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Berendsen EM, Koning RA, Boekhorst J, de Jong A, Kuipers OP, Wells-Bennik MHJ. High-Level Heat Resistance of Spores of Bacillus amyloliquefaciens and Bacillus licheniformis Results from the Presence of a spoVA Operon in a Tn 1546 Transposon. Front Microbiol 2016; 7:1912. [PMID: 27994575 PMCID: PMC5133452 DOI: 10.3389/fmicb.2016.01912] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 11/15/2016] [Indexed: 11/19/2022] Open
Abstract
Bacterial endospore formers can produce spores that are resistant to many food processing conditions, including heat. Some spores may survive heating processes aimed at production of commercially sterile foods. Recently, it was shown that a spoVA operon, designated spoVA2mob, present on a Tn1546 transposon in Bacillus subtilis, leads to profoundly increased wet heat resistance of B. subtilis spores. Such Tn1546 transposon elements including the spoVA2mob operon were also found in several strains of Bacillus amyloliquefaciens and Bacillus licheniformis, and these strains were shown to produce spores with significantly higher resistances to wet heat than their counterparts lacking this transposon. In this study, the locations and compositions of Tn1546 transposons encompassing the spoVA2mob operons in B. amyloliquefaciens and B. licheniformis were analyzed. Introduction of these spoVA2mob operons into B. subtilis 168 (producing spores that are not highly heat resistant) rendered mutant 168 strains that produced high-level heat resistant spores, demonstrating that these elements in B. amyloliquefaciens and B. licheniformis are responsible for high level heat resistance of spores. Assessment of growth of the nine strains of each species between 5.2°C and 57.7°C showed some differences between strains, especially at lower temperatures, but all strains were able to grow at 57.7°C. Strains of B. amyloliquefaciens and B. licheniformis that contain the Tn1546 elements (and produce high-level heat resistant spores) grew at temperatures similar to those of their Tn1546-negative counterparts that produce low-level heat resistant spores. The findings presented in this study allow for detection of B. amyloliquefaciens and B. licheniformis strains that produce highly heat resistant spores in the food chain.
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Affiliation(s)
- Erwin M Berendsen
- Top Institute Food and NutritionWageningen, Netherlands; Laboratory of Molecular Genetics, University of GroningenGroningen, Netherlands; NIZO Food ResearchEde, Netherlands
| | - Rosella A Koning
- Top Institute Food and NutritionWageningen, Netherlands; NIZO Food ResearchEde, Netherlands
| | - Jos Boekhorst
- Top Institute Food and NutritionWageningen, Netherlands; NIZO Food ResearchEde, Netherlands
| | - Anne de Jong
- Top Institute Food and NutritionWageningen, Netherlands; Laboratory of Molecular Genetics, University of GroningenGroningen, Netherlands
| | - Oscar P Kuipers
- Top Institute Food and NutritionWageningen, Netherlands; Laboratory of Molecular Genetics, University of GroningenGroningen, Netherlands
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Bhardwaj N, Bhardwaj S, Mehta J, Kim KH, Deep A. Highly sensitive detection of dipicolinic acid with a water-dispersible terbium-metal organic framework. Biosens Bioelectron 2016; 86:799-804. [DOI: 10.1016/j.bios.2016.07.063] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Revised: 07/13/2016] [Accepted: 07/19/2016] [Indexed: 12/31/2022]
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Intracellular pH Response to Weak Acid Stress in Individual Vegetative Bacillus subtilis Cells. Appl Environ Microbiol 2016; 82:6463-6471. [PMID: 27565617 DOI: 10.1128/aem.02063-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 08/21/2016] [Indexed: 11/20/2022] Open
Abstract
Intracellular pH (pHi) critically affects bacterial cell physiology. Hence, a variety of food preservation strategies are aimed at perturbing pHi homeostasis. Unfortunately, accurate pHi quantification with existing methods is suboptimal, since measurements are averages across populations of cells, not taking into account interindividual heterogeneity. Yet, physiological heterogeneity in isogenic populations is well known to be responsible for differences in growth and division kinetics of cells in response to external stressors. To assess in this context the behavior of intracellular acidity, we have developed a robust method to quantify pHi at single-cell levels in Bacillus subtilis Bacilli spoil food, cause disease, and are well known for their ability to form highly stress-resistant spores. Using an improved version of the genetically encoded ratiometric pHluorin (IpHluorin), we have quantified pHi in individual B. subtilis cells, cultured at an external pH of 6.4, in the absence or presence of weak acid stresses. In the presence of 3 mM potassium sorbate, a decrease in pHi and an increase in the generation time of growing cells were observed. Similar effects were observed when cells were stressed with 25 mM potassium acetate. Time-resolved analysis of individual bacteria in growing colonies shows that after a transient pH decrease, long-term pH evolution is highly cell dependent. The heterogeneity at the single-cell level shows the existence of subpopulations that might be more resistant and contribute to population survival. Our approach contributes to an understanding of pHi regulation in individual bacteria and may help scrutinizing effects of existing and novel food preservation strategies. IMPORTANCE This study shows how the physiological response to commonly used weak organic acid food preservatives, such as sorbic and acetic acids, can be measured at the single-cell level. These data are key to coupling often-observed single-cell heterogeneous growth behavior upon the addition of weak organic acid food preservatives. Generally, these data are gathered in the form of plate counting of samples incubated with the acids. Here, we visualize the underlying heterogeneity in cellular pH homeostasis, opening up avenues for mechanistic analyses of the heterogeneity in the weak acid stress response. Thus, microbial risk assessment can become more robust, widening the scope of use of these well-known weak organic acid food preservatives.
