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Vanderkelen L, Van Herreweghe JM, Michiels CW. Lysozyme Inhibitors as Tools for Lysozyme Profiling: Identification and Antibacterial Function of Lysozymes in the Hemolymph of the Blue Mussel. Molecules 2023; 28:7071. [PMID: 37894549 PMCID: PMC10609593 DOI: 10.3390/molecules28207071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2023] [Revised: 10/05/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Lysozymes are universal components of the innate immune system of animals that kill bacteria by hydrolyzing their main cell wall polymer, peptidoglycan. Three main families of lysozyme have been identified, designated as chicken (c)-, goose (g)- and invertebrate (i)-type. In response, bacteria have evolved specific protein inhibitors against each of the three lysozyme families. In this study, we developed a serial array of three affinity matrices functionalized with a c-, g-, and i-type inhibitors for lysozyme typing, i.e., to detect and differentiate lysozymes in fluids or extracts from animals. The tool was validated on the blue mussel (Mytilus edulis), whose genome carries multiple putative i-, g-, and c-type lysozyme genes. Hemolymph plasma of the animals was found to contain both i- and g-type, but not c-type lysozyme. Furthermore, hemolymph survival of Aeromonas hydrophila and E. coli strains lacking or overproducing the i- type or g-type lysozyme inhibitor, respectively, was analyzed to study the role of the two lysozymes in innate immunity. The results demonstrated an active role for the g-type lysozyme in the innate immunity of the blue mussel, but failed to show a contribution by the i-type lysozyme. Lysozyme profiling using inhibitor-based affinity chromatography will be a useful novel tool for studying animal innate immunity.
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Affiliation(s)
| | | | - Chris W. Michiels
- Leuven Food Science and Nutrition Research Centre (LFoRCe), Lab Food Microbiology, Department Microbial and Molecular Systems, KU Leuven, B-3001 Leuven, Belgium; (L.V.); (J.M.V.H.)
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2
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Goedseels M, Michiels CW. Cell Envelope Modifications Generating Resistance to Hop Beta Acids and Collateral Sensitivity to Cationic Antimicrobials in Listeria monocytogenes. Microorganisms 2023; 11:2024. [PMID: 37630584 PMCID: PMC10457916 DOI: 10.3390/microorganisms11082024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 08/03/2023] [Accepted: 08/04/2023] [Indexed: 08/27/2023] Open
Abstract
Hop beta acids (HBAs) are characteristic compounds from the hop plant that are of interest for their strong antimicrobial activity. In this work, we report a resistance mechanism against HBA in the foodborne pathogen Listeria monocytogenes. Using an evolution experiment, we isolated two HBA-resistant mutants with mutations in the mprF gene, which codes for the Multiple Peptide Resistance Factor, an enzyme that confers resistance to cationic peptides and antibiotics in several Gram-positive bacteria by lysinylating membrane phospholipids. Besides the deletion of mprF, the deletion of dltA, which mediates the alanylation of teichoic acids, resulted in increased HBA resistance, suggesting that resistance may be caused by a reduction in positive charges on the cell surface. Additionally, we found that this resistance is maintained at low pH, indicating that the resistance mechanism is not solely based on electrostatic interactions of HBA with the cell surface. Finally, we showed that the HBA-resistant mutants display collateral sensitivity to the cationic antimicrobials polymyxin B and nisin, which may open perspectives for combining antimicrobials to prevent resistance development.
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Affiliation(s)
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems, KU Leuven, B-3000 Leuven, Belgium;
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3
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Sun L, Van Loey A, Buvé C, Michiels CW. Experimental Evolution Reveals a Novel Ene Reductase That Detoxifies α,β-Unsaturated Aldehydes in Listeria monocytogenes. Microbiol Spectr 2023; 11:e0487722. [PMID: 37036358 PMCID: PMC10269891 DOI: 10.1128/spectrum.04877-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/17/2023] [Indexed: 04/11/2023] Open
Abstract
The plant essential oil component trans-cinnamaldehyde (t-CIN) exhibits antibacterial activity against a broad range of foodborne pathogenic bacteria, including L. monocytogenes, but its mode of action is not fully understood. In this study, several independent mutants of L. monocytogenes with increased t-CIN tolerance were obtained via experimental evolution. Whole-genome sequencing (WGS) analysis revealed single-nucleotide-variation mutations in the yhfK gene, encoding an oxidoreductase of the short-chain dehydrogenases/reductases superfamily, in each mutant. The deletion of yhfK conferred increased sensitivity to t-CIN and several other α,β-unsaturated aldehydes, including trans-2-hexenal, citral, and 4-hydroxy-2-nonenal. The t-CIN tolerance of the deletion mutant was restored via genetic complementation with yhfK. Based on a gas chromatography-mass spectrometry (GC-MS) analysis of the culture supernatants, it is proposed that YhfK is an ene reductase that converts t-CIN to 3-phenylpropanal by reducing the C=C double bond of the α,β-unsaturated aldehyde moiety. YhfK homologs are widely distributed in Bacteria, and the deletion of the corresponding homolog in Bacillus subtilis also caused increased sensitivity to t-CIN and trans-2-hexenal, suggesting that this protein may have a conserved function to protect bacteria against toxic α,β-unsaturated aldehydes in their environments. IMPORTANCE While bacterial resistance against clinically used antibiotics has been well studied, less is known about resistance against other antimicrobials, such as natural compounds that could replace traditional food preservatives. In this work, we report that the food pathogen Listeria monocytogenes can rapidly develop an elevated tolerance against t-cinnamaldehyde, a natural antimicrobial from cinnamon, by single base pair changes in the yhfK gene. The enzyme encoded by this gene is an oxidoreductase, but its substrates and precise role were hitherto unknown. We demonstrate that the enzyme reduces the double bond in t-cinnamaldehyde and thereby abolishes its antibacterial activity. Furthermore, the mutations linked to t-CIN tolerance increased bacterial sensitivity to a related compound, suggesting that they modify the substrate specificity of the enzyme. Since the family of oxidoreductases to which YhfK belongs is of great interest in the mediation of stereospecific reactions in biocatalysis, our work may also have unanticipated application potential in this field.
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Affiliation(s)
- Lei Sun
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Ann Van Loey
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Carolien Buvé
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
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Lenaerts L, Passos TF, Gayán E, Michiels CW, Nitschke M. Hurdle Technology Approach to Control Listeria monocytogenes Using Rhamnolipid Biosurfactant. Foods 2023; 12:foods12030570. [PMID: 36766099 PMCID: PMC9914285 DOI: 10.3390/foods12030570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/21/2023] [Accepted: 01/25/2023] [Indexed: 02/01/2023] Open
Abstract
This study evaluates the combination of mild heat with a natural surfactant for the inactivation of L. monocytogenes Scott A in low-water-activity (aw) model systems. Glycerol or NaCl was used to reduce the aw to 0.92, and different concentrations of rhamnolipid (RL) biosurfactant were added before heat treatment (60 °C, 5 min). Using glycerol, RL treatment (50-250 µg/mL) reduced bacterial population by less than 0.2 log and heat treatment up to 1.5 log, while the combination of both hurdles reached around 5.0 log reduction. In the NaCl medium, RL treatment displayed higher inactivation than in the glycerol medium at the same aw level and a larger synergistic lethal effect when combined with heat, achieving ≥ 6.0 log reduction at 10-250 µg/mL RL concentrations. The growth inhibition activity of RL was enhanced by the presence of the monovalent salts NaCl and KCl, reducing MIC values from >2500 µg/mL (without salt) to 39 µg/mL (with 7.5% salt). The enhanced antimicrobial activity of RL promoted by the presence of salts was shown to be pH-dependent and more effective under neutral conditions. Overall, results demonstrate that RL can be exploited to design novel strategies based on hurdle approaches aiming to control L. monocytogenes.
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Affiliation(s)
- Lowieze Lenaerts
- Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Center (LFoRCe), KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Tathiane Ferroni Passos
- São Carlos Institute of Chemistry (IQSC), University of São Paulo, Trabalhador São-Carlense Av., 400, P.O. Box 780, São Carlos 13560-970, São Paulo, Brazil
| | - Elisa Gayán
- Department of Animal Production and Food Science, AgriFood Institute of Aragon (IA2), Faculty of Veterinary, University of Zaragoza-CITA, Miguel Servet 177, 50013 Zaragoza, Spain
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Center (LFoRCe), KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
- Correspondence: (C.W.M.); (M.N.)
| | - Marcia Nitschke
- São Carlos Institute of Chemistry (IQSC), University of São Paulo, Trabalhador São-Carlense Av., 400, P.O. Box 780, São Carlos 13560-970, São Paulo, Brazil
- Correspondence: (C.W.M.); (M.N.)
