The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Luiz E. Bermudez - One of the best experts on this subject based on the ideXlab platform.
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Response of the respiratory mucosal cells to mycobacterium avium subsp. Hominissuis Microaggregate.
Archives of Microbiology, 2018Co-Authors: Lmar Babrak, Luiz E. BermudezAbstract:Mycobacterium avium: subsp. hominissuis (MAH) is an opportunistic pathogen that commonly infects immunocompromised individuals. Recently, we described an invasive phenotypic change MAH undergoes when incubated with lung airway epithelial host cells for 24 h, which is accompanied with Microaggregate formation in vitro. The Microaggregate phenotype also resulted in higher colonization in the lungs of mice early during infection. Previously, we identified genes highly regulated during Microaggregate formation and further characterized the function of two highly upregulated bacterial proteins, mycobacterial binding protein-1 (MBP-1) and mycobacterial inversion protein-1 (MIP-1), which were found to be involved in binding and invasion of the respiratory mucosa. While these studies are valuable in understanding the pathogenesis of MAH, they primarily investigated the bacteria during Microaggregate infection without commenting on the differences in the host response to Microaggregate and planktonic infection. The bacteria–host interaction between Microaggregates and epithelial cells was examined in a variety of assays. Using a transwell polarized epithelial cell model, Microaggregates translocated through the monolayer more efficiently than planktonic bacteria at set timepoints. In addition, during infection with Microaggregate and planktonic bacteria, host phosphorylated proteins were identified revealing differences in immune response, glutathione synthesis, and apoptosis. The host immune response was further investigated by measuring pro-inflammatory cytokine secretion during Microaggregate and planktonic infection of BEAS-2B bronchial epithelial cells. The epithelial cells secreted more CCL5 during infection with Microaggregates suggesting that this chemokine may play an important role during Microaggregate invasion. Subsequent experiments showed that Microaggregates are formed more efficiently in the presence of CCL5, suggesting that MAH had evolved a strategy to use the host response in its benefit. Collectively, this study establishes the different nature of infection by planktonic bacteria and Microaggregates.
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Microaggregate-associated protein involved in invasion of epithelial cells by Mycobacterium avium subsp. hominissuis.
Virulence, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Luiz E. BermudezAbstract:The environmental opportunistic pathogen Mycobacterium avium subsp hominissuis (MAH), a member of the nontuberculous mycobacteria (NTM) cluster, causes respiratory as well as disseminated disease in patients such as those with chronic respiratory illnesses or AIDS. Currently, there is no effective method to prevent NTM respiratory infections. The formation of mycobacterial Microaggregates comprises of phenotypic changes that lead to efficient adherence and invasion of the respiratory mucosa in vitro and in vivo. Microaggregate adhesion to the respiratory epithelium is mediated in part through the mycobacterial protein, MAV_3013 (MBP-1). Through DNA microarray analysis, the small hypothetical gene MAV_0831 (Microaggregate Invasion Protein-1, MIP-1) was identified as being upregulated during Microaggregate formation. When MIP-1 was overexpressed in poorly-invasive Mycobacterium smegmatis, it provided the bacterium the ability to bind and enter epithelial cells. In addition, incubating Microaggregates with recombinant MIP-1 protein enhanced the ability of Microaggregates to invade HEp-2 cells, and exposure to anti-MIP-1 immune serum reduced the invasion of the host epithelium. Through protein-protein interaction assays, MIP-1 was found to bind to the host protein filamin A, a cytoskeletal actin-binding protein integral to the modulation of host cell shape and migration. As visualized by immunofluorescence, filamin A was able to co-localize with Microaggregates and to a lesser extent planktonic bacteria. Invasion of HEp-2 cells by Microaggregates and planktonic bacteria was also inhibited by the addition of anti-filamin A antibody suggesting that filamin A plays an important role during infection. In addition, at earlier time points binding and invasion assay results suggest that MBP-1 participates significantly during the first interactions with the host cell while MIP-1 becomes important once the bacteria adhere to the host epithelium. In summary, we have unveiled one more step associated with MAH crossing the respiratory mucosa.