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Krawczyk AO, Berendsen EM, de Jong A, Boekhorst J, Wells-Bennik MHJ, Kuipers OP, Eijlander RT. A transposon present in specific strains ofBacillus subtilisnegatively affects nutrient- and dodecylamine-induced spore germination. Environ Microbiol 2016; 18:4830-4846. [DOI: 10.1111/1462-2920.13386] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 05/20/2016] [Indexed: 11/28/2022]
Affiliation(s)
- Antonina O. Krawczyk
- Laboratory of Molecular Genetics; University of Groningen; Nijenborgh 7 9747 AG Groningen the Netherlands
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
| | - Erwin M. Berendsen
- Laboratory of Molecular Genetics; University of Groningen; Nijenborgh 7 9747 AG Groningen the Netherlands
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
- NIZO Food Research B.V; Kernhemseweg 2 6718 ZB Ede the Netherlands
| | - Anne de Jong
- Laboratory of Molecular Genetics; University of Groningen; Nijenborgh 7 9747 AG Groningen the Netherlands
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
| | - Jos Boekhorst
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
- NIZO Food Research B.V; Kernhemseweg 2 6718 ZB Ede the Netherlands
| | - Marjon H. J. Wells-Bennik
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
- NIZO Food Research B.V; Kernhemseweg 2 6718 ZB Ede the Netherlands
| | - Oscar P. Kuipers
- Laboratory of Molecular Genetics; University of Groningen; Nijenborgh 7 9747 AG Groningen the Netherlands
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
| | - Robyn T. Eijlander
- Laboratory of Molecular Genetics; University of Groningen; Nijenborgh 7 9747 AG Groningen the Netherlands
- Top Institute Food and Nutrition (TIFN); Nieuwe Kanaal 9A 6709 PA Wageningen the Netherlands
- NIZO Food Research B.V; Kernhemseweg 2 6718 ZB Ede the Netherlands
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Francis MB, Sorg JA. Detecting Cortex Fragments During Bacterial Spore Germination. J Vis Exp 2016. [PMID: 27403726 DOI: 10.3791/54146] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The process of endospore germination in Clostridium difficile, and other Clostridia, increasingly is being found to differ from the model spore-forming bacterium, Bacillus subtilis. Germination is triggered by small molecule germinants and occurs without the need for macromolecular synthesis. Though differences exist between the mechanisms of spore germination in species of Bacillus and Clostridium, a common requirement is the hydrolysis of the peptidoglycan-like cortex which allows the spore core to swell and rehydrate. After rehydration, metabolism can begin and this, eventually, leads to outgrowth of a vegetative cell. The detection of hydrolyzed cortex fragments during spore germination can be difficult and the modifications to the previously described assays can be confusing or difficult to reproduce. Thus, based on our recent report using this assay, we detail a step-by-step protocol for the colorimetric detection of cortex fragments during bacterial spore germination.
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Characterization of Clostridium difficile Spores Lacking Either SpoVAC or Dipicolinic Acid Synthetase. J Bacteriol 2016; 198:1694-1707. [PMID: 27044622 PMCID: PMC4959285 DOI: 10.1128/jb.00986-15] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 03/17/2016] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED The spore-forming obligate anaerobe Clostridium difficile is a leading cause of antibiotic-associated diarrhea around the world. In order for C. difficile to cause infection, its metabolically dormant spores must germinate in the gastrointestinal tract. During germination, spores degrade their protective cortex peptidoglycan layers, release dipicolinic acid (DPA), and hydrate their cores. In C. difficile, cortex hydrolysis is necessary for DPA release, whereas in Bacillus subtilis, DPA release is necessary for cortex hydrolysis. Given this difference, we tested whether DPA synthesis and/or release was required for C. difficile spore germination by constructing mutations in either spoVAC or dpaAB, which encode an ion channel predicted to transport DPA into the forespore and the enzyme complex predicted to synthesize DPA, respectively. C. difficile spoVAC and dpaAB mutant spores lacked DPA but could be stably purified and were more hydrated than wild-type spores; in contrast, B. subtilis spoVAC and dpaAB mutant spores were unstable. Although C. difficile spoVAC and dpaAB mutant spores exhibited wild-type germination responses, they were more readily killed by wet heat. Cortex hydrolysis was not affected by this treatment, indicating that wet heat inhibits a stage downstream of this event. Interestingly, C. difficile spoVAC mutant spores were significantly more sensitive to heat treatment than dpaAB mutant spores, indicating that SpoVAC plays additional roles in conferring heat resistance. Taken together, our results demonstrate that SpoVAC and DPA synthetase control C. difficile spore resistance and reveal differential requirements for these proteins among the Firmicutes IMPORTANCE Clostridium difficile is a spore-forming obligate anaerobe that causes ∼500,000 infections per year in the United States. Although spore germination is essential for C. difficile to cause disease, the factors required for this process have been only partially characterized. This study describes the roles of two factors, DpaAB and SpoVAC, which control the synthesis and release of dipicolinic acid (DPA), respectively, from bacterial spores. Previous studies of these proteins in other spore-forming organisms indicated that they are differentially required for spore formation, germination, and resistance. We now show that the proteins are dispensable for C. difficile spore formation and germination but are necessary for heat resistance. Thus, our study further highlights the diverse functions of DpaAB and SpoVAC in spore-forming organisms.
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Guo X, Chen DD, Peng KS, Cui ZW, Zhang XJ, Li S, Zhang YA. Identification and characterization of Bacillus subtilis from grass carp (Ctenopharynodon idellus) for use as probiotic additives in aquatic feed. FISH & SHELLFISH IMMUNOLOGY 2016; 52:74-84. [PMID: 26988285 DOI: 10.1016/j.fsi.2016.03.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 03/04/2016] [Accepted: 03/10/2016] [Indexed: 06/05/2023]
Abstract
Bacillus subtilis is widely used as probiotic species in aquaculture for water quality control, growth promoting, or immunity enhancing. The aim of this study is to find novel B. subtilis strains from fish as potential probiotics for aquaculture. Eleven B. subtilis isolates derived from the intestinal tract of grass carp were identified by gene sequencing and biochemical tests. These isolates were classified into 4 groups, and the representatives (GC-5, GC-6, GC-21 and GC-22) of each group were further investigated for antibiotic susceptibility, sporulation rate, biofilm formation, activity against pathogenic bacteria, resistance to stress conditions of intestinal tract (high percentage of bile and low pH) and high temperature, which are important for probiotics to be used as feed additives. Additionally, the adhesion properties of the 4 characterized strains were assessed using Caco-2 cell and gut mucus models. The results showed that the 4 strains differed in their capacities to adhere to intestinal epithelial cells and mucus. Furthermore, the strains GC-21 and GC-22 up-regulated the expression levels of IL-10 and TGF-β but down-regulated IL-1β, suggesting their potential anti-inflammatory abilities. Based on physiological properties of the 4 characterized B. subtilis strains, one or more strains may have potential to be used as probiotics in aquaculture.
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Affiliation(s)
- Xia Guo
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Wuhan 430223, China
| | - Dan-Dan Chen
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Kai-Song Peng
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Anhui Agricultural University, Hefei 230036, China
| | - Zheng-Wei Cui
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xu-Jie Zhang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; Shanghai Ocean University, Shanghai 201306, China
| | - Shun Li
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Yong-An Zhang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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Berendsen EM, Boekhorst J, Kuipers OP, Wells-Bennik MHJ. A mobile genetic element profoundly increases heat resistance of bacterial spores. ISME JOURNAL 2016; 10:2633-2642. [PMID: 27105070 DOI: 10.1038/ismej.2016.59] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 02/25/2016] [Accepted: 02/29/2016] [Indexed: 01/05/2023]
Abstract
Bacterial endospores are among the most resilient forms of life on earth and are intrinsically resistant to extreme environments and antimicrobial treatments. Their resilience is explained by unique cellular structures formed by a complex developmental process often initiated in response to nutrient deprivation. Although the macromolecular structures of spores from different bacterial species are similar, their resistance to environmental insults differs widely. It is not known which of the factors attributed to spore resistance confer very high-level heat resistance. Here, we provide conclusive evidence that in Bacillus subtilis, this is due to the presence of a mobile genetic element (Tn1546-like) carrying five predicted operons, one of which contains genes that encode homologs of SpoVAC, SpoVAD and SpoVAEb and four other genes encoding proteins with unknown functions. This operon, named spoVA2mob, confers high-level heat resistance to spores. Deletion of spoVA2mob in a B. subtilis strain carrying Tn1546 renders heat-sensitive spores while transfer of spoVA2mob into B. subtilis 168 yields highly heat-resistant spores. On the basis of the genetic conservation of different spoVA operons among spore-forming species of Bacillaceae, we propose an evolutionary scenario for the emergence of extremely heat-resistant spores in B. subtilis, B. licheniformis and B. amyloliquefaciens. This discovery opens up avenues for improved detection and control of spore-forming bacteria able to produce highly heat-resistant spores.
