Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Data from: Mechanics of composite hydrogels approaching phase separation
Li, X. ; Rombouts, W.H. ; Gucht, J. van der; Vries, R.J. de; Dijksman, J.A. - \ 2019
For polymer-particle composites, limited thermodynamic compatibility of polymers and particles often leads to poor dispersal and agglomeration of the particles in the matrix, which negatively impacts the mechanics of composites. To study the impact of particle compatibility in polymer matrices on the mechanical properties of composites, we here study composite silica- protein based hydrogels. The polymer used is a previously studied telechelic protein-based polymer with end groups that form triple helices, and the particles are silica nanoparticles that only weakly associate with the polymer matrix. At 1mM protein polymer, up to 7% of silica nanoparticles can be embedded in the hydrogel. At higher concentrations the system phase separates. Oscillatory rheology shows that at high frequencies the particles strengthen the gels by acting as short-lived multivalent cross-links, while at low frequencies, the particles reduce the gel strength, presumably by sequestering part of the protein polymers in such a way that they can no longer contribute to the network strength. As is generally observed for polymer/particle composites, shear-induced polymer desorption from the particles leads to a viscous dissipation that strongly increases with increasing particle concentration. While linear rheological properties as function of particle concentration provide no signals for an approaching phase separation, this is very different for the non-linear rheology, especially fracture. Strain-at-break decreases rapidly with increasing particle concentration and vanishes as the phase boundary is approached, suggesting that the interfaces between regions of high and low particle densities in composites close to phase separation provide easy fracture planes.
Mechanics of composite hydrogels approaching phase separation
Li, Xiufeng ; Rombouts, Wolf ; Gucht, Jasper van der; Vries, Renko de; Dijksman, Joshua A. - \ 2019
PLoS ONE 14 (2019)1. - ISSN 1932-6203 - 14 p.

For polymer-particle composites, limited thermodynamic compatibility of polymers and particles often leads to poor dispersal and agglomeration of the particles in the matrix, which negatively impacts the mechanics of composites. To study the impact of particle compatibility in polymer matrices on the mechanical properties of composites, we here study composite silica- protein based hydrogels. The polymer used is a previously studied telechelic protein-based polymer with end groups that form triple helices, and the particles are silica nanoparticles that only weakly associate with the polymer matrix. At 1mM protein polymer, up to 7% of silica nanoparticles can be embedded in the hydrogel. At higher concentrations the system phase separates. Oscillatory rheology shows that at high frequencies the particles strengthen the gels by acting as short-lived multivalent cross-links, while at low frequencies, the particles reduce the gel strength, presumably by sequestering part of the protein polymers in such a way that they can no longer contribute to the network strength. As is generally observed for polymer/particle composites, shear-induced polymer desorption from the particles leads to a viscous dissipation that strongly increases with increasing particle concentration. While linear rheological properties as function of particle concentration provide no signals for an approaching phase separation, this is very different for the non-linear rheology, especially fracture. Strain-at-break decreases rapidly with increasing particle concentration and vanishes as the phase boundary is approached, suggesting that the interfaces between regions of high and low particle densities in composites close to phase separation provide easy fracture planes.

Nutrimetabolomics: An Integrative Action for Metabolomic Analyses in Human Nutritional Studies
Ulaszewska, Marynka M. ; Weinert, Christoph H. ; Trimigno, Alessia ; Portmann, Reto ; Andres Lacueva, Cristina ; Badertscher, René ; Brennan, Lorraine ; Brunius, Carl ; Bub, Achim ; Capozzi, Francesco ; Cialiè Rosso, Marta ; Cordero, Chiara E. ; Daniel, Hannelore ; Durand, Stéphanie ; Egert, Bjoern ; Ferrario, Paola G. ; Feskens, Edith J.M. ; Franceschi, Pietro ; Garcia-Aloy, Mar ; Giacomoni, Franck ; Giesbertz, Pieter ; González-Domínguez, Raúl ; Hanhineva, Kati ; Hemeryck, Lieselot Y. ; Kopka, Joachim ; Kulling, Sabine E. ; Llorach, Rafael ; Manach, Claudine ; Mattivi, Fulvio ; Migné, Carole ; Münger, Linda H. ; Ott, Beate ; Picone, Gianfranco ; Pimentel, Grégory ; Pujos-Guillot, Estelle ; Riccadonna, Samantha ; Rist, Manuela J. ; Rombouts, Caroline ; Rubert, Josep ; Skurk, Thomas ; Sri Harsha, Pedapati S.C. ; Meulebroek, Lieven Van; Vanhaecke, Lynn ; Vázquez-Fresno, Rosa ; Wishart, David ; Vergères, Guy - \ 2018
Molecular Nutrition & Food Research 63 (2018)1. - ISSN 1613-4125
GC–MS - LC–MS - metabolomics - NMR - nutrition
The life sciences are currently being transformed by an unprecedented wave of developments in molecular analysis, which include important advances in instrumental analysis as well as biocomputing. In light of the central role played by metabolism in nutrition, metabolomics is rapidly being established as a key analytical tool in human nutritional studies. Consequently, an increasing number of nutritionists integrate metabolomics into their study designs. Within this dynamic landscape, the potential of nutritional metabolomics (nutrimetabolomics) to be translated into a science, which can impact on health policies, still needs to be realized. A key element to reach this goal is the ability of the research community to join, to collectively make the best use of the potential offered by nutritional metabolomics. This article, therefore, provides a methodological description of nutritional metabolomics that reflects on the state-of-the-art techniques used in the laboratories of the Food Biomarker Alliance (funded by the European Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL)) as well as points of reflections to harmonize this field. It is not intended to be exhaustive but rather to present a pragmatic guidance on metabolomic methodologies, providing readers with useful “tips and tricks” along the analytical workflow.