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the environment of mycobacterium avium subsp hominissuis Microaggregates induces synthesis of small proteins associated with efficient infection of respiratory epithelial cells
Infection and Immunity, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.
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The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells
Infection and immunity, 2014Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.
Lmar Babrak - One of the best experts on this subject based on the ideXlab platform.
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Response of the respiratory mucosal cells to mycobacterium avium subsp. Hominissuis Microaggregate.
Archives of Microbiology, 2018Co-Authors: Lmar Babrak, Luiz E. BermudezAbstract:Mycobacterium avium: subsp. hominissuis (MAH) is an opportunistic pathogen that commonly infects immunocompromised individuals. Recently, we described an invasive phenotypic change MAH undergoes when incubated with lung airway epithelial host cells for 24 h, which is accompanied with Microaggregate formation in vitro. The Microaggregate phenotype also resulted in higher colonization in the lungs of mice early during infection. Previously, we identified genes highly regulated during Microaggregate formation and further characterized the function of two highly upregulated bacterial proteins, mycobacterial binding protein-1 (MBP-1) and mycobacterial inversion protein-1 (MIP-1), which were found to be involved in binding and invasion of the respiratory mucosa. While these studies are valuable in understanding the pathogenesis of MAH, they primarily investigated the bacteria during Microaggregate infection without commenting on the differences in the host response to Microaggregate and planktonic infection. The bacteria–host interaction between Microaggregates and epithelial cells was examined in a variety of assays. Using a transwell polarized epithelial cell model, Microaggregates translocated through the monolayer more efficiently than planktonic bacteria at set timepoints. In addition, during infection with Microaggregate and planktonic bacteria, host phosphorylated proteins were identified revealing differences in immune response, glutathione synthesis, and apoptosis. The host immune response was further investigated by measuring pro-inflammatory cytokine secretion during Microaggregate and planktonic infection of BEAS-2B bronchial epithelial cells. The epithelial cells secreted more CCL5 during infection with Microaggregates suggesting that this chemokine may play an important role during Microaggregate invasion. Subsequent experiments showed that Microaggregates are formed more efficiently in the presence of CCL5, suggesting that MAH had evolved a strategy to use the host response in its benefit. Collectively, this study establishes the different nature of infection by planktonic bacteria and Microaggregates.
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The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells
2016Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha A J. Rose, Tiffany B Kornberg, Luiz A E. BermudezaAbstract:“Mycobacterium avium subsp. hominissuis ” is an opportunistic environmental pathogen that causes respiratory illness in im-munocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the air-ways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microar-ray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 im-mune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmu-noprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal micros-copy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the de
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Microaggregate-associated protein involved in invasion of epithelial cells by Mycobacterium avium subsp. hominissuis.
Virulence, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Luiz E. BermudezAbstract:The environmental opportunistic pathogen Mycobacterium avium subsp hominissuis (MAH), a member of the nontuberculous mycobacteria (NTM) cluster, causes respiratory as well as disseminated disease in patients such as those with chronic respiratory illnesses or AIDS. Currently, there is no effective method to prevent NTM respiratory infections. The formation of mycobacterial Microaggregates comprises of phenotypic changes that lead to efficient adherence and invasion of the respiratory mucosa in vitro and in vivo. Microaggregate adhesion to the respiratory epithelium is mediated in part through the mycobacterial protein, MAV_3013 (MBP-1). Through DNA microarray analysis, the small hypothetical gene MAV_0831 (Microaggregate Invasion Protein-1, MIP-1) was identified as being upregulated during Microaggregate formation. When MIP-1 was overexpressed in poorly-invasive Mycobacterium smegmatis, it provided the bacterium the ability to bind and enter epithelial cells. In addition, incubating Microaggregates with recombinant MIP-1 protein enhanced the ability of Microaggregates to invade HEp-2 cells, and exposure to anti-MIP-1 immune serum reduced the invasion of the host epithelium. Through protein-protein interaction assays, MIP-1 was found to bind to the host protein filamin A, a cytoskeletal actin-binding protein integral to the modulation of host cell shape and migration. As visualized by immunofluorescence, filamin A was able to co-localize with Microaggregates and to a lesser extent planktonic bacteria. Invasion of HEp-2 cells by Microaggregates and planktonic bacteria was also inhibited by the addition of anti-filamin A antibody suggesting that filamin A plays an important role during infection. In addition, at earlier time points binding and invasion assay results suggest that MBP-1 participates significantly during the first interactions with the host cell while MIP-1 becomes important once the bacteria adhere to the host epithelium. In summary, we have unveiled one more step associated with MAH crossing the respiratory mucosa.
