, it was found that 20 proteins participated in the biosynthesis of secondary metabolites. Two separate PPI analyses were performed for carbon metabolism and microbial metabolism in diverse environments. After comparing and annotating the functions of proteins of the exudate, it was speculated that the exudate was involved in the construction and remodeling of the fungal cell wall. Pathogenicity, sporulation, and antioxidant effects might all be affected by the exudate.
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Huang, Xing-Feng, Jacqueline M. Chaparro, Kenneth F. Reardon, Ruifu Zhang, Qirong Shen et Jorge M. Vivanco. « Rhizosphere interactions : root exudates, microbes, and microbial communities ». Botany 92, no 4 (avril 2014) : 267–75. http://dx.doi.org/10.1139/cjb-2013-0225.
Texte intégralRésumé :
The study of the interactions between plants and their microbial communities in the rhizosphere is important for developing sustainable management practices and agricultural products such as biofertilizers and biopesticides. Plant roots release a broad variety of chemical compounds to attract and select microorganisms in the rhizosphere. In turn, these plant-associated microorganisms, via different mechanisms, influence plant health and growth. In this review, we summarize recent progress made in unraveling the interactions between plants and rhizosphere microbes through plant root exudates, focusing on how root exudate compounds mediate rhizospheric interactions both at the plant–microbe and plant–microbiome levels. We also discuss the potential of root exudates for harnessing rhizospheric interactions with microbes that could lead to sustainable agricultural practices.
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Zhang, Jiale, Qianwen Liu, Kun Li et Li Ma. « Peanut Root Exudates Suppress Fusarium solani and Modulate the Microbial Community Structure of Rhizosphere in Grape Replant Soil ». Horticulturae 8, no 10 (29 septembre 2022) : 892. http://dx.doi.org/10.3390/horticulturae8100892.
Texte intégralRésumé :
Replant disease significantly hinders the development of the grape industry, and the imbalance of the rhizosphere microecological environment is one of the fundamental reasons hindering grape replants. Peanut is a common intercropping crop, and whether the root exudates of peanut can alleviate grape replant obstacles is still unknown. In this study, the effects of exogenous peanut root exudates on replanting grapevine growth, and the microbial community structure of grapevine replant soils were studied. The results showed that peanut root exudates could promote the growth of replanting grapevine seedlings; enhance root vigor and SOD activity, increasing 55.18% and 95.71%, respectively; and reduce the MDA content of root, decreasing 31.10%. After peanut exudate treatment, the growth of Fusarium solanum, an important harmful fungus that is an obstacle to grape replant, was inhibited. The relative abundances of Gaiella in bacteria and Cystobasidium and Mortierella in fungi increased, and the potential pathogen fungi Fusicolla decreased. Peanut root exudates also modified the soil bacterial and fungal community in a certain range and increased the interaction among the bacteria of grapevine rhizosphere soil. However, they loosened the interaction among fungi. There are extensive mutualistic interactions among bacteria or fungi in grape rhizosphere assemblages after peanut exudates treatment. Therefore, peanut root exudates might be helpful in changing the soil microbial environment and alleviating the grape replanting obstacle.
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Cardenas, Julian, Fernando Santa et Eva Kaštovská. « The Exudation of Surplus Products Links Plant Functional Traits and Plant-Microbial Stoichiometry ». Land 10, no 8 (11 août 2021) : 840. http://dx.doi.org/10.3390/land10080840.
