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Bacillus cereus Toxin Repertoire: Diversity of (Iso)cereulide(s). MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27030872. [PMID: 35164132 PMCID: PMC8840689 DOI: 10.3390/molecules27030872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/14/2022] [Accepted: 01/19/2022] [Indexed: 11/17/2022]
Abstract
The emetic Bacillus cereus toxin cereulide (1) poses a significant safety risk in the food industry, causing emesis and nausea after consumption of contaminated foods. Analogously to cereulide, the structures of various isocereulides, namely, isocereulides A–G, have been recently reported and could also be identified in B. cereus-contaminated food samples. The HPLC fractionation of B. cereus extracts allows us to isolate additional isocereulides. By applying MSn sequencing, post-hydrolytic dipeptide, amino acid and α-hydroxy acid analyses using UPLC-ESI-TOF-MS to purify the analytes, seven new isocereulides H–N (2–8) could be elucidated in their chemical structures. The structure elucidation was supported by one-dimensional and two-dimensional NMR spectra of the isocereulides H (2), K (5), L and N (6 + 8) and M (7). The toxicity of 2–8 was investigated in a HEp-2 cell assay to determine their respective 50% effective concentration (EC50). Thus, 2–8 exhibited EC50 values ranging from a 0.4- to 1.4-fold value compared to cereulide (1). Missing structure-activity correlations indicate the necessity to determine the toxic potential of all naturally present isocereulides as single compounds to be able to perform a thorough toxicity evaluation of B. cereus-contaminated foods in the future.
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Walser V, Kranzler M, Ehling-Schulz M, Stark TD, Hofmann TF. Structure Revision of Isocereulide A, an Isoform of the Food Poisoning Emetic Bacillus cereus Toxin Cereulide. Molecules 2021; 26:molecules26051360. [PMID: 33806334 PMCID: PMC7961578 DOI: 10.3390/molecules26051360] [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: 02/11/2021] [Revised: 02/25/2021] [Accepted: 02/26/2021] [Indexed: 12/13/2022] Open
Abstract
The emetic Bacillus cereus toxin cereulide presents an enormous safety hazard in the food industry, inducing emesis and nausea after the consumption of contaminated foods. Additional to cereulide itself, seven structurally related isoforms, namely the isocereulides A–G, have already been elucidated in their chemical structure and could further be identified in B. cereus contaminated food samples. The newly performed isolation of isocereulide A allowed, for the first time, 1D- and 2D-NMR spectroscopy of a biosynthetically produced isocereulide, revealing results that contradict previous assumptions of an l-O-Leu moiety within its chemical structure. By furthermore applying posthydrolytical dipeptide analysis, amino acid and α-hydroxy acid analysis by means of UPLC-ESI-TOF-MS, as well as MSn sequencing, the structure of previously reported isocereulide A could be corrected. Instead of the l-O-Leu as assumed to date, one l-O-Ile unit could be verified in the cyclic dodecadepsipeptide, revising the structure of isocereulide A to [(d-O-Leu-d-Ala-l-O-Val-l-Val)2(d-O-Leu-d-Ala-l-O-Ile-l-Val)].
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Affiliation(s)
- Veronika Walser
- Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Str. 34, 85354 Freising, Germany; (V.W.); (T.F.H.)
| | - Markus Kranzler
- Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria; (M.K.); (M.E.-S.)
| | - Monika Ehling-Schulz
- Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria; (M.K.); (M.E.-S.)
| | - Timo D. Stark
- Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Str. 34, 85354 Freising, Germany; (V.W.); (T.F.H.)
- Correspondence: ; Tel.: +49-8161-71-2911
| | - Thomas F. Hofmann
- Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Str. 34, 85354 Freising, Germany; (V.W.); (T.F.H.)
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Carroll AR, Copp BR, Davis RA, Keyzers RA, Prinsep MR. Marine natural products. Nat Prod Rep 2021; 38:362-413. [PMID: 33570537 DOI: 10.1039/d0np00089b] [Citation(s) in RCA: 198] [Impact Index Per Article: 66.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.