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the environment of mycobacterium avium subsp hominissuis Microaggregates induces synthesis of small proteins associated with efficient infection of respiratory epithelial cells
Infection and Immunity, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.
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The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells
Infection and immunity, 2014Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.
Wulf Amelung - One of the best experts on this subject based on the ideXlab platform.
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Spatial organization of soil Microaggregates
Geoderma, 2021Co-Authors: Eva Lehndorff, Andrei Rodionov, Lutz Plümer, Peter Rottmann, B. Spiering, Stefan Dultz, Wulf AmelungAbstract:Abstract The physical arrangement of compounds in soil Microaggregates is controlling many ecosystem functions such as soil stability and C sequestration. However, little is known about the spatial arrangement of organic and inorganic compounds in soil Microaggregates, due to the lack of in-situ analyses of undisturbed material. We hypothesized that Microaggregates are spatially organized due to interactions between organic matter and mineral phases. To test this, we separated the water stable, occluded, large and small Microaggregate fractions (250–53 and 53–20 µm, 60 J ml−1 dispersion energy) from Ap horizons of a toposequence of sandy to loamy Luvisols (Germany) with increasing clay contents (19 to 35% clay), and subjected in total 60 individual aggregates to elemental mapping by electron probe micro analysis (EPMA), which recorded C, N, P, Al, Fe, Ca, K, Cl, and Si contents at 1 × 1 µm resolution. Stoichiometric element ratios characteristic for organic and inorganic matter were used to define discrete components of the aggregates and analyze their spatial arrangement. We found a pronounced heterogeneity in content and arrangement of discrete aggregate components, which was not reproducible for different specimens from the same soil Microaggregate fraction, and thus largely independent of clay content in soil. However, nearest neighbor analyses revealed close spatial correlations between plant detritus (C:N app. 100:10) and microbial organic matter (C:N app. 10:1) indicating a spatial relationship between source and consumer. There was no systematic relationship between soil minerals and organic matter, suggesting that well-established macroscale correlations between contents of pedogenic oxides and clay minerals with soil organic matter storage do not apply to soil Microaggregates.
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Spatial organization of soil Microaggregates
2020Co-Authors: Eva Lehndorff, Wulf Amelung, Peter Rottmann, B. Spiering, Nele Meyer, Andrey Radionov, Lutz Plümmer, Stefan DultzAbstract:<p>The physical arrangement of soil compounds in Microaggregates is important in many ways, e.g. by controlling soil stability and C sequestration. However, little is known about the spatial arrangement of organic and inorganic compounds in soil Microaggregates, due to the lack of in-situ analyses in undisturbed material. Here we hypothesize that Microaggregates are spatially organized, resulting in deterministic, predictable spatial patterns of different organic matter and mineral phases and that this organization depends on the abundance of specific phases such as on clay mineral content. We separated the water stable, occluded large and small Microaggregate fractions from Ap horizons of a sequence of sandy to loamy Luvisols (19 to 35% clay, Scheyern, Germany) and subjected in total 60 individual aggregates to elemental mapping by electron probe micro analysis (EPMA), which recorded C, N, P, Al, Fe, Ca, K, Cl, and Si contents at &#181;m scale resolution. Spatial arrangements of soil organic matter and soil minerals were extracted using cluster analyses. We found a pronounced heterogeneity in aggregate structure and composition, which was not reproducible and largely independent from clay content in soil. However, neighborhood analyses revealed close spatial correlations between organic matter debris (C:N app. 100:10) and microbial organic matter (C:N app. 10:1) indicating a spatial relationship between source and consumer. There was no systematic relationship between soil minerals and organic matter, suggesting that well-established macroscale correlations between contents of pedogenic oxides and clay minerals with soil organic matter storage do not apply to soil Microaggregates.</p>
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short term impacts of forest clear cut on p accessibility in soil Microaggregates an oxygen isotope study