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Poortmans M, Vanoirbeek K, Dorner MB, Michiels CW. Selection and Development of Nontoxic Nonproteolytic Clostridium botulinum Surrogate Strains for Food Challenge Testing. Foods 2022; 11:foods11111577. [PMID: 35681327 PMCID: PMC9180612 DOI: 10.3390/foods11111577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/18/2022] [Accepted: 05/23/2022] [Indexed: 02/05/2023] Open
Abstract
Clostridium botulinum causes severe foodborne intoxications by producing a potent neurotoxin. Challenge studies with this pathogen are an important tool to ensure the safety of new processing techniques and newly designed or modified foods, but they are hazardous and complicated by the lack of an effective selective counting medium. Therefore, this study aimed to develop selectable nontoxic surrogate strains for group II, or nonproteolytic, C. botulinum, which are psychotropic and hence of particular concern in mildly treated, refrigerated foods. Thirty-one natural nontoxic nonproteolytic strains, 16 of which were isolated in this work, were characterized in detail, revealing that 28 strains were genomically and phenotypically indistinguishable from toxic strains. Five strains, representing the genomic and phenotypic diversity of group II C. botulinum, were selected and successfully equipped with an erythromycin (Em) resistance marker in a defective structural phage gene without altering phenotypic features. Finally, a selective medium containing Em, cycloserine (Cs), gentamicin (Gm), and lysozyme (Ly) was developed, which inhibited the background microbiota of commercial cooked ham, chicken filet, and salami, but supported spore germination and growth of the Em-resistant surrogate strains. The surrogates developed in this work are expected to facilitate food challenge studies with nonproteolytic C. botulinum for the food industry and can also provide a safe alternative for basic C. botulinum research.
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Affiliation(s)
- Marijke Poortmans
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
| | - Kristof Vanoirbeek
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
| | - Martin B. Dorner
- Robert Koch Institute, ZBS3-Biological Toxins, Seestr. 10, 13353 Berlin, Germany;
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
- Correspondence: ; Tel.: +32-16321578
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Sun L, Rogiers G, Courtin P, Chapot-Chartier MP, Bierne H, Michiels CW. AsnB Mediates Amidation of Meso-Diaminopimelic Acid Residues in the Peptidoglycan of Listeria monocytogenes and Affects Bacterial Surface Properties and Host Cell Invasion. Front Microbiol 2021; 12:760253. [PMID: 34721369 PMCID: PMC8554201 DOI: 10.3389/fmicb.2021.760253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 09/24/2021] [Indexed: 11/30/2022] Open
Abstract
A mutant of Listeria monocytogenes ScottA with a transposon in the 5' untranslated region of the asnB gene was identified to be hypersensitive to the antimicrobial t-cinnamaldehyde. Here, we report the functional characterization of AsnB in peptidoglycan (PG) modification and intracellular infection. While AsnB of Listeria is annotated as a glutamine-dependent asparagine synthase, sequence alignment showed that this protein is closely related to a subset of homologs that catalyze the amidation of meso-diaminopimelic acid (mDAP) residues in the peptidoglycan of other bacterial species. Structural analysis of peptidoglycan from an asnB mutant, compared to that of isogenic wild-type (WT) and complemented mutant strains, confirmed that AsnB mediates mDAP amidation in L. monocytogenes. Deficiency in mDAP amidation caused several peptidoglycan- and cell surface-related phenotypes in the asnB mutant, including formation of shorter but thicker cells, susceptibility to lysozyme, loss of flagellation and motility, and a strong reduction in biofilm formation. In addition, the mutant showed reduced invasion of human epithelial JEG-3 and Caco-2 cells. Analysis by immunofluorescence microscopy revealed that asnB inactivation abrogated the proper display at the listerial surface of the invasion protein InlA, which normally gets cross-linked to mDAP via its LPXTG motif. Together, this work shows that AsnB of L. monocytogenes, like several of its homologs in related Gram-positive bacteria, mediates the amidation of mDAP residues in the peptidoglycan and, in this way, affects several cell wall and cell surface-related properties. It also for the first time implicates the amidation of peptidoglycan mDAP residues in cell wall anchoring of InlA and in bacterial virulence.
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Affiliation(s)
- Lei Sun
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S) and Leuven Food Science and Nutrition Research Center (LFoRCe), KU Leuven, Leuven, Belgium
| | - Gil Rogiers
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S) and Leuven Food Science and Nutrition Research Center (LFoRCe), KU Leuven, Leuven, Belgium
| | - Pascal Courtin
- INRAE, AgroParisTech, Micalis Institute, Université Paris-Saclay, Jouy-en-Josas, France
| | | | - Hélène Bierne
- INRAE, AgroParisTech, Micalis Institute, Université Paris-Saclay, Jouy-en-Josas, France
| | - Chris W Michiels
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S) and Leuven Food Science and Nutrition Research Center (LFoRCe), KU Leuven, Leuven, Belgium
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Luu-Thi H, Michiels CW. Microbiological Safety of Ready-to-Eat Foods in Hospital and University Canteens in Hanoi, Vietnam. J Food Prot 2021; 84:1915-1921. [PMID: 34189563 DOI: 10.4315/jfp-20-324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 06/25/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT The aim of this study was to analyze and document the microbiological safety and quality of ready-to-eat foods in hospital and university canteens in Hanoi, Vietnam. In total, 420 ready-to-eat food products from 21 canteens were sampled in July 2018 and May 2019. The ratio of samples exceeding the unsatisfactory level for total plate count was 31%. Escherichia coli, Listeria, and Staphylococcus aureus were detected in 35 (8.3%), 99 (24%), and 46 (11%) samples, with 3, 10, and 0% exceeding the unsatisfactory level, respectively. The total plate count, Listeria, Bacillus cereus, E. coli, and S. aureus ranged from below detection limit to 5 × 109, 4.6 × 105, 6.2 × 103, 3.4 × 103, and 7.6 × 103 CFU/g, respectively. L. monocytogenes was isolated from 3 (0.7%) of 420 samples. In addition, 21 (5%) of 410 samples were contaminated with Salmonella. Overall, our data indicate frequent problems with the microbiological quality and safety of these canteen foods in Hanoi and provide a baseline measurement that will allow environmental health officers and food microbiologists to develop targeted intervention strategies to reduce the economic and public health risk associated with these foods. HIGHLIGHTS
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Affiliation(s)
- Hue Luu-Thi
- University of Science, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hanoi, Vietnam
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Center (LFoRCe), Department Microbial and Molecular Systems, KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
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8
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Sun L, Rogiers G, Michiels CW. The Natural Antimicrobial trans-Cinnamaldehyde Interferes with UDP-N-Acetylglucosamine Biosynthesis and Cell Wall Homeostasis in Listeria monocytogenes. Foods 2021; 10:foods10071666. [PMID: 34359536 PMCID: PMC8307235 DOI: 10.3390/foods10071666] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/12/2021] [Accepted: 07/16/2021] [Indexed: 01/07/2023] Open
Abstract
Trans-cinnamaldehyde (t-CIN), an antimicrobial compound from cinnamon essential oil, is of interest because it inhibits various foodborne pathogens. In the present work, we investigated the antimicrobial mechanisms of t-CIN in Listeria monocytogenes using a previously isolated yvcK::Himar1 transposon mutant which shows hypersensitivity to t-CIN. Time-lapse microscopy revealed that t-CIN induces a bulging cell shape followed by lysis in the mutant. Complementation with wild-type yvcK gene completely restored the tolerance of yvcK::Himar1 strain to t-CIN and the cell morphology. Suppressor mutants which partially reversed the t-CIN sensitivity of the yvcK::Himar1 mutant were isolated from evolutionary experiments. Three out of five suppression mutations were in the glmU-prs operon and in nagR, which are linked to the biosynthesis of the peptidoglycan precursor uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc). GlmU catalyzes the last two steps of UDP-GlcNAc biosynthesis and NagR represses the uptake and utilization of N-acetylglucosamine. Feeding N-acetylglucosamine or increasing the production of UDP-GlcNAc synthetic enzymes fully or partially restored the t-CIN tolerance of the yvcK mutant. Together, these results suggest that YvcK plays a pivotal role in diverting substrates to UDP-GlcNAc biosynthesis in L. monocytogenes and that t-CIN interferes with this pathway, leading to a peptidoglycan synthesis defect.
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Gayán E, Van den Bergh B, Michiels J, Michiels CW, Aertsen A. Synthetic reconstruction of extreme high hydrostatic pressure resistance in Escherichia coli. Metab Eng 2020; 62:287-297. [PMID: 32979485 DOI: 10.1016/j.ymben.2020.09.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/18/2020] [Accepted: 09/21/2020] [Indexed: 12/17/2022]
Abstract
Although high hydrostatic pressure (HHP) is an interesting parameter to be applied in bioprocessing, its potential is currently limited by the lack of bacterial chassis capable of surviving and maintaining homeostasis under pressure. While several efforts have been made to genetically engineer microorganisms able to grow at sublethal pressures, there is little information for designing backgrounds that survive more extreme pressures. In this investigation, we analyzed the genome of an extreme HHP-resistant mutant of E. coli MG1655 (designated as DVL1), from which we identified four mutations (in the cra, cyaA, aceA and rpoD loci) causally linked to increased HHP resistance. Analysing the functional effect of these mutations we found that the coupled effect of downregulation of cAMP/CRP, Cra and the glyoxylate shunt activity, together with the upregulation of RpoH and RpoS activity, could mechanistically explain the increased HHP resistance of the mutant. Using combinations of three mutations, we could synthetically engineer E. coli strains able to comfortably survive pressures of 600-800 MPa, which could serve as genetic backgrounds for HHP-based biotechnological applications.
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Affiliation(s)
- Elisa Gayán
- Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 20, 3001, Leuven, Belgium.
| | - Bram Van den Bergh
- Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 20, 3001, Leuven, Belgium; VIB Center for Microbiology, Flanders Institute for Biotechnology, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Jan Michiels
- Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 20, 3001, Leuven, Belgium; VIB Center for Microbiology, Flanders Institute for Biotechnology, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Chris W Michiels
- Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 20, 3001, Leuven, Belgium
| | - Abram Aertsen
- Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 20, 3001, Leuven, Belgium.