Texte intégralRésumé :
The rhizosphere is a hot spot of soil microbial activity and is largely fed by root exudation. The carbon (C) exudation flux, coupled with plant growth, is considered a strategy of plants to facilitate nutrient uptake. C exudation is accompanied by a release of nutrients. Nitrogen (N) and phosphorus (P) co-limit the productivity of the plant-microbial system. Therefore, the C:N:P stoichiometry of exudates should be linked to plant nutrient economies, plant functional traits (PFT) and soil nutrient availability. We aimed to identify the strongest links in C:N:P stoichiometry among all rhizosphere components. A total of eight grass species (from conservative to exploitative) were grown in pots under two different soil C:nutrient conditions for a month. As a result, a wide gradient of plant–microbial–soil interactions were created. A total of 43 variables of plants, exudates, microbial and soil C:N:P stoichiometry, and PFTs were evaluated. The variables were merged into four groups in a network analysis, allowing us to identify the strongest connections among the variables and the biological meaning of these groups. The plant–soil interactions were shaped by soil N availability. Faster-growing plants were associated with lower amounts of mineral N (and P) in the soil solution, inducing a stronger competition for N with microorganisms in the rhizosphere compared to slower-growing plants. The plants responded by enhancing their N use efficiency and root:shoot ratio, and they reduced N losses via exudation. Root growth was supported either by reallocated foliar reserves or by enhanced ammonium uptake, which connected the specific leaf area (SLA) to the mineral N availability in the soil. Rapid plant growth enhanced the exudation flux. The exudates were rich in C and P relative to N compounds and served to release surplus metabolic products. The exudate C:N:P stoichiometry and soil N availability combined to shape the microbial stoichiometry, and N and P mining. In conclusion, the exudate flux and its C:N:P stoichiometry reflected the plant growth rate and nutrient constraints with a high degree of reliability. Furthermore, it mediated the plant–microbial interactions in the rhizosphere.
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Chertov, Oleg, Yakov Kuzyakov, Irina Priputina, Pavel Frolov, Vladimir Shanin et Pavel Grabarnik. « Modelling the Rhizosphere Priming Effect in Combination with Soil Food Webs to Quantify Interaction between Living Plant, Soil Biota and Soil Organic Matter ». Plants 11, no 19 (3 octobre 2022) : 2605. http://dx.doi.org/10.3390/plants11192605.
Texte intégralRésumé :
A model of rhizosphere priming effect under impact of root exudate input into rhizosphere soil was developed as an important process of the plant-soil interaction. The model was based on the concept of nitrogen (N) mining, compensating for the N scarcity in exudates for microbial growth by accelerating SOM mineralisation. In the model, N deficiency for microbial growth is covered (“mined”) by the increased SOM mineralisation depending on the C:N ratio of the soil and exudates. The new aspect in the model is a food web procedure, which calculates soil fauna feeding on microorganisms, the return of faunal by-products to SOM and mineral N production for root uptake. The model verification demonstrated similar magnitude of the priming effect in simulations as in the published experimental data. Model testing revealed high sensitivity of the simulation results to N content in exudates. Simulated CO2 emission from the priming can reach 10–40% of CO2 emission from the whole Ah horizon of boreal forest soil depending on root exudation rates. This modeling approach with including food web activity allows quantifying wider aspects of the priming effect functioning including ecologically important available N production.
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Chen, Mei-Hsing, et Eric B. Nelson. « Microbial-Induced Carbon Competition in the Spermosphere Leads to Pathogen and Disease Suppression in a Municipal Biosolids Compost ». Phytopathology® 102, no 6 (juin 2012) : 588–96. http://dx.doi.org/10.1094/phyto-08-11-0241.
Texte intégralRésumé :
The aim of this study was to understand whether competition for fatty acids in plant seed exudates by compost-derived seed-colonizing microbial communities could explain the suppression of plant infections initiated by sporangia of Pythium ultimum. The germination behavior of P. ultimum sporangia in response to cucumber seeds was measured to determine the impact of seed-colonizing microbes on pathogen suppression. Seed-colonizing microbial communities from municipal biosolids compost utilized cucumber seed exudates and linoleic acid in vitro, reducing the respective stimulatory activity of these elicitors to P. ultimum sporangial germination. However, when sporangia were observed directly in the spermosphere of seeds sown in the compost medium, levels of germination and sporangial emptying did not differ from the responses in sand. The percentage of aborted germ tubes was greater after incubating sporangia in compost medium for 12-h than the level of germ tube abortion when sporangia were incubated in sand. Abortion did not occur if previously germinated sporangia were supplemented with cucumber seed exudate. Furthermore, removal of cucumber seed exudate after various stages of germ tube emergence resulted in an increase in aborted germ tubes over time. Adding increasing levels of glucose directly to the compost medium alleviated germ tube abortion in the spermosphere and also eliminated disease suppression. These data fail to support a role for linoleic acid competition in Pythium seedling disease suppression but provide evidence for general carbon competition mediated by seed-colonizing microbial communities as a mechanism for the suppression of Pythium seed infections in municipal biosolids compost.