Geoderma, 2018Co-Authors: Nina Siebers, Sara L Bauke, Wulf Amelung, Federica TamburiniAbstract:Abstract Forest clear-cuts may have severe effects on the soil structure and related nutrient cycling, though with yet unknown consequences for nutrient pools such as phosphorus (P) within Microaggregates. We sampled the bulk mineral topsoil prior to clear cut as well as 1 and 2 years thereafter from the experimental forest site Wustebach, Germany, and we assessed the degree of oxygen isotope exchange in HCl-extractable soil phosphate of two Microaggregate size fractions ( 18 O-labeled water. We found that after the clear-cut, Microaggregate phosphates exchanged significantly more oxygen with the incubation water than before clear cut. One and two years after clear cut, the respective δ 18 O values of soil phosphates (δ 18 O P,HCl ) were elevated by 16 and 38% (
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Microaggregates in soils
Journal of Plant Nutrition and Soil Science, 2018Co-Authors: Kai Uwe Totsche, Claudia Knief, Martin Hubert Gerzabek, Erwin Klumpp, Eva Lehndorff, Robert Mikutta, Georg Guggenberger, Stephan Peth, Wulf Amelung, Alexander T PrechtelAbstract:All soils harbor Microaggregates, i.e., compound soil structures smaller than 250 µm. These Microaggregates are composed of diverse mineral, organic and biotic materials that are bound together during pedogenesis by various physical, chemical and biological processes. Consequently, Microaggregates can withstand strong mechanical and physicochemical stresses and survive slaking in water, allowing them to persist in soils for several decades. Together with the physiochemical heterogeneity of their surfaces, the three-dimensional structure of Microaggregates provides a large variety of ecological niches that contribute to the vast biological diversity found in soils. As reported for larger aggregate units, Microaggregates are composed of smaller building units that become more complex with increasing size. In this context, organo-mineral associations can be considered structural units of soil aggregates and as nanoparticulate fractions of the Microaggregates themselves. The mineral phases considered to be the most important as Microaggregate forming materials are the clay minerals and Fe- and Al-(hydr)oxides. Within Microaggregates, minerals are bound together primarily by physicochemical and chemical interactions involving cementing and gluing agents. The former comprise, among others, carbonates and the short-range ordered phases of Fe, Mn, and Al. The latter comprise organic materials of diverse origin and probably involve macromolecules and macromolecular mixtures. Work on Microaggregate structure and development has largely focused on organic matter stability and turnover. However, little is known concerning the role Microaggregates play in the fate of elements like Si, Fe, Al, P, and S. More recently, the role of Microaggregates in the formation of microhabitats and the biogeography and diversity of microbial communities has been investigated. Little is known regarding how Microaggregates and their properties change in time, which strongly limits our understanding of micro-scale soil structure dynamics. Similarly, only limited information is available on the mechanical stability of Microaggregates, while essentially nothing is known about the flow and transport of fluids and solutes within the micro- and nanoporous Microaggregate systems. Any quantitative approaches being developed for the modeling of formation, structure and properties of Microaggregates are, therefore, in their infancy. We respond to the growing awareness of the importance of Microaggregates for the structure, properties and functions of soils by reviewing what is currently known about the formation, composition and turnover of Microaggregates. We aim to provide a better understanding of their role in soil function, and to present the major unknowns in current Microaggregate research. We propose a harmonized concept for aggregates in soils that explicitly considers the structure and build-up of Microaggregates and the role of organo-mineral associations. We call for experiments, studies and modeling endeavors that will link information on aggregate forming materials with their functional properties across a range of scales in order to better understand Microaggregate formation and turnover. Finally, we hope to inspire a novel cohort of soil scientists that they might focus their research on improving our understanding of the role of Microaggregates within the system of aggregates and so help to develop a unified and quantitative concept of aggregation processes in soils.
Keith Paustian - One of the best experts on this subject based on the ideXlab platform.