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González-Angulo M, Clauwers C, Harastani R, Tonello C, Jaime I, Rovira J, Michiels CW. Evaluation of factors influencing the growth of non-toxigenic Clostridium botulinum type E and Clostridium sp. in high-pressure processed and conditioned tender coconut water from Thailand. Food Res Int 2020; 134:109278. [PMID: 32517944 DOI: 10.1016/j.foodres.2020.109278] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 04/22/2020] [Accepted: 04/25/2020] [Indexed: 11/29/2022]
Abstract
Bacterial spores survive high pressure processing (HPP). Group II Clostridium botulinum is an obligate anaerobe spore-forming pathogen that can produce the botulinum neurotoxin under refrigeration. This study assessed nontoxigenic type E C. botulinum and Group II Clostridium sp. growth in raw and HPP (550 MPa, 3 min, 10 °C) Thai coconut water (CCW; pH 5.2). No spore germination or growth occurred in HPP CCW inoculated with 105 CFU/ml after 61 days regardless of oxygen concentration (<0.5 - 11 mg/l) or storage temperature (4 and 20 °C). Spore concentration decreased by 3.0 ± 0.1 log CFU/ml in a worst-case scenario consisting of non-HPP filter-sterilized CCW (pH 7.0) under anoxic incubation at 30 °C during 61 days, suggesting spore germination followed by cellular death. Supplementing filter-sterilized CCW (pH 7.0) with selected germinants and free amino acids did not support spore development, but the addition of nutrient-rich laboratory media (TPGY broth) at low concentrations (6.25%) promoted growth, suggesting that a lack of nutrients prevents C. botulinum development in CCW. Further risk assessment will require evaluating other CCW varieties and toxin production.
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Affiliation(s)
- Mario González-Angulo
- Hiperbaric, S.A., C/ Condado de Treviño, 6, 09001 Burgos, Spain; Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain.
| | - Charlien Clauwers
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Rania Harastani
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Carole Tonello
- Hiperbaric, S.A., C/ Condado de Treviño, 6, 09001 Burgos, Spain
| | - Isabel Jaime
- Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain
| | - Jordi Rovira
- Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain
| | - Chris W Michiels
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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11
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Clauwers C, Lood C, Van den Bergh B, van Noort V, Michiels CW. Author Correction: Canonical germinant receptor is dispensable for spore germination in Clostridium botulinum group II strain NCTC 11219. Sci Rep 2020; 10:4348. [PMID: 32132564 PMCID: PMC7055312 DOI: 10.1038/s41598-020-60486-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Charlien Clauwers
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Cédric Lood
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | | | - Vera van Noort
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium.
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12
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Gayán E, Geens E, Berdejo D, García-Gonzalo D, Pagán R, Aertsen A, Michiels CW. Combination of mild heat and plant essential oil constituents to inactivate resistant variants of Escherichia coli in buffer and in coconut water. Food Microbiol 2020; 87:103388. [PMID: 31948629 DOI: 10.1016/j.fm.2019.103388] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 10/20/2019] [Accepted: 11/20/2019] [Indexed: 12/25/2022]
Abstract
The growing demand for minimally processed foods with clean labels has stimulated research into mild processing methods and natural antimicrobials to replace intensive heating and conventional preservatives, respectively. However, we have previously demonstrated that repetitive exposure of some bacteria to mild heat or subinhibitory concentrations of essential oil constituents (EOCs) may induce the emergence of mutants with increased resistance to these treatments. Since the combination of mild heat with some EOCs has a synergistic effect on microbial inactivation, we evaluated the potential of such combinations against our resistant E. coli mutants. While citral, carvacrol and t-cinnamaldehyde synergistically increased heat inactivation (53.0 °C, 10 min) of the wild-type MG1655 suspended in buffer, only the combination with carvacrol (200 μl/l) was able to mitigate the increased resistance of all the mutants. Moreover, the combination of heat and carvacrol acted synergistically inactivating heat-resistant variants of E. coli O157:H7 (ATCC 43888). This combined treatment could synergistically achieve more than 5 log10 reductions of the most resistant mutants in coconut water, although the temperature had to be raised to 57.0 °C. Therefore, the combination of mild heat with carvacrol appears to hold promise for mild processing, and it is expected to counteract the development of heat resistance.
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Affiliation(s)
- Elisa Gayán
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000, Leuven, Belgium; Tecnología de Los Alimentos, Departamento de Producción Animal y Ciencia de Los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Miguel Servet 177, 50013, Zaragoza, Spain
| | - Elise Geens
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000, Leuven, Belgium
| | - Daniel Berdejo
- Tecnología de Los Alimentos, Departamento de Producción Animal y Ciencia de Los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Miguel Servet 177, 50013, Zaragoza, Spain
| | - Diego García-Gonzalo
- Tecnología de Los Alimentos, Departamento de Producción Animal y Ciencia de Los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Miguel Servet 177, 50013, Zaragoza, Spain
| | - Rafael Pagán
- Tecnología de Los Alimentos, Departamento de Producción Animal y Ciencia de Los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Miguel Servet 177, 50013, Zaragoza, Spain
| | - Abram Aertsen
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000, Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000, Leuven, Belgium.
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Clauwers C, Lood C, Van den Bergh B, van Noort V, Michiels CW. Canonical germinant receptor is dispensable for spore germination in Clostridium botulinum group II strain NCTC 11219. Sci Rep 2017; 7:15426. [PMID: 29133849 PMCID: PMC5684421 DOI: 10.1038/s41598-017-15839-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 11/03/2017] [Indexed: 02/07/2023] Open
Abstract
Clostridium botulinum is an anaerobic sporeforming bacterium that is notorious for producing a potent neurotoxin. Spores of C. botulinum can survive mild food processing treatments and subsequently germinate, multiply, produce toxin and cause botulism. Control of spore germination and outgrowth is therefore essential for the safety of mildly processed foods. However, little is known about the process of spore germination in group II C. botulinum (gIICb), which are a major concern in chilled foods because they are psychrotrophic. The classical model of spore germination states that germination is triggered by the binding of a germinant molecule to a cognate germinant receptor. Remarkably, unlike many other sporeformers, gIICb has only one predicted canonical germinant receptor although it responds to multiple germinants. Therefore, we deleted the gerBAC locus that encodes this germinant receptor to determine its role in germination. Surprisingly, the deletion did not affect germination by any of the nutrient germinants, nor by the non-nutrient dodecylamine. We conclude that one or more other, so far unidentified, germinant receptors must be responsible for nutrient induced germination in gIICb. Furthermore, the gerBAC locus was strongly conserved with intact open reading frames in 159 gIICb genomes, suggesting that it has nevertheless an important function.
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Affiliation(s)
- Charlien Clauwers
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Cédric Lood
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | | | - Vera van Noort
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium.
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Gayán E, Cambré A, Michiels CW, Aertsen A. RpoS-independent evolution reveals the importance of attenuated cAMP/CRP regulation in high hydrostatic pressure resistance acquisition in E. coli. Sci Rep 2017; 7:8600. [PMID: 28819154 PMCID: PMC5561100 DOI: 10.1038/s41598-017-08958-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 07/20/2017] [Indexed: 11/09/2022] Open
Abstract
High hydrostatic pressure (HHP) processing is an attractive non-thermal alternative to food pasteurization. Nevertheless, the large inter- and intra-species variations in HHP resistance among foodborne pathogens and the ease by which they can acquire extreme resistance are an issue of increasing concern. Since RpoS activity has been considered as a central determinant in the HHP resistance of E. coli and its pathovars, this study probed for the potential of an E. coli MG1655 ΔrpoS mutant to acquire HHP resistance by directed evolution. Despite the higher initial HHP sensitivity of the ΔrpoS mutant compared to the wild-type strain, evolved lineages of the former readily managed to restore or even succeed wild-type levels of resistance. A number of these ΔrpoS derivatives were affected in cAMP/CRP regulation, and this could be causally related to their HHP resistance. Subsequent inspection revealed that some of previously isolated HHP-resistant mutants derived from the wild-type strain also incurred a causal decrease in cAMP/CRP regulation. cAMP/CRP attenuated HHP-resistant mutants also exhibited higher resistance to fosfomycin, a preferred treatment for STEC infections. As such, this study reveals attenuation of cAMP/CRP regulation as a relevant and RpoS-independent evolutionary route towards HHP resistance in E. coli that coincides with fosfomycin resistance.
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Affiliation(s)
- Elisa Gayán
- KU Leuven, Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, Leuven, Belgium
| | - Alexander Cambré
- KU Leuven, Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, Leuven, Belgium
| | - Chris W Michiels
- KU Leuven, Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, Leuven, Belgium
| | - Abram Aertsen
- KU Leuven, Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, Leuven, Belgium.
