Journal articles on the topic 'Microbial exudated'
To see the other types of publications on this topic, follow the link: Microbial exudated.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Microbial exudated.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Rieusset, Laura, Marjolaine Rey, Florence Gerin, Florence Wisniewski-Dyé, Claire Prigent-Combaret, and Gilles Comte. "A Cross-Metabolomic Approach Shows that Wheat Interferes with Fluorescent Pseudomonas Physiology through Its Root Metabolites." Metabolites 11, no. 2 (January 31, 2021): 84. http://dx.doi.org/10.3390/metabo11020084.
Full textAbstract:
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.
2
Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips, and 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 (February 7, 2013): 821–38. http://dx.doi.org/10.5194/bg-10-821-2013.
Full textAbstract:
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.
3
Drake, J. E., B. A. Darby, M. A. Giasson, M. A. Kramer, R. P. Phillips, and 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 (June 13, 2012): 6899–945. http://dx.doi.org/10.5194/bgd-9-6899-2012.
Full textAbstract:
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.
4
Wang, Haining, Xiaohe Yang, Songhong Wei, and Yan Wang. "Proteomic Analysis of Mycelial Exudates of Ustilaginoidea virens." Pathogens 10, no. 3 (March 18, 2021): 364. http://dx.doi.org/10.3390/pathogens10030364.
Full textAbstract:
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.
5
Huang, Xing-Feng, Jacqueline M. Chaparro, Kenneth F. Reardon, Ruifu Zhang, Qirong Shen, and Jorge M. Vivanco. "Rhizosphere interactions: root exudates, microbes, and microbial communities." Botany 92, no. 4 (April 2014): 267–75. http://dx.doi.org/10.1139/cjb-2013-0225.
Full textAbstract:
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.
6
Zhang, Jiale, Qianwen Liu, Kun Li, and Li Ma. "Peanut Root Exudates Suppress Fusarium solani and Modulate the Microbial Community Structure of Rhizosphere in Grape Replant Soil." Horticulturae 8, no. 10 (September 29, 2022): 892. http://dx.doi.org/10.3390/horticulturae8100892.
Full textAbstract:
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.
7
Cardenas, Julian, Fernando Santa, and Eva Kaštovská. "The Exudation of Surplus Products Links Plant Functional Traits and Plant-Microbial Stoichiometry." Land 10, no. 8 (August 11, 2021): 840. http://dx.doi.org/10.3390/land10080840.
Full textAbstract:
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.
8
Chertov, Oleg, Yakov Kuzyakov, Irina Priputina, Pavel Frolov, Vladimir Shanin, and 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 (October 3, 2022): 2605. http://dx.doi.org/10.3390/plants11192605.
Full textAbstract:
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.
9
Chen, Mei-Hsing, and 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 (June 2012): 588–96. http://dx.doi.org/10.1094/phyto-08-11-0241.
Full textAbstract:
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.
10
Anandyawati, Enok Sumarsih, Budi Nugroho, and 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 (January 2, 2017): 29–36. http://dx.doi.org/10.5400/jts.2017.v22i1.29-36.
Full textAbstract:
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
11
Koch, B. P., G. Kattner, M. Witt, and U. Passow. "Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?" Biogeosciences Discussions 11, no. 2 (February 25, 2014): 3065–111. http://dx.doi.org/10.5194/bgd-11-3065-2014.
Full textAbstract:
Abstract. The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle and dependent on the DOM composition. For our understanding of the kinetics of organic matter cycling in the ocean, it is therefore crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids, and transparent exopolymer particles (TEP) for two years. Ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) allowed the molecular characterization of extracted DOM after 70 days and after ∼2 years of incubation. Although glucose was quickly degraded, a DOC background was generated in glucose incubations. Only 20% of the organic carbon from algal exudate was degraded within the 2 years of incubation. TEP, which are released by micro-organisms, were produced during glucose degradation but decreased within less than three weeks back to half of the maximum concentration and were below detection in all treatments after 2 years. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM produced during the degradation of the algal exudates. Our results led to several conclusions: (i) Higher substrate levels result in a higher level of non-labile DOC which is an important prerequisite for carbon sequestration in the ocean; (ii) TEP are generated by bacteria but are also degraded rapidly, thus limiting their potential contribution to carbon sequestration; (iii) The molecular signatures of DOM derived from algal exudates or glucose after 70 days of incubation differed strongly from refractory DOM. After 2 years, however, the molecular patterns of DOM in glucose incubations were more similar to deep ocean DOM whereas the degraded exudate was still different.
12
Patchett, Aurora, and Jonathan A. Newman. "Comparison of Plant Metabolites in Root Exudates of Lolium perenne Infected with Different Strains of the Fungal Endophyte Epichloë festucae var. lolii." Journal of Fungi 7, no. 2 (February 18, 2021): 148. http://dx.doi.org/10.3390/jof7020148.
Full textAbstract:
Lolium perenne infected with the fungal endophyte Epichloë festucae var. lolii have specific, endophyte strain-dependent, chemical phenotypes in their above-ground tissues. Differences in these chemical phenotypes have been largely associated with classes of fungal-derived alkaloids which protect the plant against many insect pests. However, the use of new methodologies, such as various omic techniques, has demonstrated that many other chemical changes occur in both primary and secondary metabolites. Few studies have investigated changes in plant metabolites exiting the plant in the form of root exudates. As root exudates play an essential role in the acquisition of nutrients, microbial associations, and defense in the below-ground environment, it is of interest to understand how plant root exudate chemistry is influenced by the presence of strains of a fungal endophyte. In this study, we tested the influence of four strains of E. festucae var. lolii (E+ (also known as Lp19), AR1, AR37, NEA2), and uninfected controls (E−), on L. perenne growth and the composition of root exudate metabolites. Root exudates present in the hydroponic water were assessed by untargeted metabolomics using Accurate-Mass Quadrupole Time-of-Flight (Q–TOF) liquid chromatography–mass spectrometry (LC–MS). The NEA2 endophyte strain resulted in the greatest plant biomass and the lowest endophyte concentration. We found 84 metabolites that were differentially expressed in at least one of the endophyte treatments compared to E− plants. Two compounds were strongly associated with one endophyte treatment, one in AR37 (m/z 135.0546 RT 1.17), and one in E+ (m/z 517.1987 RT 9.26). These results provide evidence for important changes in L. perenne physiology in the presence of different fungal endophyte strains. Further research should aim to connect changes in root exudate chemical composition with soil ecosystem processes.
13
Koch, B. P., G. Kattner, M. Witt, and U. Passow. "Molecular insights into the microbial formation of marine dissolved organic matter: recalcitrant or labile?" Biogeosciences 11, no. 15 (August 11, 2014): 4173–90. http://dx.doi.org/10.5194/bg-11-4173-2014.
Full textAbstract:
Abstract. The degradation of marine dissolved organic matter (DOM) is an important control variable in the global carbon cycle. For our understanding of the kinetics of organic matter cycling in the ocean, it is crucial to achieve a mechanistic and molecular understanding of its transformation processes. A long-term microbial experiment was performed to follow the production of non-labile DOM by marine bacteria. Two different glucose concentrations and dissolved algal exudates were used as substrates. We monitored the bacterial abundance, concentrations of dissolved and particulate organic carbon (DOC, POC), nutrients, amino acids and transparent exopolymer particles (TEP) for 2 years. The molecular characterization of extracted DOM was performed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) after 70 days and after ∼2 years of incubation. Although glucose quickly degraded, a non-labile DOC background (5–9% of the initial DOC) was generated in the glucose incubations. Only 20% of the organic carbon from the algal exudate degraded within the 2 years of incubation. The degradation rates for the non-labile DOC background in the different treatments varied between 1 and 11 μmol DOC L−1 year−1. Transparent exopolymer particles, which are released by microorganisms, were produced during glucose degradation but decreased back to half of the maximum concentration within less than 3 weeks (degradation rate: 25 μg xanthan gum equivalents L−1 d−1) and were below detection in all treatments after 2 years. Additional glucose was added after 2 years to test whether labile substrate can promote the degradation of background DOC (co-metabolism; priming effect). A priming effect was not observed but the glucose addition led to a slight increase of background DOC. The molecular analysis demonstrated that DOM generated during glucose degradation differed appreciably from DOM transformed during the degradation of the algal exudates. Our results led to several conclusions: (i) based on our experimental setup, higher substrate concentration resulted in a higher concentration of non-labile DOC; (ii) TEP, generated by bacteria, degrade rapidly, thus limiting their potential contribution to carbon sequestration; (iii) the molecular signatures of DOM derived from algal exudates and glucose after 70 days of incubation differed strongly from refractory DOM. After 2 years, however, the molecular patterns of DOM in glucose incubations were more similar to deep ocean DOM whereas the degraded exudate was still different.