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Affiliation(s)
- Erwin M Berendsen
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands.,University of Groningen, Laboratory of Molecular Genetics, Groningen, The Netherlands.,NIZO Food Research B.V., Ede, The Netherlands
| | - Jos Boekhorst
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands.,NIZO Food Research B.V., Ede, The Netherlands
| | - Oscar P Kuipers
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands.,University of Groningen, Laboratory of Molecular Genetics, Groningen, The Netherlands
| | - Marjon H J Wells-Bennik
- Top Institute Food and Nutrition (TIFN), Wageningen, The Netherlands.,NIZO Food Research B.V., Ede, The Netherlands
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59
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Viscoelastic behavior and physico-chemical characteristics of heated swai-fish (Pangasius hypophthalmus) based emulsion containing fermented soybeans. Lebensm Wiss Technol 2016. [DOI: 10.1016/j.lwt.2015.10.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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60
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Wells-Bennik MH, Eijlander RT, den Besten HM, Berendsen EM, Warda AK, Krawczyk AO, Nierop Groot MN, Xiao Y, Zwietering MH, Kuipers OP, Abee T. Bacterial Spores in Food: Survival, Emergence, and Outgrowth. Annu Rev Food Sci Technol 2016; 7:457-82. [DOI: 10.1146/annurev-food-041715-033144] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marjon H.J. Wells-Bennik
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- NIZO Food Research, 6718 ZB Ede, The Netherlands;
| | - Robyn T. Eijlander
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- NIZO Food Research, 6718 ZB Ede, The Netherlands;
| | - Heidy M.W. den Besten
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, 6700 AA Wageningen, The Netherlands
| | - Erwin M. Berendsen
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- NIZO Food Research, 6718 ZB Ede, The Netherlands;
- Molecular Genetics Department, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Alicja K. Warda
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, 6700 AA Wageningen, The Netherlands
- Wageningen UR Food & Biobased Research, 6700 AA Wageningen, The Netherlands
| | - Antonina O. Krawczyk
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Molecular Genetics Department, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Masja N. Nierop Groot
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Wageningen UR Food & Biobased Research, 6700 AA Wageningen, The Netherlands
| | - Yinghua Xiao
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, 6700 AA Wageningen, The Netherlands
| | - Marcel H. Zwietering
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, 6700 AA Wageningen, The Netherlands
| | - Oscar P. Kuipers
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Molecular Genetics Department, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Tjakko Abee
- TI Food and Nutrition, 6700 AN Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, 6700 AA Wageningen, The Netherlands
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61
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Comparison of spore inactivation with novel agitating retort, static retort and combined high pressure-temperature treatments. Food Control 2016. [DOI: 10.1016/j.foodcont.2015.08.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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62
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Hayrapetyan H, Abee T, Nierop Groot M. Sporulation dynamics and spore heat resistance in wet and dry biofilms of Bacillus cereus. Food Control 2016. [DOI: 10.1016/j.foodcont.2015.08.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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63
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Pandey R, Pieper GH, Beek AT, Vischer NO, Smelt JP, Manders EM, Brul S. Quantifying the effect of sorbic acid, heat and combination of both on germination and outgrowth of Bacillus subtilis spores at single cell resolution. Food Microbiol 2015; 52:88-96. [DOI: 10.1016/j.fm.2015.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 05/10/2015] [Accepted: 06/19/2015] [Indexed: 11/26/2022]
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64
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de Boer P, Caspers M, Sanders JW, Kemperman R, Wijman J, Lommerse G, Roeselers G, Montijn R, Abee T, Kort R. Amplicon sequencing for the quantification of spoilage microbiota in complex foods including bacterial spores. MICROBIOME 2015; 3:30. [PMID: 26217487 PMCID: PMC4515881 DOI: 10.1186/s40168-015-0096-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 07/14/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND Spoilage of food products is frequently caused by bacterial spores and lactic acid bacteria. Identification of these organisms by classic cultivation methods is limited by their ability to form colonies on nutrient agar plates. In this study, we adapted and optimized 16S rRNA amplicon sequencing for quantification of bacterial spores in a canned food matrix and for monitoring the outgrowth of spoilage microbiota in a ready-to-eat food matrix. RESULTS The detection limit of bar-coded 16S rRNA amplicon sequencing was determined for the number of bacterial spores in a canned food matrix. Analysis of samples from a canned food matrix spiked with a mixture of equinumerous spores from the thermophiles, Geobacillus stearothermophilus and Geobacillus thermoglucosidans, and the mesophiles, Bacillus sporothermodurans, Bacillus cereus, and Bacillus subtilis, led to the detection of these spores with an average limit of 2 × 10(2) spores ml(-1). The data were normalized by setting the number of sequences resulting from DNA of an inactivated bacterial species, present in the matrix at the same concentration in all samples, to a fixed value for quantitative sample-to-sample comparisons. The 16S rRNA amplicon sequencing method was also employed to monitor population dynamics in a ready-to-eat rice meal, incubated over a period of 12 days at 7 °C. The most predominant outgrowth was observed by the genera Leuconostoc, Bacillus, and Paenibacillus. Analysis of meals pre-treated with weak acids showed inhibition of outgrowth of these three genera. The specificity of the amplicon synthesis was improved by the design of oligonucleotides that minimize the amplification of 16S rRNA genes from chloroplasts originating from plant-based material present in the food. CONCLUSION This study shows that the composition of complex spoilage populations, including bacterial spores, can be monitored in complex food matrices by bar-coded amplicon sequencing in a quantitative manner. In order to allow sample-to-sample comparisons, normalizations based on background DNA are described. This method offers a solution for the identification and quantification of spoilage microbiota, which cannot be cultivated under standard laboratory conditions. The study indicates variable detection limits among species of bacterial spores resulting from differences in DNA extraction efficiencies.