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Rogiers G, Kebede BT, Van Loey A, Michiels CW. Membrane fatty acid composition as a determinant of Listeria monocytogenes sensitivity to trans-cinnamaldehyde. Res Microbiol 2017; 168:536-546. [PMID: 28342836 DOI: 10.1016/j.resmic.2017.03.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 03/07/2017] [Accepted: 03/07/2017] [Indexed: 11/19/2022]
Abstract
trans-Cinnamaldehyde, the major compound of cinnamon essential oil, is a potentially interesting natural antimicrobial food preservative. Although a number of studies have addressed its mode of action, the factors that determine bacterial sensitivity or tolerance to trans-cinnamaldehyde are poorly understood. We report the detailed characterization of a Listeria monocytogenes Scott A trans-cinnamaldehyde hypersensitive mutant defective in IlvE, which catalyzes the reversible transamination of branched-chain amino acids to the corresponding short-chain α-ketoacids. This mutant showed an 8.4 fold extended lag phase during growth in sublethal concentrations (4 mM), and faster inactivation in lethal concentrations of trans-cinnamaldehyde (6 mM). trans-Cinnamaldehyde hypersensitivity could be corrected by genetic complementation with the ilvE gene and supplementation with branched-chain α-ketoacids. Whole-cell fatty acid analyses revealed an almost complete loss of anteiso branched-chain fatty acids (BCFAs), which was compensated by elevated levels of unbranched saturated fatty acids and iso-BCFAs. Sub-inhibitory concentrations of trans-cinnamaldehyde induced membrane fatty acid adaptations predicted to reduce membrane fluidity, possibly as a response to counteract the membrane fluidizing effect of trans-cinnamaldehyde. These results demonstrate the role of IlvE in BCFA production and the role of membrane composition as an important determinant of trans-cinnamaldehyde sensitivity in L. monocytogenes.
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Affiliation(s)
- Gil Rogiers
- KU Leuven, Department of Microbial and Molecular Systems (M(2)S), Leuven Food Science and Nutrition Research Center (LFoRCe), Laboratory of Food Microbiology, Kasteelpark Arenberg 22, 3001 Leuven, Belgium.
| | - Biniam T Kebede
- KU Leuven, Department of Microbial and Molecular Systems (M(2)S), Leuven Food Science and Nutrition Research Center (LFoRCe), Laboratory of Food Technology, Kasteelpark Arenberg 22, 3001 Leuven, Belgium
| | - Ann Van Loey
- KU Leuven, Department of Microbial and Molecular Systems (M(2)S), Leuven Food Science and Nutrition Research Center (LFoRCe), Laboratory of Food Technology, Kasteelpark Arenberg 22, 3001 Leuven, Belgium
| | - Chris W Michiels
- KU Leuven, Department of Microbial and Molecular Systems (M(2)S), Leuven Food Science and Nutrition Research Center (LFoRCe), Laboratory of Food Microbiology, Kasteelpark Arenberg 22, 3001 Leuven, Belgium.
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16
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Gayán E, Govers SK, Michiels CW, Aertsen A. Severely Heat Injured Survivors of E. coli O157:H7 ATCC 43888 Display Variable and Heterogeneous Stress Resistance Behavior. Front Microbiol 2016; 7:1845. [PMID: 27917163 PMCID: PMC5114269 DOI: 10.3389/fmicb.2016.01845] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 11/02/2016] [Indexed: 12/02/2022] Open
Abstract
Although minimal food processing strategies aim to eliminate foodborne pathogens and spoilage microorganisms through a combination of mild preservation techniques, little is actually known on the resistance behavior of the small fraction of microorganisms surviving an inimical treatment. In this study, the conduct of severely heat stressed survivors of E. coli O157:H7 ATCC 43888, as an indicator for the low infectious dose foodborne enterohemorrhagic strains, was examined throughout their resuscitation and outgrowth. Despite the fact that these survivors were initially sublethally injured, they were only marginally more sensitive to a subsequent heat treatment and actually much more resistant to a subsequent high hydrostatic pressure (HHP) shock in comparison with unstressed control cells. Throughout further resuscitation, however, their initial HHP resistance rapidly faded out, while their heat resistance increased and surpassed the initial heat resistance of unstressed control cells. Results also indicated that the population eventually emerging from the severely heat stressed survivors heterogeneously consisted of both growing and non-growing cells. Together, these observations provide deeper insights into the particular behavior and heterogeneity of stressed foodborne pathogens in the context of food preservation.
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Affiliation(s)
- Elisa Gayán
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Sander K Govers
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
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17
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Uytterhoeven B, Lathouwers T, Voet M, Michiels CW, Lavigne R. A Protein Interaction Map of the Kalimantacin Biosynthesis Assembly Line. Front Microbiol 2016; 7:1726. [PMID: 27853452 PMCID: PMC5089993 DOI: 10.3389/fmicb.2016.01726] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 10/17/2016] [Indexed: 12/04/2022] Open
Abstract
The antimicrobial secondary metabolite kalimantacin (also called batumin) is produced by a hybrid polyketide/non-ribosomal peptide system in Pseudomonas fluorescens BCCM_ID9359. In this study, the kalimantacin biosynthesis gene cluster is analyzed by yeast two-hybrid analysis, creating a protein–protein interaction map of the entire assembly line. In total, 28 potential interactions were identified, of which 13 could be confirmed further. These interactions include the dimerization of ketosynthase domains, a link between assembly line modules 9 and 10, and a specific interaction between the trans-acting enoyl reductase BatK and the carrier proteins of modules 8 and 10. These interactions reveal fundamental insight into the biosynthesis of secondary metabolites. This study is the first to reveal interactions in a complete biosynthetic pathway. Similar future studies could build a strong basis for engineering strategies in such clusters.
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Affiliation(s)
- Birgit Uytterhoeven
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven Leuven, Belgium
| | - Thomas Lathouwers
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven Leuven, Belgium
| | - Marleen Voet
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven Leuven, Belgium
| | - Chris W Michiels
- Centre for Food and Microbial Technology, Department of Microbial and Molecular Systems, KU Leuven Leuven, Belgium
| | - Rob Lavigne
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven Leuven, Belgium
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18
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Vivijs B, Aertsen A, Michiels CW. Identification of Genes Required for Growth of Escherichia coli MG1655 at Moderately Low pH. Front Microbiol 2016; 7:1672. [PMID: 27826291 PMCID: PMC5078493 DOI: 10.3389/fmicb.2016.01672] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 10/06/2016] [Indexed: 01/27/2023] Open
Abstract
The survival of some pathotypes of Escherichia coli in very low pH environments like highly acidic foods and the stomach has been well documented and contributes to their success as foodborne pathogens. In contrast, the ability of E. coli to grow at moderately low pH has received less attention, although this property can be anticipated to be also very important for the safety of mildly acidic foods. Therefore, the objective of this study was to identify cellular functions required for growth of the non-pathogenic strain E. coli MG1655 at low pH. First, the role of the four E. coli amino acid decarboxylase systems, which are the major cellular mechanisms allowing extreme acid survival, was investigated using mutants defective in each of the systems. Only the lysine decarboxylase (CadA) was required for low pH growth. Secondly, a screening of 8544 random transposon insertion mutants resulted in the identification of six genes affecting growth in LB broth acidified to pH 4.50 with HCl. Two of the genes, encoding the transcriptional regulator LeuO and the elongation factor P-β-lysine ligase EpmA, can be linked to CadA production. Two other genes, encoding the diadenosine tetraphosphatase ApaH and the tRNA modification GTPase MnmE, have been previously implicated in the bacterial response to stresses other than low pH. A fifth gene encodes the LPS heptosyltransferase WaaC, and its mutant has a deep rough colony phenotype, which has been linked to reduced acid tolerance in earlier work. Finally, tatC encodes a secA-independent protein translocase that exports a few dozen proteins and thus is likely to have a pleiotropic phenotype. For mnmE, apaH, epmA, and waaC, de novo in frame deletion and genetic complementation confirmed their role in low pH growth, and these deletion mutants were also affected in growth in apple juice and tomato juice. However, the mutants were not affected in survival in gastric simulation medium at pH 2.5, indicating that growth at moderately low pH and survival of extremely low pH depend mostly on different cellular functions.
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Affiliation(s)
| | | | - Chris W. Michiels
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU LeuvenLeuven, Belgium
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Uytterhoeven B, Appermans K, Song L, Masschelein J, Lathouwers T, Michiels CW, Lavigne R. Systematic analysis of the kalimantacin assembly line NRPS module using an adapted targeted mutagenesis approach. Microbiologyopen 2015; 5:279-86. [PMID: 26666990 PMCID: PMC4831472 DOI: 10.1002/mbo3.326] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/26/2015] [Accepted: 11/04/2015] [Indexed: 01/10/2023] Open
Abstract
Kalimantacin is an antimicrobial compound with strong antistaphylococcal activity that is produced by a hybrid trans‐acyltransferase polyketide synthase/nonribosomal peptide synthetase system in Pseudomonas fluorescens BCCM_ID9359. We here present a systematic analysis of the substrate specificity of the glycine‐incorporating adenylation domain from the kalimantacin biosynthetic assembly line by a targeted mutagenesis approach. The specificity‐conferring code was adapted for use in Pseudomonas and mutated adenylation domain active site sequences were introduced in the kalimantacin gene cluster, using a newly adapted ligation independent cloning method. Antimicrobial activity screens and LC‐MS analyses revealed that the production of the kalimantacin analogues in the mutated strains was abolished. These results support the idea that further insight in the specificity of downstream domains in nonribosomal peptide synthetases and polyketide synthases is required to efficiently engineer these strains in vivo.