14
Carvalhais, Lilia C., Paul G. Dennis, Dayakar V. Badri, Brendan N. Kidd, Jorge M. Vivanco, and Peer M. Schenk. "Linking Jasmonic Acid Signaling, Root Exudates, and Rhizosphere Microbiomes." Molecular Plant-Microbe Interactions® 28, no. 9 (September 2015): 1049–58. http://dx.doi.org/10.1094/mpmi-01-15-0016-r.
Full textAbstract:
Jasmonic acid (JA) is an essential hormone in plant development and defense responses in Arabidopsis thaliana. Exogenous treatment with JA has recently been shown to alter root exudate profiles and the composition of root-associated bacterial communities. However, it is currently unknown whether disruptions of the JA in the rhizosphere affect root exudation profiles and the relative abundance of bacteria and archaea in the rhizosphere. In the present study, two Arabidopsis mutants that are disrupted in different branches of the jasmonate pathway, namely myc2 and med25, were cultivated in nutrient solution and soil to profile root exudates and bacterial and archaeal communities, respectively. Compared with the wild type, both mutants showed distinct exudation patterns, including lower amounts of asparagine, ornithine, and tryptophan, as well as distinct bacterial and archaeal community composition, as illustrated by an increased abundance of Streptomyces, Bacillus, and Lysinibacillus taxa in the med25 rhizosphere and an Enterobacteriaceae population in myc2. Alternatively, the Clostridiales population was less abundant in the rhizosphere of both mutants. Similarities between plant genotypes were highly correlated, as determined by operational taxonomic units in the rhizosphere and metabolites in root exudates. This strongly suggests that root exudates play a major role in modulating changes in microbial community composition upon plant defense responses.
15
WANG, CHUNHUA, and PETER M. MURIAN A. "Incidence of Listeria monocytogenes in Packages of Retail Franks." Journal of Food Protection 57, no. 5 (May 1, 1994): 382–86. http://dx.doi.org/10.4315/0362-028x-57.5.382.
Full textAbstract:
Twenty brands of retail frankfurters obtained from local supermarkets were examined for the presence of Listeria spp. Listeria spp. were found in 8 of 20 brands and Listeria monocytogenes in 6 of the 20 brands tested. In retail samples from 19 brands of frankfurters, Listeria spp. were found at an overall incidence of 10% (9 of 93 packages) of which 7.5% (7 of 93) contained L. monocytogenes and 2.5% (2 of 93) Listeria innocua. However, another brand (No. 20) had incidence levels as high as 71% (17 of 24) for L. monocytogenes and 81% for all Listeria spp. Testing the internal meats versus liquid exudates demonstrated that Listeria spp. were found only in the exudate, indicating that the presence of Listeria was likely due to postprocess contamination. Most probable number (MPN) analysis indicated that L. monocytogenes was present at levels of 0.34 to 2.3 MPN per ml of exudate, or 4.3 to 27.6 MPN per package. Chemical and microbial analyses found brand No. 20 to have the highest pH and NaCl levels among five brands tested; this combination may favor Listeria spp. and suppress competing microorganisms. A prior outbreak of listeriosis from the consumption of nonreheated franks, together with the data presented herein, indicates there is a potential foodborne hazard in consuming uncooked franks or in cross-contamination of other foods from handling package exudate.
16
Panchenko, L. V., D. A. Kuzyanov, Ye V. Pleshakova, N. N. Pozdnyakova, A. Yu Muratova, and O. V. Turkovskaya. "Effect of plant root exudate constituents on the degradation of phenanthrene by rhizobacterium Mycolicibacterium gilvum (Mycobacteriaceae, Actinobacteria)." Povolzhskiy Journal of Ecology, no. 2 (November 10, 2022): 193–205. http://dx.doi.org/10.35885/1684-7318-2022-2-193-205.
Full textAbstract:
The influence of the major components of plant root exudates, namely, carboxylic acids (succinic acid as an example) and secondary plant phenolic metabolites – flavonoids (rutin as an example), on the microbial degradation of the three-ring polycyclic aromatic hydrocarbon (PAH) phenanthrene by rhizobacterium Mycolicibacterium gilvum was studied. The destructive activity of this microorganism relative to PAH was studied by cultivating it in a liquid mineral medium containing phenanthrene (0.2 g/L), succinic acid (5 g/L), and rutin (0, 0.05, 0.1 or 0.2 mmol/L) at 30°C under aeration on a shaker (130 rpm) for 14 days. The stimulating effect of succinic acid and rutin on the microbial degradation of phenanthrene was revealed. It was found that carboxylate was utilized as the main growth substrate for the microorganism, while flavonol and PAH had little effect on bacterial growth. Rutin had no antimicrobial effect on the microorganisms studied; on the contrary, in combination with succinic acid, it significantly increased the biomass growth. At high concentrations (0.1 and 0.2 mmol/L), rutin inhibited the degradation of phenanthrene by 22 and 56%, respectively. However, at a concentration of 0.05 mmol/L rutin increased phenanthrene degradation by 10%. Thus, the results obtained showed the dependence of the PAH microbial degradation efficiency on the presence, combination, and concentration of the plant root exudate constituents.
17
Gao, Yuji, Dat T. Nguyen, Trifanny Yeo, Su Bin Lim, Wei Xian Tan, Leigh Edward Madden, Lin Jin, et al. "A flexible multiplexed immunosensor for point-of-care in situ wound monitoring." Science Advances 7, no. 21 (May 2021): eabg9614. http://dx.doi.org/10.1126/sciadv.abg9614.
Full textAbstract:
Chronic wounds arise from interruption of normal healing due to many potential pathophysiological factors. Monitoring these multivariate factors can provide personalized diagnostic information for wound management, but current sensing technologies use complex laboratory tests or track a limited number of wound parameters. We report a flexible biosensing platform for multiplexed profiling of the wound microenvironment, inflammation, and infection state at the point of care. This platform integrates a sensor array for measuring inflammatory mediators [tumor necrosis factor–α, interleukin-6 (IL-6), IL-8, and transforming growth factor–β1], microbial burden (Staphylococcus aureus), and physicochemical parameters (temperature and pH) with a microfluidic wound exudate collector and flexible electronics for wireless, smartphone-based data readout. We demonstrate in situ multiplexed monitoring in a mouse wound model and also profile wound exudates from patients with venous leg ulcers. This technology may facilitate more timely and personalized wound management to improve chronic wound healing outcomes.
18
Ghosh, Rakesh Kumar, and Deb Prasad Ray. "Root-exudates in relation to microbial activity." International Journal of Bioresource Science 4, no. 1 (2017): 17. http://dx.doi.org/10.5958/2454-9541.2017.00005.6.
