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Van der Veken D, Poortmans M, Dewulf L, Fraeye I, Michiels C, Leroy F. Challenge tests reveal limited outgrowth of proteolytic Clostridium botulinum during the production of nitrate- and nitrite-free fermented sausages. Meat Sci 2023; 200:109158. [PMID: 36905786 DOI: 10.1016/j.meatsci.2023.109158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 10/15/2022] [Accepted: 03/02/2023] [Indexed: 03/08/2023]
Abstract
Nitrate and nitrite salts perform a versatile role in fermented meats, including the inhibition of food pathogens (in particular proteolytic group I Clostridium botulinum). Despite the increasing interest in clean-label products, little is known about the behaviour of this pathogen in response to the removal of chemical preservatives from fermented meat formulations. Therefore, challenge tests with a cocktail of nontoxigenic group I C. botulinum strains were performed to produce nitrate/nitrite-free fermented sausages under different acidification conditions and starter culture formulations, including the use of an anticlostridial Mammaliicoccus sciuri strain. Results showed limited outgrowth of C. botulinum, even in the absence of acidification. The anticlostridial starter culture did not lead to an additional inhibitory effect. The selective plating procedure adopted within this study proofed robust to follow germination and growth of C. botulinum, inhibiting common fermentative meat microbiota. The challenge tests constitute a suitable tool to assess the behaviour of this food pathogen within fermented meats upon nitrate- and nitrite omission.
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Affiliation(s)
- David Van der Veken
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Marijke Poortmans
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Lore Dewulf
- Meat Technology & Science of Protein-Rich Foods, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven Technology Campus Ghent, Ghent, Belgium
| | - Ilse Fraeye
- Meat Technology & Science of Protein-Rich Foods, Department of Microbial and Molecular Systems, Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven Technology Campus Ghent, Ghent, Belgium
| | - Chris Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Frédéric Leroy
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.
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2
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Inanoglu S, Barbosa-Cánovas GV, Sablani SS, Zhu MJ, Keener L, Tang J. High-pressure pasteurization of low-acid chilled ready-to-eat food. Compr Rev Food Sci Food Saf 2022; 21:4939-4970. [PMID: 36329575 DOI: 10.1111/1541-4337.13058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/31/2022] [Accepted: 09/08/2022] [Indexed: 11/06/2022]
Abstract
The working population growth have created greater consumer demand for ready-to-eat (RTE) foods. Pasteurization is one of the most common preservation methods for commercial production of low-acid RTE cold-chain products. Proper selection of a pasteurization method plays an important role not only in ensuring microbial safety but also in maintaining food quality during storage. Better retention of flavor, color, appearance, and nutritional value of RTE products is one of the reasons for the food industry to adopt novel technologies such as high-pressure processing (HPP) as a substitute or complementary technology for thermal pasteurization. HPP has been used industrially for the pasteurization of high-acid RTE products. Yet, this method is not commonly used for pasteurization of low-acid RTE food products, due primarily to the need of additional heating to thermally inactivate spores, coupled with relatively long treatment times resulting in high processing costs. Practical Application: Food companies would like to adopt novel technologies such as HPP instead of using conventional thermal processes, yet there is a lack of information on spoilage and the shelf-life of pasteurized low-acid RTE foods (by different novel pasteurization methods including HPP) in cold storage. This article provides an overview of the microbial concerns and related regulatory guidelines for the pasteurization of low-acid RTE foods and summarizes the effects of HPP in terms of microbiology (both pathogens and spoilage microorganisms), quality, and shelf-life on low-acid RTE foods. This review also includes the most recent research articles regarding a comparison between HPP pasteurization and thermal pasteurization treatments and the limitations of HPP for low-acid chilled RTE foods.