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Affiliation(s)
- Birgit Uytterhoeven
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, Heverlee, B-3001, Belgium
| | - Kenny Appermans
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, Heverlee, B-3001, Belgium
| | - Lijiang Song
- Department of Chemistry, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, United Kingdom
| | - Joleen Masschelein
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, Heverlee, B-3001, Belgium.,Department of Chemistry, University of Warwick, Gibbet Hill, Coventry, CV4 7AL, United Kingdom
| | - Thomas Lathouwers
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, Heverlee, B-3001, Belgium
| | - Chris W Michiels
- Centre for Food and Microbial Technology, KU Leuven, Kasteelpark Arenberg 23 box 2457, Heverlee, B-3001, Belgium
| | - Rob Lavigne
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, Heverlee, B-3001, Belgium
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Vivijs B, Haberbeck LU, Baiye Mfortaw Mbong V, Bernaerts K, Geeraerd AH, Aertsen A, Michiels CW. Formate hydrogen lyase mediates stationary-phase deacidification and increases survival during sugar fermentation in acetoin-producing enterobacteria. Front Microbiol 2015; 6:150. [PMID: 25762991 PMCID: PMC4340222 DOI: 10.3389/fmicb.2015.00150] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/09/2015] [Indexed: 12/02/2022] Open
Abstract
Two fermentation types exist in the Enterobacteriaceae family. Mixed-acid fermenters produce substantial amounts of lactate, formate, acetate, and succinate, resulting in lethal medium acidification. On the other hand, 2,3-butanediol fermenters switch to the production of the neutral compounds acetoin and 2,3-butanediol and even deacidify the environment after an initial acidification phase, thereby avoiding cell death. We equipped three mixed-acid fermenters (Salmonella Typhimurium, S. Enteritidis and Shigella flexneri) with the acetoin pathway from Serratia plymuthica to investigate the mechanisms of deacidification. Acetoin production caused attenuated acidification during exponential growth in all three bacteria, but stationary-phase deacidification was only observed in Escherichia coli and Salmonella, suggesting that it was not due to the consumption of protons accompanying acetoin production. To identify the mechanism, 34 transposon mutants of acetoin-producing E. coli that no longer deacidified the culture medium were isolated. The mutations mapped to 16 genes, all involved in formate metabolism. Formate is an end product of mixed-acid fermentation that can be converted to H2 and CO2 by the formate hydrogen lyase (FHL) complex, a reaction that consumes protons and thus can explain medium deacidification. When hycE, encoding the large subunit of hydrogenase 3 that is part of the FHL complex, was deleted in acetoin-producing E. coli, deacidification capacity was lost. Metabolite analysis in E. coli showed that introduction of the acetoin pathway reduced lactate and acetate production, but increased glucose consumption and formate and ethanol production. Analysis of a hycE mutant in S. plymuthica confirmed that medium deacidification in this organism is also mediated by FHL. These findings improve our understanding of the physiology and function of fermentation pathways in Enterobacteriaceae.
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Affiliation(s)
- Bram Vivijs
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Leticia U Haberbeck
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium ; Division of Mechatronics, Biostatistics and Sensors, Department of Biosystems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Victor Baiye Mfortaw Mbong
- Division of Mechatronics, Biostatistics and Sensors, Department of Biosystems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Kristel Bernaerts
- Chemical and Biochemical Process Technology and Control Section, Department of Chemical Engineering, Faculty of Engineering Science KU Leuven, Leuven, Belgium
| | - Annemie H Geeraerd
- Division of Mechatronics, Biostatistics and Sensors, Department of Biosystems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, KU Leuven Leuven, Belgium
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Feyaerts J, Rogiers G, Corthouts J, Michiels CW. Thiol-reactive natural antimicrobials and high pressure treatment synergistically enhance bacterial inactivation. INNOV FOOD SCI EMERG 2015. [DOI: 10.1016/j.ifset.2014.12.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Luu-Thi H, Corthouts J, Passaris I, Grauwet T, Aertsen A, Hendrickx M, Michiels CW. Carvacrol suppresses high pressure high temperature inactivation of Bacillus cereus spores. Int J Food Microbiol 2014; 197:45-52. [PMID: 25560915 DOI: 10.1016/j.ijfoodmicro.2014.12.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 10/20/2014] [Accepted: 12/14/2014] [Indexed: 12/30/2022]
Abstract
The inactivation of bacterial spores generally proceeds faster and at lower temperatures when heat treatments are conducted under high pressure, and high pressure high temperature (HPHT) processing is, therefore, receiving an increased interest from food processors. However, the mechanisms of spore inactivation by HPHT treatment are poorly understood, particularly at moderately elevated temperature. In the current work, we studied inactivation of the spores of Bacillus cereus F4430/73 by HPHT treatment for 5 min at 600MPa in the temperature range of 50-100°C, using temperature increments of 5°C. Additionally, we investigated the effect of the natural antimicrobial carvacrol on spore germination and inactivation under these conditions. Spore inactivation by HPHT was less than about 1 log unit at 50 to 70°C, but gradually increased at higher temperatures up to about 5 log units at 100°C. DPA release and loss of spore refractility in the spore population were higher at moderate (≤65°C) than at high (≥70°C) treatment temperatures, and we propose that moderate conditions induced the normal physiological pathway of spore germination resulting in fully hydrated spores, while at higher temperatures this pathway was suppressed and replaced by another mechanism of pressure-induced dipicolinic acid (DPA) release that results only in partial spore rehydration, probably because spore cortex hydrolysis is inhibited. Carvacrol strongly suppressed DPA release and spore rehydration during HPHT treatment at ≤65°C and also partly inhibited DPA release at ≥65°C. Concomitantly, HPHT spore inactivation was reduced by carvacrol at 65-90°C but unaffected at 95-100°C.
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Affiliation(s)
- Hue Luu-Thi
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Jorinde Corthouts
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Ioannis Passaris
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Tara Grauwet
- Laboratory of Food Technology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Marc Hendrickx
- Laboratory of Food Technology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium.
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Vanoirbeek K, Aertsen A, Michiels CW. Role of 1-acyl-sn-glycerol-3-phosphate acyltransferase in psychrotrophy and stress tolerance of Serratia plymuthica RVH1. Res Microbiol 2014; 166:28-37. [PMID: 25446612 DOI: 10.1016/j.resmic.2014.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 11/19/2022]
Abstract
A mutant with a transposon insertion just upstream of the lysophosphatidic acid acyltansferase gene plsC was isolated in a screen for mutants affected in growth at low temperature of the psychrotroph Serratia plymuthica RVH1. This mutant had lost its ability to grow at 4 °C and was severely affected in growth at 10 °C, but showed only slightly reduced growth at 30 °C. Fatty acid analysis of membrane extracts showed that the ratio of C16:1/C18:1 fatty acids was six-to sevenfold reduced in the mutant, although the ratio of unsaturated to saturated fatty acids was unaffected. The homeoviscous adaptation ability of the mutant was also unaffected. Growth and fatty acid composition were mostly restored by overexpressing plsC on a plasmid. Supplementation of C16:1 (palmitoleic acid) into the growth medium partially rescued low temperature growth, indicating that a balanced ratio of the two main unsaturated fatty acids is required for psychrotrophy. The mutant was significantly more strongly inactivated by high pressure treatment at 250 MPa, but not at higher pressures. It also showed reduced growth at low pH, but not at increased NaCl concentrations. This work provides novel information on the role of membrane fatty acid composition in stress tolerance.
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Affiliation(s)
- Kristof Vanoirbeek
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium.
| | - Abram Aertsen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium.
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium.
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Luu-Thi H, Khadka DB, Michiels CW. Thermal inactivation parameters of spores from different phylogenetic groups of Bacillus cereus. Int J Food Microbiol 2014; 189:183-8. [DOI: 10.1016/j.ijfoodmicro.2014.07.027] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/09/2014] [Accepted: 07/21/2014] [Indexed: 11/17/2022]
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Vivijs B, Moons P, Aertsen A, Michiels CW. Acetoin synthesis acquisition favors Escherichia coli growth at low pH. Appl Environ Microbiol 2014; 80:6054-61. [PMID: 25063653 PMCID: PMC4178668 DOI: 10.1128/aem.01711-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 07/17/2014] [Indexed: 11/20/2022] Open
Abstract
Some members of the family Enterobacteriaceae ferment sugars via the mixed-acid fermentation pathway. This yields large amounts of acids, causing strong and sometimes even lethal acidification of the environment. Other family members employ the 2,3-butanediol fermentation pathway, which generates comparatively less acidic and more neutral end products, such as acetoin and 2,3-butanediol. In this work, we equipped Escherichia coli MG1655 with the budAB operon, encoding the acetoin pathway, from Serratia plymuthica RVH1 and investigated how this affected the ability of E. coli to cope with acid stress during growth. Acetoin fermentation prevented lethal medium acidification by E. coli in lysogeny broth (LB) supplemented with glucose. It also supported growth and higher stationary-phase cell densities in acidified LB broth with glucose (pH 4.10 to 4.50) and in tomato juice (pH 4.40 to 5.00) and reduced the minimal pH at which growth could be initiated. On the other hand, the acetoin-producing strain was outcompeted by the nonproducer in a mixed-culture experiment at low pH, suggesting a fitness cost associated with acetoin production. Finally, we showed that acetoin production profoundly changes the appearance of E. coli on several diagnostic culture media. Natural E. coli strains that have laterally acquired budAB genes may therefore have escaped detection thus far. This study demonstrates the potential importance of acetoin fermentation in the ecology of E. coli in the food chain and contributes to a better understanding of the microbiological stability and safety of acidic foods.