Full text
19
Diz, Mariângela S. S., André O. Carvalho, and Valdirene M. Gomes. "Purification and molecular mass determination of a lipid transfer protein exuded from Vigna unguiculata seeds." Brazilian Journal of Plant Physiology 15, no. 3 (December 2003): 171–75. http://dx.doi.org/10.1590/s1677-04202003000300007.
Full textAbstract:
Plants exude a variety of substances through their surface especially of roots and germinating seeds. Some of these released compounds seem to have an inhibitory action against certain pathogens. Lipid transfer proteins (LTPs) are 9 kDa cysteine-rich cationic peptides and are thought to play a role in the protection of plants against microbial infections. The aim of this work was to isolate and determine the molecular mass of a LTP present in the exudates of imbibed cowpea seeds. For exudation induction, 50 seeds were submerged in 50 mL sterile 100 mmol.L-1 Na-acetate buffer, pH 4.5 and shaken at 30 ºC for 24 h. The resulting exudate was subjected to ammonium sulphate fractionation and the pellet formed between 0 and 70 % saturation was dialysed and recovered by freeze drying. Further purification steps were carried out using chromatographic methods and the molecular mass of the LTP determined. All of these steps were monitored by SDS-Tricine gel electrophoresis and Western blotting using an anti-LTP serum. The purified LTP showed a relative molecular mass of 9 kDa.
20
Chen, Siyu, Da Yang, Yufei Wei, Lizhen He, Zujian Li, and Shangdong Yang. "Changes in Soil Phosphorus Availability and Microbial Community Structures in Rhizospheres of Oilseed Rapes Induced by Intercropping with White Lupins." Microorganisms 11, no. 2 (January 28, 2023): 326. http://dx.doi.org/10.3390/microorganisms11020326.
Full textAbstract:
Oilseed rape is sensitive to soil phosphorus deficiencies. In contrast, white lupin is widely used as a model plant because it has efficient phosphorus utilization. Therefore, soil fertility and microbial composition in the rhizospheres of oilseed rapes and root exudate metabolites were compared under monocropping and intercropping systems. The main purpose was to explore whether the phosphorus absorption of rapeseed can be promoted by intercropping with white lupine. In comparison with oilseed rape monoculture (RR), the results showed that the contents of soil-available phosphorus, microbial biomass and phosphorus in the rhizospheres of oilseed rapes in the intercropping system (RL) were all higher than those of RR. Meanwhile, in comparison with RR, not only phosphorus-solubilizing bacteria, such as Streptomyces, Actinomadura and Bacillus, but also phosphorus-solubilizing fungi, such as Chaetomium, Aspergillus, Penicillium, were enriched in the rhizospheres of the oilseed rape under the RL system. Moreover, more abundant soil bacterial functions, organic acids and metabolites were also detected in root exudates of the oilseed rapes under the RL system. All of the above results suggest that soil phosphorus availability in the rhizospheres of oilseed rape could be improved by intercropping with white lupin. Additionally, soil phosphorus-solubilizing microorganisms, that are enriched in the rhizospheres of oilseed rapes under RL systems, have an important function in the improvement of phosphorus absorption of rapeseed by intercropping with white lupin.
21
Tong, Xin-nan, Xin-ze Wang, Xiao-juan He, Zhe Wang, and Wen-xuan Li. "Effects of antibiotics on microbial community structure and microbial functions in constructed wetlands treated with artificial root exudates." Environmental Science: Processes & Impacts 22, no. 1 (2020): 217–26. http://dx.doi.org/10.1039/c9em00458k.
Full text
22
Shi, Jibo, Xiaoya Gong, Muhammad Khashi u. Rahman, Qing Tian, Xingang Zhou, and Fengzhi Wu. "Effects of wheat root exudates on bacterial communities in the rhizosphere of watermelon." Plant, Soil and Environment 67, No. 12 (December 10, 2021): 721–28. http://dx.doi.org/10.17221/419/2021-pse.
Full textAbstract:
In this study, we investigated the effects of wheat root exudates on soil bacterial communities in the watermelon rhizosphere using quantitative PCR and Illumina MiSeq sequencing. The qPCR results showed that wheat root exudates significantly increased the abundance of total bacteria, Pseudomonas, Bacillus and Streptomyces spp. Illumina MiSeq sequencing results showed that wheat root exudates significantly changed the bacterial community structure and composition. These results indicated that plant root exudates play a role in plant-to-plant signalling, strongly affect the microbial community composition.
23
Bataillou, Grégory, Naoufel Haddour, and Christian Vollaire. "Bioelectricity production of PMFC using Lobelia Queen Cardinalis in individual and shared soil configurations." E3S Web of Conferences 334 (2022): 08001. http://dx.doi.org/10.1051/e3sconf/202233408001.
Full textAbstract:
Plant Microbial Fuel Cell (PMFC) creates electricity from oxidation of root exudates by microbia anaerobic digestion, and reduction of dioxygen to water. In this study, Lobelia Queen Cardinalis was used as a plant model to investigate the impact of ionic connection between stacked Plant microbial fuel cell (shared soil). 10mm thickness carbon felt woven with stainless steel wire was used for both anode and cathode, and soil was a mix of potting soil and ground from pond banks (30\%-70\% weight, respectively). Independent performances did not show any difference between individual and shared soil PMFCs. Stacking independent PMFC in series sums both open circuit potential (OCP) and internal resistance, while stacking in parallel sums current, keeping open circuit potential to the mean of the OCPs. Although series stacking seems to output best performances, this configuration may cause voltage reversal in one PMFC when current is strong, leading to biofilm damage, so stacking in parallel is recommended.
24
Vasilevskaya, L. A. "The microbial landscape action on development destructive erysipelas forms." Modern medical technologies 41 part 1, no. 2 (April 6, 2019): 17–19. http://dx.doi.org/10.34287/mmt.2(41).2019.3.
Full textAbstract:
Objective. Changes in the monoculture of the pathogen in the microbial association of bacterial pathogens is accompanied, depending on their species composition, the progression of the inflammatory process with the development of destructive forms. The object was to install the value of microbial landscape in predicting the development of destructive forms of erysipelas. Material and methods. The diseases histories and cultures of wound secretions with the definition of sensitivity of microorganisms to antibiotics were analyses. Results. Of our studies indicate that the microflora of the primary cells in destructive forms of the erysipelas changed both quantitatively and qualitatively. Detected microbial pathogens in bacteriological studies of soft tissue exudates allowed installing criteria for forecasting the development of purulent complications. Conclusion. Bacteriological studies indicate that necrotizing skin lesions are preceded by the presence of S. Pyogenes in the exudates. Keywords: microbial landscape, erysipelas, gram-positive and gram-negative microflora, microbial associations.
25
Luo, Zhong, Xisha Yang, Jing Li, Shizhi Wen, Lili Yang, Li Ji, and Gongxiu He. "Divergent Effects of Fertilizer Regimes on Taxonomic and Functional Compositions of Rhizosphere Bacteria and Fungi in Phoebe bournei Young Plantations Are Associated with Root Exudates." Forests 14, no. 1 (January 10, 2023): 126. http://dx.doi.org/10.3390/f14010126.