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Affiliation(s)
- Sumeyye Inanoglu
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA
| | - Gustavo V Barbosa-Cánovas
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA.,Center for Nonthermal Processing of Food, Washington State University, Pullman, Washington, USA
| | - Shyam S Sablani
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA
| | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, Washington, USA
| | - Larry Keener
- International Product Safety Consultants, Seattle, Washington, USA
| | - Juming Tang
- Department of Biological Systems Engineering, Washington State University, Pullman, Washington, USA
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3
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Poortmans M, Vanoirbeek K, Dorner MB, Michiels CW. Selection and Development of Nontoxic Nonproteolytic Clostridium botulinum Surrogate Strains for Food Challenge Testing. Foods 2022; 11:1577. [PMID: 35681327 PMCID: PMC9180612 DOI: 10.3390/foods11111577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/18/2022] [Accepted: 05/23/2022] [Indexed: 02/05/2023] Open
Abstract
Clostridium botulinum causes severe foodborne intoxications by producing a potent neurotoxin. Challenge studies with this pathogen are an important tool to ensure the safety of new processing techniques and newly designed or modified foods, but they are hazardous and complicated by the lack of an effective selective counting medium. Therefore, this study aimed to develop selectable nontoxic surrogate strains for group II, or nonproteolytic, C. botulinum, which are psychotropic and hence of particular concern in mildly treated, refrigerated foods. Thirty-one natural nontoxic nonproteolytic strains, 16 of which were isolated in this work, were characterized in detail, revealing that 28 strains were genomically and phenotypically indistinguishable from toxic strains. Five strains, representing the genomic and phenotypic diversity of group II C. botulinum, were selected and successfully equipped with an erythromycin (Em) resistance marker in a defective structural phage gene without altering phenotypic features. Finally, a selective medium containing Em, cycloserine (Cs), gentamicin (Gm), and lysozyme (Ly) was developed, which inhibited the background microbiota of commercial cooked ham, chicken filet, and salami, but supported spore germination and growth of the Em-resistant surrogate strains. The surrogates developed in this work are expected to facilitate food challenge studies with nonproteolytic C. botulinum for the food industry and can also provide a safe alternative for basic C. botulinum research.
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Affiliation(s)
- Marijke Poortmans
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
| | - Kristof Vanoirbeek
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
| | - Martin B. Dorner
- Robert Koch Institute, ZBS3-Biological Toxins, Seestr. 10, 13353 Berlin, Germany;
| | - Chris W. Michiels
- Department of Microbial and Molecular Systems, KU Leuven, 3000 Leuven, Belgium; (M.P.); (K.V.)
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Nowakowska MB, Selby K, Przykopanski A, Krüger M, Krez N, Dorner BG, Dorner MB, Jin R, Minton NP, Rummel A, Lindström M. Construction and validation of safe Clostridium botulinum Group II surrogate strain producing inactive botulinum neurotoxin type E toxoid. Sci Rep 2022; 12:1790. [PMID: 35110559 PMCID: PMC8810926 DOI: 10.1038/s41598-022-05008-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 12/24/2021] [Indexed: 01/05/2023] Open
Abstract
Botulinum neurotoxins (BoNTs), produced by the spore-forming bacterium Clostridium botulinum, cause botulism, a rare but fatal illness affecting humans and animals. Despite causing a life-threatening disease, BoNT is a multipurpose therapeutic. Nevertheless, as the most potent natural toxin, BoNT is classified as a Select Agent in the US, placing C. botulinum research under stringent governmental regulations. The extreme toxicity of BoNT, its impact on public safety, and its diverse therapeutic applications urge to devise safe solutions to expand C. botulinum research. Accordingly, we exploited CRISPR/Cas9-mediated genome editing to introduce inactivating point mutations into chromosomal bont/e gene of C. botulinum Beluga E. The resulting Beluga Ei strain displays unchanged physiology and produces inactive BoNT (BoNT/Ei) recognized in serological assays, but lacking biological activity detectable ex- and in vivo. Neither native single-chain, nor trypsinized di-chain form of BoNT/Ei show in vivo toxicity, even if isolated from Beluga Ei sub-cultured for 25 generations. Beluga Ei strain constitutes a safe alternative for the BoNT research necessary for public health risk management, the development of food preservation strategies, understanding toxinogenesis, and for structural BoNT studies. The example of Beluga Ei generation serves as template for future development of C. botulinum producing different inactive BoNT serotypes.