Genome sequence of the rat gut bacterium Romboutsia ilealis CRIB
Gerritsen, J. ; Timmerman, H.M. ; Fuentes, S. ; Minnen, L.P. van; Panneman, H. ; Konstantinov, S.R. ; Rombouts, F.M. ; Gooszen, H.G. ; Akkermans, L.M.A. ; Smidt, H. ; Rijkers, G.T. - \ 2017
Romboutsia ilealis - PRJEB4727 - ERP004037
The rat illeum bacterium Romboutsia ilealis CRIB was sequenced and assembled, using a hybrid approach, consisting out of different data types (Illumina paired end, mate pair, PacBio), as well as a custom assembly workflow.
Recombinant Protein Polymers for Colloidal Stabilization and Improvement of Cellular Uptake of Diamond Nanosensors
Zheng, Tingting ; Perona Martínez, Felipe ; Storm, Ingeborg Maria ; Rombouts, Wolf ; Sprakel, Joris ; Schirhagl, Romana ; Vries, Renko De - \ 2017
Analytical Chemistry 89 (2017)23. - ISSN 0003-2700 - p. 12812 - 12820.
Fluorescent nanodiamonds are gaining increasing attention as fluorescent labels in biology in view of the fact that they are essentially nontoxic, do not bleach, and can be used as nanoscale sensors for various physical and chemical properties. To fully realize the nanosensing potential of nanodiamonds in biological applications, two problems need to be addressed: their limited colloidal stability, especially in the presence of salts, and their limited ability to be taken up by cells. We show that the physical adsorption of a suitably designed recombinant polypeptide can address both the colloidal stability problem and the problem of the limited uptake of nanodiamonds by cells in a very straightforward way, while preserving both their spectroscopic properties and their excellent biocompatibility.
Enhanced stiffness of silk-like fibers by loop formation in the corona leads to stronger gels
Rombouts, Wolf H. ; Domeradzka, Natalia E. ; Werten, Marc W.T. ; Leermakers, Frans A.M. ; Vries, Renko J. de; Wolf, Frits A. de; Gucht, Jasper van der - \ 2016
Biopolymers (2016). - ISSN 0006-3525 - p. 795 - 801.
fibers - hydrogels - protein polymers - rheology - self-assembly

We study the self-assembly of protein polymers consisting of a silk-like block flanked by two hydrophilic blocks, with a cysteine residue attached to the C-terminal end. The silk blocks self-assemble to form fibers while the hydrophilic blocks form a stabilizing corona. Entanglement of the fibers leads to the formation of hydrogels. Under oxidizing conditions the cysteine residues form disulfide bridges, effectively connecting two corona chains at their ends to form a loop. We find that this leads to a significant increase in the elastic modulus of the gels. Using atomic force microscopy, we show that this stiffening is due to an increase of the persistence length of the fibers. Self-consistent-field calculations indicate a slight decrease of the lateral pressure in the corona upon loop formation. We argue that this small decrease in the repulsive interactions affects the stacking of the silk-like blocks in the core, resulting in a more rigid fiber.

