1
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A Genomic Island of Vibrio cholerae Encodes a Three-Component Cytotoxin with Monomer and Protomer Forms Structurally Similar to Alpha-Pore-Forming Toxins. J Bacteriol 2022; 204:e0055521. [PMID: 35435721 DOI: 10.1128/jb.00555-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Alpha-pore-forming toxins (α-PFTs) are secreted by many species of bacteria, including Escherichia coli, Aeromonas hydrophila, and Bacillus thuringiensis, as part of their arsenal of virulence factors, and are often cytotoxic. In particular, for α-PFTs, the membrane-spanning channel they form is composed of hydrophobic α-helices. These toxins oligomerize at the surface of target cells and transition from a soluble to a protomer state in which they expose their hydrophobic regions and insert into the membrane to form a pore. The pores may be composed of homooligomers of one component or heterooligomers with two or three components, resulting in bi- or tripartite toxins. The multicomponent α-PFTs are often expressed from a single operon. Recently, motility-associated killing factor A (MakA), an α-PFT, was discovered in Vibrio cholerae. We report that makA is found on the V. cholerae GI-10 genomic island within an operon containing genes for two other potential α-PFTs, MakB and MakE. We determined the X-ray crystal structures for MakA, MakB, and MakE and demonstrated that all three are structurally related to the α-PFT family in the soluble state, and we modeled their protomer state based on the α-PFT AhlB from A. hydrophila. We found that MakA alone is cytotoxic at micromolar concentrations. However, combining MakA with MakB and MakE is cytotoxic at nanomolar concentrations, with specificity for J774 macrophage cells. Our data suggest that MakA, -B, and -E are α-PFTs that potentially act as a tripartite pore-forming toxin with specificity for phagocytic cells. IMPORTANCE The bacterium Vibrio cholerae causes gastrointestinal, wound, and skin infections. The motility-associated killing factor A (MakA) was recently shown to be cytotoxic against colon, prostate, and other cancer cells. However, at the outset of this study, the capacity of MakA to damage cells in combination with other Mak proteins encoded in the same operon had not been elucidated. We determined the structures of three Mak proteins and established that they are structurally related to the α-PFTs. Compared to MakA alone, the combination of all three toxins was more potent specifically in mouse macrophages. This study highlights the idea that the Mak toxins are selectively cytotoxic and thus may function as a tripartite toxin with cell type specificity.
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Jessberger N, Diedrich R, Janowski R, Niessing D, Märtlbauer E. Presence and function of Hbl B', the fourth protein component encoded by the hbl operon in Bacillus cereus. Virulence 2022; 13:483-501. [PMID: 35291913 PMCID: PMC8932913 DOI: 10.1080/21505594.2022.2046951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The genes hblC, hblD and hblA encode the components Hbl L2, L1 and B of the pore forming enterotoxin haemolysin BL of Bacillus cereus. Two variants of the operon existand the more common one additionally contains hblB downstream of hblCDA. Up to now, it was completely unclear whether the corresponding protein, Hbl B', is widely expressed among B. cereus strains and if it has a distinct function. In the present study, it was shown that the hblB gene is indeed expressed and the Hbl B' protein is secreted by nearly all analysed B. cereus strains. For the latter, a detection system was developed based on monoclonal antibody 11A5. Further, a distinct reduction of cytotoxic and haemolytic activity was observed when recombinant (r)Hbl B' was applied simultaneously with L2, L1 and B. This effect was due to direct interaction of rHbl B' with L1. D-6B. cereusAltogether, we present the first simple tool for the detection of Hbl B' in B. cereus culture supernatants. Moreover, an important regulatory function of Hbl B' in the mechanism of Hbl was determined, which is best described as an additional control of complex formation, balancing the amounts of Hbl B-L1 complexes and the corresponding free subunits.
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Affiliation(s)
- Nadja Jessberger
- Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Richard Diedrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
| | - Robert Janowski
- Institute of Structural Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany
| | - Dierk Niessing
- Institute of Structural Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany.,Institute of Pharmaceutical Biotechnology, Ulm University, Ulm, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Oberschleißheim, Germany
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Nadeem A, Berg A, Pace H, Alam A, Toh E, Ådén J, Zlatkov N, Myint SL, Persson K, Gröbner G, Sjöstedt A, Bally M, Barandun J, Uhlin BE, Wai SN. Protein-lipid interaction at low pH induces oligomerization of the MakA cytotoxin from Vibrio cholerae. eLife 2022; 11:73439. [PMID: 35131030 PMCID: PMC8824476 DOI: 10.7554/elife.73439] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 01/19/2022] [Indexed: 12/29/2022] Open
Abstract
The α-pore-forming toxins (α-PFTs) from pathogenic bacteria damage host cell membranes by pore formation. We demonstrate a remarkable, hitherto unknown mechanism by an α-PFT protein from Vibrio cholerae. As part of the MakA/B/E tripartite toxin, MakA is involved in membrane pore formation similar to other α-PFTs. In contrast, MakA in isolation induces tube-like structures in acidic endosomal compartments of epithelial cells in vitro. The present study unravels the dynamics of tubular growth, which occurs in a pH-, lipid-, and concentration-dependent manner. Within acidified organelle lumens or when incubated with cells in acidic media, MakA forms oligomers and remodels membranes into high-curvature tubes leading to loss of membrane integrity. A 3.7 Å cryo-electron microscopy structure of MakA filaments reveals a unique protein-lipid superstructure. MakA forms a pinecone-like spiral with a central cavity and a thin annular lipid bilayer embedded between the MakA transmembrane helices in its active α-PFT conformation. Our study provides insights into a novel tubulation mechanism of an α-PFT protein and a new mode of action by a secreted bacterial toxin.
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Affiliation(s)
- Aftab Nadeem
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Alexandra Berg
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.,Science for Life Laboratory (SciLifeLab), Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Hudson Pace
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,Department of Clinical Microbiology, Umeå University, Umeå, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden
| | - Athar Alam
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.,Department of Clinical Microbiology, Umeå University, Umeå, Sweden
| | - Eric Toh
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Jörgen Ådén
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,Department of Chemistry, Umeå University, Umeå, Sweden
| | - Nikola Zlatkov
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Si Lhyam Myint
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Karina Persson
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,Department of Chemistry, Umeå University, Umeå, Sweden
| | - Gerhard Gröbner
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,Department of Chemistry, Umeå University, Umeå, Sweden
| | - Anders Sjöstedt
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.,Department of Clinical Microbiology, Umeå University, Umeå, Sweden
| | - Marta Bally
- Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,Department of Clinical Microbiology, Umeå University, Umeå, Sweden.,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden
| | - Jonas Barandun
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Bernt Eric Uhlin
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
| | - Sun Nyunt Wai
- Department of Molecular Biology, Umeå University, Umeå, Sweden.,Umeå Centre for Microbial Research (UCMR), Umeå University, Umeå, Sweden.,The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden
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4
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Categorizing sequences of concern by function to better assess mechanisms of microbial pathogenesis. Infect Immun 2021; 90:e0033421. [PMID: 34780277 PMCID: PMC9119117 DOI: 10.1128/iai.00334-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
To identify sequences with a role in microbial pathogenesis, we assessed the adequacy of their annotation by existing controlled vocabularies and sequence databases. Our goal was to regularize descriptions of microbial pathogenesis for improved integration with bioinformatic applications. Here, we review the challenges of annotating sequences for pathogenic activity. We relate the categorization of more than 2,750 sequences of pathogenic microbes through a controlled vocabulary called Functions of Sequences of Concern (FunSoCs). These allow for an ease of description by both humans and machines. We provide a subset of 220 fully annotated sequences in the supplemental material as examples. The use of this compact (∼30 terms), controlled vocabulary has potential benefits for research in microbial genomics, public health, biosecurity, biosurveillance, and the characterization of new and emerging pathogens.
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5
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Ramm F, Stech M, Zemella A, Frentzel H, Kubick S. The Pore-Forming Hemolysin BL Enterotoxin from Bacillus cereus: Subunit Interactions in Cell-Free Systems. Toxins (Basel) 2021; 13:toxins13110807. [PMID: 34822591 PMCID: PMC8623112 DOI: 10.3390/toxins13110807] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/05/2021] [Accepted: 11/12/2021] [Indexed: 11/16/2022] Open
Abstract
The tripartite enterotoxin Hemolysin BL (Hbl) has been widely characterized as a hemolytic and cytotoxic virulence factor involved in foodborne diarrheal illness caused by Bacillus cereus. Previous studies have described the formation of the Hbl complex and aimed to identify the toxin’s mode of action. In this study, we analyzed the assembly of Hbl out of its three individual subunits L1, L2 and B in a soluble as well as a putative membrane bound composition using a Chinese hamster ovary (CHO) cell-free system. Subunits were either coexpressed or synthesized individually in separate cell-free reactions and mixed together afterwards. Hemolytic activity of cell-free synthesized subunits was demonstrated on 5% sheep blood agar and identified both synthesis procedures, coexpression as well as individual synthesis of each subunit, as functional for the synthesis of an active Hbl complex. Hbl’s ability to perforate cell membranes was evaluated using a propidium iodide uptake assay. These data suggested that coexpressed Hbl subunits augmented cytotoxic activity with increasing concentrations. Further, a pre-pore-complex of L1-L2 showed cytotoxic effects suggesting the possibility of an interaction between the cell membrane and the pre-pore-complex. Overall, this study shows that cell-free protein synthesis is a fast and efficient way to study the assembly of multiple protein subunits in soluble as well as vesicular fractions.