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Anandyawati, Enok Sumarsih, Budi Nugroho et Rahayu Widyastuti. « Study of Root Exudate Organic Acids and Microbial Population in the Rhizosphere of Oil Palm Seedling ». Journal of Tropical Soils 22, no 1 (2 janvier 2017) : 29–36. http://dx.doi.org/10.5400/jts.2017.v22i1.29-36.
Texte intégralRésumé :
Mutual interaction between plants and microbes occured in the rhizosphere is expected to increase productivity of crops or soil fertility for agriculture. Plants excrete root exudates to attract microbes, and then microbes obtain habitat and food supply from plants and can fulfill the nutrient requirements through assisted enzymatic activity. The objective of the research was to study the types and amounts of root exudate organic acids, microbial population, and the relationship between root exudate organic acids and microbial population in the rhizosphere of oil palm seedlings. The study was conducted in a greenhouse using a planting medium of sterile quartz sand. The study was conducted using two factorials completely randomized design with three replications. The first factor was oil palm seedling age (control / no oil palm seed, 1, 3, 6, 9 and 12 months-old of oil palm seedlings) and the second factor was the periods of seedling growth (45, 90, 135 and 180 days), so in total there were 72 experimental units. The result of High Pressure Liquid Chromatography (HPLC) analysis revealed that four kinds of organic acids were observed in the rhizosphere of oil palm seedlings, with the highest concentration were: acetic acid (1.66 ppm), citric acid (0.157 ppm), malic acid (2.061 ppm) and oxalic acid (0.675) ppm. The highest total population of microbes, fungi, Azotobacter, phosphate solubilizing bacteria (PSB) and phosphate solubilizing fungi (PSF) were 19.38 × 106 cfu g-1 soil, 3.28 × 104 cfu g-1 soil, 12.09 × 105 cfu g-1 soil, 8.39 × 104 cfu g-1 soil and 1.15 × 104 cfu g-1 soil, respectively. There are positive correlations between root exudate organic acids and total microbes, fungi, Azotobacter, PSB and PSF are.Keywords: microbes, organic acids, rhizosphere, root exudates
Thèses sur le sujet "Microbial exudated"
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Shi, Shengjing. « Influence of root exudates on soil microbial diversity and activity ». Lincoln University, 2009. http://hdl.handle.net/10182/1549.
Texte intégralRésumé :
Interactions between plant roots and soil microorganisms in the rhizosphere are critical for plant growth. However, understanding of precisely how root exudates influence the diversity and activity of rhizosphere microorganisms is limited. The main objective of this study was to investigate the effect of radiata pine (Pinus radiata) root exudates on rhizosphere soil microbial communities, with an emphasis on the role of low molecular weight organic anions. The study involved the development and validation of new methods for investigating rhizosphere processes in a purpose-built facility. This included development of an in situ sampling technique using an anion exchange membrane strip to collect a range of organic anions exuded from radiata pine roots grown in large-scale rhizotrons. These included tartarate, quinate, formate, malate, malonate, shikimate, lactate, acetate, maleate, citrate, succinate and fumarate. Soil microbial activity and diversity were determined using dehydrogenase activity and denaturing gradient gel electrophoresis. Links between organic anions in root exudates and rhizosphere soil microbial community structures were investigated by comparing wild type and genetically modified radiata pine trees which were grown in rhizotrons for 10 months. As expected, there was considerable temporal and spatial variability in the amounts and composition of organic anions collected, and there were no consistent or significant differences determined between the two tree lines. Significant differences in rhizosphere microbial communities were detected between wild type and genetically modified pine trees; however, they were inconsistent throughout the experiment. The shifts in microbial communities could have been related to changes in exudate production and composition. Based on results from the main rhizotron experiment, a microcosm study was carried out to investigate the influence of selected pine root exudate sugars (glucose, sucrose and fructose) and organic anions (quinate, lactate and maleate) on soil microbial activity and diversity. Soil microbial activity increased up to 3-fold in all of the sugar and organic anion treatments compared to the control, except for a mixture of sugars and maleate where it decreased. The corresponding impacts on soil microbial diversity were assessed using denaturing gradient gel electrophoresis and 16S rRNA phylochips. Addition of the exudate compounds had a dramatic impact on the composition and diversity of the soil microbial community. A large number of bacterial taxa (88 to 1043) responded positively to the presence of exudate compounds, although some taxa (12 to 24) responded negatively. Organic anions had a greater impact on microbial communities than sugars, which indicated that they may have important roles in rhizosphere ecology of radiata pine. In addition, a diverse range of potentially beneficial bacterial taxa were detected in soil amended with organic anions, indicating specific regulation of rhizosphere microbial communities by root exudates. This project highlighted the considerable challenges and difficulties involved in detailed investigation of in situ rhizosphere processes. Nonetheless, the findings of this study represent a significant contribution to advancing understanding of relationships between root exudates and soil microbial diversity, which will be further enhanced by refinement and application of the specific methodologies and techniques developed.