Nanoparticle-Templated Formation and Growth Mechanism of Curved Protein Polymer Fibrils
Pham, Thao T.H. ; Rombouts, Wolf H. ; Fokkink, Remco ; Stuart, Marc C.A. ; Cohen Stuart, Martien A. ; Kleijn, Mieke - \ 2016
Biomacromolecules 17 (2016)7. - ISSN 1525-7797 - p. 2392 - 2398.

We investigated the growth of biosynthetic protein polymers with templated curvature on pluronic nanospheres. The protein has a central silk-like block containing glutamic residues (SE) and collagen-like end-blocks (C). The SE blocks stack into filaments when their charge is removed (pH <5). Indeed, at low pH curved and circular fibers are formed at the surface of the nanospheres, which keep their shape after removal of the pluronics. The data reveal the mechanism of the templated fibril-growth: The growth of protein assemblies is nucleated in solution; small protein fibrils adsorb on the nanospheres, presumably due to hydrogen bond formation between the silk-like blocks and the pluronic PEO blocks. The surface of the pluronic particles templates further growth. At relatively low protein/pluronic weight ratios, only a fraction of the nanospheres bears protein fibers, pointing to a limiting amount of nuclei in solution. Because the nanospheres capture fibrils at an early stage of growth, they can be used to separate growth and nucleation rates in protein fibril formation. Moreover, the nanoparticle-templated growth of stable curved fibers opens ways to build proteinaceous nanocapsules from designed protein polymers

Workshop compost: een zegen voor bodem, opbrengst en boer
Haan, Janjo de - \ 2016
Wageningen, 60 aanwezigen. Overige auteurs: Piet Rombouts. Proj.nr. 3750204212
Workshop verhogen organische stof in de bodem; waarom en hoe?
Hanegraaf, Marjoleine - \ 2016
overige auteurs: Janjo de Haan, Piet Rombouts. Proj.nr. 3750204212
Composite hydrogels of bio-inspired protein polymers : mechanical and structural characterization
Rombouts, W.H. - \ 2015
Wageningen University. Promotor(en): Jasper van der Gucht. - Wageningen : Wageningen University - ISBN 9789462575721 - 172
gels - formation - proteins - polymers - networks - mechanical properties - formatie - eiwitten - polymeren - netwerken - mechanische eigenschappen

In this thesis we presented various combinations of custom-designed protein polymers that formed composite hydrogels. In chapter 2, composite hydrogels were prepared by mixing silk-like block copolymers (CP2SE48CP2) with collagen-like block copolymers (T9CR4T9). We found that by adding the collagen-like protein polymer the storage modulus, the critical stress and critical strain values of the composite hydrogels were significantly improved in comparison to the single networks. With cryo-transmission electron microscopy (cryo-TEM) we observed that the silk-like fibers were bundled in the presence of the collagen-like protein polymer, probably due to depletion attraction interactions. In follow-up research on these composite hydrogels in chapter 3, we tried to get more insight into the exact toughening mechanism and self-healing capabilities of the composite network by performing cyclic loading/unloading tests. We found that mechanical hysteresis occurred in these composite hydrogels. The energy that was dissipated could be split into two contributions: a part belonging to the permanent rupture of silk-like fibers, and a viscoelastic part belonging to the assembly and disassembly of collagen-like triple helices. Both these contributions increased as the concentration of the collagen-like protein polymer in the composite network was increased, resulting in toughening of the composite network. Furthermore, it was observed that the silk-like fiber network was not able to recover, while the composites could recover up to 70% of the original storage modulus after failure. In chapter 4 we studied composite networks of silk-like block copolymers (CP2SE48CP2) and a FMOC-functionalized dipeptide (FMOC-LG) which could both form fibers. With cryo-TEM and atomic force microscopy (AFM) we found that two different types of fibers were formed, indicating that orthogonal self-assembly occurred in this system. We found with rheology that the storage moduli of the composite fiber networks were significantly higher (75 kPa vs. 400 kPa) than that of the single networks. Strain-hardening present in the FMOC-LG fiber network disappeared when the silk-like protein polymer was present. In chapter 5 hydrogels with both physical and chemical crosslinks were prepared from collagen-like protein polymers (T9CRT9). The chemical crosslinks were introduced by crosslinking lysine residues present in the random-coil middle blocks with glutaraldehyde. We found with rheology that the order in which the physical and chemical networks were formed did not influence the final storage modulus of the hydrogel. Depending on the amount of glutaraldehyde added we found an increase of up to an order of magnitude in the storage modulus for the collagen-like hydrogels. To investigate effects on the