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Affiliation(s)
- Franziska Ramm
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; (F.R.); (M.S.); (A.Z.)
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
| | - Marlitt Stech
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; (F.R.); (M.S.); (A.Z.)
| | - Anne Zemella
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; (F.R.); (M.S.); (A.Z.)
| | - Hendrik Frentzel
- Department of Biological Safety, German Federal Institute for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany;
| | - Stefan Kubick
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), Branch Bioanalytics and Bioprocesses (IZI-BB), Am Mühlenberg 13, 14476 Potsdam, Germany; (F.R.); (M.S.); (A.Z.)
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany
- Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus–Senftenberg, Brandenburg Medical School Theodor Fontane and the University of Potsdam, 14476 Potsdam, Germany
- Correspondence: ; Tel.: +49-331-58-187-306; Fax: +49-331-58-187-199
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6
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Jovanovic J, Ornelis VFM, Madder A, Rajkovic A. Bacillus cereus food intoxication and toxicoinfection. Compr Rev Food Sci Food Saf 2021; 20:3719-3761. [PMID: 34160120 DOI: 10.1111/1541-4337.12785] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 05/13/2021] [Accepted: 05/15/2021] [Indexed: 12/12/2022]
Abstract
Bacillus cereus is one of the leading etiological agents of toxin-induced foodborne diseases. Its omnipresence in different environments, spore formation, and its ability to adapt to varying conditions and produce harmful toxins make this pathogen a health hazard that should not be underestimated. Food poisoning by B. cereus can manifest itself as an emetic or diarrheal syndrome. The former is caused by the release of the potent peptide toxin cereulide, whereas the latter is the result of proteinaceous enterotoxins (e.g., hemolysin BL, nonhemolytic enterotoxin, and cytotoxin K). The final harmful effect is not only toxin and strain dependent, but is also affected by the stress responses, accessory virulence factors, and phenotypic properties under extrinsic, intrinsic, and explicit food conditions and host-related environment. Infamous portrait of B. cereus as a foodborne pathogen, as well as a causative agent of nongastrointestinal infections and even nosocomial complications, has inspired vast volumes of multidisciplinary research in food and clinical domains. As a result, extensive original data became available asking for a new, both broad and deep, multifaceted look into the current state-of-the art regarding the role of B. cereus in food safety. In this review, we first provide an overview of the latest knowledge on B. cereus toxins and accessory virulence factors. Second, we describe the novel taxonomy and some of the most pertinent phenotypic characteristics of B. cereus related to food safety. We link these aspects to toxin production, overall pathogenesis, and interactions with its human host. Then we reflect on the prevalence of different toxinotypes in foods opening the scene for epidemiological aspects of B. cereus foodborne diseases and methods available to prevent food poisoning including overview of the different available methods to detect B. cereus and its toxins.
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Affiliation(s)
- Jelena Jovanovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Vincent F M Ornelis
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Annemieke Madder
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Andreja Rajkovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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7
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Worthy HL, Williamson LJ, Auhim HS, Leppla SH, Sastalla I, Jones DD, Rizkallah PJ, Berry C. The Crystal Structure of Bacillus cereus HblL 1. Toxins (Basel) 2021; 13:253. [PMID: 33807365 PMCID: PMC8065917 DOI: 10.3390/toxins13040253] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 02/07/2023] Open
Abstract
The Hbl toxin is a three-component haemolytic complex produced by Bacillus cereus sensu lato strains and implicated as a cause of diarrhoea in B. cereus food poisoning. While the structure of the HblB component of this toxin is known, the structures of the other components are unresolved. Here, we describe the expression of the recombinant HblL1 component and the elucidation of its structure to 1.36 Å. Like HblB, it is a member of the alpha-helical pore-forming toxin family. In comparison to other members of this group, it has an extended hydrophobic beta tongue region that may be involved in pore formation. Molecular docking was used to predict possible interactions between HblL1 and HblB, and suggests a head to tail dimer might form, burying the HblL1 beta tongue region.
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Affiliation(s)
- Harley L. Worthy
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
- The Henry Wellcome Building for Biocatalysis, Exeter University, Stocker Road, Exeter EX4 4QD, UK
| | - Lainey J. Williamson
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
| | - Husam Sabah Auhim
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
- Department of Biology, College of Science, University of Baghdad, Baghdad, Iraq
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (S.H.L.); (I.S.)
| | - Inka Sastalla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA; (S.H.L.); (I.S.)
- Scientific Review Program, Division of Extramural Activities, NIAID, NIH, Rockville, MD 20892, USA
| | - D. Dafydd Jones
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
| | | | - Colin Berry
- School of Biosciences, Cardiff University, Park Place, Cardiff CF10 3AX, UK; (H.L.W.); (L.J.W.); (H.S.A.); (D.D.J.)
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8
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
Abstract
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.
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Characteristics of the Protein Complexes and Pores Formed by Bacillus cereus Hemolysin BL. Toxins (Basel) 2020; 12:toxins12110672. [PMID: 33114414 PMCID: PMC7694065 DOI: 10.3390/toxins12110672] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/13/2020] [Accepted: 10/21/2020] [Indexed: 11/25/2022] Open
Abstract
Bacillus cereus Hemolysin BL is a tripartite toxin responsible for a diarrheal type of food poisoning. Open questions remain regarding its mode of action, including the extent to which complex formation prior to cell binding contributes to pore-forming activity, how these complexes are composed, and the properties of the pores formed in the target cell membrane. Distinct complexes of up to 600 kDa were found on native gels, whose structure and size were primarily defined by Hbl B. Hbl L1 and L2 were also identified in these complexes using Western blotting and an LC-MS approach. LC-MS also revealed that many other proteins secreted by B. cereus exist in complexes. Further, a decrease of toxic activity at temperatures ≥60 °C was shown, which was unexpectedly restored at higher temperatures. This could be attributed to a release of Hbl B monomers from tight complexation, resulting in enhanced cell binding. In contrast, Hbl L1 was rather susceptible to heat, while heat treatment of Hbl L2 seemed not to be crucial. Furthermore, Hbl-induced pores had a rather small single-channel conductance of around 200 pS and a probable channel diameter of at least 1 nm on planar lipid bilayers. These were highly instable and had a limited lifetime, and were also slightly cation-selective. Altogether, this study provides astonishing new insights into the complex mechanism of Hbl pore formation, as well as the properties of the pores.
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Schwenk V, Riegg J, Lacroix M, Märtlbauer E, Jessberger N. Enteropathogenic Potential of Bacillus thuringiensis Isolates from Soil, Animals, Food and Biopesticides. Foods 2020; 9:foods9101484. [PMID: 33080854 PMCID: PMC7603059 DOI: 10.3390/foods9101484] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 12/14/2022] Open
Abstract
Despite its benefits as biological insecticide, Bacillus thuringiensis bears enterotoxins, which can be responsible for a diarrhoeal type of food poisoning. Thus, all 24 isolates from foodstuffs, animals, soil and commercially used biopesticides tested in this study showed the genetic prerequisites necessary to provoke the disease. Moreover, though highly strain-specific, various isolates were able to germinate and also to actively move, which are further requirements for the onset of the disease. Most importantly, all isolates could grow under simulated intestinal conditions and produce significant amounts of enterotoxins. Cytotoxicity assays classified 14 isolates as highly, eight as medium and only two as low toxic. Additionally, growth inhibition by essential oils (EOs) was investigated as preventive measure against putatively enteropathogenic B. thuringiensis. Cinnamon Chinese cassia showed the highest antimicrobial activity, followed by citral, oregano and winter savory. In all tests, high strain-specific variations appeared and must be taken into account when evaluating the hazardous potential of B. thuringiensis and using EOs as antimicrobials. Altogether, the present study shows a non-negligible pathogenic potential of B. thuringiensis, independently from the origin of isolation. Generally, biopesticide strains were indistinguishable from other isolates. Thus, the use of these pesticides might indeed increase the risk for consumers’ health. Until complete information about the safety of the applied strains and formulations is available, consumers or manufacturers might benefit from the antimicrobial activity of EOs to reduce the level of contamination.