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Guo, Jingqi. « THE INFLUENCE OF TALL FESCUE CULTIVAR AND ENDOPHYTE STATUS ON ROOT EXUDATE CHEMISTRY AND RHIZOSPHERE PROCESSES ». UKnowledge, 2014. http://uknowledge.uky.edu/pss_etds/50.
Texte intégralRésumé :
Tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stress. However, the alkaloids produced by the common variety of the endophyte cause severe animal health issues resulting in a considerable amount of research focused on eliminating the toxic class of alkaloids while retaining the positive abiotic and biotic stress tolerance attributes of the other alkaloids. In doing so, very little attention has been paid to the direct influence the fungal-plant symbiosis has on rhizosphere processes. Therefore, my objectives were to study the influence of this relationship on plant biomass production, root exudate composition, and soil biogeochemical processes using tall fescue cultivars PDF and 97TF1 without an endophyte (E-), or infected with the common toxic endophyte (CTE+), or with two novel endophytes (AR542E+, AR584E+). I found that root exudate composition and plant biomass production were influenced by endophyte status, tall fescue cultivar, and the interaction of cultivar and endophyte. Cluster analysis showed that the interaction between endophyte and cultivar results in a unique exudate profile. These interactions had a small but perceptible impact on soil microbial community structure and function with an equally small and perceptible impact on carbon and nitrogen cycling in soils from rhizobox and field sites. These studies represent the first comprehensive analysis of root exudate chemistry from common toxic and novel endophyte infected tall fescue cultivars and can be used to help explain in part the observed changes in C and N cycling and storage in pastures throughout the Southeast U.S..
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Rezgui, Cyrine. « Etude du potentiel d'introduction de la culture du pois d'hiver dans les successions culturales en Normandie : conséquences sur les communautés microbiennes du sol et les flux d'azote Impacts of the winter pea crop (instead of rapeseed) on soil microbial communities, nitrogen balance and wheat yield Quantification et analyse des exsudats racinaires de pois, de blé et de colza : mise au point d’une méthodologie de collecte des exsudats racinaires N rhizodeposition quantification and root exudates characterization of pea (Pisum Sativum L.), rapeseed (Brassica napus L.) and wheat (Triticum aestivum L.) under controlled conditions Linking soil microbial community to C and N dynamics during crop residues decomposition ». Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR047.
Texte intégralRésumé :
La transition agroécologique vise la triple performance agronomique, écologique et sociétale des exploitations agricoles. Un certain nombre de pratiques agricoles permet d’envisager la construction et le développement de systèmes de culture répondant à ces contraintes. Les légumineuses, par leur capacité à fixer l’azote atmosphérique, sont une alternative intéressante aux intrants azotés. Outre l’absence de fertilisation lors de leur culture, elles fournissent de l’azote à la culture suivante. Il existe cependant un manque de références sur certaines légumineuses à graines et notamment la culture du pois d’hiver. En effet, si des données acquises dans différentes régions françaises sont disponibles, aucune référence n’a été publiée pour la Normandie où la culture du pois d’hiver connaît un récent regain d’intérêt. Cette thèse propose d’évaluer, sur une période de deux ans, l’effet du remplacement du colza par le pois d’hiver en tête de rotation en réalisant une analyse comparative de ces deux successions (pois d’hiver-blé et colza-blé). L’objectif était d’évaluer l’effet de ce changement de tête de rotation (pois d’hiver vs colza) sur l’état biologique du sol et les flux d’azote à différentes échelles spatiotemporelles. Les résultats ont révélé une forte variabilité spatio-temporelle dans la réponse des communautés microbiennes du sol, et mis en évidence l’importance du contexte pédoclimatique dans le déterminisme de l’abondance et de l’activité des communautés microbiennes du sol. Ils ont montré par ailleurs, l’effet positif du pois d’hiver sur la disponibilité de l’azote minéral au cours du cycle cultural et pour les cultures suivantes, ici le blé puis l’orge. Les apports d’azote minéral dans le sol lié à la contribution des parties racinaires via la rhizodéposition et à la dégradation des résidus de culture après récolte ont été évalués au cours de ce travail de thèse. En effet, si