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Affiliation(s)
- Anthony R Carroll
- School of Environment and Science, Griffith University, Gold Coast, Australia. and Griffith Institute for Drug Discovery, Griffith University, Brisbane, Australia
| | - Brent R Copp
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Rohan A Davis
- Griffith Institute for Drug Discovery, Griffith University, Brisbane, Australia and School of Enivironment and Science, Griffith University, Brisbane, Australia
| | - Robert A Keyzers
- Centre for Biodiscovery, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Michèle R Prinsep
- Chemistry, School of Science, University of Waikato, Hamilton, New Zealand
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Doellinger J, Schneider A, Stark TD, Ehling-Schulz M, Lasch P. Evaluation of MALDI-ToF Mass Spectrometry for Rapid Detection of Cereulide From Bacillus cereus Cultures. Front Microbiol 2020; 11:511674. [PMID: 33329410 PMCID: PMC7709880 DOI: 10.3389/fmicb.2020.511674] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 09/16/2020] [Indexed: 12/20/2022] Open
Abstract
Bacillus cereus plays an often unrecognized role in food borne diseases. Food poisoning caused by this pathogen is manifested by either diarrhea or emesis. Due to the relatively high prevalence of emetic toxin cereulide associated food poisoning, methods for simple and reliable detection of cereulide producing strains are of utmost importance. Recently, two different studies reported on the application of MALDI-ToF MS for either the differentiation of emetic and non-emetic strains of B. cereus or for direct detection of cereulide from bacterial colony smears. However, for implementation of cereulide detection using MALDI-ToF MS in routine microbiological diagnostics additional investigations on the sensitivity and specificity as well as on the fitting into common workflows for bacterial identification are needed. These aspects prompted us to investigate open issues and to test sample preparation methods, commonly used for microbial identification for their suitability to detect the emetic toxin from bacteria. Based on our experimental findings we propose a workflow that allows identification of B. cereus and sensitive detection of cereulide in parallel, using linear-mode MALDI-ToF MS equipment. The protocol was validated in a blinded study and is based on the well-established ethanol/formic acid extraction method. Cereulide is detected in the ethanol wash solution of samples identified as B. cereus as peaks at m/z 1175 and 1191. Peak position difference of 16 Th (Thomson) indicates detection of the sodium and potassium adducts of cereulide. This sample treatment offers possibilities for further characterization by more sophisticated LC-MS-based methods. In summary, the ease of use and the achieved level of analytical sensitivity as well as the wide-spread availability of MALDI-ToF MS equipment in clinical microbiological laboratories provides a promising tool to improve and to facilitate routine diagnostics of B. cereus associated food intoxications.
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Affiliation(s)
- Joerg Doellinger
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Andy Schneider
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Timo D Stark
- Food Chemistry and Molecular Sensory Science, Technical University of Munich, Munich, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Peter Lasch
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
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Naka T, Takaki Y, Hattori Y, Takenaka H, Ohta Y, Kirihata M, Tanimori S. Chemical structure of hydrolysates of cereulide and their time course profile. Bioorg Med Chem Lett 2020; 30:127050. [DOI: 10.1016/j.bmcl.2020.127050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 02/10/2020] [Accepted: 02/18/2020] [Indexed: 11/17/2022]
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Ducrest PJ, Pfammatter S, Stephan D, Vogel G, Thibault P, Schnyder B. Rapid detection of Bacillus ionophore cereulide in food products. Sci Rep 2019; 9:5814. [PMID: 30967595 PMCID: PMC6456620 DOI: 10.1038/s41598-019-42167-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 03/22/2019] [Indexed: 12/17/2022] Open
Abstract
Cereulide is a toxic cyclic depsipeptide produced by certain strains of Bacillus cereus found in soil and food products. While some harmless strains of Bacillus are used as probiotic, others can cause nausea and vomiting, and represent an important food safety concern. Current detection methods are time consuming and do not necessarily detect toxic cereulide. Here, we developed a rapid protocol using Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometry that detects the toxin originating from a colony smear of B. cereus. The distinct molecular feature of the toxin peak at m/z 1,191 was clearly identified from bacterial extracts with a limit of detection (LOD) of 30 ng/mL. Final optimisation of the sample preparation was based on cereulide chelating cations to produce the alkali adduct [M + K]+ without the use of a MALDI matrix, and provided a 1,000-fold improvement of LOD with 30 pg/mL of cereulide. We evaluated the application of this method for the detection of cereulide in rice, milk, and different ready-to-eat meals. The proposed protocol is quick, easy and provides an improvement over conventional methods for the detection of B. cereus toxin.
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Affiliation(s)
- P J Ducrest
- University of Applied Sciences, HES-SO Valais//Wallis, Institute of Life Technologies, Sion, Switzerland
| | - S Pfammatter
- University of Montreal, Institute for Research in Immunology and Cancer, Montreal, Quebec, Canada
| | - D Stephan
- University of Applied Sciences, HES-SO Valais//Wallis, Institute of Life Technologies, Sion, Switzerland
| | - G Vogel
- Mabritec AG, Riehen, Switzerland
| | - P Thibault
- University of Montreal, Institute for Research in Immunology and Cancer, Montreal, Quebec, Canada
| | - B Schnyder
- University of Applied Sciences, HES-SO Valais//Wallis, Institute of Life Technologies, Sion, Switzerland.
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