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Affiliation(s)
- Valerie Schwenk
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (V.S.); (J.R.); (E.M.)
| | - Janina Riegg
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (V.S.); (J.R.); (E.M.)
| | - Monique Lacroix
- Centre Armand-Frappier Santé Biotechnologie, 531, boul. des Prairies, Laval, QC H7V 1B7, Canada;
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (V.S.); (J.R.); (E.M.)
| | - Nadja Jessberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (V.S.); (J.R.); (E.M.)
- Correspondence:
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11
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Bacillus cereus: Epidemiology, Virulence Factors, and Host-Pathogen Interactions. Trends Microbiol 2020; 29:458-471. [PMID: 33004259 DOI: 10.1016/j.tim.2020.09.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 09/03/2020] [Accepted: 09/04/2020] [Indexed: 12/30/2022]
Abstract
The toxin-producing bacterium Bacillus cereus is an important and neglected human pathogen and a common cause of food poisoning. Several toxins have been implicated in disease, including the pore-forming toxins hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE). Recent work revealed that HBL binds to the mammalian surface receptors LITAF and CDIP1 and that both HBL and NHE induce potassium efflux and activate the NLRP3 inflammasome, leading to pyroptosis. These mammalian receptors, in part, contribute to inflammation and pathology. Other putative virulence factors of B. cereus include cytotoxin K, cereulide, metalloproteases, sphingomyelinase, and phospholipases. In this review, we highlight the latest progress in our understanding of B. cereus biology, epidemiology, and pathogenesis, and discuss potential new directions for research in this field.
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Unique inducible filamentous motility identified in pathogenic Bacillus cereus group species. ISME JOURNAL 2020; 14:2997-3010. [PMID: 32770116 PMCID: PMC7784679 DOI: 10.1038/s41396-020-0728-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 07/11/2020] [Accepted: 07/23/2020] [Indexed: 01/03/2023]
Abstract
Active migration across semi-solid surfaces is important for bacterial success by facilitating colonization of unoccupied niches and is often associated with altered virulence and antibiotic resistance profiles. We isolated an atmospheric contaminant, subsequently identified as a new strain of Bacillus mobilis, which showed a unique, robust, rapid, and inducible filamentous surface motility. This flagella-independent migration was characterized by formation of elongated cells at the expanding edge and was induced when cells were inoculated onto lawns of metabolically inactive Campylobacter jejuni cells, autoclaved bacterial biomass, adsorbed milk, and adsorbed blood atop hard agar plates. Phosphatidylcholine (PC), bacterial membrane components, and sterile human fecal extracts were also sufficient to induce filamentous expansion. Screening of eight other Bacillus spp. showed that filamentous motility was conserved amongst B. cereus group species to varying degrees. RNA-Seq of elongated expanding cells collected from adsorbed milk and PC lawns versus control rod-shaped cells revealed dysregulation of genes involved in metabolism and membrane transport, sporulation, quorum sensing, antibiotic synthesis, and virulence (e.g., hblA/B/C/D and plcR). These findings characterize the robustness and ecological significance of filamentous surface motility in B. cereus group species and lay the foundation for understanding the biological role it may play during environment and host colonization.
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Rajkovic A, Jovanovic J, Monteiro S, Decleer M, Andjelkovic M, Foubert A, Beloglazova N, Tsilla V, Sas B, Madder A, De Saeger S, Uyttendaele M. Detection of toxins involved in foodborne diseases caused by Gram‐positive bacteria. Compr Rev Food Sci Food Saf 2020; 19:1605-1657. [DOI: 10.1111/1541-4337.12571] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/10/2020] [Accepted: 04/14/2020] [Indexed: 12/11/2022]
Affiliation(s)
- Andreja Rajkovic
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
| | - Jelena Jovanovic
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
| | - Silvia Monteiro
- Laboratorio Analises, Instituto Superior TecnicoUniversidade de Lisboa Lisbon Portugal
| | - Marlies Decleer
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
- Laboratory of Food Analysis, Department of Bioanalysis, Faculty of Pharmaceutical SciencesGhent University Ghent Belgium
| | - Mirjana Andjelkovic
- Operational Directorate Food, Medicines and Consumer SafetyService for Chemical Residues and Contaminants Brussels Belgium
| | - Astrid Foubert
- Laboratory of Food Analysis, Department of Bioanalysis, Faculty of Pharmaceutical SciencesGhent University Ghent Belgium
| | - Natalia Beloglazova
- Laboratory of Food Analysis, Department of Bioanalysis, Faculty of Pharmaceutical SciencesGhent University Ghent Belgium
- Nanotechnology Education and Research CenterSouth Ural State University Chelyabinsk Russia
| | - Varvara Tsilla
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
| | - Benedikt Sas
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
| | - Annemieke Madder
- Laboratorium for Organic and Biomimetic Chemistry, Department of Organic and Macromolecular ChemistryGhent University Ghent Belgium
| | - Sarah De Saeger
- Laboratory of Food Analysis, Department of Bioanalysis, Faculty of Pharmaceutical SciencesGhent University Ghent Belgium
| | - Mieke Uyttendaele
- Laboratory of Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience EngineeringGhent University Ghent Belgium
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Huang B, Liang Y, Pan H, Xie L, Jiang T, Jiang T. Hemolytic and cytotoxic activity from cultures of Aureococcus anophagefferens-a causative species of brown tides in the north-western Bohai Sea, China. CHEMOSPHERE 2020; 247:125819. [PMID: 31927184 DOI: 10.1016/j.chemosphere.2020.125819] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 12/20/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
Brown tides were first observed in 2009 in the north-western Bohai Sea (Qinhuangdao sea area), China, and blooms have occurred at different scales in late spring every year since then. Although the detrimental effects on marine organisms of the causative phytoplankton species Aureococcus anophagefferens have been extensively studied, the mechanism remains poorly understood. We used erythrocytes and adrenal gland chromaffin tumor cells (PC12) to explore the hemolytic activity and cytotoxicity, respectively, of chloroform and methanol extracts of cultured A. anophagefferens isolated from the north-western Bohai Sea area. The methanol extracts showed no hemolytic or cytotoxic activity. Chloroform extracts had a potent hemolytic effect on rabbit erythrocytes; thin layer chromatography (TLC) indicated that the hemolysin was a kind of glycolipid compound. Erythrocyte lysis assay showed that erythrocytes of sea bream were sensitive to the hemolysin, whereas those of human and chicken erythrocytes were insensitive. The hemolytic effects were elevated as temperatures rose from 4 °C to 37 °C. Hemolytic blocking experiments showed that sphingomyelin and d-xylose can inhibit hemolysis significantly, while osmotic protectants with different hydrated molecular diameters had no inhibition, and the hemolysins had no obvious phospholipase activity. The chloroform extracts of A. anophagefferens had significant inhibitory effects on the viability of PC12 cells, and can induce efflux of lactic dehydrogenase (LDH) of PC12 cells and lead to their necrosis.
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Affiliation(s)
- Baiqiang Huang
- Research Center of Harmful Algae & Marine Biology, Jinan University, Guangzhou, 510632, China
| | - Yanlan Liang
- Research Center of Harmful Algae & Marine Biology, Jinan University, Guangzhou, 510632, China
| | - Huizhu Pan
- Research Center of Harmful Algae & Marine Biology, Jinan University, Guangzhou, 510632, China
| | - Lei Xie
- Research Center of Harmful Algae & Marine Biology, Jinan University, Guangzhou, 510632, China
| | - Tao Jiang
- Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Key Laboratory of Sustainable Development of Marine Fisheries, Ministry of Agriculture, Qingdao, 266071, China; Function Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266200, China.
| | - Tianjiu Jiang
- Research Center of Harmful Algae & Marine Biology, Jinan University, Guangzhou, 510632, China.