la rhizodéposition s’est révélée plus importante sous pois d’hiver, elle n’a pas eu d’impact significatif sur les communautés microbiennes rhizosphériques. Contrairement à ces observations, la dégradation des résidus de culture a significativement modifié la composition des communautés bactériennes en lien avec leur composition biochimique initiale. La succession culturale incluant le pois a enrichi le sol en azote minéral mais des risques de perte d’azote par lixiviation de l’ordre de 23 kg N. ha-1 ont été estimés. Ces constats soulignent l’importance d’adapter la conduite des systèmes de culture incluant le pois d’hiver, en limitant les pertes d’azote par lixiviation et en maximisant son utilisation par les cultures suivantes. Les résultats de ces travaux ont confirmé la diminution des quantités d’engrais azoté utilisées dans la succession contenant le pois, sans préjudice de productivité, ni pour le pois, ni pour la culture suivante, ici, le blé. Finalement, introduire le pois d’hiver dans la rotation de culture en région Normandie, semble permettre de répondre à la problématique d’augmentation du coût des intrants, et aux enjeux de transition agroécologique et d’autonomie protéique régionaleThe agroecological transition targets triple agronomic, ecological, and societal performance of farms. Some new agricultural practices had emerged to develop a new cropping system to respond to these constraints. Legumes constitute an interesting alternative. Indeed, legumes are advantageous for soils due to their symbiotic relationship with nitrogen-fixing bacteria. The presence of compatible rhizobia combined to nitrogen-limited conditions promotes symbiosis which is the most efficient way for legumes to acquire more nitrogen. Compared with non-nodulated plants, symbiosis provides a competitive advantage by increasing soil nitrogen pool. However, some grain legumes, notably winter pea, are rarely studied, especially in the Normandy region where no reference has been published for this crop. The objective of this study is to compare two crop successions for a period of two years (winter pea-wheat and rapeseed-wheat), in order to assess the effect of replacing rapeseed by winter pea at the head of the rotation .We evaluated the effect of these two crops (winter pea vs rapeseed) on the biological state of the soil and nitrogen fluxes at different spatio-temporal scales. The results showed a significant spatio-temporal effect on the response of soil microbial communities and highlighted the importance of the pedoclimatic context in determining the abundance and activity of soil microbial communities. A positive effect of winter pea has been demonstrated on the availability of mineral nitrogen during the crop cycle and for following crops (wheat and barley). The supply of nitrogen to the soil is linked to the rhizodeposition of nitrogen via plants roots and the degradation of crop residues after harvest. Our results showed that winter pea exhibited the greatest amount of nitrogen rhizodeposition. However, rhizodeposition did not have a significant impact on rhizospheric microbial communities. Contrary to these observations, the degradation of crop residues significantly modified the composition of bacterial communities linked to their initial biochemical composition. Crop succession including winter pea enriched the soil with mineral nitrogen but simulation with STICS software revealed a nitrogen leaching around of 23 kg N. ha-1 during the cropping cycle. These findings underline the importance of adapting an adequate crop management system, including winter pea, to limit nitrogen losses. The results showed also that wheat yields after winter pea without the use of nitrogen fertilizers were equivalent to those obtained after rapeseed. However, rapeseed required significant nitrogen fertilization. Including winter pea in crop rotation in Normandy region may be a key to enhance productivity, to respond to the challenges of agroecological transition, regional protein autonomy, and to reduce environmental and economic costs, by reducing notably, the costs of fertilizers production and uses
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ROSSI, FEDERICO. « Study of exopolysaccharide-producing cyanobacteria in biofilm growing on lithic substrate and in extreme environments ». Doctoral thesis, 2010. http://hdl.handle.net/2158/547903.
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Modise, Lorato. « Isolation and Characterization of Rhizosphere Bacterial Community from cultivated plants in Mahikeng, NorthWest Province, South Africa / Lorato Modise ». Thesis, 2014. http://hdl.handle.net/10394/16198.