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Affiliation(s)
- Paulo de Boer
- />TI Food and Nutrition, Wageningen, The Netherlands
- />TNO Microbiology and Systems Biology, Utrechtseweg 48, 3704 HE Zeist, The Netherlands
| | - Martien Caspers
- />TI Food and Nutrition, Wageningen, The Netherlands
- />TNO Microbiology and Systems Biology, Utrechtseweg 48, 3704 HE Zeist, The Netherlands
| | | | | | | | | | - Guus Roeselers
- />TI Food and Nutrition, Wageningen, The Netherlands
- />TNO Microbiology and Systems Biology, Utrechtseweg 48, 3704 HE Zeist, The Netherlands
| | - Roy Montijn
- />TI Food and Nutrition, Wageningen, The Netherlands
| | - Tjakko Abee
- />TI Food and Nutrition, Wageningen, The Netherlands
- />Laboratory of Food Microbiology, Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Remco Kort
- />TI Food and Nutrition, Wageningen, The Netherlands
- />TNO Microbiology and Systems Biology, Utrechtseweg 48, 3704 HE Zeist, The Netherlands
- />Molecular Cell Physiology, VU University Amsterdam, Amsterdam, The Netherlands
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65
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Lenz CA, Reineke K, Knorr D, Vogel RF. High pressure thermal inactivation of Clostridium botulinum type E endospores - kinetic modeling and mechanistic insights. Front Microbiol 2015; 6:652. [PMID: 26191048 PMCID: PMC4490342 DOI: 10.3389/fmicb.2015.00652] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 06/15/2015] [Indexed: 12/03/2022] Open
Abstract
Cold-tolerant, neurotoxigenic, endospore forming Clostridium (C.) botulinum type E belongs to the non-proteolytic physiological C. botulinum group II, is primarily associated with aquatic environments, and presents a safety risk for seafood. High pressure thermal (HPT) processing exploiting the synergistic effect of pressure and temperature can be used to inactivate bacterial endospores. We investigated the inactivation of C. botulinum type E spores by (near) isothermal HPT treatments at 300–1200 MPa at 30–75°C for 1 s to 10 min. The occurrence of heat and lysozyme susceptible spore fractions after such treatments was determined. The experimental data were modeled to obtain kinetic parameters and represented graphically by isoeffect lines. In contrast to findings for spores of other species and within the range of treatment parameters applied, zones of spore stabilization (lower inactivation than heat treatments alone), large heat susceptible (HPT-induced germinated) or lysozyme-dependently germinable (damaged coat layer) spore fractions were not detected. Inactivation followed first order kinetics. Dipicolinic acid release kinetics allowed for insights into possible inactivation mechanisms suggesting a (poorly effective) physiologic-like (similar to nutrient-induced) germination at ≤450 MPa/≤45°C and non-physiological germination at >500 MPa/>60–70°C. Results of this study support the existence of some commonalities in the HPT inactivation mechanism of C. botulinum type E spores and Bacillus spores although both organisms have significantly different HPT resistance properties. The information presented here contributes to closing the gap in knowledge regarding the HPT inactivation of spore formers relevant to food safety and may help industrial implementation of HPT processing. The markedly lower HPT resistance of C. botulinum type E spores compared with the resistance of spores from other C. botulinum types could allow for the implementation of milder processes without endangering food safety.
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Affiliation(s)
- Christian A Lenz
- Lehrstuhl für Technische Mikrobiologie, Technische Universität München Freising, Germany
| | - Kai Reineke
- Quality and Safety of Food and Feed, Leibniz Institute for Agricultural Engineering (ATB), Potsdam Germany ; Department of Food Biotechnology and Food Process Engineering, Technische Universität Berlin Berlin, Germany
| | - Dietrich Knorr
- Department of Food Biotechnology and Food Process Engineering, Technische Universität Berlin Berlin, Germany
| | - Rudi F Vogel
- Lehrstuhl für Technische Mikrobiologie, Technische Universität München Freising, Germany
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Xiao Y, van Hijum SAFT, Abee T, Wells-Bennik MHJ. Genome-Wide Transcriptional Profiling of Clostridium perfringens SM101 during Sporulation Extends the Core of Putative Sporulation Genes and Genes Determining Spore Properties and Germination Characteristics. PLoS One 2015; 10:e0127036. [PMID: 25978838 PMCID: PMC4433262 DOI: 10.1371/journal.pone.0127036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/11/2015] [Indexed: 11/19/2022] Open
Abstract
The formation of bacterial spores is a highly regulated process and the ultimate properties of the spores are determined during sporulation and subsequent maturation. A wide variety of genes that are expressed during sporulation determine spore properties such as resistance to heat and other adverse environmental conditions, dormancy and germination responses. In this study we characterized the sporulation phases of C. perfringens enterotoxic strain SM101 based on morphological characteristics, biomass accumulation (OD600), the total viable counts of cells plus spores, the viable count of heat resistant spores alone, the pH of the supernatant, enterotoxin production and dipicolinic acid accumulation. Subsequently, whole-genome expression profiling during key phases of the sporulation process was performed using DNA microarrays, and genes were clustered based on their time-course expression profiles during sporulation. The majority of previously characterized C. perfringens germination genes showed upregulated expression profiles in time during sporulation and belonged to two main clusters of genes. These clusters with up-regulated genes contained a large number of C. perfringens genes which are homologs of Bacillus genes with roles in sporulation and germination; this study therefore suggests that those homologs are functional in C. perfringens. A comprehensive homology search revealed that approximately half of the upregulated genes in the two clusters are conserved within a broad range of sporeforming Firmicutes. Another 30% of upregulated genes in the two clusters were found only in Clostridium species, while the remaining 20% appeared to be specific for C. perfringens. These newly identified genes may add to the repertoire of genes with roles in sporulation and determining spore properties including germination behavior. Their exact roles remain to be elucidated in future studies.
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Affiliation(s)
- Yinghua Xiao
- NIZO food research, Ede, The Netherlands
- Top Institute Food and Nutrition, Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, Wageningen, The Netherlands
| | - Sacha A. F. T. van Hijum
- NIZO food research, Ede, The Netherlands
- Top Institute Food and Nutrition, Wageningen, The Netherlands
- Center for Molecular and Biomolecular Informatics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Tjakko Abee
- Top Institute Food and Nutrition, Wageningen, The Netherlands
- Laboratory of Food Microbiology, Wageningen University, Wageningen, The Netherlands
| | - Marjon H. J. Wells-Bennik
- NIZO food research, Ede, The Netherlands
- Top Institute Food and Nutrition, Wageningen, The Netherlands
- * E-mail:
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67
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Spore Cortex Hydrolysis Precedes Dipicolinic Acid Release during Clostridium difficile Spore Germination. J Bacteriol 2015; 197:2276-83. [PMID: 25917906 DOI: 10.1128/jb.02575-14] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/21/2015] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED Bacterial spore germination is a process whereby a dormant spore returns to active, vegetative growth, and this process has largely been studied in the model organism Bacillus subtilis. In B. subtilis, the initiation of germinant receptor-mediated spore germination is divided into two genetically separable stages. Stage I is characterized by the release of dipicolinic acid (DPA) from the spore core. Stage II is characterized by cortex degradation, and stage II is activated by the DPA released during stage I. Thus, DPA release precedes cortex hydrolysis during B. subtilis spore germination. Here, we investigated the timing of DPA release and cortex hydrolysis during Clostridium difficile spore germination and found that cortex hydrolysis precedes DPA release. Inactivation of either the bile acid germinant receptor, cspC, or the cortex hydrolase, sleC, prevented both cortex hydrolysis and DPA release. Because both cortex hydrolysis and DPA release during C. difficile spore germination are dependent on the presence of the germinant receptor and the cortex hydrolase, the release of DPA from the core may rely on the osmotic swelling of the core upon cortex hydrolysis. These results have implications for the hypothesized glycine receptor and suggest that the initiation of germinant receptor-mediated C. difficile spore germination proceeds through a novel germination pathway. IMPORTANCE Clostridium difficile infects antibiotic-treated hosts and spreads between hosts as a dormant spore. In a host, spores germinate to the vegetative form that produces the toxins necessary for disease. C. difficile spore germination is stimulated by certain bile acids and glycine. We recently identified the bile acid germinant receptor as the germination-specific, protease-like CspC. CspC is likely cortex localized, where it can transmit the bile acid signal to the cortex hydrolase, SleC. Due to the differences in location of CspC compared to the Bacillus subtilis germinant receptors, we hypothesized that there are fundamental differences in the germination processes between the model organism and C. difficile. We found that C. difficile spore germination proceeds through a novel pathway.