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Sun Y, Zhang G, Hou X, Xiao S, Yang X, Xie Y, Huang X, Wang F, Mo X, Ding X, Xia L, Hu S. SrfABC Toxin from Xenorhabdus stockiae Induces Cytotoxicity and Apoptosis in HeLa Cells. Toxins (Basel) 2019; 11:toxins11120685. [PMID: 31766712 PMCID: PMC6950479 DOI: 10.3390/toxins11120685] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/11/2019] [Accepted: 11/14/2019] [Indexed: 11/16/2022] Open
Abstract
Our previous study showed that the srfABC operon, which was originally identified in Salmonella enterica as an SsrB-regulated operon clustered with the flagellar class 2 operon, exhibited significant cytotoxicity against insect midgut CF-203 cells and injectable insecticidal activity against Helicoverpa armigera larvae. The srfABC operon was widely distributed among bacteria, which raises the question of their biological roles in different species. In this study, we investigated the cytotoxic effect of SrfABC toxin on mammalian cell lines. When simultaneously expressed in the Escherichia coli cytoplasm, SrfABC exhibited cytotoxicity against all tested mammalian cancer cell lines (B16, 4T-1, Hep-3B, and HeLa) in a dose-dependent manner. Intracellular expression of SrfA-FLAG, SrfB-FLAG, or SrfC-FLAG also resulted in inhibition of proliferation and apoptosis on HeLa cells. When incubated with HeLa cells separately, SrfA, SrfB, and SrfC proteins alone could enter HeLa cells, then induce apoptosis and cytotoxicity. SrfC protein shifts its localization from cytoplasm to nucleus with the aid of SrfA and/or SrfB protein. Although SrfA, SrfB, and SrfC proteins alone exhibited a cytotoxic effect against HeLa cells, all three components were essential for the full cytotoxicity. Native PAGE and co-immunoprecipitation assay demonstrated that SrfA, SrfB, and SrfC proteins could interact with each other and form a heteromeric complex.
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Chen D, Li Y, Lv J, Liu X, Gao P, Zhen G, Zhang W, Wu D, Jing H, Li Y, Zhao Y, Ma X, Ma H, Zhang L. A foodborne outbreak of gastroenteritis caused by Norovirus and Bacillus cereus at a university in the Shunyi District of Beijing, China 2018: a retrospective cohort study. BMC Infect Dis 2019; 19:910. [PMID: 31664944 PMCID: PMC6819576 DOI: 10.1186/s12879-019-4570-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 10/16/2019] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND On September 4, 2018, a boarding school in the Shunyi District of Beijing, China reported an outbreak of acute gastroenteritis. At least 209 suspected students caused of diarrhea and vomiting. The case was investigated, and control measures were taken to prevent further spread. METHODS A retrospective cohort study was conducted among the school students and staff in order to test hypothesis that high risk of food served at the school canteen. We collected information on demographics, refectory records, person to person transmission by uniform epidemiological questionnaire. Risk ratios (RR) and 95% confidence intervals (CI) were calculated. Stool specimens of cases and canteen employees, retained food, water, and environmental swabs were investigated by laboratory analysis. RESULTS We identified 209 cases (including 28 laboratory-confirmed cases) which occurred from August 29 to September 10. All cases were students, and the average age was 20, 52% were male. The outbreak lasted for 13 days, and peaked on September 5. Consumption of Drinks stall and Rice flour stall on September 1 (RR:3.4, 95%CI:1.5-7.8, and RR:7.6, 95%CI:2.8-20.2), Rice flour stall and Fish meal stall on September 2 (RR:4.0, 95%CI:1.2-13.6, and RR:4.6, 95%CI:1.7-12.5), muslim meal stall on September 4 (RR:2.7, 95%CI:1.3-5.4), Barbeque stall on September 5 (RR:3.0, 95%CI:1.2-7.0) were independently associated with increased risk of disease within the following 2 days. Among 35 specimens of rectal swabs or feces from students, 28 specimens were positive. Norovirus GI.6 alone was detected in 23 specimens, Bacillus cereus alone in 3 specimens and both norovirus GI.6 and Bacillus cereus in 2 specimens. Ten specimens of rectal swabs from canteen employees were positive for norovirus GI, and 2 specimens were positive for Bacillus cereus. Four retained food specimens were positive for Bacillus cereus, and environmental samples were negative for any viruses or bacteria. CONCLUSION Our investigation indicated that canteen employees were infected by two pathogens (norovirus and Bacillus cereus) and transmission may have been possible due to unhygienic practices. Student consumption of food or drink at high-risk stalls was determined as the probable cause of the outbreak.
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Affiliation(s)
- Dongwan Chen
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China.
| | - Yongjin Li
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Jinchang Lv
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Xiufeng Liu
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Peng Gao
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Guoxin Zhen
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Wenzeng Zhang
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Dan Wu
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Hongbo Jing
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Ying Li
- Shunyi Center for Disease Control and Prevention, No. 1 Guangming South Street, Shunyi District, Beijing, China
| | - Yao Zhao
- Beijing Center for Disease Control and Prevention, Beijing, China
| | - Xiaochen Ma
- Beijing Center for Disease Control and Prevention, Beijing, China
| | - Huilai Ma
- Chinese Center for Disease Control and Prevention, Beijing, China
| | - Lijie Zhang
- Chinese Center for Disease Control and Prevention, Beijing, China
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Binding to The Target Cell Surface Is The Crucial Step in Pore Formation of Hemolysin BL from Bacillus cereus. Toxins (Basel) 2019; 11:toxins11050281. [PMID: 31137585 PMCID: PMC6563250 DOI: 10.3390/toxins11050281] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/13/2019] [Accepted: 05/16/2019] [Indexed: 12/19/2022] Open
Abstract
A major virulence factor involved in Bacillus cereus food poisoning is the three-component enterotoxin hemolysin BL. It consists of the binding component B and the two lytic components L1 and L2. Studying its mode of action has been challenging, as natural culture supernatants additionally contain Nhe, the second three-component enterotoxin, and purification of recombinant (r) Hbl components has been difficult. In this study, we report on pore-forming, cytotoxic, cell binding and hemolytic activity of recently generated rHbl components expressed in E. coli. It is known that all three Hbl components are necessary for cytotoxicity and pore formation. Here we show that an excess of rHbl B enhances, while an excess of rHbl L1 hinders, the velocity of pore formation. Most rapid pore formation was observed with ratios L2:L1:B = 1:1:10 and 10:1:10. It was further verified that Hbl activity is due to sequential binding of the components B - L1 - L2. Accordingly, all bioassays proved that binding of Hbl B to the cell surface is the crucial step for pore formation and cytotoxic activity. Binding of Hbl B took place within minutes, while apposition of the following L1 and L2 occurred immediately. Further on, applying toxin components simultaneously, it seemed that Hbl L1 enhanced binding of B to the target cell surface. Overall, these data contribute significantly to the elucidation of the mode of action of Hbl, and suggest that its mechanism of pore formation differs substantially from that of Nhe, although both enterotoxin complexes are sequentially highly related.
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Nguyen AT, Tallent SM. Screening food for Bacillus cereus toxins using whole genome sequencing. Food Microbiol 2019; 78:164-170. [DOI: 10.1016/j.fm.2018.10.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2018] [Revised: 08/24/2018] [Accepted: 10/21/2018] [Indexed: 11/24/2022]
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A multicomponent toxin from Bacillus cereus incites inflammation and shapes host outcome via the NLRP3 inflammasome. Nat Microbiol 2018; 4:362-374. [PMID: 30531979 DOI: 10.1038/s41564-018-0318-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 11/07/2018] [Indexed: 12/25/2022]
Abstract
Host recognition of microbial components is essential in mediating an effective immune response. Cytosolic bacteria must secure entry into the host cytoplasm to facilitate replication and, in doing so, liberate microbial ligands that activate cytosolic innate immune sensors and the inflammasome. Here, we identified a multicomponent enterotoxin, haemolysin BL (HBL), that engages activation of the inflammasome. This toxin is highly conserved among the human pathogen Bacillus cereus. The three subunits of HBL bind to the cell membrane in a linear order, forming a lytic pore and inducing activation of the NLRP3 inflammasome, secretion of interleukin-1β and interleukin-18, and pyroptosis. Mechanistically, the HBL-induced pore results in the efflux of potassium and triggers the activation of the NLRP3 inflammasome. Furthermore, HBL-producing B. cereus induces rapid inflammasome-mediated mortality. Pharmacological inhibition of the NLRP3 inflammasome using MCC950 prevents B. cereus-induced lethality. Overall, our results reveal that cytosolic sensing of a toxin is central to the innate immune recognition of infection. Therapeutic modulation of this pathway enhances host protection against deadly bacterial infections.