nonlinear rheological properties cyclic loading/unloading tests were performed. It was observed that before hydrogel failure occurred no hysteresis was observed between consecutive cycles. Both physical and chemical crosslinks ruptured when the hydrogel was fractured. In chapter 6 we studied hydrogels formed by the co- assembly of an asymmetric silk-collagen-like protein polymer (SH8CR4T9) with a symmetric oppositely charged silk-like protein polymer (CP2SE48CP2). This was done in a step-wise approach: (1) the S blocks were co-assembled into silk-like fibers. (2) the T blocks were assembled into triple helical nodes by reducing the temperature. We confirmed with confocal laser scanning microscopy and NMR that both monomers were present in the same fibers. With rheology we found that these composite hydrogels did respond in a reversible manner to temperature changes, with which the mechanical strength of the hydrogel can be tuned. In chapter 7 hydrogel formation of a modified silk-like protein polymer with a cysteine-residue attached to the C-terminal side (CP2SH48CP2-Cys) was studied. With rheology we showed that hydrogels that were formed in oxidizing conditions, where disulfide-bridges could form, were much stronger than those formed in reducing conditions. Both hydrogels formed in oxidizing and reducing conditions showed a scaling of modulus versus concentration consistent with entangled semi-flexible networks. This result implied that the disulfide-bridges formed between cysteine-residues formed loops in the coronae of the fibers. The increase in mechanical strength of the fibers was related to the increase in persistence length of the fibers in oxidizing conditions observed with AFM. With self-consistent field theory-simulations it was shown that the formation of loops in the corona resulted in a slight reduction of the lateral pressure in the corona of the fibers. However, this effect is by itself not sufficient to cause a significant change in persistence length. Due to the reduction in lateral pressure, the stacking of monomers into fibers is probably influenced: fibers with a more crystalline structure and with less detects are formed, resulting in improved mechanical properties of the hydrogels. In the general discussion in chapter 8, we reflect on our work, discuss about future directions of research, and possible applications of protein polymers.

Scaling Behavior of Dendritic Nanoparticle Mobility in Semidilute Polymer Solutions
Kort, D.W. de; Rombouts, W.H. ; Hoeben, F.J.M. ; Janssen, H.M. ; As, H. van; Duynhoven, J.P.M. van - \ 2015
Macromolecules 48 (2015)20. - ISSN 0024-9297 - p. 7585 - 7591.
In our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly(ethylene glycol) (PEG, Mw = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (dh = 3.4–11.0 nm) and with internal 19F moieties allow for background-free 19F NMR diffusion measurements. This way, we were able to assess the self-diffusion coefficients as a function of particle diameter and length scales (correlation length, tube diameter, polymer radius of gyration) with high resolution. Scaling arguments allowed us to visualize a clear crossover between particles probing a lower apparent viscosity to near macroviscosity when the nanoparticle size is comparable to the PEG polymer coil size. The same arguments are shown to correctly predict particle diffusion coefficients as a function of polymer concentration when the particles are smaller than the polymer coils.
Dolfijn met spionageapparatuur (interview met Mardik Leopold)
Leopold, Mardik - \ 2015
Reversible Temperature-Switching of Hydrogel Stiffness of Coassembled, Silk-Collagen-Like Hydrogels
Rombouts, W.H. ; Kort, D.W. de; Pham, T.T.H. ; Mierlo, C.P.M. van; Werten, M.W.T. ; Wolf, F.A. de; Gucht, J. van der - \ 2015
Biomacromolecules 16 (2015)8. - ISSN 1525-7797 - p. 2506 - 2513.
block-copolymers - gels - ph - gelatin - elastin - biosynthesis - proteins - polymers
Recombinant protein polymers, which can combine different bioinspired self-assembly motifs in a well-defined block sequence, have large potential as building blocks for making complex, hierarchically structured materials. In this paper we demonstrate the stepwise formation of thermosensitive hydrogels by combination of two distinct, orthogonal self-assembly mechanisms. In the first step, fibers are coassembled from two recombinant protein polymers: (a) a symmetric silk-like block copolymer consisting of a central silk-like block flanked by two soluble random coil blocks and (b) an asymmetric silk-collagen-like block copolymer consisting of a central random-coil block flanked on one side by a silk-like block and on the other side a collagen-like block. In the second step, induced by cooling, the collagen-like blocks form triple helices and thereby cross-link the fibers, leading to hydrogels with a thermo-reversibly switchable stiffness. Our work demonstrates how complex self-assembled materials can be formed through careful control of the self-assembly pathway.