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68
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Luu-Thi H, Corthouts J, Passaris I, Grauwet T, Aertsen A, Hendrickx M, Michiels CW. Carvacrol suppresses high pressure high temperature inactivation of Bacillus cereus spores. Int J Food Microbiol 2014; 197:45-52. [PMID: 25560915 DOI: 10.1016/j.ijfoodmicro.2014.12.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 10/20/2014] [Accepted: 12/14/2014] [Indexed: 12/30/2022]
Abstract
The inactivation of bacterial spores generally proceeds faster and at lower temperatures when heat treatments are conducted under high pressure, and high pressure high temperature (HPHT) processing is, therefore, receiving an increased interest from food processors. However, the mechanisms of spore inactivation by HPHT treatment are poorly understood, particularly at moderately elevated temperature. In the current work, we studied inactivation of the spores of Bacillus cereus F4430/73 by HPHT treatment for 5 min at 600MPa in the temperature range of 50-100°C, using temperature increments of 5°C. Additionally, we investigated the effect of the natural antimicrobial carvacrol on spore germination and inactivation under these conditions. Spore inactivation by HPHT was less than about 1 log unit at 50 to 70°C, but gradually increased at higher temperatures up to about 5 log units at 100°C. DPA release and loss of spore refractility in the spore population were higher at moderate (≤65°C) than at high (≥70°C) treatment temperatures, and we propose that moderate conditions induced the normal physiological pathway of spore germination resulting in fully hydrated spores, while at higher temperatures this pathway was suppressed and replaced by another mechanism of pressure-induced dipicolinic acid (DPA) release that results only in partial spore rehydration, probably because spore cortex hydrolysis is inhibited. Carvacrol strongly suppressed DPA release and spore rehydration during HPHT treatment at ≤65°C and also partly inhibited DPA release at ≥65°C. Concomitantly, HPHT spore inactivation was reduced by carvacrol at 65-90°C but unaffected at 95-100°C.
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Affiliation(s)
- Hue Luu-Thi
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Jorinde Corthouts
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Ioannis Passaris
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Tara Grauwet
- Laboratory of Food Technology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Marc Hendrickx
- Laboratory of Food Technology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium
| | - Chris W Michiels
- Laboratory of Food Microbiology, Leuven Food Science and Nutrition Research Center (LFoRCe), Department of Microbial and Molecular Systems (M(2)S), KU Leuven, Kasteelpark Arenberg 22, B-3001 Heverlee, Belgium.
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69
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Effect of sporulation medium on wet-heat resistance and structure of Alicyclobacillus acidoterrestris DSM 3922-type strain spores and modeling of the inactivation kinetics in apple juice. Int J Food Microbiol 2014; 189:82-8. [DOI: 10.1016/j.ijfoodmicro.2014.07.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 06/04/2014] [Accepted: 07/26/2014] [Indexed: 11/20/2022]
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70
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Two distinct groups within the Bacillus subtilis group display significantly different spore heat resistance properties. Food Microbiol 2014; 45:18-25. [PMID: 25481058 DOI: 10.1016/j.fm.2014.04.009] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/04/2014] [Accepted: 04/21/2014] [Indexed: 11/21/2022]
Abstract
The survival of bacterial spores after heat treatment and the subsequent germination and outgrowth in a food product can lead to spoilage of the food product and economical losses. Prediction of time-temperature conditions that lead to sufficient inactivation requires access to detailed spore thermal inactivation kinetics of relevant model strains. In this study, the thermal inactivation kinetics of spores of fourteen strains belonging to the Bacillus subtilis group were determined in detail, using both batch heating in capillary tubes and continuous flow heating in a micro heater. The inactivation data were fitted using a log linear model. Based on the spore heat resistance data, two distinct groups (p < 0.001) within the B. subtilis group could be identified. One group of strains had spores with an average D120 °C of 0.33 s, while the spores of the other group displayed significantly higher heat resistances, with an average D120 °C of 45.7 s. When comparing spore inactivation data obtained using batch- and continuous flow heating, the z-values were significantly different, hence extrapolation from one system to the other was not justified. This study clearly shows that heat resistances of spores from different strains in the B. subtilis group can vary greatly. Strains can be separated into two groups, to which different spore heat inactivation kinetics apply.
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71
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Abhyankar W, Pandey R, Ter Beek A, Brul S, de Koning LJ, de Koster CG. Reinforcement of Bacillus subtilis spores by cross-linking of outer coat proteins during maturation. Food Microbiol 2014; 45:54-62. [PMID: 25481062 DOI: 10.1016/j.fm.2014.03.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/03/2014] [Accepted: 03/06/2014] [Indexed: 10/25/2022]
Abstract
Resistance characteristics of bacterial endospores towards various environmental stresses such as chemicals and heat are in part attributed to their coat proteins. Heat resistance is developed in a late stage of sporulation and during maturation of released spores. Using our gel-free proteomic approach and LC-FT-ICR-MS/MS analysis we have monitored the efficiency of the tryptic digestion of proteins in the coat during spore maturation over a period of eight days, using metabolically (15)N labeled mature spores as reference. The results showed that during spore maturation the loss of digestion efficiency of outer coat and crust proteins synchronized with the increase in heat resistance. This implicates that spore maturation involves chemical cross-linking of outer coat and crust layer proteins leaving the inner coat layer proteins unmodified. It appears that digestion efficiencies of spore surface proteins can be linked to their location within the coat and crust layers. We also attempted to study a possible link between spore maturation and the observed heterogeneity in spore germination.