Full textAbstract:
Fertilization is widely acknowledged as being an essential practice to improve forest productivity in forest ecosystems. However, too little consideration has been given to the taxonomic and functional compositions of rhizosphere soil microbes and their interactions with root exudates under different fertilizer regimes in forest plantations. Here, we investigated the effects of four typical fertilizer regimes (CK, no fertilizer; CF, compound fertilizer; OF, organic fertilizer; CMF, compound microbial fertilizer) on soil microbial communities and their potential functional groups in Phoebe bournei young plantations, as well as their associations with soil physicochemical properties and root exudates. These results showed that fertilizer regimes strikingly affected the rhizosphere soil microbial community compositions and alpha diversity indices. The pathotroph was the dominant fungal guild. With the applications of three fertilizations, the relative abundances of the plant pathogen and arbuscular mycorrhiza increased. The alpha diversity of soil bacteria was highest under the OF regime, and soil fungal diversity was more powerfully affected by the amendment of CMF. Additionally, while the fungal community was simultaneously influenced by soil physiochemical factors and root exudates, the bacterial community in the rhizosphere was mostly impacted by root exudates. More importantly, the application of OF and CF induced dramatic growths of Fusarium, while CMF treatment including Bacillus suppressed the development of Fusarium via adjusting bacterial species. Overall, our findings exhibit the divergent responses of rhizosphere bacteria and fungi to fertilizer regimes in P. bournei young plantations. The application of organic fertilizer provides benefits for rhizosphere bacteria, and microbial fertilizer can help alleviate inhibition through changing pathogens.
26
Kibalina, I. V., N. N. Tsybikov, and E. V. Fefelova. "Dynamics of the chemokine ENA-78/CXCL5 levels in blood serum and skin exudate in patients with atopic dermatitis." Medical Immunology (Russia) 24, no. 2 (April 20, 2022): 401–6. http://dx.doi.org/10.15789/1563-0625-dot-2461.
Full textAbstract:
Currently, there are only scarce data on dynamics of biologically active substances in the lesions associated with atopic dermatitis. Persistence of microorganisms in atopic dermatitis is high on the skin surface. However, pathophysiological significance of ENA-78/CXCL5 for development of atopic dermatitis was not studied so far. The ENA-78/CXCL5 is known to be produced by endotheliocytes, keratinocytes, eosinophils, fibroblasts to activate neutrophil migration, especially under the influence of LPS-containing microorganisms. The aim of this study was to evaluate the dynamics of ENA-78/CXCL5 chemokine levels in blood serum and skin exudates in the patients with atopic dermatitis, as well as to determine pathophysiological role of the chemokine in pathogenesis of dermatosis. 80 patients with limited and widespread forms of atopic dermatitis and 15 volunteers were under observation. The dynamics of ENA-78/CXCL5 levels was studied in blood sera and skin exudates. Blood samples for the study were drawn at the time periods of exacerbation and remission. Skin exudates were taken from the patients during the exacerbation period using disposable insulin syringes and 20-G disposable needles. In healthy volunteers, the skin exudate was obtained by the “skin window” technique as described by V.V. Klimov and coauthors “A method for assessing minimal inflammatory activity of skin in atopic dermatitis in remission”. The cell analysis was conducted by flow cytofluorimetry using the LEGEND plex TM Human Proinflammatory Chemokine Panel (USA) according to the manufacturer’s protocol. Serum concentrations of chemokine ENA-78/CXCL5 in adolescents with atopic dermatitis, exceeded the range for healthy volunteers. During remission of dermatitis, the chemokine level did not reach the indices in the control group. In adults, the ENA-78/CXCL5 concentration, both at the onset of symptoms and upon their resolution, was below the control levels. Maximal concentrations of ENA-78/CXCL5 chemokine were detected in the skin exudates. As based on our data on the dynamics of ENA-78/CXCL5 chemokine levels, it could be assumed that this substance may represent a sufficient link in pathogenesis of atopic dermatitis, by causing migration of neutrophils and monocytes to the affected area. The ENA-78/CXCL5 chemokine may be a marker of microbial pathogenesis and cellular damage in atopic dermatitis.
27
Thomas, John C., and Robert T. Dabkowski. "Glucose and plant exudate enhanced enumeration of bacteria capable of degrading polycyclic aromatic hydrocarbons." Canadian Journal of Microbiology 57, no. 12 (December 2011): 1067–72. http://dx.doi.org/10.1139/w11-097.
Full textAbstract:
Enumerating environmental microbial isolates capable of polycyclic aromatic hydrocarbon (PAH) degradation can provide insight into the microbe–plant interactions that facilitate PAH removal. We examined a known PAH degrader ( Pseudomonas putida G7), a nondegrader ( Agrobacterium tumefaciens LBA4404), and several microorganisms isolated from the environment by using a PAH cocktail in an enumeration medium with or without 0.025% (m/v) glucose and (or) root exudates. Compared with the standard most probable number (MPN), the addition of glucose and root exudates in a modified MPN method resulted in a 3- to 11-fold enhancement of PAH degraders being enumerated among microorganisms found in PAH-contaminated soils. High-performance liquid chromatography analysis verified that PAH levels were reduced using this modified enumeration method. Low levels of glucose, perhaps in concert with other materials in exudates, may promote microbial metabolism, thereby enhancing PAH degradation.
28
Walker, Angela, and Jacalyn Brace. "A multipurpose dressing: role of a Hydrofiber foam dressing in managing wound exudate." Journal of Wound Care 28, Sup9a (September 1, 2019): S4—S10. http://dx.doi.org/10.12968/jowc.2019.28.sup9a.s4.
Full textAbstract:
Chronic wound exudate is associated with stalled or delayed healing. Excess amounts will break down healthy tissue, increasing the production of slough and necrotic tissue. This will also create an ideal environment for microbial proliferation and place the surrounding skin at risk of maceration. It is vital, therefore, to select an absorbent dressing that can retain excessive exudate. This article describes how to achieve this. It introduces an absorbent dressing, Aquacel Foam, which not only retains exudate, but can also help remove devitalised tissue and promote healing
29
Agorsor, Israel D. K., Brian T. Kagel, and Cristian H. Danna. "The Arabidopsis LHT1 Amino Acid Transporter Contributes to Pseudomonas simiae-Mediated Plant Growth Promotion by Modulating Bacterial Metabolism in the Rhizosphere." Plants 12, no. 2 (January 12, 2023): 371. http://dx.doi.org/10.3390/plants12020371.
Full textAbstract:
The root microbiome structure ensures optimal plant host health and fitness, and it is, at least in part, defined by the plant genotype. It is well documented that root-secreted amino acids promote microbial chemotaxis and growth in the rhizosphere. However, whether the plant-mediated re-uptake of amino acids contributes to maintaining optimal levels of amino acids in the root exudates, and, in turn, microbial growth and metabolism, remains to be established. Here, we show that Lysine-Histidine Transporter-1 (LHT1), an amino acid inward transporter expressed in Arabidopsis thaliana roots, limits the growth of the plant-growth-promoting bacteria Pseudomonas simiae WCS417r (Ps WCS417r). The amino acid profiling of the lht1 mutant root exudates showed increased levels of glutamine, among other amino acids. Interestingly, lht1 exudates or Gln-supplemented wild-type exudates enhance Ps WCS417r growth. However, despite promoting bacterial growth and robust root colonization, lht1 exudates and Gln-supplemented wild-type exudates inhibited plant growth in a Ps WCS417r-dependent manner. The transcriptional analysis of defense and growth marker genes revealed that plant growth inhibition was not linked to the elicitation of plant defense but likely to the impact of Ps WCS417r amino acids metabolism on auxin signaling. These data suggest that an excess of amino acids in the rhizosphere impacts Ps WCS417r metabolism, which, in turn, inhibits plant growth. Together, these results show that LHT1 regulates the amino-acid-mediated interaction between plants and Ps WCS417r and suggest a complex relationship between root-exuded amino acids, root colonization by beneficial bacteria, bacterial metabolism, and plant growth promotion.
30
Widyati, E., M. Siarudin, and Y. Yonky Indrajaya. "The Dynamic of Functional Microbes Community Under Auri (Acacia auriculiformis Cunn. Ex Benth) Agroforestry System." Jurnal Manajemen Hutan Tropika (Journal of Tropical Forest Management) 28, no. 2 (August 9, 2022): 119–27. http://dx.doi.org/10.7226/jtfm.28.2.119.