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Affiliation(s)
- Maria B Nowakowska
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Katja Selby
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Adina Przykopanski
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Maren Krüger
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Nadja Krez
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Brigitte G Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Martin B Dorner
- Biological Toxins, Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA
| | - Nigel P Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, Biodiscovery Institute, University of Nottingham, Nottingham, UK
| | - Andreas Rummel
- Institut Für Toxikologie, Medizinische Hochschule Hannover, Hannover, Germany
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
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Koukou I, Dahl Devitt T, Dalgaard P. Extensive growth and growth boundary model for non-proteolytic Clostridium botulinum - Evaluation and validation with MAP and smoked foods. Food Microbiol 2021; 102:103931. [PMID: 34809957 DOI: 10.1016/j.fm.2021.103931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/27/2021] [Accepted: 10/29/2021] [Indexed: 11/29/2022]
Abstract
The growth inhibiting effect of lactic acid bacteria (LAB) on non-proteolytic Clostridium botulinum was studied. LAB had no significant effect on growth of C. botulinum and their effect was not included in the model to be evaluated. An available cardinal parameter growth and growth boundary model for non-proteolytic C. botulinum (Koukou et al., 2021; https://doi.org/10.1016/j.ijfoodmicro.2021.109162) was evaluated using a total of 822 time-to-toxin (TTT) formation data extracted from the scientific literature for seafood, poultry, vegetables and meat products. These data included smoked products and food stored in air, vacuum or modified atmosphere packaging (MAP) with added CO2. The available extensive model predicted TTT formation without bias (Bf-TTT value = 0.99) and with a reasonable accuracy (Af-TTT value = 1.76). The model was successfully validated for seafood and poultry products. This study substantially increased the range of applicability of the available growth and growth boundary model for non-proteolytic C. botulinum. The performed evaluation showed this model can be used to predict environmental conditions to prevent growth in seafood and poultry products including smoked fish and MAP foods. It is expected that this validated model will contribute to product development and innovation including new sodium reduced foods.
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Affiliation(s)
- Ioulia Koukou
- National Food Institute (DTU Food), Technical University of Denmark, Kemitorvet Building 202, DK-2800 Kgs. Lyngby, Denmark.
| | - Tina Dahl Devitt
- National Food Institute (DTU Food), Technical University of Denmark, Kemitorvet Building 202, DK-2800 Kgs. Lyngby, Denmark
| | - Paw Dalgaard
- National Food Institute (DTU Food), Technical University of Denmark, Kemitorvet Building 202, DK-2800 Kgs. Lyngby, Denmark
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Mertaoja A, Nowakowska MB, Mascher G, Heljanko V, Groothuis D, Minton NP, Lindström M. CRISPR-Cas9-Based Toolkit for Clostridium botulinum Group II Spore and Sporulation Research. Front Microbiol 2021; 12:617269. [PMID: 33584620 PMCID: PMC7873358 DOI: 10.3389/fmicb.2021.617269] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 01/05/2021] [Indexed: 01/05/2023] Open
Abstract
The spores of Clostridium botulinum Group II strains pose a significant threat to the safety of modern packaged foods due to the risk of their survival in pasteurization and their ability to germinate into neurotoxigenic cultures at refrigeration temperatures. Moreover, spores are the infectious agents in wound botulism, infant botulism, and intestinal toxemia in adults. The identification of factors that contribute to spore formation is, therefore, essential to the development of strategies to control related health risks. Accordingly, development of a straightforward and versatile gene manipulation tool and an efficient sporulation-promoting medium is pivotal. Our strategy was to employ CRISPR-Cas9 and homology-directed repair (HDR) to replace targeted genes with mutant alleles incorporating a unique 24-nt "bookmark" sequence that could act as a single guide RNA (sgRNA) target for Cas9. Following the generation of the sporulation mutant, the presence of the bookmark allowed rapid generation of a complemented strain, in which the mutant allele was replaced with a functional copy of the deleted gene using CRISPR-Cas9 and the requisite sgRNA. Then, we selected the most appropriate medium for sporulation studies in C. botulinum Group II strains by measuring the efficiency of spore formation in seven different media. The most effective medium was exploited to confirm the involvement of a candidate gene in the sporulation process. Using the devised sporulation medium, subsequent comparisons of the sporulation efficiency of the wild type (WT), mutant and "bookmark"-complemented strain allowed the assignment of any defective sporulation phenotype to the mutation made. As a strain generated by complementation with the WT gene in the original locus would be indistinguishable from the parental strain, the gene utilized in complementation studies was altered to contain a unique "watermark" through the introduction of silent nucleotide changes. The mutagenesis system and the devised sporulation medium provide a solid basis for gaining a deeper understanding of spore formation in C. botulinum, a prerequisite for the development of novel strategies for spore control and related food safety and public health risk management.