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Affiliation(s)
- Wishwas Abhyankar
- Mass Spectrometry of Biomacromolecules, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands; Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Rachna Pandey
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Alexander Ter Beek
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Stanley Brul
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Leo J de Koning
- Mass Spectrometry of Biomacromolecules, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Chris G de Koster
- Mass Spectrometry of Biomacromolecules, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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72
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Pandey R, Ter Beek A, Vischer NOE, Smelt JPPM, Kemperman R, Manders EMM, Brul S. Quantitative analysis of the effect of specific tea compounds on germination and outgrowth of Bacillus subtilis spores at single cell resolution. Food Microbiol 2014; 45:63-70. [PMID: 25481063 DOI: 10.1016/j.fm.2014.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 03/03/2014] [Accepted: 03/06/2014] [Indexed: 01/31/2023]
Abstract
Tea is one of the most widely consumed beverages in the world and known for its antimicrobial activity against many microorganisms. Preliminary studies have shown that tea polyphenols can inhibit the growth of a wide range of Gram-positive bacteria. However, the effect of these compounds on germination and outgrowth of bacterial spores is unclear. Spore-forming bacteria are an aggravating problem for the food industry due to spore formation and their subsequent returning to vegetative state during food storage, thus posing spoilage and food safety challenges. Here we analysed the effect of tea compounds: gallic acid, gallocatechin gallate, Teavigo (>90% epigallocatechin gallate), and theaflavin 3,3'-digallate on spore germination and outgrowth and subsequent growth of vegetative cells of Bacillus subtilis. To quantitatively analyse the effect of these compounds, live cell images were tracked from single phase-bright spores up to microcolony formation and analysed with the automated image analysis tool "SporeTracker". In general, the tested compounds had a significant effect on most stages of germination and outgrowth. However, germination efficiency (ability of spores to become phase-dark) was not affected. Gallic acid most strongly reduced the ability to grow out. Additionally, all compounds, in particular theaflavin 3,3'-digallate, clearly affected the growth of emerging vegetative cells.
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Affiliation(s)
- Rachna Pandey
- Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands; Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | - Alexander Ter Beek
- Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | - Norbert O E Vischer
- Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | - Jan P P M Smelt
- Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | | | - Erik M M Manders
- Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | - Stanley Brul
- Molecular Biology & Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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73
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Characterization of Bacillus spp. strains for use as probiotic additives in pig feed. Appl Microbiol Biotechnol 2013; 98:1105-18. [PMID: 24201893 DOI: 10.1007/s00253-013-5343-6] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Revised: 10/16/2013] [Accepted: 10/17/2013] [Indexed: 12/31/2022]
Abstract
Bacillus spp. are commonly used as probiotic species in the feed industry, however, their benefits need to be confirmed. This study describes a high throughput screening combined with the detailed characterization of endospore-forming bacteria with the aim to identify new Bacillus spp. strains for use as probiotic additives in pig feed. A total of 245 bacterial isolates derived from African fermented food, feces and soil were identified by 16S rRNA gene sequencing and screened for antimicrobial activity and growth in the presence of antibiotics, bile salts and at pH 4.0. Thirty-three Bacillus spp. isolates with the best characteristics were identified by gyrB and rpoB gene sequencing as B. amyloliquefaciens subsp. plantarum, B. amyloliquefaciens subsp. amyloliquefaciens, B. subtilis subsp. subtilis, B. licheniformis, B. mojavensis, B. pumilus and B. megaterium. These isolates were further investigated for their activity against the pathogenic bacteria, antibiotic susceptibility, sporulation rates, biofilm formation and production of glycosyl hydrolytic enzymes. Additionally, ten selected isolates were assessed for heat resistance of spores and the effect on porcine epithelial cells IPEC-J2. Isolates of B. amyloliquefaciens, B. subtilis and B. mojavensis, showed the best overall characteristics and, therefore, potential for usage as probiotic additives in feed. A large number of taxonomically diverse strains made it possible to reveal species and subspecies-specific trends, contributing to our understanding of the probiotic potential of Bacillus species.
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74
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Clear KJ, Stroud S, Smith BD. Dual colorimetric and luminescent assay for dipicolinate, a biomarker of bacterial spores. Analyst 2013; 138:7079-82. [PMID: 24106737 DOI: 10.1039/c3an01658g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A binary mixture of Tb(3+) and pyrocatechol violet (PV) forms a 1 : 1 Tb(3+)/PV complex that can be used in a dye displacement assay. Addition of dipicolinate (DPA) to the Tb(3+)/DPA complex simultaneously produces a PV color change from blue to yellow and luminescence emission from the newly formed Tb(3+)/DPA complex.
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Affiliation(s)
- Kasey J Clear
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
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75
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Lücking G, Stoeckel M, Atamer Z, Hinrichs J, Ehling-Schulz M. Characterization of aerobic spore-forming bacteria associated with industrial dairy processing environments and product spoilage. Int J Food Microbiol 2013; 166:270-9. [DOI: 10.1016/j.ijfoodmicro.2013.07.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 07/03/2013] [Accepted: 07/07/2013] [Indexed: 11/30/2022]
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76
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Abiotic and microbiotic factors controlling biofilm formation by thermophilic sporeformers. Appl Environ Microbiol 2013; 79:5652-60. [PMID: 23851093 DOI: 10.1128/aem.00949-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One of the major concerns in the production of dairy concentrates is the risk of contamination by heat-resistant spores from thermophilic bacteria. In order to acquire more insight in the composition of microbial communities occurring in the dairy concentrate industry, a bar-coded 16S amplicon sequencing analysis was carried out on milk, final products, and fouling samples taken from dairy concentrate production lines. The analysis of these samples revealed the presence of DNA from a broad range of bacterial taxa, including a majority of mesophiles and a minority of (thermophilic) spore-forming bacteria. Enrichments of fouling samples at 55°C showed the accumulation of predominantly Brevibacillus and Bacillus, whereas enrichments at 65°C led to the accumulation of Anoxybacillus and Geobacillus species. Bacterial population analysis of biofilms grown using fouling samples as an inoculum indicated that both Anoxybacillus and Geobacillus preferentially form biofilms on surfaces at air-liquid interfaces rather than on submerged surfaces. Three of the most potent biofilm-forming strains isolated from the dairy factory industrial samples, including Geobacillus thermoglucosidans, Geobacillus stearothermophilus, and Anoxybacillus flavithermus, have been characterized in detail with respect to their growth conditions and spore resistance. Strikingly, Geobacillus thermoglucosidans, which forms the most thermostable spores of these three species, is not able to grow in dairy intermediates as a pure culture but appears to be dependent for growth on other spoilage organisms present, probably as a result of their proteolytic activity. These results underscore the importance of abiotic and microbiotic factors in niche colonization in dairy factories, where the presence of thermophilic sporeformers can affect the quality of end products.