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Affiliation(s)
- Bram Vivijs
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Pieter Moons
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium
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Cambré A, Zimmermann M, Sauer U, Vivijs B, Cenens W, Michiels CW, Aertsen A, Loessner MJ, Noben JP, Ayala JA, Lavigne R, Briers Y. Metabolite profiling and peptidoglycan analysis of transient cell wall-deficient bacteria in a new Escherichia coli model system. Environ Microbiol 2014; 17:1586-99. [PMID: 25142185 DOI: 10.1111/1462-2920.12594] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 08/11/2014] [Indexed: 12/01/2022]
Abstract
Many bacteria are able to assume a transient cell wall-deficient (or L-form) state under favourable osmotic conditions. Cell wall stress such as exposure to β-lactam antibiotics can enforce the transition to and maintenance of this state. L-forms actively proliferate and can return to the walled state upon removal of the inducing agent. We have adopted Escherichia coli as a model system for the controlled transition to and reversion from the L-form state, and have studied these dynamics with genetics, cell biology and 'omics' technologies. As such, a transposon mutagenesis screen underscored the requirement for the Rcs phosphorelay and colanic acid synthesis, while proteomics show only little differences between rods and L-forms. In contrast, metabolome comparison reveals the high abundance of lysophospholipids and phospholipids with unsaturated or cyclopropanized fatty acids in E. coli L-forms. This increase of membrane lipids associated with increased membrane fluidity may facilitate proliferation through bud formation. Visualization of the residual peptidoglycan with a fluorescently labelled peptidoglycan binding protein indicates de novo cell wall synthesis and a role for septal peptidoglycan synthesis during bud constriction. The DD-carboxypeptidases PBP5 and PBP6 are threefold and fourfold upregulated in L-forms, indicating a specific role for regulation of crosslinking during L-form proliferation.
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Affiliation(s)
- Alexander Cambré
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, B-3001, Heverlee, Belgium; Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven, B-3001, Heverlee, Belgium
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Vanlint D, Tesfazgi Mebhratu M, Michiels CW, Aertsen A. Using Mild High-pressure Shock to Generate Bacterial Ghosts of Escherichia coli. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-2008-0626] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In the context of vaccine development, bacterial ghosts are inert cells that retain the capacity to activate the immune system, and that can be used as vaccine or carrier for subunit or DNA vaccines. In this study we provide evidence that increasing the copynumber of the E. coli K12 mrr locus can render naturally occurring and virulent avian pathogenic E. coli (APEC) strains hypersensitive to high pressure. We further demonstrate that mild HP shock generates inactive bacterial ghosts from these cells that have not incurred any microscopically visible structural damage. Possible benefits of high-pressure generated bacterial ghosts as a vaccine are discussed.
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Affiliation(s)
- Dietrich Vanlint
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Mehari Tesfazgi Mebhratu
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Chris W. Michiels
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M²S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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Passaris I, Ghosh A, Cenens W, Michiels CW, Lammertyn J, Aertsen A. Isolation and validation of an endogenous fluorescent nucleoid reporter in Salmonella Typhimurium. PLoS One 2014; 9:e93785. [PMID: 24695782 PMCID: PMC3973593 DOI: 10.1371/journal.pone.0093785] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 03/10/2014] [Indexed: 01/24/2023] Open
Abstract
In this study we adapted a Mud-based delivery system to construct a random yfp reporter gene (encoding the yellow fluorescent protein) insertion library in the genome of Salmonella Typhimurium LT2, and used fluorescence activated cell sorting and fluorescence microscopy to screen for translational fusions that were able to clearly and specifically label the bacterial nucleoid. Two such fusions were obtained, corresponding to a translational yfp insertion in iscR and iolR, respectively. Both fusions were further validated, and the IscR::YFP fluorescent nucleoid reporter together with time-lapse fluorescence microscopy was subsequently used to monitor nucleoid dynamics in response to the filamentation imposed by growth of LT2 at high hydrostatic pressure (40-45 MPa). As such, we were able to reveal that upon decompression the apparently entangled LT2 chromosomes in filamentous cells rapidly and efficiently segregate, after which septation of the filament occurs. In the course of the latter process, however, cells with a "trilobed" nucleoid were regularly observed, indicative for an imbalance between septum formation and chromosome segregation.
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Affiliation(s)
- Ioannis Passaris
- Laboratory of Food Micobiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
| | - Anirban Ghosh
- Laboratory of Food Micobiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
| | - William Cenens
- Laboratory of Food Micobiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
| | - Chris W. Michiels
- Laboratory of Food Micobiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
| | - Jeroen Lammertyn
- BIOSYST-MeBios, Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Micobiology, Department of Microbial and Molecular Systems (M2S), Faculty of Bioscience Engineering, KU Leuven, University of Leuven, Belgium
- * E-mail:
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Zhou K, Aertsen A, Michiels CW. The role of variable DNA tandem repeats in bacterial adaptation. FEMS Microbiol Rev 2013; 38:119-41. [PMID: 23927439 DOI: 10.1111/1574-6976.12036] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 07/13/2013] [Accepted: 07/26/2013] [Indexed: 01/05/2023] Open
Abstract
DNA tandem repeats (TRs), also designated as satellite DNA, are inter- or intragenic nucleotide sequences that are repeated two or more times in a head-to-tail manner. Because TR tracts are prone to strand-slippage replication and recombination events that cause the TR copy number to increase or decrease, loci containing TRs are hypermutable. An increasing number of examples illustrate that bacteria can exploit this instability of TRs to reversibly shut down or modulate the function of specific genes, allowing them to adapt to changing environments on short evolutionary time scales without an increased overall mutation rate. In this review, we discuss the prevalence and distribution of inter- and intragenic TRs in bacteria and the mechanisms of their instability. In addition, we review evidence demonstrating a role of TR variations in bacterial adaptation strategies, ranging from immune evasion and tissue tropism to the modulation of environmental stress tolerance. Nevertheless, while bioinformatic analysis reveals that most bacterial genomes contain a few up to several dozens of intra- and intergenic TRs, only a small fraction of these have been functionally studied to date.
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Affiliation(s)
- Kai Zhou
- Department of Microbial and Molecular Systems (M²S), Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
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Frans I, Dierckens K, Crauwels S, Van Assche A, Leisner J, Larsen MH, Michiels CW, Willems KA, Lievens B, Bossier P, Rediers H. Does virulence assessment of Vibrio anguillarum using sea bass (Dicentrarchus labrax) larvae correspond with genotypic and phenotypic characterization? PLoS One 2013; 8:e70477. [PMID: 23936439 PMCID: PMC3735585 DOI: 10.1371/journal.pone.0070477] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 06/10/2013] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus Vibrio such as Vibrio (Listonella) anguillarum. Despite a lot of research efforts, the virulence factors and mechanism of V. anguillarum are still insufficiently known, in part because of the lack of standardized virulence assays. METHODOLOGY/PRINCIPAL FINDINGS We investigated and compared the virulence of 15 V. anguillarum strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (Dicentrarchus labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog's Phenotype MicroArray™ technology and some virulence factor assays. CONCLUSIONS/SIGNIFICANCE Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of V. anguillarum virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different V. anguillarum strains in vivo. In this way, the bioassay contributes to the study of mechanisms underlying virulence in V. anguillarum.
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Affiliation(s)
- Ingeborg Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
- Centre for Food and Microbial Technology, M2S, KU Leuven, Heverlee, Belgium
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Kristof Dierckens
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Sam Crauwels
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Ado Van Assche
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Jørgen Leisner
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Marianne H. Larsen
- Department of Veterinary Disease Biology, University of Copenhagen, Frederiksberg, Denmark
| | - Chris W. Michiels
- Centre for Food and Microbial Technology, M2S, KU Leuven, Heverlee, Belgium
| | - Kris A. Willems
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Bart Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
| | - Peter Bossier
- Laboratory of Aquaculture and Artemia Reference Center, Department of Animal Production, Ghent University, Gent, Belgium
| | - Hans Rediers
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Thomas More Mechelen, Campus De Nayer, Department of Microbial and Molecular Systems (M2S), KU Leuven Association, Sint-Katelijne-Waver, Belgium
- Scientia Terrae Research Institute, Sint-Katelijne-Waver, Belgium
- * E-mail:
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Myrnes B, Seppola M, Johansen A, Overbø K, Callewaert L, Vanderkelen L, Michiels CW, Nilsen IW. Enzyme characterisation and gene expression profiling of Atlantic salmon chicken- and goose-type lysozymes. Dev Comp Immunol 2013; 40:11-19. [PMID: 23396098 DOI: 10.1016/j.dci.2013.01.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 01/13/2013] [Accepted: 01/14/2013] [Indexed: 06/01/2023]
Abstract
Lysozymes represent important innate immune components against bacteria. In this study, Atlantic salmon (Salmo salar) goose (g-) and chicken (c-) types of lysozyme were subjected to protein characterisations and tissue expression analyses. Specific bacterial protein inhibitors of g- and c-type lysozymes were employed to discriminate between respective enzyme activities. Blood, gills and liver contained activities exclusive for the g-type lysozyme. Only haematopoietic organs (head kidney and spleen) contained enzyme activities of both g- and c-lysozyme enzymes and c-type activity was not found outside these organs. Gene transcript levels proportional to enzyme activity levels were detected for the g-type lysozyme but not for the c-type. In vitro studies revealed significant induction of c-type gene expression and enzyme activity in macrophages after incubation with lipopolysaccharide (LPS) while expression of the g-type lysozyme gene was unaffected. The activity of purified native c-type enzyme was profoundly reduced by divalent cations and displayed low tolerance to monovalent cations, while the native g-type lysozyme was stimulated by monovalent cations and tolerated low concentrations of divalent cations. Activities of both enzymes increased with temperature elevations up to 60°C. The native g-type lysozyme responses to temperature in particular are in apparent conflict to the ones for the recombinant salmon g-lysozyme. Our results imply separate expression regulations and different functions of c- and g-type lysozymes in salmon. LPS-induced expression of c-type lysozyme and broad constitutive tissue distribution of g-type lysozyme in salmon is different from findings in other studied fish species.