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Affiliation(s)
- Anna Mertaoja
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Maria B. Nowakowska
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Gerald Mascher
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Viivi Heljanko
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
| | - Daphne Groothuis
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Nigel P. Minton
- Clostridia Research Group, BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), Biodiscovery Institute, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland
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González-Angulo M, Clauwers C, Harastani R, Tonello C, Jaime I, Rovira J, Michiels CW. Evaluation of factors influencing the growth of non-toxigenic Clostridium botulinum type E and Clostridium sp. in high-pressure processed and conditioned tender coconut water from Thailand. Food Res Int 2020; 134:109278. [PMID: 32517944 DOI: 10.1016/j.foodres.2020.109278] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 04/22/2020] [Accepted: 04/25/2020] [Indexed: 11/29/2022]
Abstract
Bacterial spores survive high pressure processing (HPP). Group II Clostridium botulinum is an obligate anaerobe spore-forming pathogen that can produce the botulinum neurotoxin under refrigeration. This study assessed nontoxigenic type E C. botulinum and Group II Clostridium sp. growth in raw and HPP (550 MPa, 3 min, 10 °C) Thai coconut water (CCW; pH 5.2). No spore germination or growth occurred in HPP CCW inoculated with 105 CFU/ml after 61 days regardless of oxygen concentration (<0.5 - 11 mg/l) or storage temperature (4 and 20 °C). Spore concentration decreased by 3.0 ± 0.1 log CFU/ml in a worst-case scenario consisting of non-HPP filter-sterilized CCW (pH 7.0) under anoxic incubation at 30 °C during 61 days, suggesting spore germination followed by cellular death. Supplementing filter-sterilized CCW (pH 7.0) with selected germinants and free amino acids did not support spore development, but the addition of nutrient-rich laboratory media (TPGY broth) at low concentrations (6.25%) promoted growth, suggesting that a lack of nutrients prevents C. botulinum development in CCW. Further risk assessment will require evaluating other CCW varieties and toxin production.
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Affiliation(s)
- Mario González-Angulo
- Hiperbaric, S.A., C/ Condado de Treviño, 6, 09001 Burgos, Spain; Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain.