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aggregate associated soil organic matter as an ecosystem property and a measurement tool
Soil Biology & Biochemistry, 2014Co-Authors: Keith PaustianAbstract:Abstract Our 2000 paper Soil macroaggregate turnover and Microaggregate formation: A mechanism for C sequestration under no-tillage agriculture had its genesis in attempts to identify and isolate soil organic matter (SOM) fractions that reflect the impacts of climate, soil physiochemical properties and physical disturbance on the soil organic carbon balance. A key prerequisite for the investigation was the development of a simple device to isolate the Microaggregates (53–250 μm) contained within stable (i.e., resistant to slaking) macroaggregates (>250 μm) obtained by conventional wet-sieving. By comparing the abundance and C content of micro-within-macroaggregates, the size distribution of intra-aggregate particulate organic matter (iPOM) and isotopically-based estimates of the age of the organic matter in the different fractions, we were able to corroborate our hypothesis that the absence of tillage (i.e., in no-till and native soils) promotes greater longevity of newly-formed macroaggregates, resulting in greater SOM stabilization in Microaggregates formed within stable macroaggregates. Follow-up research has indicated that the Microaggregate-within-macroaggregate fraction is 1) potentially a robust indicator for management-induced SOC changes over decadal time scales, 2) of biological origin and therefore useful in interpreting impacts of soil biota on soil C and N dynamics, but not in-situ CO 2 and N 2 O fluxes, 3) useful in complimentary chemical and spectroscopic approaches to relate SOM dynamics to soil structure and attributes of the soil pore space, and 4) a good candidate for being incorporated into models as a measurable fraction.
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carbon sequestration in Microaggregates of no tillage soils with different clay mineralogy
Soil Science Society of America Journal, 2004Co-Authors: Karolien Denef, Roel Merckx, Keith PaustianAbstract:Identification of diagnostic soil organic matter (SOM) fractions and the mechanisms controlling their formation and turnover is critical for better understanding of C dynamics in soils. Enhanced Microaggregate formation and stabilization of C due to reduced macroaggregate turnover has been proposed as a mechanism promoting C sequestration in no-tillage (NT) compared with conventional tillage (CT) systems in temperate soils dominated by 2:1 clay mineralogy. We evaluated the contribution of macroaggregate-protected Microaggregates to total soil organic carbon (SOC) sequestration in NT relative to CT in three soils differing in clay mineralogy: a 2:1 clay-dominated soil (2:1), a soil with mixed clay mineralogy [2:1 and 1:11 and oxides (mixed), and a soil dominated by (1:1) clay minerals and oxides (1:1). Microaggregates (mM) were isolated from macroaggregates from 0- to 5- and 5- to 20-cm soil layers. Particulate organic matter (POM) located within the Microaggregates (intra-mM-POM) was separated from POM outside of the Microaggregates (inter-mM-POM) and the mineral fraction of the Microaggregates (mineral-mM). In all three soils, total SOC as well as Microaggregate-associated C (mM-C) was greater with NT compared with CT. Although less than half of the total SOC under NT was associated with the Microaggregate fraction, more than 90% of the total difference in SOC between NT and CT was explained by the difference in mM-C in all three soils. Thus, we identified and isolated a fraction that explains almost the entire difference in total SOC between NT and CT across soils characterized by drastically different clay mineralogy.
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soil macroaggregate turnover and Microaggregate formation a mechanism for c sequestration under no tillage agriculture
Soil Biology & Biochemistry, 2000Co-Authors: E T Elliott, Keith PaustianAbstract:Soil disturbance from tillage is a major cause of organic matter depletion and reduction in the number and stability of soil aggregates when native ecosystems are converted to agriculture. No-till (NT) cropping systems usually exhibit increased aggregation and soil organic matter relative to conventional tillage (CT). However, the extent of soil organic matter changes in response to NT management varies between soils and the mechanisms of organic matter stabilization in NT systems are unclear. We evaluated a conceptual model which links the turnover of aggregates to soil organic matter dynamics in NT and CT systems; we argue that the rate of macroaggregate formation and degradation (i.e. aggregate turnover) is reduced under NT compared to CT and leads to a formation of stable Microaggregates in which carbon is stabilized and sequestered in the long term. Therefore, the link between macroaggregate turnover, Microaggregate formation, and C stabilization within Microaggregates partly determines the observed soil organic matter increases under NT.