Equivalent pathways in melding and gelation of well-defined biopolymer networks
Cingil, E.H. ; Rombouts, W.H. ; Gucht, J. van der; Cohen Stuart, M.A. ; Sprakel, J.H.B. - \ 2015
Biomacromolecules 16 (2015)1. - ISSN 1525-7797 - p. 304 - 310.
multiple-particle tracking - actin filament networks - microheterogeneity - copolymers - hydrogels
We use multiple particle tracking microrheology to study the melting and gelation behavior of well-defined collagen-inspired designer biopolymers expressed by the transgenic yeast P. Pastoris. The system consists of a hydrophilic random coil-like middle block and collagen-like end block. Upon cooling, the end blocks assemble into well-defined transient nodes with exclusively 3-fold functionality. We apply the method of time-cure superposition of the mean-square displacement of tracer beads embedded in the biopolymer matrix to study the kinetics and thermodynamics of approaching the gel point from both the liquid and the solid side. The melting point, gel point, and critical relaxation exponents are determined from the shift factors of the mean-square displacement and we discuss the use of dynamic scaling exponents to correctly determine the critical transition. Critical relaxation exponents obtained for different concentrations in both systems are compared with the currently existing dynamic models in literature. In our study, we find that, while the time scales of gelation and melting are different by orders of magnitude, and show inverse dependence on concentration, that the pathways followed are completely equivalent.
Duurzaam bodemgebruik op Brabantse zandgronden : Goede productie, handhaven bodemkwaliteit en schoon water als uitdaging
Postma, R. ; Rombouts, P. ; Haan, J.J. de; Harthoorn, L.F. - \ 2014
Bodem 24 (2014)6. - ISSN 0925-1650 - p. 10 - 12.
duurzaam bodemgebruik - zandgronden - grondwaterkwaliteit - nitraatuitspoeling - mestbeleid - landbouw en milieu - noord-brabant - limburg - sustainable land use - sandy soils - groundwater quality - nitrate leaching - manure policy - agriculture and environment
De landbouwpraktijk op de zuidoostelijke zandgronden heeft geleid tot hoge nitraatgehalten in grondwater en hoge fosfaattoestanden in de bodem. Het mestbeleid wordt daarom steeds verder aangescherpt, wat ten koste kan gaan van gewasopbrengsten en het organische stofgehalte in de bodem. Vandaar de vraag: is het mogelijk landbouwkundige en milieukundige doelen te verenigen?
Synergistic stiffening in double-fiber networks
Rombouts, W.H. ; Giesbers, M. ; Lent, J.W.M. van; Wolf, F.A. de; Gucht, J. van der - \ 2014
Biomacromolecules 15 (2014)4. - ISSN 1525-7797 - p. 1233 - 1239.
gelation properties - living cells - hydrogels - gels - copolymers - dipeptides - strength
Many biological materials are composite structures, interpenetrating networks of different types of fibers. The composite nature of such networks leads to superior mechanical properties, but the origin of this mechanical synergism is still poorly understood. Here we study soft composite networks, made by mixing two self-assembling fiber-forming components. We find that the elastic moduli of the composite networks significantly exceed the sum of the moduli of the two individual networks. This mechanical enhancement is in agreement with recent simulations, where it was attributed to a suppression of non-affine deformation modes in the most rigid fiber network due to the reaction forces in the softer network. The increase in affinity also causes a loss of strain hardening and an increase in the critical stress and stain at which the network fails.
What is the future for therapies derived from the microbiome (pharmabiotics)?
Rijkers, G.T. ; Mulder, L. ; Rombouts, F.M. ; Akkermans, L.M.A. - \ 2013
In: Probiotic bacteria and their effect on human health and well-being / Guarino, A., Quigley, E.M.M., Walker, W.A., Basel : Karger (World Review of Nutrition and Dietetics 107) - ISBN 9783318023244 - p. 186 - 196.
The personal gut microbiota is characterized by species composition, enterotype, and bacterial gene counts. Gut microbiota can be viewed as a complex microecosystem. Regulation of the diversity and stability of the gut microbiota is therefore critical for the development of future therapies. The areas with high potential for personalized management of gut microbiota are obesity and the metabolic syndrome, prevention and control of (recurrent) infections, immune-mediated disorders, and the gut-brain axis. A true and deeper understanding of the interaction between the microbiota and the host, as well as a better matching of probiotic and prebiotic mechanisms with clinical indications will be required for successful future implementation of these therapies.