Texte intégralRésumé :
The rhizosphere is characterized by the presence of high microbial activities which are
influenced by plant root exudates. This study examined bacterial diversity and physiological
functions plants rhizosphere using both culture-dependent and culture-independent techniques of
seven cultivated. Physico-chemical properties of soil samples revealed that the rhizobacteria
adapted well to pH ranging from 7.5 to 9.1. Macronutrients (carbon, nitrogen, calcium,
magnesium, phosphorous, potassium, sodium and iron) had a wide range of concentration
between 0 to 4380.1 mg/kg. Concentrations of metal elements (cadmium, cobalt, chromium,
copper and zinc) from all rhizosphere samples were below the amount of 3.1 mg/kg, indicating
that the samples were free from metal contaminations. Sole carbon substrates utilization of
bacteria in rhizosphere samples were measured as Average Well Colour Development (A WCD)
and Group-wise Average Well Colour Development (AWCDg) patterns. At seventy two hours,
there was no significant difference in AWCD patterns between bacteria in all samples and there
was a significant difference in AWCDg patterns. Biochemical tests showed majority of isolates
had similar physiological properties to members of Bacillus genus. All the bacterial isolates
exhibited positive antifungal trait, fifteen solubilized phosphate and three had cyanide production
traits during in vitro plant growth promotion assays. In vitro plant growth revealed that bacterial
isolate RL1 (Bacillus licheniformis) produced the highest concentration of indole acetic acid
(IAA) at 25 mg/ml. Bacterial isolate RG3 (Bacillus pumilus) had the highest amino cyclopropane
carboxylase (ACC) deaminase activity indicated by the high production of α-ketobutyrate
produced at 4.8 mg/ml. There were significant differences in shoot length at P ≤ 5% level of
significance and there was no significant difference in the number of leaves across all three
inoculated plants at P ≥ 5% level of significance. Sequence and phylogenetic analysis of
identified culture-dependent bacteria revealed a homologous similarity of 94 to 100% between
isolates sequences and GenBank sequences. From this, 81% of the sequences were closely
related to Firmicutes, 13% to Actinobacteria and 6% to Proteobacteria. From cultureindependent
method, only 8 PCR-DGGE bands were detected, the 200 bp sequences in the 16S
rRNA fragment showed 91 to 100% homologous similarity to GenBank sequences. Their 16S
rRNA sequences was closely related to 50% uncultured bacterium clones, 25% Firmicutes, 13%
Proteobacteria and 12% Bacteroidetes sequences. Both culture-dependent and cultureindependent
techniques were precise in the identification and description of bacterial community
in rhizosphere.Thesis (M.Sc) North-West University, Mafikeng Campus, 2014
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Lemanski, Kathleen. « Structure of and carbon flux through soil food webs of temperate grassland as affected by land use management ». Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-992E-7.
Texte intégralChapitres de livres sur le sujet "Microbial exudated"
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Bhutia, Dawa Dolma, Saroj Belbase, Jiwan Paudel et Shrvan Kumar. « Plant Exudates and Microbial Interaction—A Change in Dynamics ». Dans Climate Change Management, 83–95. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-21079-2_6.
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Yang, Kwang Mo, Toemthip Poolpak et Prayad Pokethitiyook. « Rhizodegradation : The Plant Root Exudate and Microbial Community Relationship ». Dans Phytoremediation, 209–29. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-17988-4_11.
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Uren, Nicholas C. « Root Exudates and Soil : Crucial for Molecular Understanding of Interactions in the Rhizosphere ». Dans Molecular Microbial Ecology of the Rhizosphere, 221–27. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118297674.ch21.
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Hirsch, Penny R., Anthony J. Miller et Paul G. Dennis. « Do Root Exudates Exert More Influence on Rhizosphere Bacterial Community Structure Than Other Rhizodeposits ? » Dans Molecular Microbial Ecology of the Rhizosphere, 229–42. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118297674.ch22.
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Shi, Shengjing, Alan E. Richardson, Maureen O'Callaghan, Mary Firestone et Leo Condron. « Challenges in Assessing Links Between Root Exudates and the Structure and Function of Soil Microbial Communities ». Dans Molecular Microbial Ecology of the Rhizosphere, 125–35. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118297674.ch11.