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Evidence for Complex Formation of the Bacillus cereus Haemolysin BL Components in Solution. Toxins (Basel) 2017; 9:toxins9090288. [PMID: 28926954 PMCID: PMC5618221 DOI: 10.3390/toxins9090288] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 09/11/2017] [Accepted: 09/12/2017] [Indexed: 02/08/2023] Open
Abstract
Haemolysin BL is an important virulence factor regarding the diarrheal type of food poisoning caused by Bacillus cereus. However, the pathogenic importance of this three-component enterotoxin is difficult to access, as nearly all natural B. cereus culture supernatants additionally contain the highly cytotoxic Nhe, the second three-component toxin involved in the aetiology of B. cereus-induced food-borne diseases. To better address the toxic properties of the Hbl complex, a system for overexpression and purification of functional, cytotoxic, recombinant (r)Hbl components L2, L1 and B from E. coli was established and an nheABC deletion mutant was constructed from B. cereus reference strain F837/76. Furthermore, 35 hybridoma cell lines producing monoclonal antibodies (mAbs) against Hbl L2, L1 and B were generated. While mAbs 1H9 and 1D8 neutralized Hbl toxicity and thus, represent important tools for future investigations of the mode-of-action of Hbl on the target cell surface, mAb 1D7, in contrast, even enhanced Hbl toxicity by supporting the binding of Hbl B to the cell surface. By using the specific mAbs in Dot blots, indirect and hybrid sandwich enzyme immuno assays (EIAs), complex formation between Hbl L1 and B, as well as L1 and L2 in solution could be shown for the first time. Surface plasmon resonance experiments with the rHbl components confirmed these results with KD values of 4.7 × 10−7 M and 1.5 × 10−7 M, respectively. These findings together with the newly created tools lay the foundation for the detailed elucidation of the molecular mode-of-action of the highly complex three-component Hbl toxin.
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McHugh AJ, Feehily C, Hill C, Cotter PD. Detection and Enumeration of Spore-Forming Bacteria in Powdered Dairy Products. Front Microbiol 2017; 8:109. [PMID: 28197144 PMCID: PMC5281614 DOI: 10.3389/fmicb.2017.00109] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 01/16/2017] [Indexed: 01/28/2023] Open
Abstract
With the abolition of milk quotas in the European Union in 2015, several member states including Ireland, Luxembourg, and Belgium have seen year on year bi-monthly milk deliveries to dairies increase by up to 35%. Milk production has also increased outside of Europe in the past number of years. Unsurprisingly, there has been a corresponding increased focus on the production of dried milk products for improved shelf life. These powders are used in a wide variety of products, including confectionery, infant formula, sports dietary supplements and supplements for health recovery. To ensure quality and safety standards in the dairy sector, strict controls are in place with respect to the acceptable quantity and species of microorganisms present in these products. A particular emphasis on spore-forming bacteria is necessary due to their inherent ability to survive extreme processing conditions. Traditional microbiological detection methods used in industry have limitations in terms of time, efficiency, accuracy, and sensitivity. The following review will explore the common spore-forming bacterial contaminants of milk powders, will review the guidelines with respect to the acceptable limits of these microorganisms and will provide an insight into recent advances in methods for detecting these microbes. The various advantages and limitations with respect to the application of these diagnostics approaches for dairy food will be provided. It is anticipated that the optimization and application of these methods in appropriate ways can ensure that the enhanced pressures associated with increased production will not result in any lessening of safety and quality standards.
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Affiliation(s)
- Aoife J McHugh
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; School of Microbiology, University College CorkCork, Ireland
| | - Conor Feehily
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; APC Microbiome InstituteCork, Ireland
| | - Colin Hill
- School of Microbiology, University College CorkCork, Ireland; APC Microbiome InstituteCork, Ireland
| | - Paul D Cotter
- Food Bioscience Department, Teagasc Food Research CentreCork, Ireland; APC Microbiome InstituteCork, Ireland
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Formation of small transmembrane pores: An intermediate stage on the way to Bacillus cereus non-hemolytic enterotoxin (Nhe) full pores in the absence of NheA. Biochem Biophys Res Commun 2015; 469:613-8. [PMID: 26654951 DOI: 10.1016/j.bbrc.2015.11.126] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 11/27/2015] [Indexed: 02/03/2023]
Abstract
The non-hemolytic enterotoxin (Nhe) of Bacillus cereus is a three-partite toxin formed of the components NheA, -B and -C. Pore formation and subsequent lysis of target cells caused by Nhe is an orchestrated process comprising three steps: (i) formation of NheB/C oligomers in solution, (ii) attachment of the oligomers to the cell membrane, (iii) binding of NheA to the oligomers. The present study aimed to characterize the properties of the NheB/C complex and the fate of the target cell upon binding. An enzyme immunoassay allowing kinetic measurements and surface plasmon resonance revealed the fast and high affinity formation of the NheB/C oligomers. The benefit of these complexes is a more stable cell binding as well as stronger and earlier cytotoxic effect. High molecular mass hetero-oligomers (620 kDa) probably consisting of one NheC and up to 15 NheB were detected by size-exclusion chromatography and on native PAGE immunoblots. Due to the NheBC application the morphology and membrane permeability of Vero cells is partly disturbed. Formation of stable transmembrane channels with a conductance of about 870 pS and a diameter of about 2 nm due to the application of NheBC could be demonstrated in lipid bilayer experiments. Thus, the NheBC complex itself has a tendency to increase the membrane permeability prior to the emergence of full pores containing also NheA.
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Bacillus cereus NVH 0500/00 Can Adhere to Mucin but Cannot Produce Enterotoxins during Gastrointestinal Simulation. Appl Environ Microbiol 2015; 82:289-96. [PMID: 26497468 DOI: 10.1128/aem.02940-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 10/16/2015] [Indexed: 12/30/2022] Open
Abstract
Adhesion to the intestinal epithelium could constitute an essential mechanism of Bacillus cereus pathogenesis. However, the enterocytes are protected by mucus, a secretion composed mainly of mucin glycoproteins. These may serve as nutrients and sites of adhesion for intestinal bacteria. In this study, the food poisoning bacterium B. cereus NVH 0500/00 was exposed in vitro to gastrointestinal hurdles prior to evaluation of its attachment to mucin microcosms and its ability to produce nonhemolytic enterotoxin (Nhe). The persistence of mucin-adherent B. cereus after simulated gut emptying was determined using a mucin adhesion assay. The stability of Nhe toward bile and pancreatin (intestinal components) in the presence of mucin agar was also investigated. B. cereus could grow and simultaneously adhere to mucin during in vitro ileal incubation, despite the adverse effect of prior exposure to a low pH or intestinal components. The final concentration of B. cereus in the simulated lumen at 8 h of incubation was 6.62 ± 0.87 log CFU ml(-1). At that point, the percentage of adhesion was approximately 6%. No enterotoxin was detected in the ileum, due to either insufficient bacterial concentrations or Nhe degradation. Nevertheless, mucin appears to retain B. cereus and to supply it to the small intestine after simulated gut emptying. Additionally, mucin may play a role in the protection of enterotoxins from degradation by intestinal components.
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Distribution of six exotoxin genes and production of L2-HBL and nheA proteins in six Bacillus cereus isolates from infant formula and produce. Food Sci Biotechnol 2015. [DOI: 10.1007/s10068-015-0050-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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Cytochrome c551 and the cytochrome c maturation pathway affect virulence gene expression in Bacillus cereus ATCC 14579. J Bacteriol 2014; 197:626-35. [PMID: 25422307 DOI: 10.1128/jb.02125-14] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Loss of the cytochrome c maturation system in Bacillus cereus results in increased transcription of the major enterotoxin genes nhe, hbl, and cytK and the virulence regulator plcR. Increased virulence factor production occurs at 37°C under aerobic conditions, similar to previous findings in Bacillus anthracis. Unlike B. anthracis, much of the increased virulence gene expression can be attributed to loss of only c551, one of the two small c-type cytochromes. Additional virulence factor expression occurs with loss of resBC, encoding cytochrome c maturation proteins, independently of the presence of the c-type cytochrome genes. Hemolytic activity of strains missing either cccB or resBC is increased relative to that in the parental strain, while sporulation efficiency is unaffected in the mutants. Increased virulence gene expression in the ΔcccB and ΔresBC mutants occurs only in the presence of an intact plcR gene, indicating that this process is PlcR dependent. These findings suggest a new mode of regulation of B. cereus virulence and reveal intriguing similarities and differences in virulence regulation between B. cereus and B. anthracis.
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Celandroni F, Salvetti S, Senesi S, Ghelardi E. Bacillus thuringiensis membrane-damaging toxins acting on mammalian cells. FEMS Microbiol Lett 2014; 361:95-103. [PMID: 25283838 DOI: 10.1111/1574-6968.12615] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 01/20/2023] Open
Abstract
Bacillus thuringiensis is widely used as a biopesticide in forestry and agriculture, being able to produce potent species-specific insecticidal toxins and considered nonpathogenic to other animals. More recently, however, repeated observations are documenting the association of this microorganism with various infectious diseases in humans, such as food-poisoning-associated diarrheas, periodontitis, bacteremia, as well as ocular, burn, and wound infections. Similar to B. cereus, B. thuringiensis produces an array of virulence factors acting against mammalian cells, such as phosphatidylcholine- and phosphatidylinositol-specific phospholipase C (PC-PLC and PI-PLC), hemolysins, in particular hemolysin BL (HBL), and various enterotoxins. The contribution of some of these toxins to B. thuringiensis pathogenicity has been studied in animal models of infection, following intravitreous, intranasal, or intratracheal inoculation. These studies lead to the speculation that the activities of PC-PLC, PI-PLC, and HBL are responsible for most of the pathogenic properties of B. thuringiensis in nongastrointestinal infections in mammals. This review summarizes data regarding the biological activity, the genetic basis, and the structural features of these membrane-damaging toxins.