Full textAbstract:
Microbes are important rhizosphere constituents for providing nutrients in the soil. This study analyzes the dynamic of soil functional microbes' populations on land managed as an agroforestry (AF) system. The AF system consists of a 2-years old auri tree combined with several crops, i.e., wild grasses, peanuts (Arachis hypogaea), pigeon pea (Cajanus cajan), and maize (Zea mays). Soil samples were collected from each rhizosphere and then analyzed for their chemical properties such as N, P, K, pH, and C organic contents. The population of functional microbes was observed by isolation of the non-symbiotic N-fixer microbes (BNF), the cellulose-degrading microbes (CDM), and the phosphate solubilizing microbes (PSM) in their selective media. The total soil sugars were also tested for root exudates. The results showed that in an auri agroforestry system, the kind of crops determines the content of the soil organic material that is turned-offer into the soil. This affects the population structure and functional microbial abundance in the rhizosphere. Furthermore, microbial colonization in the rhizosphere affects plants in producing root exudates. Then, root exudates shape the structures of the microbial community, as well as an influence among inhabitants in defining mineralization of soil organic matter, nutrient availability, and trees performance.
31
PELZ-STELINSKI, KIRSTEN S., EDWARD D. WALKER, and MICHAEL G. KAUFMAN. "Senescent leaf exudate increases mosquito survival and microbial activity." Ecological Entomology 35, no. 3 (February 28, 2010): 329–40. http://dx.doi.org/10.1111/j.1365-2311.2010.01183.x.
Full text
32
Fu, Ruixin, Haichao Feng, Francisco Dini-Andreote, Zhen Wang, Chunbin Bo, Wenhui Cao, Keming Yang, et al. "Modulation of the Tomato Rhizosphere Microbiome via Changes in Root Exudation Mediated by the Ethylene Receptor NR." Microorganisms 9, no. 12 (November 28, 2021): 2456. http://dx.doi.org/10.3390/microorganisms9122456.
Full textAbstract:
Plant hormones have been recently shown to exert an indirect influence on the recruitment of plant-associated microbiomes. However, it remains unclear the extent to which the disruption of the ethylene (ET) signaling pathway affects the assembly and functioning of plant-root microbiomes. In this study, the Never-ripe tomato mutant (Nr) was profiled for differences compared to the wild type (control). Tomato plants were subjected to root exudate profiling and the characterization of bacterial and fungal communities. Compared to the control, Nr revealed differences in the composition of root exudates, including lower amounts of esculetin, gallic acid, L-fucose, eicosapentaenoic acid, and higher amounts of β-aldehyde. Interestingly, Nr significantly differed in the composition and functioning of the rhizosphere bacterial community. We also identified the taxa that occurred at relatively higher abundances in Nr, including the genus Lysobacter, which displayed a significant negative correlation with changes in eicosapentaenoic acid and esculetin, and a significant positive correlation with changes in β-aldehyde. Taken together, our study provides evidence that a mutation in the ET receptor exerts predictable changes in the root-associated microbial taxa of tomato plants. These indirect effects can potentially be explored towards new strategies to engineer beneficial plant microbiomes via targeted changes in plant genetics and physiology.
33
Shahanenko, R., N. Ilnitskiy, V. Shahanenko, and S. Rublenko. "Ozonetherapy as a new antimicrobic strategy." Naukovij vìsnik veterinarnoï medicini, no. 2(160) (November 24, 2020): 195–200. http://dx.doi.org/10.33245/2310-4902-2020-160-2-195-200.
Full textAbstract:
Development of antibiotic-resistant strains of microorganisms is a dangerous phenomenon, actively progressing every year. The uncontrolled use of antibiotics for animals, accumulation in products of animal origin ultimately poses a danger to human health. That is why a decrease in the use of antibiotics and searching alternatives of antibiotic is acute and relevant issues. Therefore, the aim of our research was to study the antimicrobial properties of ozone in relation to pathogens of purulent infection and to show the possibility of using ozone therapy as a potential method of antimicrobial therapy for animals. The materials for determining antimicrobial effect of ozone was 12 samples of purulent exudate in an amount of 2 ml, taken from dogs with purulent wounds before and after sanitation by ozonized 0.87% NaCl solution. Complexity course of wound process with purulent inflammation largely depends on from degree of microbial contamination of the wound and species composition of microorganisms. Therefore, an important aspect in our research was the study of the antimicrobial properties of ozone on its action of purulent exudate «in vitro» and «in vivo» and the determination of the bactericidal effect on microorganisms. The most stable and informative indicator of assessing nature of purulent-inflammatory process is the determination of total number of microorganisms in 1 ml of discharge from a purulent wound. The total microbial number was determined by the method of serial dilutions according to Pasteur. Serial ten-fold dilutions from 10-1 to 10-9 were prepared from purulent exudate in test tubes with sterile MPB (9 ml each). Species composition of microorganisms was determined by cultural and biochemical properties of cultivated microbial colonies, followed microscopy of smears from pure cultures stained using method of Gram. Samples of purulent exudate were subjected to microbiological examination before treatment, and after 30 minutes of washing by ozonized isotonic solution NaCl (ozone concentration of 7 mg/ml). A microbiological study of purulent exudate was also carried out, pre-treated with ozone at a concentration of 7 mg/ml «in vitro» in a test tube in an amount of 2 ml by passing it through exudate (sparging) at a flow rate of 0.5 L/min and a processing time of 10 min. Samples were examined immediately after sampling and sparging. "Microbial landscapes" of purulent wounds were presented by associations of Staph. aureus, Str. faecalis, E. coli. Microbial seeding of purulent exudate for treatment ranged from 6.6 • 10-10 to 3.7 • 10-8 CFU/ml, however, after 10 min of bubbling «in vitro» at an ozone concentration of 7 mg/ml, the degree of microbial seeding of samples did not exceed 10-4 CFU/ml and ranged from 3.1 • 10-4 to 2.3• 10-3 CFU/ml. As shown by the results of microbiological studies, the growth of microorganisms on a nutrient medium in bacteriological plates with purulent exudate samples treated with ozone with concentration of 7 mg/ml was already absent at 10-5 degrees of dilution, which indicates the pronounced antimicrobial properties of ozone. The study «in vivo»also indicates that even after a single use of an ozonized isotonic NaCl solution at an ozone concentration of 7 mg/ml, it completely prevents the growth of Staph. aureus, Str. faecalis, E. coli. and causes 100% death mentioned associations of microorganisms. The results of microbiological studies are confirmed by clinical data. So, on the third day of treatment, the animals in the lesion zone had a small amount of wound exudate, and the microbial number of the latter was 1.4 • 10-4 − 3.1 • 10-³ CFU/ml, below the critical level of contamination and in most cases not leads to the progression of a purulent-inflammatory process. Ozone destroys all types of bacteria, viruses, fungi and protozoa. At the same time, ozone at a concentration of 7 mg/ ml does not have an irritating effect on body tissues, therefore, ozone therapy can be considered as an additional or alternative therapy of bacterial infection. Key words: ozone, ozonetherapy, purulent wounds, antibiotic resistance.
34
Zhao, Jia-Yin, Zhi-Hong Ye, and Huan Zhong. "Rice root exudates affect microbial methylmercury production in paddy soils." Environmental Pollution 242 (November 2018): 1921–29. http://dx.doi.org/10.1016/j.envpol.2018.07.072.
Full text
35
Schilling, Günther, Andreas Gransee, Annette Deuhel, Grit Ležoviž, and Silke Ruppel. "Phosphorus availability, root exudates, and microbial activity in the rhizosphere." Zeitschrift für Pflanzenernährung und Bodenkunde 161, no. 4 (August 1998): 465–78. http://dx.doi.org/10.1002/jpln.1998.3581610413.