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Affiliation(s)
- Bjørnar Myrnes
- Marine Biotechnology, Nofima, Muninbakken 9-13, 9291 Tromsø, Norway
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Vanlint D, Rutten N, Govers SK, Michiels CW, Aertsen A. Exposure to high hydrostatic pressure rapidly selects for increased RpoS activity and general stress-resistance in Escherichia coli O157:H7. Int J Food Microbiol 2013; 163:28-33. [PMID: 23500612 DOI: 10.1016/j.ijfoodmicro.2013.02.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 02/03/2013] [Accepted: 02/06/2013] [Indexed: 11/19/2022]
Abstract
Exposure to high hydrostatic pressure (HHP) is increasingly being used in food preservation as a non-thermal pasteurization process, and its further implementation necessitates a more thorough understanding of bacterial resistance development and intraspecies variability with regard to inactivation by HHP. In this report, we discovered that exposure to high hydrostatic pressure stress can rapidly select for strongly increased RpoS activity in a hypersensitive Escherichia coli O157:H7 strain (ATCC 43888), leading to a simultaneous increase in HHP and heat resistance. Moreover, the level of RpoS activity correlated well with the original hypersensitivity and the extent of acquired HHP resistance, and extremely HHP-resistant mutants of ATCC 43888 clearly incurred a number of additional RpoS-dependent phenotypes. These findings suggest that implementation of novel processing techniques in the food production chain can readily affect the physiology of food-borne pathogens.
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Affiliation(s)
- Dietrich Vanlint
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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Frans I, Busschaert P, Dierckens K, Michiels CW, Willems KA, Lievens B, Bossier P, Rediers H. Are type IV pili involved in <i>Vibrio anguillarum</i> virulence towards sea bass (<i>Dicentrarchus labrax</i> L.) larvae? ACTA ACUST UNITED AC 2013. [DOI: 10.4236/as.2013.46a005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Zhou K, Michiels CW, Aertsen A. Variation of intragenic tandem repeat tract of tolA modulates Escherichia coli stress tolerance. PLoS One 2012; 7:e47766. [PMID: 23094082 PMCID: PMC3477136 DOI: 10.1371/journal.pone.0047766] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 09/20/2012] [Indexed: 11/18/2022] Open
Abstract
In recent work we discovered that the intragenic tandem repeat (TR) region of the tolA gene is highly variable among different Escherichia coli strains. The aim of this study was therefore to investigate the biological function and dynamics of TR variation in E. coli tolA. The biological impact of TR variation was examined by comparing the ability of a set of synthetic tolA variants with in frame repeat copies varying from 2 to 39 to rescue the altered susceptibility of an E. coli ΔtolA mutant to deoxycholic acid, sodium dodecyl sulfate, hyperosmolarity, and infection with filamentous bacteriophage. Interestingly, although each of the TolA variants was able to at least partly rescue the ΔtolA mutant, the extent was clearly dependent on both the repeat number and the type of stress imposed, indicating the existence of opposing selective forces with regard to the optimal TR copy number. Subsequently, TR dynamics in a clonal population were assayed, and we could demonstrate that TR contractions are RecA dependent and enhanced in a DNA repair deficient uvrD background, and can occur at a frequency of 6.9×10−5.
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Affiliation(s)
- Kai Zhou
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
| | - Chris W. Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
- * E-mail:
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Vercammen A, Vanoirbeek KG, Lemmens L, Lurquin I, Hendrickx ME, Michiels CW. High pressure pasteurization of apple pieces in syrup: Microbiological shelf-life and quality evolution during refrigerated storage. INNOV FOOD SCI EMERG 2012. [DOI: 10.1016/j.ifset.2012.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Callewaert L, Van Herreweghe JM, Vanderkelen L, Leysen S, Voet A, Michiels CW. Guards of the great wall: bacterial lysozyme inhibitors. Trends Microbiol 2012; 20:501-10. [DOI: 10.1016/j.tim.2012.06.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 06/22/2012] [Accepted: 06/29/2012] [Indexed: 10/28/2022]
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Vanlint D, Rutten N, Michiels CW, Aertsen A. Emergence and stability of high-pressure resistance in different food-borne pathogens. Appl Environ Microbiol 2012; 78:3234-41. [PMID: 22344661 PMCID: PMC3346480 DOI: 10.1128/aem.00030-12] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 02/13/2012] [Indexed: 11/20/2022] Open
Abstract
High hydrostatic pressure (HHP) processing is becoming a valuable nonthermal food pasteurization technique, although there is reasonable concern that bacterial HHP resistance could compromise the safety and stability of HHP-processed foods. While the degree of natural HHP resistance has already been shown to vary greatly among and within bacterial species, a still unresolved question remains as to what extent different food-borne pathogens can actually develop HHP resistance. In this study, we therefore examined and compared the intrinsic potentials for HHP resistance development among strains of Escherichia coli, Shigella flexneri, Salmonella enterica serovars Typhimurium and Enteritidis, Yersinia enterocolitica, Aeromonas hydrophila, Pseudomonas aeruginosa, and Listeria innocua using a selective enrichment approach. Interestingly, of all strains examined, the acquisition of extreme HHP resistance could be detected in only some of the E. coli strains, indicating that a specific genetic predisposition might be required for resistance development. Furthermore, once acquired, HHP resistance proved to be a very stable trait that was maintained for >80 generations in the absence of HHP exposure. Finally, at the mechanistic level, HHP resistance was not necessarily linked to derepression of the heat shock genes and was not related to the phenomenon of persistence.
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Affiliation(s)
- Dietrich Vanlint
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty ofBioscience Engineering, KU Leuven, Leuven, Belgium.
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Vanderkelen L, van der Sar A, Goddeeris BM, Michiels CW. Are bacterial lysozyme inhibitors important in bacteria-host interactions? Commun Agric Appl Biol Sci 2012; 77:61-65. [PMID: 22558757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Affiliation(s)
- L Vanderkelen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, 3001 Leuven, Belgium
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Vercammen A, Vivijs B, Lurquin I, Michiels CW. Germination and inactivation of Bacillus coagulans and Alicyclobacillus acidoterrestris spores by high hydrostatic pressure treatment in buffer and tomato sauce. Int J Food Microbiol 2012; 152:162-7. [DOI: 10.1016/j.ijfoodmicro.2011.02.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 01/12/2011] [Accepted: 02/16/2011] [Indexed: 11/24/2022]
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Leleu S, Messens W, De Reu K, De Preter S, Herman L, Heyndrickx M, De Baerdemaeker J, Michiels CW, Bain M. Effect of egg washing on the cuticle quality of brown and white table eggs. J Food Prot 2011; 74:1649-54. [PMID: 22004811 DOI: 10.4315/0362-028x.jfp-11-013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Egg washing is currently not permitted within the European Union, with few exceptions. This is mainly because there are concerns that cuticle damage could occur during or after the washing process, as a result of a suboptimal operation. In this study, the cuticle coverage levels of 400 washed or unwashed eggs, derived from either a brown or a white egg-laying flock at the end of lay, were compared. The eggs from older hens inherently have poorer cuticle coverage and as a result arguably constitute a greater risk to consumer safety if they are then washed. Thus, the effects of the washing procedure used in this study on cuticle quality were tested under the worst-case scenario. A standard Swedish egg washing process was used. The cuticle coverage of the eggs was assessed by a colorimeter by quantifying the color difference before and after staining with Tartrazine and Green S. The cuticle of an additional 30 eggs from each of the four groups was then visually assessed by scanning electron microscopy. The staining characteristics of the cuticle varied greatly within each group of eggs and showed that the washing process did not lead to cuticle damage. Scanning electron microscopy confirmed that there was no irreversible damage to the cuticle of the washed eggs and that it was not possible to correctly assign the treatment (washed or not) based on a visual assessment. In conclusion, no evidence could be found to suggest that the washing procedure used in this investigation irreversibly changed the quality of the cuticle.
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Affiliation(s)
- S Leleu
- Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium.
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Vercammen A, Vanoirbeek KG, Lurquin I, Steen L, Goemaere O, Szczepaniak S, Paelinck H, Hendrickx ME, Michiels CW. Shelf-life extension of cooked ham model product by high hydrostatic pressure and natural preservatives. INNOV FOOD SCI EMERG 2011. [DOI: 10.1016/j.ifset.2011.07.009] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Frans I, Michiels CW, Bossier P, Willems KA, Lievens B, Rediers H. Vibrio anguillarum as a fish pathogen: virulence factors, diagnosis and prevention. J Fish Dis 2011; 34:643-661. [PMID: 21838709 DOI: 10.1111/j.1365-2761.2011.01279.x] [Citation(s) in RCA: 262] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Vibrio anguillarum, also known as Listonella anguillarum, is the causative agent of vibriosis, a deadly haemorrhagic septicaemic disease affecting various marine and fresh/brackish water fish, bivalves and crustaceans. In both aquaculture and larviculture, this disease is responsible for severe economic losses worldwide. Because of its high morbidity and mortality rates, substantial research has been carried out to elucidate the virulence mechanisms of this pathogen and to develop rapid detection techniques and effective disease-prevention strategies. This review summarizes the current state of knowledge pertaining to V. anguillarum, focusing on pathogenesis, known virulence factors, diagnosis, prevention and treatment.