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Affiliation(s)
- Francesco Celandroni
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
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Zhu K, Acaröz U, Märtlbauer E. A cellular logic circuit for the detection of bacterial pore-forming toxins. Chem Commun (Camb) 2013; 49:5198-200. [PMID: 23632899 DOI: 10.1039/c3cc41932k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We present a cellular logic circuit for deciphering the profiles of toxin production in B. cereus, using multiple readout techniques based on the pore formation on the cell membrane. This new assay enables the simultaneous detection of seven biomarkers in pathogenic strains from various samples.
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Affiliation(s)
- Kui Zhu
- Institute of Food Safety, Faculty of Veterinary Medicine, Ludwig-Maximilians-University Munich, Schönleutnerstr. 8, 85764 Oberschleissheim, Germany.
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Jeßberger N, Dietrich R, Bock S, Didier A, Märtlbauer E. Bacillus cereus enterotoxins act as major virulence factors and exhibit distinct cytotoxicity to different human cell lines. Toxicon 2013; 77:49-57. [PMID: 24211313 DOI: 10.1016/j.toxicon.2013.10.028] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/29/2013] [Indexed: 11/17/2022]
Abstract
A comparative analysis on the relevance of the Bacillus cereus enterotoxins Nhe (nonhemolytic enterotoxin), HBL (haemolysin BL) and CytK (cytotoxin K) was accomplished, concerning their toxic activity towards different target cell lines. Overall, among the components secreted by the reference strains for Nhe and HBL, the enterotoxin complexes accounted for over 90% of the total toxicity. Vero and primary endothelial cells (HUVEC) were highly susceptible to Nhe, whereas Hep-G2, Vero and A549 reacted most sensitive to Nhe plus HBL. For CytK the highest toxicity was observed on CaCo-2 cells. As HBL positive strains always produce Nhe in parallel, the specific contribution of both enterotoxin complexes to the overall observed cytotoxic effects was determined by consecutively removing their single components. While in most cell lines Nhe and HBL contributed more or less equally (40-60%) to cytotoxicity, the relative activity of Nhe was approximately 90% in HUVEC, and that of HBL 75% in A549 cells. With U937, a nearly Nhe resistant cell line was identified for the first time. This distinct susceptibility of cell lines was confirmed by investigating a set of 37 B. cereus strains. Interestingly, whereas Nhe is the enterotoxin mainly responsible for cell death as determined by WST-1 bioassays, more rapid pore formation was observed when HBL was present, pointing to a different mode of action of the two enterotoxin complexes. Furthermore, correlation was observed between cytotoxicity of solely Nhe producing strains and NheB. Cytotoxicity of Nhe/HBL producing isolates correlated with the expression of HBL L1, NheB and HBL B. In conclusion, the observed susceptibilities of target cell lines of different histological origin underline that B. cereus enterotoxins represent major virulence factors and that toxicity is not restricted to gastrointestinal infections. The varying contribution of Nhe and HBL to total cytotoxicity strongly indicates that Nhe as well as HBL specific B. cereus enterotoxin receptors exist.
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Affiliation(s)
- Nadja Jeßberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany.
| | - Richard Dietrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany
| | - Stefanie Bock
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany
| | - Andrea Didier
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany
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Sastalla I, Fattah R, Coppage N, Nandy P, Crown D, Pomerantsev AP, Leppla SH. The Bacillus cereus Hbl and Nhe tripartite enterotoxin components assemble sequentially on the surface of target cells and are not interchangeable. PLoS One 2013; 8:e76955. [PMID: 24204713 PMCID: PMC3799921 DOI: 10.1371/journal.pone.0076955] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/28/2013] [Indexed: 02/06/2023] Open
Abstract
Bacillus cereus is a spore-forming, Gram-positive bacterium commonly associated with outbreaks of food poisoning. It is also known as an opportunistic pathogen causing clinical infections such as bacteremia, meningitis, pneumonia, and gas gangrene-like cutaneous infections, mostly in immunocompromised patients. B. cereus secretes a plethora of toxins of which four are associated with the symptoms of food poisoning. Two of these, the non-hemolytic enterotoxin Nhe and the hemolysin BL (Hbl) toxin, are predicted to be structurally similar and are unique in that they require the combined action of three toxin proteins to induce cell lysis. Despite their dominant role in disease, the molecular mechanism of their toxic function is still poorly understood. We report here that B. cereus strain ATCC 10876 harbors not only genes encoding Nhe, but also two copies of the hbl genes. We identified Hbl as the major secreted toxin responsible for inducing rapid cell lysis both in cultured cells and in an intraperitoneal mouse toxicity model. Antibody neutralization and deletion of Hbl-encoding genes resulted in significant reductions of cytotoxic activity. Microscopy studies with Chinese Hamster Ovary cells furthermore showed that pore formation by both Hbl and Nhe occurs through a stepwise, sequential binding of toxin components to the cell surface and to each other. This begins with binding of Hbl-B or NheC to the eukaryotic membrane, and is followed by the recruitment of Hbl-L1 or NheB, respectively, followed by the corresponding third protein. Lastly, toxin component complementation studies indicate that although Hbl and Nhe can be expressed simultaneously and are predicted to be structurally similar, they are incompatible and cannot complement each other.
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Affiliation(s)
- Inka Sastalla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Rasem Fattah
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Nicole Coppage
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Poulomi Nandy
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Devorah Crown
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Andrei P. Pomerantsev
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
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Samundeeswari A, Dhas SP, Nirmala J, John SP, Mukherjee A, Chandrasekaran N. Biosynthesis of silver nanoparticles using actinobacteriumStreptomyces albogriseolusand its antibacterial activity. Biotechnol Appl Biochem 2012; 59:503-7. [PMID: 23586961 DOI: 10.1002/bab.1054] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 10/18/2012] [Indexed: 11/09/2022]
Affiliation(s)
| | - Sindhu Priya Dhas
- Centre for Nanobiotechnology; VIT University; Vellore; Tamil Nadu; India
| | - Joyce Nirmala
- Centre for Nanobiotechnology; VIT University; Vellore; Tamil Nadu; India
| | - Shiny Punalur John
- Centre for Nanobiotechnology; VIT University; Vellore; Tamil Nadu; India
| | - Amitava Mukherjee
- Centre for Nanobiotechnology; VIT University; Vellore; Tamil Nadu; India
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Temperature-dependent production of various PlcR-controlled virulence factors in Bacillus weihenstephanensis strain KBAB4. Appl Environ Microbiol 2012; 78:2553-61. [PMID: 22307282 DOI: 10.1128/aem.07446-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus cereus sensu lato complex has recently been divided into several phylogenetic groups with clear differences in growth temperature range. However, only a few studies have investigated the actual pathogenic potential of the psychrotolerant strains of the B. cereus group at low temperature, and little information is available concerning gene expression at low temperature. We found that vegetative cells of the psychrotolerant B. weihenstephanensis strain KBAB4 were pathogenic against the model insect Galleria mellonella at 15°C but not at 30°C. A similar temperature-dependent difference also was observed for the supernatant, which was cytotoxic to Vero epithelial cell lines and to murine macrophage J774 cells at 15°C but not at 30°C. We therefore determined the effect of low temperature on the production of various proteins putatively involved in virulence using two-dimensional protein gel electrophoresis, and we showed that the production of the Hbl enterotoxin and of two proteases, NprB and NprP2, was greater at a growth temperature of 15°C than at 30°C. The quantification of the mRNA levels for these virulence genes by real-time quantitative PCR at both temperatures showed that there was also more mRNA present at 15°C than at 30°C. We also found that at 15°C, hbl mRNA levels were maximal in the mid- to late exponential growth phase. In conclusion, we found that the higher virulence of the B. cereus KBAB4 strain at low temperature was accompanied by higher levels of the production of various known PlcR-controlled virulence factors and by a higher transcriptional activity of the corresponding genes.
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Ceuppens S, Rajkovic A, Heyndrickx M, Tsilia V, Van De Wiele T, Boon N, Uyttendaele M. Regulation of toxin production by Bacillus cereus and its food safety implications. Crit Rev Microbiol 2011; 37:188-213. [PMID: 21417966 DOI: 10.3109/1040841x.2011.558832] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Toxin expression is of utmost importance for the food-borne pathogen B. cereus, both in food poisoning and non-gastrointestinal host infections as well as in interbacterial competition. Therefore it is no surprise that the toxin gene expression is tightly regulated by various internal and environmental signals. An overview of the current knowledge regarding emetic and diarrheal toxin transcription and expression is presented in this review. The food safety aspects and management tools such as temperature control, food preservatives and modified atmosphere packaging are discussed specifically for B. cereus emetic and diarrheal toxin production.