Full text
36
Mishra, Ajay Kumar, Naganeeswaran Sudalaimuthuasari, Khaled M. Hazzouri, Esam Eldin Saeed, Iltaf Shah, and Khaled M. A. Amiri. "Tapping into Plant–Microbiome Interactions through the Lens of Multi-Omics Techniques." Cells 11, no. 20 (October 17, 2022): 3254. http://dx.doi.org/10.3390/cells11203254.
Full textAbstract:
This review highlights the pivotal role of root exudates in the rhizosphere, especially the interactions between plants and microbes and between plants and plants. Root exudates determine soil nutrient mobilization, plant nutritional status, and the communication of plant roots with microbes. Root exudates contain diverse specialized signaling metabolites (primary and secondary). The spatial behavior of these metabolites around the root zone strongly influences rhizosphere microorganisms through an intimate compatible interaction, thereby regulating complex biological and ecological mechanisms. In this context, we reviewed the current understanding of the biological phenomenon of allelopathy, which is mediated by phytotoxic compounds (called allelochemicals) released by plants into the soil that affect the growth, survival, development, ecological infestation, and intensification of other plant species and microbes in natural communities or agricultural systems. Advances in next-generation sequencing (NGS), such as metagenomics and metatranscriptomics, have opened the possibility of better understanding the effects of secreted metabolites on the composition and activity of root-associated microbial communities. Nevertheless, understanding the role of secretory metabolites in microbiome manipulation can assist in designing next-generation microbial inoculants for targeted disease mitigation and improved plant growth using the synthetic microbial communities (SynComs) tool. Besides a discussion on different approaches, we highlighted the advantages of conjugation of metabolomic approaches with genetic design (metabolite-based genome-wide association studies) in dissecting metabolome diversity and understanding the genetic components of metabolite accumulation. Recent advances in the field of metabolomics have expedited comprehensive and rapid profiling and discovery of novel bioactive compounds in root exudates. In this context, we discussed the expanding array of metabolomics platforms for metabolome profiling and their integration with multivariate data analysis, which is crucial to explore the biosynthesis pathway, as well as the regulation of associated pathways at the gene, transcript, and protein levels, and finally their role in determining and shaping the rhizomicrobiome.
37
Corgi�, S. C., T. Beguiristain, and C. Leyval. "Spatial Distribution of Bacterial Communities and Phenanthrene Degradation in the Rhizosphere of Lolium perenne L." Applied and Environmental Microbiology 70, no. 6 (June 2004): 3552–57. http://dx.doi.org/10.1128/aem.70.6.3552-3557.2004.
Full textAbstract:
ABSTRACT Rhizodegradation of organic pollutants, such as polycyclic aromatic hydrocarbons, is based on the effect of root-produced compounds, known as exudates. These exudates constitute an important and constant carbon source that selects microbial populations in the plant rhizosphere, modifying global as well as specific microbial activities. We conducted an experiment in two-compartment devices to show the selection of bacterial communities by root exudates and phenanthrene as a function of distance to roots. Using direct DNA extraction, PCR amplification, and thermal gradient gel electrophoresis screening, bacterial population profiles were analyzed in parallel to bacterial counts and quantification of phenanthrene biodegradation in three layers (0 to 3, 3 to 6, and 6 to 9 mm from root mat) of unplanted-polluted (phenanthrene), planted-polluted, and planted-unpolluted treatments. Bacterial community differed as a function of the distance to roots, in both the presence and the absence of phenanthrene. In the planted and polluted treatment, biodegradation rates showed a strong gradient with higher values near the roots. In the nonplanted treatment, bacterial communities were comparable in the three layers and phenanthrene biodegradation was high. Surprisingly, no biodegradation was detected in the section of planted polluted treatment farthest from the roots, where the bacterial community structure was similar to those of the nonplanted treatment. We conclude that root exudates and phenanthrene induce modifications of bacterial communities in polluted environments and spatially modify the activity of degrading bacteria.
38
Zhalnina, Kateryna, Katherine B. Louie, Zhao Hao, Nasim Mansoori, Ulisses Nunes da Rocha, Shengjing Shi, Heejung Cho, et al. "Dynamic root exudate chemistry and microbial substrate preferences drive patterns in rhizosphere microbial community assembly." Nature Microbiology 3, no. 4 (March 19, 2018): 470–80. http://dx.doi.org/10.1038/s41564-018-0129-3.
Full text
39
Lünsmann, Vanessa, Uwe Kappelmeyer, Anja Taubert, Ivonne Nijenhuis, Martin von Bergen, Hermann J. Heipieper, Jochen A. Müller, and Nico Jehmlich. "Aerobic Toluene Degraders in the Rhizosphere of a Constructed Wetland Model Show Diurnal Polyhydroxyalkanoate Metabolism." Applied and Environmental Microbiology 82, no. 14 (April 29, 2016): 4126–32. http://dx.doi.org/10.1128/aem.00493-16.
Full textAbstract:
ABSTRACTConstructed wetlands (CWs) are successfully applied for the treatment of waters contaminated with aromatic compounds. In these systems, plants provide oxygen and root exudates to the rhizosphere and thereby stimulate microbial degradation processes. Root exudation of oxygen and organic compounds depends on photosynthetic activity and thus may show day-night fluctuations. While diurnal changes in CW effluent composition have been observed, information on respective fluctuations of bacterial activity are scarce. We investigated microbial processes in a CW model system treating toluene-contaminated water which showed diurnal oscillations of oxygen concentrations using metaproteomics. Quantitative real-time PCR was applied to assess diurnal expression patterns of genes involved in aerobic and anaerobic toluene degradation. We observed stable aerobic toluene turnover byBurkholderialesduring the day and night. Polyhydroxyalkanoate synthesis was upregulated in these bacteria during the day, suggesting that they additionally feed on organic root exudates while reutilizing the stored carbon compounds during the night via the glyoxylate cycle. Although mRNA copies encoding the anaerobic enzyme benzylsuccinate synthase (bssA) were relatively abundant and increased slightly at night, the corresponding protein could not be detected in the CW model system. Our study provides insights into diurnal patterns of microbial processes occurring in the rhizosphere of an aquatic ecosystem.IMPORTANCEConstructed wetlands are a well-established and cost-efficient option for the bioremediation of contaminated waters. While it is commonly accepted knowledge that the function of CWs is determined by the interplay of plants and microorganisms, the detailed molecular processes are considered a black box. Here, we used a well-characterized CW model system treating toluene-contaminated water to investigate the microbial processes influenced by diurnal plant root exudation. Our results indicated stable aerobic toluene degradation by members of theBurkholderialesduring the day and night. Polyhydroxyalkanoate synthesis in these bacteria was higher during the day, suggesting that they additionally fed on organic root exudates and reutilized the stored carbon compounds during the night. Our study illuminates microbial processes occurring in the rhizosphere of an aquatic ecosystem.
40
Markelova, Ekaterina, Christopher T. Parsons, Raoul-Marie Couture, Christina M. Smeaton, Benoit Madé, Laurent Charlet, and Philippe Van Cappellen. "Deconstructing the redox cascade: what role do microbial exudates (flavins) play?" Environmental Chemistry 14, no. 8 (2017): 515. http://dx.doi.org/10.1071/en17158.