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77
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Hofstetter S, Gebhardt D, Ho L, Gänzle M, McMullen LM. Effects of nisin and reutericyclin on resistance of endospores of Clostridium spp. to heat and high pressure. Food Microbiol 2013; 34:46-51. [DOI: 10.1016/j.fm.2012.11.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 09/18/2012] [Accepted: 11/08/2012] [Indexed: 11/29/2022]
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78
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Pandey R, Ter Beek A, Vischer NOE, Smelt JPPM, Brul S, Manders EMM. Live cell imaging of germination and outgrowth of individual bacillus subtilis spores; the effect of heat stress quantitatively analyzed with SporeTracker. PLoS One 2013; 8:e58972. [PMID: 23536843 PMCID: PMC3607599 DOI: 10.1371/journal.pone.0058972] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/08/2013] [Indexed: 11/25/2022] Open
Abstract
Spore-forming bacteria are a special problem for the food industry as some of them are able to survive preservation processes. Bacillus spp. spores can remain in a dormant, stress resistant state for a long period of time. Vegetative cells are formed by germination of spores followed by a more extended outgrowth phase. Spore germination and outgrowth progression are often very heterogeneous and therefore, predictions of microbial stability of food products are exceedingly difficult. Mechanistic details of the cause of this heterogeneity are necessary. In order to examine spore heterogeneity we made a novel closed air-containing chamber for live imaging. This chamber was used to analyze Bacillus subtilis spore germination, outgrowth, as well as subsequent vegetative growth. Typically, we examined around 90 starting spores/cells for ≥4 hours per experiment. Image analysis with the purposely built program “SporeTracker” allows for automated data processing from germination to outgrowth and vegetative doubling. In order to check the efficiency of the chamber, growth and division of B. subtilis vegetative cells were monitored. The observed generation times of vegetative cells were comparable to those obtained in well-aerated shake flask cultures. The influence of a heat stress of 85°C for 10 min on germination, outgrowth, and subsequent vegetative growth was investigated in detail. Compared to control samples fewer spores germinated (41.1% less) and fewer grew out (48.4% less) after the treatment. The heat treatment had a significant influence on the average time to the start of germination (increased) and the distribution and average of the duration of germination itself (increased). However, the distribution and the mean outgrowth time and the generation time of vegetative cells, emerging from untreated and thermally injured spores, were similar.
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Affiliation(s)
- Rachna Pandey
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Alex Ter Beek
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
- * E-mail:
| | - Norbert O. E. Vischer
- Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan P. P. M. Smelt
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Stanley Brul
- Molecular Biology and Microbial Food Safety, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Erik M. M. Manders
- Van Leeuwenhoek Centre for Advanced Microscopy Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
- Department of Molecular Biotechnology, Faculty of Bioscience Engineering, University of Ghent, Ghent, Belgium
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79
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Inactivation of foodborne pathogens in ground beef by cooking with highly controlled radio frequency energy. Int J Food Microbiol 2013; 160:219-26. [DOI: 10.1016/j.ijfoodmicro.2012.10.017] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 09/30/2012] [Accepted: 10/01/2012] [Indexed: 01/24/2023]
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80
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Hofstetter S, Denter C, Winter R, McMullen LM, Gänzle MG. Use of the fluorescent probe LAURDAN to label and measure inner membrane fluidity of endospores of Clostridium spp. J Microbiol Methods 2012; 91:93-100. [PMID: 22884687 DOI: 10.1016/j.mimet.2012.07.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 07/17/2012] [Accepted: 07/17/2012] [Indexed: 11/29/2022]
Abstract
A method for measuring the fluidity of inner membranes of populations of endospores of Clostridium spp. with a fluorescent dye was developed. Cells of Clostridium beijerinckii ATCC 8260 and Clostridium sporogenes ATCC 7955 were allowed to sporulate in the presence of 6-dodecanoyl-2-dimethylaminonaphthalene (LAURDAN) on a soil-based media. Labeling of endospores with LAURDAN did not affect endospore viability. Removal of the outer membranes of endospores was done using a chemical treatment and confirmed using transmission electron microscopy (TEM). Two-photon confocal laser scanning microscopy (CLSM), and generalized polarization (GP) measurements were used to assess fluorescence of endospores. Lipid composition analysis of cells and endospores was done to determine whether differences in GP values are attributable to differences in membrane composition. Removal of the outer membranes of endospores did not significantly impact GP values. Decoated, labeled endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 exhibited GP values of 0.77±0.031 and 0.74±0.027 respectively. Differences in ratios of fatty acids between cells and endospores are unlikely to be responsible for high GP values observed in endospores. These GP values indicate high levels of lipid order and the exclusion of water from within inner membranes of endospores.
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Affiliation(s)
- Simmon Hofstetter
- University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Alberta, Canada, T6G 2P5.
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81
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Barnes L, Kaneshige K, Strong J, Tan K, von Bremen H, Mogul R. Effects of terbium chelate structure on dipicolinate ligation and the detection of Bacillus spores. J Inorg Biochem 2011; 105:1580-8. [DOI: 10.1016/j.jinorgbio.2011.08.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 07/30/2011] [Accepted: 08/01/2011] [Indexed: 10/17/2022]
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82
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Abhyankar W, Beek AT, Dekker H, Kort R, Brul S, de Koster CG. Gel-free proteomic identification of the Bacillus subtilis insoluble spore coat protein fraction. Proteomics 2011; 11:4541-50. [PMID: 21905219 DOI: 10.1002/pmic.201100003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 08/25/2011] [Accepted: 08/31/2011] [Indexed: 11/11/2022]
Abstract
Species from the genus Bacillus have the ability to form endospores, dormant cellular forms that are able to survive heat and acid preservation techniques commonly used in the food industry. Resistance characteristics of spores towards various environmental stresses are in part attributed to their coat proteins. Previously, 70 proteins have been assigned to the spore coat of Bacillus subtilis using SDS-PAGE, 2-DE gel approaches, protein localization studies and genome-wide transcriptome studies. Here, we present a "gel-free" protocol that is capable of comprehensive B. subtilis spore coat protein extraction and addresses the insoluble coat fraction. Using LC-MS/MS we identified 55 proteins from the insoluble B. subtilis spore coat protein fraction, of which 21 are putative novel spore coat proteins not assigned to the spore coat until now. Identification of spore coat proteins from a B. subtilis food-spoilage isolate corroborated a generic and "applied" use of our protocol. To develop specific and sensitive spore detection and/or purification systems from food stuff or patient material, suitable protein targets can be derived from our proteomic approach. Finally, the protocol can be extended to study cross-linking among the spore coat proteins as well as for their quantification.
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Affiliation(s)
- Wishwas Abhyankar
- Swammerdam Institute for Life Sciences, Department of Mass Spectrometry of Biomacromolecules, University of Amsterdam, The Netherlands.