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soil structure and organic matter i distribution of aggregate size classes and aggregate associated carbon
Soil Science Society of America Journal, 2000Co-Authors: Keith Paustian, E T Elliott, C CombrinkAbstract:Cultivation reduces soil C content and changes the distribution and stability of soil aggregates. We investigated the effect of cultivation intensity on aggregate distribution and aggregate C in three soils dominated by 2:1 clay mineralogy and one soil characterized by a mixed (2:1 and 1:1) mineralogy. Each site had native vegetation (NV), no-tillage (NT), and conventional tillage (CT) treatments. Slaked (i.e., air-dried and fast-rewetted) and capillary rewetted soils were separated into four aggregate-size classes ( 2000 μm) by wet sieving. In rewetted soils, the proportion of macroaggregates accounted for 85% of the dry soil weight and was similar across management treatments. In contrast, aggregate distribution from slaked soils increasingly shifted toward more Microaggregates and fewer macroaggregates with increasing cultivation intensity. In soils dominated by 2:1 clay mineralogy, the C content of macroaggregates was 1.65 times greater compared to Microaggregates. These observations support an aggregate hierarchy in which Microaggregates are bound together into macroaggregates by organic binding agents in 2:1 clay-dominated soils. In the soil with mixed mineralogy, aggregate C did not increase with increasing aggregate size. At all sites, rewetted macro- and Microaggregate C and slaked Microaggregate C differed in the order NV > NT > CT, In contrast, slaked macroaggregate C concentration was similar across management treatments, except in the soil with mixed clay mineralogy. We conclude that increasing cultivation intensity leads to a loss of C-rich macroaggregates and an increase of C-depleted Microaggregates in soils that express aggregate hierarchy.
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aggregate and soil organic matter dynamics under conventional and no tillage systems
Soil Science Society of America Journal, 1999Co-Authors: E T Elliott, Keith PaustianAbstract:Tillage generally reduces aggregation and particulate organic matter (POM) content. We hypothesized that reduced C sequestration in conventional tillage (CT) compared with no-tillage (NT) is related to differences in aggregate turnover. Four soils (Haplustoll, Fragiudalf, Hapludalf, and Paleudalf), each with NT, CT, and native vegetation (NV) treatments, were separated into aggregates. Free light fraction (LF) and intraaggregate POM (iPOM) were isolated. At one site we used 13 C natural abundance to differentiate crop- and grassland-derived C. Concentrations of coarse iPOM C (250-2000 μm iPOM in macroaggregates), expressed on a per unit aggregate weight (g iPOM C kg -1 aggregate), did not differ between tillage treatments. In contrast, concentrations of fine iPOM C (53-250 μm iPOM in macroaggregates) were less in CT compared to NT macroaggregates. On a whole soil basis, fine iPOM C was on average 51% less in CT than in NT, and accounted for 21% of the total C difference between NT and CT. The concentration of free LF C was not affected by tillage, but was on average 45% less in the cultivated systems than NV. Proportions of crop-derived C in macroaggregates were similar in NT and CT, but were three times greater in Microaggregates from NT than Microaggregates from CT. We suggest that a faster turnover rate of macroaggregates in CT compared with NT leads to a slower rate of Microaggregate formation within macroaggregates and less stabilization of new SOM in free Microaggregates under CT.
Lia Danelishvili - One of the best experts on this subject based on the ideXlab platform.
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The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells
2016Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha A J. Rose, Tiffany B Kornberg, Luiz A E. BermudezaAbstract:“Mycobacterium avium subsp. hominissuis ” is an opportunistic environmental pathogen that causes respiratory illness in im-munocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the air-ways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microar-ray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 im-mune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmu-noprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal micros-copy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the de
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Microaggregate-associated protein involved in invasion of epithelial cells by Mycobacterium avium subsp. hominissuis.