Full textAbstract:
Environmental contextRedox potential is a controlling variable in aquatic chemistry. Through time series data, we show that microbial exudates released by bacteria may control trends in redox potential observed in natural waters. In particular, electron transfer between these exudates and the electrode could explain the values measured in the presence of abundant oxidants such as oxygen and nitrate. AbstractRedox electrodes are commonly used to measure redox potentials (EH) of natural waters. The recorded EH values are usually interpreted in terms of the dominant inorganic redox couples. To further advance the interpretation of measured EH distributions along temporal and spatial redox gradients, we performed a series of reactor experiments in which oxidising and reducing conditions were alternated by switching between sparging with air and N2. Starting from a simple electrolyte solution and ending with a complex biogeochemical system, common groundwater solutes, metabolic substrates (NO3− and C3H5O3−), bacteria (Shewanella oneidensis MR-1) and goethite (α-FeOOH(s)) were tested by increasing the system complexity with each subsequent experiment. This systematic approach yielded a redox cascade ranging from +500 to −350 mV (pH ~7.4). The highest and lowest EH values registered by the platinum (Pt) electrode agreed with Nernstian redox potentials predicted for the O2/H2O2 and FeOOH/Fe2+(aq) couples respectively. Electrode poisoning by the organic pH buffer (MOPS) and addition of bacteria to the aerated solutions resulted in marked decreases in measured EH values. The latter effect is attributed to the release of flavins by Shewanella oneidensis MR-1 to the medium. As expected, equilibrium with the non-electroactive NO3−/NO2−/NH4+ redox couples could not account for the EH values recorded during dissimilatory nitrate reduction to ammonium (DNRA). However, the observed EH range for DNRA coincided with that bracketed by EH values measured in separate abiotic solutions containing either the oxidised (+324 ± 29 mV) or reduced (−229 ± 40 mV) forms of flavins. The results therefore suggest that the Pt electrode detected the presence of the electroactive flavins, even at submicromolar concentrations. In particular, flavins help explain the fairly low EH values measured in the presence of strong oxidants, such as O2 and NO3−.
41
Yuan, Hongzhao, Zhenke Zhu, Shoulong Liu, Tida Ge, Hongzhen Jing, Baozhen Li, Qiong Liu, Tin Mar Lynn, Jinshui Wu, and Yakov Kuzyakov. "Microbial utilization of rice root exudates: 13C labeling and PLFA composition." Biology and Fertility of Soils 52, no. 5 (March 1, 2016): 615–27. http://dx.doi.org/10.1007/s00374-016-1101-0.
Full text
42
Qu, Tongbao, Xue Du, Yulan Peng, Weiqiang Guo, Chunli Zhao, and Gianalberto Losapio. "Invasive species allelopathy decreases plant growth and soil microbial activity." PLOS ONE 16, no. 2 (February 9, 2021): e0246685. http://dx.doi.org/10.1371/journal.pone.0246685.
Full textAbstract:
According to the ‘novel weapons hypothesis’, invasive success depends on harmful plant biochemicals, including allelopathic antimicrobial roots exudate that directly inhibit plant growth and soil microbial activity. However, the combination of direct and soil-mediated impacts of invasive plants via allelopathy remains poorly understood. Here, we addressed the allelopathic effects of an invasive plant species (Rhus typhina) on a cultivated plant (Tagetes erecta), soil properties and microbial communities. We grew T. erecta on soil samples at increasing concentrations of R. typhina root extracts and measured both plant growth and soil physiological profile with community-level physiological profiles (CLPP) using Biolog Eco-plates incubation. We found that R. typhina root extracts inhibit both plant growth and soil microbial activity. Plant height, Root length, soil organic carbon (SOC), total nitrogen (TN) and AWCD were significantly decreased with increasing root extract concentration, and plant above-ground biomass (AGB), below-ground biomass (BGB) and total biomass (TB) were significantly decreased at 10 mg·mL-1 of root extracts. In particular, root extracts significantly reduced the carbon source utilization of carbohydrates, carboxylic acids and polymers, but enhanced phenolic acid. Redundancy analysis shows that soil pH, TN, SOC and EC were the major driving factors of soil microbial activity. Our results indicate that strong allelopathic impact of root extracts on plant growth and soil microbial activity by mimicking roots exudate, providing novel insights into the role of plant–soil microbe interactions in mediating invasion success.
43
BOROZAN, Aurica Breica, Sorina POPESCU, and Oana Maria BOLDURA. "Plants Root Interference Area, A Benefit To The Microbial Community." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Horticulture 74, no. 1 (May 19, 2017): 1. http://dx.doi.org/10.15835/buasvmcn-hort:12302.
Full textAbstract:
Part of byproducts synthesized by plants through photosynthesis reach the ground, where create selective microenvironments for micro-flora and associations of plant - micro-organisms, which are a benefit for plant growth Setting the interference effect of the root interference area of vines and herbaceous plants and of radicular exudates from vine rhizosphere on microbial community and estimating microbial population present on the vine leaves. The biological material was represented by leaves (Fa, Fb), and soil rhizosphere (Ra, Rb) of two varieties of vines (Tamaioasa Romanian white and black / TA, TN), and from the vine roots interference area with other herbaceous plants (Ma, Mb). The soil has never been chemically treated. The microbiological study of biological samples was performed by classical and molecular methods. Overall, bacteria had a significant presence in soil samples taken from the root interference zone (Ma, Mb). Actinomycetes quantitatively dominated the root interference area of herbaceous plant with variety TA. The range of actinomycetes species and leaves microflora was reduced. In this study we have shown that significant growth of microorganisms occurs in the interference area of vine with other herbal plants as a result of the cumulative effect of radicular exudates.
44
Casey, C. E., O. B. O'Sullivan, F. O'Gara, and J. D. Glennon. "Ion chromatographic analysis of nutrients in seed exudate for microbial colonisation." Journal of Chromatography A 804, no. 1-2 (April 1998): 311–18. http://dx.doi.org/10.1016/s0021-9673(97)01297-1.
Full text
45
Roach, Ty N. F., Mark Little, Milou G. I. Arts, Joel Huckeba, Andreas F. Haas, Emma E. George, Robert A. Quinn, et al. "A multiomic analysis of in situ coral–turf algal interactions." Proceedings of the National Academy of Sciences 117, no. 24 (June 1, 2020): 13588–95. http://dx.doi.org/10.1073/pnas.1915455117.
Full textAbstract:
Viruses, microbes, and host macroorganisms form ecological units called holobionts. Here, a combination of metagenomic sequencing, metabolomic profiling, and epifluorescence microscopy was used to investigate how the different components of the holobiont including bacteria, viruses, and their associated metabolites mediate ecological interactions between corals and turf algae. The data demonstrate that there was a microbial assemblage unique to the coral-turf algae interface displaying higher microbial abundances and larger microbial cells. This was consistent with previous studies showing that turf algae exudates feed interface and coral-associated microbial communities, often at the detriment of the coral. Further supporting this hypothesis, when the metabolites were assigned a nominal oxidation state of carbon (NOSC), we found that the turf algal metabolites were significantly more reduced (i.e., have higher potential energy) compared to the corals and interfaces. The algae feeding hypothesis was further supported when the ecological outcomes of interactions (e.g., whether coral was winning or losing) were considered. For example, coral holobionts losing the competition with turf algae had higher Bacteroidetes-to-Firmicutes ratios and an elevated abundance of genes involved in bacterial growth and division. These changes were similar to trends observed in the obese human gut microbiome, where overfeeding of the microbiome creates a dysbiosis detrimental to the long-term health of the metazoan host. Together these results show that there are specific biogeochemical changes at coral–turf algal interfaces that predict the competitive outcomes between holobionts and are consistent with algal exudates feeding coral-associated microbes.
46
Kremer, Robert J. "Environmental Implications of Herbicide Resistance: Soil Biology and Ecology." Weed Science 62, no. 2 (June 2014): 415–26. http://dx.doi.org/10.1614/ws-d-13-00114.1.