| | - Charlien Clauwers
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Rania Harastani
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
| | - Carole Tonello
- Hiperbaric, S.A., C/ Condado de Treviño, 6, 09001 Burgos, Spain
| | - Isabel Jaime
- Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain
| | - Jordi Rovira
- Universidad de Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain
| | - Chris W Michiels
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
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Van der Veken D, Benhachemi R, Charmpi C, Ockerman L, Poortmans M, Van Reckem E, Michiels C, Leroy F. Exploring the Ambiguous Status of Coagulase-Negative Staphylococci in the Biosafety of Fermented Meats: The Case of Antibacterial Activity Versus Biogenic Amine Formation. Microorganisms 2020; 8:microorganisms8020167. [PMID: 31991613 PMCID: PMC7074764 DOI: 10.3390/microorganisms8020167] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 01/20/2020] [Accepted: 01/20/2020] [Indexed: 01/06/2023] Open
Abstract
A total of 332 staphylococcal strains, mainly isolated from meat, were screened for antibacterial activity. Eighteen strains exhibited antibacterial activity towards species within the same genus. These antibacterial strains were further screened against Clostridium botulinum, to assess their potential as anticlostridial starter cultures for the development of fermented meat products without added nitrate or nitrite. Only Staphylococcus sciuri IMDO-S72 had the ability to inhibit all clostridial strains tested, whilst displaying additional activity against Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus. Apart from their potential as bioprotective cultures, the staphylococcal collection was also screened for biogenic amine production, as these compounds may compromise food quality. To this end, ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) was applied. A low incidence of biogenic amine production was found, with tyramine and β-phenylethylamine being the most prevalent ones. Concentrations remained relatively low (< 52 mg/L) after a prolonged incubation period, posing no or little threat towards food safety. Taken together, S. sciuri IMDO-S72 could serve as an interesting candidate for the bioprotection of fermented meats as it showed promising antibacterial activity as well as absence of biogenic amine production.
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Affiliation(s)
- David Van der Veken
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium; (D.V.d.V.); (C.C.); (L.O.); (E.V.R.)
| | - Rafik Benhachemi
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, B-3001 Leuven, Belgium; (R.B.); (M.P.); (C.M.)
| | - Christina Charmpi
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium; (D.V.d.V.); (C.C.); (L.O.); (E.V.R.)
| | - Lore Ockerman
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium; (D.V.d.V.); (C.C.); (L.O.); (E.V.R.)
| | - Marijke Poortmans
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, B-3001 Leuven, Belgium; (R.B.); (M.P.); (C.M.)
| | - Emiel Van Reckem
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium; (D.V.d.V.); (C.C.); (L.O.); (E.V.R.)
| | - Chris Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, B-3001 Leuven, Belgium; (R.B.); (M.P.); (C.M.)
| | - Frédéric Leroy
- Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, 1050 Brussels, Belgium; (D.V.d.V.); (C.C.); (L.O.); (E.V.R.)
- Correspondence:
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9
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Clauwers C, Lood C, Van den Bergh B, van Noort V, Michiels CW. Canonical germinant receptor is dispensable for spore germination in Clostridium botulinum group II strain NCTC 11219. Sci Rep 2017; 7:15426. [PMID: 29133849 PMCID: PMC5684421 DOI: 10.1038/s41598-017-15839-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 11/03/2017] [Indexed: 02/07/2023] Open
Abstract
Clostridium botulinum is an anaerobic sporeforming bacterium that is notorious for producing a potent neurotoxin. Spores of C. botulinum can survive mild food processing treatments and subsequently germinate, multiply, produce toxin and cause botulism. Control of spore germination and outgrowth is therefore essential for the safety of mildly processed foods. However, little is known about the process of spore germination in group II C. botulinum (gIICb), which are a major concern in chilled foods because they are psychrotrophic. The classical model of spore germination states that germination is triggered by the binding of a germinant molecule to a cognate germinant receptor. Remarkably, unlike many other sporeformers, gIICb has only one predicted canonical germinant receptor although it responds to multiple germinants. Therefore, we deleted the gerBAC locus that encodes this germinant receptor to determine its role in germination. Surprisingly, the deletion did not affect germination by any of the nutrient germinants, nor by the non-nutrient dodecylamine. We conclude that one or more other, so far unidentified, germinant receptors must be responsible for nutrient induced germination in gIICb. Furthermore, the gerBAC locus was strongly conserved with intact open reading frames in 159 gIICb genomes, suggesting that it has nevertheless an important function.
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Affiliation(s)
- Charlien Clauwers
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium
| | - Cédric Lood
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | | | - Vera van Noort
- Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), KU Leuven, Leuven, Belgium.
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