Virulence, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Luiz E. BermudezAbstract:The environmental opportunistic pathogen Mycobacterium avium subsp hominissuis (MAH), a member of the nontuberculous mycobacteria (NTM) cluster, causes respiratory as well as disseminated disease in patients such as those with chronic respiratory illnesses or AIDS. Currently, there is no effective method to prevent NTM respiratory infections. The formation of mycobacterial Microaggregates comprises of phenotypic changes that lead to efficient adherence and invasion of the respiratory mucosa in vitro and in vivo. Microaggregate adhesion to the respiratory epithelium is mediated in part through the mycobacterial protein, MAV_3013 (MBP-1). Through DNA microarray analysis, the small hypothetical gene MAV_0831 (Microaggregate Invasion Protein-1, MIP-1) was identified as being upregulated during Microaggregate formation. When MIP-1 was overexpressed in poorly-invasive Mycobacterium smegmatis, it provided the bacterium the ability to bind and enter epithelial cells. In addition, incubating Microaggregates with recombinant MIP-1 protein enhanced the ability of Microaggregates to invade HEp-2 cells, and exposure to anti-MIP-1 immune serum reduced the invasion of the host epithelium. Through protein-protein interaction assays, MIP-1 was found to bind to the host protein filamin A, a cytoskeletal actin-binding protein integral to the modulation of host cell shape and migration. As visualized by immunofluorescence, filamin A was able to co-localize with Microaggregates and to a lesser extent planktonic bacteria. Invasion of HEp-2 cells by Microaggregates and planktonic bacteria was also inhibited by the addition of anti-filamin A antibody suggesting that filamin A plays an important role during infection. In addition, at earlier time points binding and invasion assay results suggest that MBP-1 participates significantly during the first interactions with the host cell while MIP-1 becomes important once the bacteria adhere to the host epithelium. In summary, we have unveiled one more step associated with MAH crossing the respiratory mucosa.
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the environment of mycobacterium avium subsp hominissuis Microaggregates induces synthesis of small proteins associated with efficient infection of respiratory epithelial cells
Infection and Immunity, 2015Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.
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The Environment of “Mycobacterium avium subsp. hominissuis” Microaggregates Induces Synthesis of Small Proteins Associated with Efficient Infection of Respiratory Epithelial Cells
Infection and immunity, 2014Co-Authors: Lmar Babrak, Lia Danelishvili, Sasha J. Rose, Tiffany Kornberg, Luiz E. BermudezAbstract:“Mycobacterium avium subsp. hominissuis” is an opportunistic environmental pathogen that causes respiratory illness in immunocompromised patients, such as those with cystic fibrosis as well as other chronic respiratory diseases. Currently, there is no efficient approach to prevent or treat M. avium subsp. hominissuis infection in the lungs. During initial colonization of the airways, M. avium subsp. hominissuis forms Microaggregates composed of 3 to 20 bacteria on human respiratory epithelial cells, which provides an environment for phenotypic changes leading to efficient mucosal invasion in vitro and in vivo. DNA microarray analysis was employed to identify genes associated with the Microaggregate phenotype. The gene encoding Microaggregate-binding protein 1 (MBP-1) (MAV_3013) is highly expressed during Microaggregate formation. When expressed in noninvasive Mycobacterium smegmatis, MBP-1 increased the ability of the bacteria to bind to HEp-2 epithelial cells. Using anti-MBP-1 immune serum, Microaggregate binding to HEp-2 cells was significantly reduced. By far-Western blotting, and verified by coimmunoprecipitation, we observed that MBP-1 interacts with the host cytoskeletal protein vimentin. As visualized by confocal microscopy, Microaggregates, as well as MBP-1, induced vimentin polymerization at the site of bacterium-host cell contact. Binding of Microaggregates to HEp-2 cells was inhibited by treatment with an antivimentin antibody, suggesting that MBP-1 expression is important for M. avium subsp. hominissuis adherence to the host cell. MBP-1 immune serum significantly inhibited M. avium subsp. hominissuis infection throughout the respiratory tracts of mice. This study characterizes a pathogenic mechanism utilized by M. avium subsp. hominissuis to bind and invade the host respiratory epithelium, suggesting new potential targets for the development of antivirulence therapy.