Full textAbstract:
Soil microbial community structure and activity are linked to plant communities. Weeds may alter their soil environment, selecting for specific rhizosphere microbial communities. Rhizosphere modification occurs for many crop and horticultural plants. However, impacts of weeds in agroecosystems on soil biology and ecology have received less attention because effective weed management practices were developed to minimize their impacts on crop production. The recent development of herbicide resistance (HR) in several economically important weeds leading to widespread infestations in crop fields treated with a single herbicide has prompted a re-evaluation of the effects of weed growth on soil biology and ecology. The objective of this article is to review the potential impacts of herbicide-resistant weeds on soil biological and ecological properties based on reports for crops, weeds, and invasive plants. Persistent weed infestations likely establish extensive root systems and release various plant metabolites through root exudation. Many exudates are selective for specific soil microbial groups mediating biochemical and nutrient acquisition processes. Exudates may stimulate development of microbial groups beneficial to weed but detrimental to crop growth or beneficial to both. Changes in symbiotic and associative microbial interactions occur, especially for arbuscular mycorrhizal fungi (AMF) that are important in plant uptake of nutrients and water, and protecting from phytopathogens. Mechanisms used by weeds to disrupt symbioses in crops are not clearly described. Many herbicide-resistant weeds includingAmaranthusandChenopodiumdo not support AMF symbioses, potentially reducing AMF propagule density and establishment with crop plants. Herbicides applied to control HR weeds may compound effects of weeds on soil microorganisms. Systemic herbicides released through weed roots may select microbial groups that mediate detrimental processes such as nutrient immobilization or serve as opportunistic pathogens. Understanding complex interactions of weeds with soil microorganisms under extensive infestations is important in developing effective management of herbicide-resistant weeds.
47
Kemerov, S. V., T. S. Dorzhieva, D. A. Stepin, and Z. St Kemerova. "Studying the microbial landscape of peritoneal exudate in acute diffuse purulent peritonitis." Kazan medical journal 97, no. 5 (October 15, 2016): 806–11. http://dx.doi.org/10.17750/kmj2016-806.
Full textAbstract:
Aim. To study current trends in changing microbial landscape of peritoneal exudate for improving treatment outcomes, as well as the generalization of the methods of predicting fatal outcomes of postoperative peritonitis, its etiological and pathogenetic treatment.Methods. A bacteriological study of peritoneal exudate in 60 patients with purulent peritonitis at toxic and terminal phases, who were treated in the department of purulent surgery, and their comparison with the results obtained 10 years ago were performed. Laboratory testing was performed, APACHE II (Acute Physiology And Chronic Health Evaluation - scale for the evaluation of various acute and chronic diseases), Mannheim peritoneal index, albumin-globulin ratio, leukocyte index of intoxication were calculated.Results.During the 10-year period change in the microbial landscape of peritoneal exudate in patients with postoperative peritonitis was registered, with a statistically significant decrease in representation of Enterobacter, Staphylococcus, Escherichia coli, Pseudomonas aeruginosa bacteria, and increase in representation of Streptococci, Enterococci and anaerobic gram-negative cocci, Citrobacter, Klebsiella. Study results of microflora sensitivity to antibiotics showed that the vast majority (over 90%) of peritoneal infection pathogens has full or partial resistance to all antibiotics; antimicrobial effect increased in case of combined treatment using two or three drugs with a synergistic effect. With a decrease in the albumin-globulin ratio by 0.1 from 1.5 the mortality rate increased by 5-10%, and in patients with multiple organ failure was doubled (pConclusion. Prediction of postoperative peritonitis, complications and outcomes allows their timely prevention and treatment; basic conditions of preventing peritonitis are primary qualitative debridement of the abdominal cavity, the right choice of surgical volume, starting adequate antibiotic therapy, qualified perioperative anesthetic management and a complex of adequate pathogenetic treatment.
48
Dundek, Peter, Ladislav Holík, Tomáš Rohlík, Ladislav Hromádko, Valerie Vranová, Klement Rejšek, and Pavel Formánek. "Methods of plant root exudates analysis: a review." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 59, no. 3 (2011): 241–46. http://dx.doi.org/10.11118/actaun201159030241.
Full textAbstract:
The aim of this review is to summarise current knowledge on methods being used to determine individual compounds and properties of water-soluble plant root exudates. These compounds include amino acids, organic acids and simple sugars, as well as polysaccharides, proteins and organic substances. Qualitative composition of water-soluble root exudates and exudation rate are commonly measured with the aim of consequent synthetic preparation of plant root exudates to be supplied to soil to create artificial rhizosphere for different experimental purposes. Root exudates collection usually requires consequent filtration or centrifugation to remove solids, root detritus and microbial cell debris, and consequent concentration using an evaporator, lyophilizator or ultrafiltration. Methods used for analysis of total groups of compounds (total proteins and total carbohydrates) and total organic carbon are simple. On the other hand, HPLC or GS/MS are commonly used to analyse individual low molecular weight organic molecules (sugars, organic acids and amino acids) with separation using different columns. Other properties such as pH, conductivity or activity of different enzymes as well as gel electrophoresis of proteins are sometimes assessed. All of these methods are discussed in this work.
49
Norton, J. M., and G. E. Harman. "Responses of soil microorganisms to volatile exudates from germinating pea seeds." Canadian Journal of Botany 63, no. 6 (June 1, 1985): 1040–45. http://dx.doi.org/10.1139/b85-142.
Full textAbstract:
Responses of soil microorganisms to volatile exudates from germinating pea seeds of differing quality were determined. Germination of sclerotia of Rhizoctonia solani and Sclerotium rolfsii and subsequent hyphal growth were stimulated by exposure to volatiles from aged but not nonaged pea seeds. Hyphae grew preferentially toward aged seeds. In natural soil, bacterial and fungal populations showed significant increases after exposure to volatiles from aged seed. For example, Fusarium spp. and Pseudomonas spp. showed increases of 79 and 2200%, respectively, over their original population levels after a 48-h exposure to volatiles. Conversely, Pythium populations and associated seed-rotting potential of soil decreased in natural soils exposed to volatiles. In autoclaved soils infested with P. ultimum (PHP4), Pythium populations increased dramatically after exposure to volatiles from aged pea seeds. In soils infested with either soil fungi or bacteria in addition to P. ultimum, Pythium levels remained constant or decreased, respectively, with time of exposure. Exposure to the volatiles from aged pea seeds stimulated soil microbial activity. These results suggest that Pythium germlings, when unable to reach a host, are subjected to microbial antagonism in the presence of the native soil microflora. A decrease in cucumber seed rot coincided with decreases in Pythium numbers.
50
Yang, Ching-Hong, and David E. Crowley. "Rhizosphere Microbial Community Structure in Relation to Root Location and Plant Iron Nutritional Status." Applied and Environmental Microbiology 66, no. 1 (January 1, 2000): 345–51. http://dx.doi.org/10.1128/aem.66.1.345-351.2000.
Full textAbstract:
ABSTRACT Root exudate composition and quantity vary in relation to plant nutritional status, but the impact of the differences on rhizosphere microbial communities is not known. To examine this question, we performed an experiment with barley (Hordeum vulgare) plants under iron-limiting and iron-sufficient growth conditions. Plants were grown in an iron-limiting soil in root box microcosms. One-half of the plants were treated with foliar iron every day to inhibit phytosiderophore production and to alter root exudate composition. After 30 days, the bacterial communities associated with different root zones, including the primary root tips, nonelongating secondary root tips, sites of lateral root emergence, and older roots distal from the tip, were characterized by using 16S ribosomal DNA (rDNA) fingerprints generated by PCR-denaturing gradient gel electrophoresis (DGGE). Our results showed that the microbial communities associated with the different root locations produced many common 16S rDNA bands but that the communities could be distinguished by using correspondence analysis. Approximately 40% of the variation between communities could be attributed to plant iron nutritional status. A sequence analysis of clones generated from a single 16S rDNA band obtained at all of the root locations revealed that there were taxonomically different species in the same band, suggesting that the resolving power of DGGE for characterization of community structure at the species level is limited. Our results suggest that the bacterial communities in the rhizosphere are substantially different in different root zones and that a rhizosphere community may be altered by changes in root exudate composition caused by changes in plant iron nutritional status.