Enhanced rigidity and rupture strength of composite hydrogel networks of bio-inspired block copolymers
Rombouts, W.H. ; Colomb-Delsuc, M. ; Werten, M.W.T. ; Otto, S. ; Wolf, F.A. de; Gucht, J. van der - \ 2013
Soft Matter 9 (2013). - ISSN 1744-683X - p. 6936 - 6942.
stereocomplex formation - biomedical applications - periodic polypeptides - reversible hydrogels - triblock copolymers - secreted production - actin networks - gels - polymers - proteins
We study self-assembled composite networks consisting of silk-like protein fibers dispersed in a soft gel matrix formed by collagen-like block copolymers. Rheological analysis shows that the composite networks have significantly higher storage moduli than either of the single networks. This is caused by bundling of the fibrils due to depletion attraction induced by the collagen-like polymers. Moreover, the soft background network significantly modifies the non-linear response of the fibrillar network; the strain-hardening disappears almost completely and the stress and strain at which the gel breaks increase strongly, resulting in tougher hydrogels.
Disulfide bond-stabilized physical gels of an asymmetric collagen-inspired telechelic protein polymer
Pham, T.H.T. ; Skrzeszewska, P.J. ; Werten, M.W.T. ; Rombouts, W.H. ; Cohen Stuart, M.A. ; Wolf, F.A. de; Gucht, J. van der - \ 2013
Soft Matter 9 (2013). - ISSN 1744-683X - p. 6391 - 6397.
We designed and produced an asymmetric collagen-inspired telechelic protein polymer with end blocks that can form triple helices of different thermal stabilities. Both end blocks consist of a motif that can form triple helices at low temperature, but one of these blocks carries an additional cysteine residue at the end. The cysteine residues can form disulfide bridges under oxidizing conditions, leading to dimer formation. This effectively stabilizes the triple helices, resulting in a double melting peak in differential scanning calorimetry: one corresponding to helices without disulfide bridges and one at significantly higher temperature, corresponding to stabilized helices. Under reducing conditions, the disulfide bridges are broken and the molecule behaves similarly to the symmetric variant. We find that these disulfide bridges also lead to an increase of the elastic modulus of the helical polymer network, probably because the number of helices in the system increases and also the disulfide bridges can crosslink different triple helical nodes.
Correlation between protection against sepsis by probiotic therapy and stimulation of a novel bacterial phylotype
Gerritsen, J. ; Timmerman, H.M. ; Fuentes, S. ; Minnen, L.P. van; Panneman, H. ; Konstantinov, S.R. ; Rombouts, F.M. ; Gooszen, H.G. ; Akkermans, L.M.A. ; Smidt, H. ; Rijkers, G.T. - \ 2011
Applied and Environmental Microbiology 77 (2011)21. - ISSN 0099-2240 - p. 7749 - 7756.
severe acute-pancreatitis - ribosomal-rna - necrotizing pancreatitis - clinical-course - sequence data - overgrowth - gut - translocation - microbiota - cirrhosis
Prophylactic probiotic therapy has shown beneficial effects in an experimental rat model for acute pancreatitis on the health status of the animals. Mechanisms by which probiotic therapy interferes with severity of acute pancreatitis and associated sepsis, however, are poorly understood. The aims of this study were to identify the probiotic-induced changes in the gut microbiota and to correlate these changes to disease outcome. Duodenum and ileum samples were obtained from healthy and diseased rats subjected to pancreatitis for 7 days and prophylactically treated with either a multispecies probiotic mixture or a placebo. Intestinal microbiota was characterized by terminal-restriction fragment length polymorphism (T-RFLP) analyses of PCR-amplified 16S rRNA gene fragments. These analyses showed that during acute pancreatitis the host-specific ileal microbiota was replaced by an “acute pancreatitis-associated microbiota.” This replacement was not reversed by administration of the probiotic mixture. An increase, however, was observed in the relative abundance of a novel bacterial phylotype most closely related to Clostridium lituseburense and referred to as commensal rat ileum bacterium (CRIB). Specific primers targeting the CRIB 16S rRNA gene sequence were developed to detect this phylotype by quantitative PCR. An ileal abundance of CRIB 16S rRNA genes of more than 7.5% of the total bacterial 16S rRNA gene pool was correlated with reduced duodenal bacterial overgrowth, reduced bacterial translocation to remote organs, improved pancreas pathology, and reduced proinflammatory cytokine levels in plasma. Our current findings and future studies involving this uncharacterized bacterial phylotype will contribute to unraveling one of the potential mechanisms of probiotic therapy.
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