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Affiliation(s)
- I Frans
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Consortium for Industrial Microbiology and Biotechnology, Department of Microbial and Molecular Systems, K.U. Leuven Association, Lessius Mechelen, Sint-Katelijne-Waver, Belgium
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Tesfazgi Mebrhatu M, Wywial E, Ghosh A, Michiels CW, Lindner AB, Taddei F, Bujnicki JM, Van Melderen L, Aertsen A. Evidence for an evolutionary antagonism between Mrr and Type III modification systems. Nucleic Acids Res 2011; 39:5991-6001. [PMID: 21504983 PMCID: PMC3152355 DOI: 10.1093/nar/gkr219] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The Mrr protein of Escherichia coli is a laterally acquired Type IV restriction endonuclease with specificity for methylated DNA. While Mrr nuclease activity can be elicited by high-pressure stress in E. coli MG1655, its (over)expression per se does not confer any obvious toxicity. In this study, however, we discovered that Mrr of E. coli MG1655 causes distinct genotoxicity when expressed in Salmonella typhimurium LT2. Genetic screening enabled us to contribute this toxicity entirely to the presence of the endogenous Type III restriction modification system (StyLTI) of S. typhimurium LT2. The StyLTI system consists of the Mod DNA methyltransferase and the Res restriction endonuclease, and we revealed that expression of the LT2 mod gene was sufficient to trigger Mrr activity in E. coli MG1655. Moreover, we could demonstrate that horizontal acquisition of the MG1655 mrr locus can drive the loss of endogenous Mod functionality present in S. typhimurium LT2 and E. coli ED1a, and observed a strong anti-correlation between close homologues of MG1655 mrr and LT2 mod in the genome database. This apparent evolutionary antagonism is further discussed in the light of a possible role for Mrr as defense mechanism against the establishment of epigenetic regulation by foreign DNA methyltransferases.
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Affiliation(s)
- Mehari Tesfazgi Mebrhatu
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Centre for Food and Microbial Technology, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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Voet A, Callewaert L, Ulens T, Vanderkelen L, Vanherreweghe JM, Michiels CW, De Maeyer M. Structure based discovery of small molecule suppressors targeting bacterial lysozyme inhibitors. Biochem Biophys Res Commun 2011; 405:527-32. [PMID: 21256115 DOI: 10.1016/j.bbrc.2011.01.053] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 01/15/2011] [Indexed: 11/28/2022]
Abstract
The production of lysozyme inhibitors, competitively binding to the lysozyme active site, is a bacterial strategy to prevent the lytic activity of host lysozymes. Therefore, suppression of the lysozyme-inhibitor interaction is an interesting new approach for drug development since restoration of the bacterial lysozyme sensitivity will support bacterial clearance from the infected sites. Using molecular modelling techniques the interaction of the Salmonella PliC inhibitor with c-type lysozyme was studied and a protein-protein interaction based pharmacophore model was created. This model was used as a query to identify molecules, with potential affinity for the target, and subsequently, these molecules were filtered using molecular docking. The retained molecules were validated as suppressors of lysozyme inhibitory proteins using in vitro experiments revealing four active molecules.
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Affiliation(s)
- Arnout Voet
- Laboratory for Biomolecular Modelling and BioMacS, Katholieke Universiteit Leuven, Celestijnenlaan 200G bus 2403, 3001 Heverlee, Leuven, Belgium.
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Leysen S, Van Herreweghe JM, Callewaert L, Heirbaut M, Buntinx P, Michiels CW, Strelkov SV. Molecular basis of bacterial defense against host lysozymes: X-ray structures of periplasmic lysozyme inhibitors PliI and PliC. J Mol Biol 2010; 405:1233-45. [PMID: 21146533 DOI: 10.1016/j.jmb.2010.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 11/25/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
Abstract
Lysozymes play a key role in the innate immune system of vertebrates and invertebrates by hydrolyzing peptidoglycan, a vital component of the bacterial cell wall. Gram-negative bacteria produce various types of lysozyme inhibitors that allow them to survive the bactericidal action of lysozyme when their outer membrane is permeabilized. So far, three lysozyme inhibitor families have been described: the Ivy (inhibitor of vertebrate lysozyme) family, the MliC/PliC (membrane-associated/periplasmic lysozyme inhibitor of C-type lysozyme) family, and the PliI (periplasmic lysozyme inhibitor of I-type lysozyme) family. Here, we report high-resolution crystal structures of Salmonella typhimurium PliC (PliC-St) and Aeromonas hydrophila PliI (PliI-Ah). The structure of PliI-Ah is the first in the recently discovered PliI family of lysozyme inhibitors, while the structure of PliC-St is the first structure of a periplasmic lysozyme inhibitor from the PliC/MliC family. Using small-angle X-ray scattering, we demonstrate that both PliC-St and PliI-Ah form stable dimers in solution. The functional dimer architecture of PliC-St is very different from that of the recently described MliC from Pseudomonas aeruginosa (MliC-Pa), despite the close resemblance of their monomers. Furthermore, PliI-Ah has distinctly different monomer and dimer folds compared to PliC, MliC, and Ivy proteins. Site-directed mutagenesis suggests that the inhibitory action of PliI-Ah proceeds via an insertion of a loop containing the conserved SGxY motif into the active center of I-type lysozymes. This motif is related to the functional SGxxY motif found in the MliC/PliC family.
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Affiliation(s)
- S Leysen
- Laboratory for Biocrystallography, Department of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Herestraat 49 bus 822, 3000 Leuven, Belgium
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Cebrián G, Michiels CW, Mañas P, Condón S. Biological approach to modeling of Staphylococcus aureus high-hydrostatic-pressure inactivation kinetics. Appl Environ Microbiol 2010; 76:6982-90. [PMID: 20817808 PMCID: PMC2976245 DOI: 10.1128/aem.00900-10] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 08/24/2010] [Indexed: 12/14/2022] Open
Abstract
Graphs for survival under high hydrostatic pressure (450 MPa; 25°C; citrate-phosphate buffer, pH 7.0) of stationary-growth-phase cells of eight Staphylococcus aureus strains were found to be nonlinear. The strains could be classified into two groups on the basis of the shoulder length. Some of them showed long shoulders of up to 20 min at 450 MPa, while others had shoulders of <3.5 min. All strains showed tails. No significant differences in the inactivation rate were found during the log-linear death phase among the eight strains. The entry into stationary growth phase resulted both in an increase in shoulder length and in a decrease in the inactivation rate. However, whereas shoulder length proved to depend on sigma B factor activity, the inactivation rate did not. Recovery in anaerobiosis decreased the inactivation rate but did not affect the shoulder length. Addition of the minimum noninhibitory concentration of sodium chloride to the recovery medium resulted in a decrease in shoulder length and in an increase in the inactivation rate for stationary-growth-phase cells. In the tail region, up to 90% of the population remained sensitive to sodium chloride.
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Affiliation(s)
- Guillermo Cebrián
- Tecnología de los Alimentos, Facultad de Veterinaria de Zaragoza, Universidad de Zaragoza, C/ Miguel Servet 177, 50013 Zaragoza, Spain
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Vanderkelen L, Van Herreweghe JM, Vanoirbeek KGA, Baggerman G, Myrnes B, Declerck PJ, Nilsen IW, Michiels CW, Callewaert L. Identification of a bacterial inhibitor against g-type lysozyme. Cell Mol Life Sci 2010; 68:1053-64. [PMID: 20734102 DOI: 10.1007/s00018-010-0507-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 07/12/2010] [Accepted: 08/10/2010] [Indexed: 01/17/2023]
Abstract
Lysozymes are antibacterial effectors of the innate immune system in animals that hydrolyze peptidoglycan. Bacteria have evolved protective mechanisms that contribute to lysozyme tolerance such as the production of lysozyme inhibitors, but only inhibitors of chicken (c-) and invertebrate (i-) type lysozyme have been identified. We here report the discovery of a novel Escherichia coli inhibitor specific for goose (g-) type lysozymes, which we designate PliG (periplasmic lysozyme inhibitor of g-type lysozyme). Although it does not inhibit c- or i-type lysozymes, PliG shares a structural sequence motif with the previously described PliI and MliC/PliC lysozyme inhibitor families, suggesting a common ancestry and mode of action. Deletion of pliG increased the sensitivity of E. coli to g-type lysozyme. The existence of inhibitors against all major types of animal lysozyme and their contribution to lysozyme tolerance suggest that lysozyme inhibitors may play a role in bacterial interactions with animal hosts.
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Affiliation(s)
- L Vanderkelen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre, Katholieke Universiteit Leuven, Belgium
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Abstract
The ability of many bacteria to adhere to surfaces and to form biofilms has major implications in a variety of industries including the food industry, where biofilms create a persistent source of contamination. The formation of a biofilm is determined not only by the nature of the attachment surface, but also by the characteristics of the bacterial cell and by environmental factors. This review focuses on the features of the bacterial cell surface such as flagella, surface appendages and polysaccharides that play a role in this process, in particular for bacteria linked to food-processing environments. In addition, some aspects of the attachment surface, biofilm control and eradication will be highlighted.
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Affiliation(s)
- R Van Houdt
- Unit of Microbiology, Expert Group Molecular and Cellular Biology, Belgian Nuclear Research Centre (SCK·CEN), Mol, Belgium
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