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Nannipieri, P., J. Ascher, M. T. Ceccherini, L. Landi, G. Pietramellara, G. Renella et F. Valori. « Effects of Root Exudates in Microbial Diversity and Activity in Rhizosphere Soils ». Dans Soil Biology, 339–65. Berlin, Heidelberg : Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75575-3_14.
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Yu, Guanghui. « Root Exudates and Microbial Communities Drive Mineral Dissolution and the Formation of Nano-size Minerals in Soils : Implications for Soil Carbon Storage ». Dans Soil Biology, 143–66. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-75910-4_5.
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« The Effect of Root Exudates on Rhizosphere Microbial Populations ». Dans The Rhizosphere, 111–56. CRC Press, 2000. http://dx.doi.org/10.1201/9780849384974-10.
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Sposito, Garrison. « Soil Humus ». Dans The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0007.
Texte intégralRésumé :
Biomoleculesare compounds synthesized to sustain the life cycles of organisms. In soil humus, they are usually products of litter degradation, root excretion, and microbial metabolism, ranging in molecular structure from simple organic acids to complex biopolymers. Organic acids are among the best-characterized biomolecules. Table 3.1 lists five aliphatic (meaning the C atoms are arranged in open-chain structures) organic acids associated commonly with the soil microbiome. These acids contain the unit R—COOH, where COOH is the carboxyl groupand R represents either H or an organic moiety. The carboxyl group can lose its proton easily within the normal range of soil pH (see the third column of Table 3.1) and so is an example of a Brønsted acid. The released proton, in turn, can attack soil minerals to induce their decomposition (see Eq. 1.2), whereas the carboxylate anion (COO-) can form soluble complexes with metal cations, such as Al3+, that are released by mineral weathering [for example, in Eq. 1.7, rewrite oxalate, C2O42-, as (COO-) 2]. The total concentration of organic acids in the soil solution ranges up to 5 mM. These acids tend to have very short lifetimes because of biocycling, but they abide as a component of soil humus, especially its water-soluble fraction, because they are produced continually by microorganisms and plant roots. Formic acid (methanoic acid), the first entry in Table 3.1, is a monocarboxylic acid produced by bacteria and found in the root exudates of maize. Acetic acid (ethanoic acid) also is produced microbially—especially under anaerobic conditions—and is found in root exudates of grasses and herbs. Formic and acetic acid concentrations in the soil solution range from 2 to 5 mM. Oxalic acid (ethanedioic acid), which is ubiquitous in soils, and tartaric acid (D- 2,3-dihydroxybutanedioic acid) are dicarboxylic acids produced by fungi and excreted by plant roots; their soil solution concentrations range from 0.05 to 1 mM. The tricarboxylic citric acid (2-hydroxypropane- 1,2,3-tricarboxylic acid) is also produced by fungi and excreted by plant roots. Its soil solution concentration is less than 0.05 mM.
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Jibawi, Abdullah, Mohamed Baguneid et Arnab Bhowmick. « Principles of wound care ». Dans Current Surgical Guidelines, sous la direction de Abdullah Jibawi, Mohamed Baguneid et Arnab Bhowmick, 105–14. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198794769.003.0010.
Texte intégralRésumé :
It’s important to be aware of healing process, associated comorbidities, and the role of nutrition in wound care management. Assessment of the amount and type of wound exudate plays an important role in deciding the type of dressing used. Infection or underlying osteomyelitis needs careful assessment, further investigation, and administration of systemic/oral anti-microbial therapy. Early use of non-surgical or surgical debridement is necessary to speed up the healing process. Diagnostic criteria of surgical site infection are increasingly used in postoperative wounds in hospitals for audit of infection control measures. No one type of dressing appears superior over other. Dressings should be cost effective, acceptable to the patients, and easy to use. In addition, in recent decades newer non-surgical debriding method, e.g. larvae therapy and negative pressure wound therapy, are increasingly being used and supported by recent NICE guidelines, especially in diabetic foot care.
Rapports d'organisations sur le sujet "Microbial exudated"
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Kemner, K. M., E. J. O'Loughlin, S. D. Kelly et K. H. Nealson. An integrated approach to characterization of microbial exudates and investigation of their role in the spatial distribution and transformations of uranium at the mineral-microbe interface. Office of Scientific and Technical Information (OSTI), juin 2006. http://dx.doi.org/10.2172/896242.
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