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Affiliation(s)
- Siele Ceuppens
- Ghent University, Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Food Preservation, Ghent, Belgium
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Cytotoxicity of the Bacillus cereus Nhe enterotoxin requires specific binding order of its three exoprotein components. Infect Immun 2010; 78:3813-21. [PMID: 20624910 DOI: 10.1128/iai.00247-10] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study focuses on the interaction of the three components of the Bacillus cereus Nhe enterotoxin with particular emphasis on the functional roles of NheB and NheC. The results demonstrated that both NheB and NheC were able to bind to Vero cells directly while NheA lacked this ability. It was also shown that Nhe-induced cytotoxicity required a specific binding order of the individual components whereby the presence of NheC in the priming step as well as the presence of NheA in the final incubation step was mandatory. Priming of cells with NheB alone and addition of NheA plus NheC in the second step failed to induce toxic effects. Furthermore, in solution, excess NheC inhibited binding of NheB to Vero cells, whereas priming of cells with excess NheC resulted in full toxicity if unbound NheC was removed before addition of NheB. By using mutated NheC proteins where the two cysteine residues in the predicted beta-tongue were replaced with glycine (NheCcys-) or where the entire hydrophobic stretch was deleted (NheChr-), the predicted hydrophobic beta-tongue of NheC was found essential for binding to cell membranes but not for interaction with NheB in solution. All data presented here are compatible with the following model. The first step in the mode of action of Nhe is associated with binding of NheC and NheB to the cell surface and probably accompanied by conformational changes. These events allow subsequent binding of NheA, leading to cell lysis.
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37
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Production, secretion and biological activity of Bacillus cereus enterotoxins. Toxins (Basel) 2010; 2:1690-703. [PMID: 22069656 PMCID: PMC3153264 DOI: 10.3390/toxins2071690] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 06/14/2010] [Accepted: 06/28/2010] [Indexed: 11/17/2022] Open
Abstract
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.
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38
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Molva C, Sudagidan M, Okuklu B. Extracellular enzyme production and enterotoxigenic gene profiles of Bacillus cereus and Bacillus thuringiensis strains isolated from cheese in Turkey. Food Control 2009. [DOI: 10.1016/j.foodcont.2008.10.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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39
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Park YB, Kim JB, Shin SW, Kim JC, Cho SH, Lee BK, Ahn J, Kim JM, Oh DH. Prevalence, genetic diversity, and antibiotic susceptibility of Bacillus cereus strains isolated from rice and cereals collected in Korea. J Food Prot 2009; 72:612-7. [PMID: 19343952 DOI: 10.4315/0362-028x-72.3.612] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Incidence and properties of Bacillus cereus strains naturally present in cereals were evaluated by phenotypic characterization, antibiotic susceptibility testing, and pulsed-field gel electrophoresis. Of 293 cereal samples tested, 73 (25%) contained B. cereus strains. Incidence of B. cereus isolates varied with respect to sample; they were found in 15 (37%) of 83 brown rice samples, 23 (37%) of 63 glutinous rice samples, 16 (21%) of 76 barley samples, and 19 (27%) of 71 Job's tears samples. All B. cereus isolates from cereals were positive for diarrheal toxin genes. The isolates were susceptible to most of the antibiotics tested, but they were highly resistant to ampicillin, cefepime, oxacillin, and penicillin. Of the genes assayed by the PCR technique, a high frequency of nheA (99%) and hblDC (84%) was found in the genomic DNA of cereal-associated isolates, whereas cytK was less common (55%). From the strains carrying the hblDC genes, 93% produced enterotoxin HBL. B. cereus isolates did not have significant genetic homology. The genetic diversity and toxic potential differ among the strains isolated from cereals. These results provide important information on toxin gene profiles of cereal-associated B. cereus for population studies.
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Affiliation(s)
- Yong-Bae Park
- Division of Health Research & Planning, Gyeonggi-do Research Institute of Health & Environment, Pajang-dong 324-1, Gyeonggi-do, Suwon 440-290, Republic of Korea
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40
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Construction of a non toxic chimeric protein (L1–L2–B) of Haemolysin BL from Bacillus cereus and its application in HBL toxin detection. J Microbiol Methods 2008; 75:472-7. [DOI: 10.1016/j.mimet.2008.07.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 06/23/2008] [Accepted: 07/21/2008] [Indexed: 11/23/2022]
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41
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Cobo Molinos A, Abriouel H, Lucas López R, Ben Omar N, Valdivia E, Gálvez A. Inhibition of Bacillus cereus and Bacillus weihenstephanensis in raw vegetables by application of washing solutions containing enterocin AS-48 alone and in combination with other antimicrobials. Food Microbiol 2008; 25:762-70. [PMID: 18620967 DOI: 10.1016/j.fm.2008.05.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 04/29/2008] [Accepted: 05/04/2008] [Indexed: 11/19/2022]
Abstract
Enterocin AS-48 is a broad-spectrum cyclic antimicrobial peptide produced by Enterococcus faecalis. In the present study, the bacteriocin was tested alone and in combination with other antimicrobials for decontamination of Bacillus inoculated on alfalfa, soybean sprouts and green asparagus. Washing with enterocin AS-48 solutions reduced viable cell counts of Bacillus cereus and Bacillus weihenstephanensis by 1.0-1.5 and by 1.5-2.38 log units right after application of treatment, respectively. In both cases, the bacteriocin was effective in reducing the remaining viable population below detection levels during further storage of the samples at 6 degrees C, but failed to prevent regrowth in samples stored at 15 or 22 degrees C. Application of washing treatments containing enterocin AS-48 in combination with several other antimicrobials and sanitizers (cinnamic and hydrocinnamic acids, carvacrol, polyphosphoric acid, peracetic acid, hexadecylpyridinium chloride and sodium hypochlorite) greatly enhanced the bactericidal effects. The combinations of AS-48 and sodium hypochlorite, peracetic acid or hexadecylpyridinium chloride provided the best results. After application of the combined treatments on alfalfa sprouts contaminated with B. cereus or with B. weihenstephanensis, viable bacilli were not detected or remained at very low concentrations in the treated samples during a 1-week storage period at 15 degrees C. Inhibition of B. cereus by in situ produced bacteriocin was tested by cocultivation with the AS-48 producer strain E. faecalis A-48-32 inoculated on soybean sprouts. Strain A-48-32 was able to grow and produce bacteriocin on sprouts both at 15 and 22 degrees C. At 15 degrees C, growth of B. cereus was completely inhibited in the cocultures, while a much more limited effect was observed at 22 degrees C. The results obtained for washing treatments are very encouraging for the application of enterocin AS-48 in the decontamination of sprouts. Application of washing treatments containing AS-48 alone can serve to reduce viable cell counts of bacilli in samples stored under refrigeration, while application of combined treatments should be recommended to avoid proliferation of the surviving bacilli under temperature-abuse conditions.
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Affiliation(s)
- Antonio Cobo Molinos
- Area de Microbiología, Departamento de Ciencias de la Salud, Facultad de Ciencias Experimentales, Universidad de Jaén, 23071 Jaén, Spain
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42
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Stenfors Arnesen LP, Fagerlund A, Granum PE. From soil to gut:Bacillus cereusand its food poisoning toxins. FEMS Microbiol Rev 2008; 32:579-606. [DOI: 10.1111/j.1574-6976.2008.00112.x] [Citation(s) in RCA: 676] [Impact Index Per Article: 42.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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43
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Ouoba LII, Thorsen L, Varnam AH. Enterotoxins and emetic toxins production by Bacillus cereus and other species of Bacillus isolated from Soumbala and Bikalga, African alkaline fermented food condiments. Int J Food Microbiol 2008; 124:224-30. [DOI: 10.1016/j.ijfoodmicro.2008.03.026] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 03/07/2008] [Accepted: 03/24/2008] [Indexed: 11/16/2022]
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44
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Ngamwongsatit P, Banada PP, Panbangred W, Bhunia AK. WST-1-based cell cytotoxicity assay as a substitute for MTT-based assay for rapid detection of toxigenic Bacillus species using CHO cell line. J Microbiol Methods 2008; 73:211-5. [DOI: 10.1016/j.mimet.2008.03.002] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 03/04/2008] [Accepted: 03/05/2008] [Indexed: 11/25/2022]
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Madegowda M, Eswaramoorthy S, Burley SK, Swaminathan S. X-ray crystal structure of the B component of Hemolysin BL from Bacillus cereus. Proteins 2008; 71:534-40. [PMID: 18175317 DOI: 10.1002/prot.21888] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Bacillus cereus Hemolysin BL enterotoxin, a ternary complex of three proteins, is the causative agent of food poisoning and requires all three components for virulence. The X-ray structure of the binding domain of HBL suggests that it may form a pore similar to other soluble channel forming proteins. A putative pathway of pore formation is discussed.
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Affiliation(s)
- Mahendra Madegowda
- Biology Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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46
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Gray KM, Banada PP, O'Neal E, Bhunia AK. Rapid Ped-2E9 cell-based cytotoxicity analysis and genotyping of Bacillus species. J Clin Microbiol 2005; 43:5865-72. [PMID: 16333068 PMCID: PMC1317164 DOI: 10.1128/jcm.43.12.5865-5872.2005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/22/2005] [Accepted: 09/25/2005] [Indexed: 11/20/2022] Open
Abstract
Bacillus species causing food-borne disease produce multiple toxins eliciting gastroenteritis. Toxin assays with mammalian cell cultures are reliable but may take 24 to 72 h to complete and also lack sensitivity. Here, a sensitive and rapid assay was developed using a murine hybridoma Ped-2E9 cell model. Bacillus culture supernatants containing toxins were added to a Ped-2E9 cell line and analyzed for cytotoxicity with an alkaline phosphatase release assay. Most Bacillus cereus strains produced positive cytotoxicity results within 1 h, and data were comparable to those obtained with the standard Chinese hamster ovary (CHO)-based cytotoxicity assay, which took about 72 h to complete. Moreover, the Ped-2E9 cell assay had 25- to 58-fold-higher sensitivity than the CHO assay. Enterotoxin-producing Bacillus thuringiensis also gave positive results with Ped-2E9 cells, while several other Bacillus species were negative. Eight isolates from food suspected of Bacillus contamination were also tested, and only one strain, which was later confirmed as B. cereus, gave a positive result. In comparison with two commercial diarrheal toxin assay kits (BDE-VIA and BCET-RPLA), the Ped-2E9 assay performed more reliably. Toxin fractions of >30 kDa showed the highest degree of cytotoxicity effects, and heat treatment significantly reduced the toxin activity, indicating the involvement of a heat-labile high-molecular-weight component in Ped-2E9 cytotoxicity. PCR results, in most cases, were in agreement with the cytotoxic potential of each strain. Ribotyping was used to identify cultures and indicated differences for several previously reported isolates. This Ped-2E9 cell assay could be used as a rapid (approximately 1-h) alternative to current methods for sensitive detection of enterotoxins from Bacillus species.
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Affiliation(s)
- Kristen M Gray
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA
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47
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Sergeev N, Distler M, Vargas M, Chizhikov V, Herold KE, Rasooly A. Microarray analysis of Bacillus cereus group virulence factors. J Microbiol Methods 2005; 65:488-502. [PMID: 16242802 DOI: 10.1016/j.mimet.2005.09.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Revised: 09/12/2005] [Accepted: 09/12/2005] [Indexed: 11/19/2022]
Abstract
Bacillus cereus, B. thuringiensis and B. anthracis are closely related medically and economically important bacterial species that belong to the B. cereus group. Members of the B. cereus group carry genes encoding several important virulence factors, including enterotoxins, phospholipases and exotoxins. Since it is difficult to differentiate among B. cereus group members, and because Bacillus virulence factors are very important for pathogenesis, we explored the use of microarray-based detection of virulence factor genes as a tool for strain identification and for determining virulence. Our method requires an initial multiplex PCR amplification step, followed by identification of the PCR amplicons by hybridization to an oligonucleotide microarray containing genes for all three types of Bacillus virulence factors including B. anthracis virulence factors. The DNA chip described here contains 21 identical arrays used for analysis of seven samples in triplicates. Using the arrays, we found that virulence factors are present in several combinations in the strains analyzed. This work also demonstrates the potential of oligonucleotide microarrays for medical, food safety and biodefense analysis of microbial pathogens.
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48
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Yang IC, Shih DYC, Huang TP, Huang YP, Wang JY, Pan TM. Establishment of a novel multiplex PCR assay and detection of toxigenic strains of the species in the Bacillus cereus group. J Food Prot 2005; 68:2123-30. [PMID: 16245717 DOI: 10.4315/0362-028x-68.10.2123] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Five different enterotoxins and one emetic toxin of Bacillus cereus have been characterized. To amplify all of the enterotoxin and emetic-specific sequences of the species in the B. cereus group, a multiplex PCR with 12 primer pairs was established. In developing the assay method, a common terminal sequence at the 3' ends of all primers was chosen and a hot start Taq polymerase was used to overcome primer dimer formation. The assay was successfully applied to analyze the toxigenic potential of 162 food-poisoning and food-related strains. Results showed that there were 10 toxigenic patterns for all the test strains. All of the B. cereus strains carried at least one toxin gene. More than 70% of Bacillus mycoides strains carried no known toxin genes. The toxin profiles and toxin genes of B. mycoides strains were significantly different from B. cereus strains (P < 0.05), although the two species were closely related. The results suggest that many B. mycoides strains might be less prone to cause food poisoning. They also indicate the importance of detecting the toxin genes together with the detection of the species in the B. cereus group.
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Affiliation(s)
- I-Chen Yang
- Institute of Microbiology and Biochemistry, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan, Republic of China
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49
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Ryu JH, Kim H, Beuchat LR. Spore formation by Bacillus cereus in broth as affected by temperature, nutrient availability, and manganese. J Food Prot 2005; 68:1734-8. [PMID: 21132988 DOI: 10.4315/0362-028x-68.8.1734] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A study was done to determine the effect of interacting factors on sporulation of Bacillus cereus in broth. Vegetative cells (1.4 to 2.2 log CFU/ml) of B. cereus strain 038-2 (capable of growing at 12 degrees C) and strain F3812/84 (capable of growing at 8 degrees C) were inoculated into 30 ml of tryptic soy broth (TSB), TSB supplemented with manganese (50 microg/ml), diluted (10%) TSB (dTSB), and dTSB supplemented with manganese (50 microg/ml) and incubated at 8, 12, or 22 degrees C for up to 30, 30, or 10 days, respectively. Unheated and heated (80 degrees C for 10 min) cultures were plated on brain heart infusion agar to determine total cell counts (vegetative cells plus spores) and the number of spores produced, respectively. Both strains of B. cereus survived in TSB and dTSB for 30 days at 8 degrees C but did not sporulate. At 12 degrees C, cells grew in TSB to a population of 6.0 +/- 0.8 log CFU/ml, which was maintained for 30 days. Neither strain grew in dTSB at 12 degrees C and survived for at least 30 days. Spores were not produced in any of the test broths at 12 degrees C. At 22 degrees C, cells reached a stationary growth phase between 12 and 24 h in TSB, TSB supplemented with manganese, and dTSB supplemented with manganese, and approximately 1% of the CFU were spores. In dTSB, cell growth and spore formation were retarded at 22 degrees C and a significantly lower number of spores was produced compared with the number of spores produced in TSB, TSB supplemented with manganese, and dTSB supplemented with manganese. The addition of manganese to TSB did not affect cell growth or spore formation, but manganese did enhance sporulation in dTSB. This study provides useful information on spore formation by B. cereus as affected by conditions that may be imposed in liquid milieus on the surface of foods and on food contact surfaces in processing environments.
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Affiliation(s)
- Jee-Hoon Ryu
- Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797, USA
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Abstract
The genus Bacillus includes members that demonstrate a wide range of diversity from physiology and ecological niche to DNA sequence and gene regulation. The species of most interest tend to be known for their pathogenicity and are closely linked genetically. Bacillus anthracis causes anthrax, and Bacillus thuringiensis is widely used for its insecticidal properties but has also been associated with foodborne disease. Bacillus cereus causes two types of food poisoning, the emetic and diarrheal syndromes, and a variety of local and systemic infections. Although in this review we provide information on the genus and a variety of species, the primary focus is on the B. cereus strains and toxins that are involved in foodborne illness. B. cereus produces a large number of potential virulence factors, but for the majority of these factors their roles in specific infections have not been established. To date, only cereulide and the tripartite hemolysin BL have been identified specifically as emetic and diarrheal toxins, respectively. Nonhemolytic enterotoxin, a homolog of hemolysin BL, also has been associated with the diarrheal syndrome. Recent findings regarding these and other putative enterotoxins are discussed.
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Affiliation(s)
- Jean L Schoeni
- Department of Food Microbiology and Toxicology, Food Research Institute, University of Wisconsin, Madison, Wisconsin 53706, USA
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