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83
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Maturation of released spores is necessary for acquisition of full spore heat resistance during Bacillus subtilis sporulation. Appl Environ Microbiol 2011; 77:6746-54. [PMID: 21821751 DOI: 10.1128/aem.05031-11] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The first ∼10% of spores released from sporangia (early spores) during Bacillus subtilis sporulation were isolated, and their properties were compared to those of the total spores produced from the same culture. The early spores had significantly lower resistance to wet heat and hypochlorite than the total spores but identical resistance to dry heat and UV radiation. Early and total spores also had the same levels of core water, dipicolinic acid, and Ca and germinated similarly with several nutrient germinants. The wet heat resistance of the early spores could be increased to that of total spores if early spores were incubated in conditioned sporulation medium for ∼24 h at 37°C (maturation), and some hypochlorite resistance was also restored. The maturation of early spores took place in pH 8 buffer with Ca(2+) but was blocked by EDTA; maturation was also seen with early spores of strains lacking the CotE protein or the coat-associated transglutaminase, both of which are needed for normal coat structure. Nonetheless, it appears to be most likely that it is changes in coat structure that are responsible for the increased resistance to wet heat and hypochlorite upon early spore maturation.
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84
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Lima LJR, Kamphuis HJ, Nout MJR, Zwietering MH. Microbiota of cocoa powder with particular reference to aerobic thermoresistant spore-formers. Food Microbiol 2010; 28:573-82. [PMID: 21356467 DOI: 10.1016/j.fm.2010.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 11/17/2010] [Accepted: 11/18/2010] [Indexed: 10/18/2022]
Abstract
The microbiological criteria of commercial cocoa powder are defined in guidelines instituted by the cocoa industry. Twenty-five commercial samples were collected with the aim of assessing the compliance with the microbiological quality guidelines and investigating the occurrence and properties of aerobic Thermoresistant Spores (ThrS). Seventeen samples complied with the guidelines, but one was positive for Salmonella, five for Enterobacteriaceae and two had mould levels just exceeding the maximum admissible level. The treatment of the cocoa powder suspensions from 100 °C to 170 °C for 10 min, revealed the presence of ThrS in 36% of the samples. In total 61 ThrS strains were isolated, of which the majority belonged to the Bacillus subtilis complex (65.6%). Strains resporulation and spore crops inactivation at 110 °C for 5 min showed a wide diversity of heat-resistance capacities. Amplified fragment length polymorphism analysis revealed not only a large intraspecies diversity, but also different clusters of heat-resistant spore-forming strains. The heat-resistance of spores of six B. subtilis complex strains was further examined by determination of their D and z-values. We concluded that B. subtilis complex spores, in particular those from strain M112, were the most heat-resistant and these may survive subsequent preservation treatments, being potentially problematic in food products, such as chocolate milk.
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Affiliation(s)
- Lídia J R Lima
- Laboratory of Food Microbiology, Wageningen University, P.O. box 8129, 6700 EV Wageningen, The Netherlands
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85
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van Zuijlen A, Periago PM, Amézquita A, Palop A, Brul S, Fernández PS. Characterization of Bacillus sporothermodurans IC4 spores; putative indicator microorganism for optimisation of thermal processes in food sterilisation. Food Res Int 2010. [DOI: 10.1016/j.foodres.2009.11.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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86
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Challenges and advances in systems biology analysis of Bacillus spore physiology; molecular differences between an extreme heat resistant spore forming Bacillus subtilis food isolate and a laboratory strain. Food Microbiol 2010; 28:221-7. [PMID: 21315977 DOI: 10.1016/j.fm.2010.06.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 06/02/2010] [Accepted: 06/24/2010] [Indexed: 01/13/2023]
Abstract
Bacterial spore formers are prime organisms of concern in the food industry. Spores from the genus Bacillus are extremely stress resistant, most notably exemplified by high thermotolerance. This sometimes allows surviving spores to germinate and grow out to vegetative cells causing food spoilage and possible intoxication. Similar issues though more pending toward spore toxigenicity are observed for the anaerobic Clostridia. The paper indicates the nature of stress resistance and highlights contemporary molecular approaches to analyze the mechanistic basis of it in Bacilli. A molecular comparison between a laboratory strain and a food borne isolate, very similar at the genomic level to the laboratory strain but generating extremely heat resistant spores, is discussed. The approaches cover genome-wide genotyping, proteomics and genome-wide expression analyses studies. The analyses aim at gathering sufficient molecular information to be able to put together an initial framework for dynamic modelling of spore germination and outgrowth behaviour. Such emerging models should be developed both at the population and at the single spore level. Tools and challenges in achieving the latter are succinctly discussed.
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87
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Kort R, Nocker A, de Kat Angelino-Bart A, van Veen S, Verheij H, Schuren F, Montijn R. Real-time detection of viable microorganisms by intracellular phototautomerism. BMC Biotechnol 2010; 10:45. [PMID: 20565844 PMCID: PMC2906424 DOI: 10.1186/1472-6750-10-45] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 06/18/2010] [Indexed: 11/23/2022] Open
Abstract
Background To date, the detection of live microorganisms present in the environment or involved in infections is carried out by enumeration of colony forming units on agar plates, which is time consuming, laborious and limited to readily cultivable microorganisms. Although cultivation-independent methods are available, they involve multiple incubation steps and do mostly not discriminate between dead or live microorganisms. We present a novel generic method that is able to specifically monitor living microorganisms in a real-time manner. Results The developed method includes exposure of cells to a weak acid probe at low pH. The neutral probe rapidly permeates the membrane and enters the cytosol. In dead cells no signal is obtained, as the cytosolic pH reflects that of the acidic extracellular environment. In live cells with a neutral internal pH, the probe dissociates into a fluorescent phototautomeric anion. After reaching peak fluorescence, the population of live cells decays. This decay can be followed real-time as cell death coincides with intracellular acidification and return of the probe to its uncharged non-fluorescent state. The rise and decay of the fluorescence signal depends on the probe structure and appears discriminative for bacteria, fungi, and spores. We identified 13 unique probes, which can be applied in the real-time viability method described here. Under the experimental conditions used in a microplate reader, the reported method shows a detection limit of 106 bacteria ml-1, while the frequently used LIVE/DEAD BacLight™ Syto9 and propidium iodide stains show detection down to 106 and 107 bacteria ml-1, respectively. Conclusions We present a novel fluorescence-based method for viability assessment, which is applicable to all bacteria and eukaryotic cell types tested so far. The RTV method will have a significant impact in many areas of applied microbiology including research on biocidal activity, improvement of preservation strategies and membrane permeation and stability. The assay allows for high-throughput applications and has great potential for rapid monitoring of microbial content in air, liquids or on surfaces.
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Affiliation(s)
- Remco Kort
- Business Unit Food and Biotechnology Innovations, Microbial Genomics Group, TNO Quality of Life, Zeist, The Netherlands.
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88
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Evaluation of a stochastic inactivation model for heat-activated spores of Bacillus spp. Appl Environ Microbiol 2010; 76:4402-12. [PMID: 20453137 DOI: 10.1128/aem.02976-09] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heat activates the dormant spores of certain Bacillus spp., which is reflected in the "activation shoulder" in their survival curves. At the same time, heat also inactivates the already active and just activated spores, as well as those still dormant. A stochastic model based on progressively changing probabilities of activation and inactivation can describe this phenomenon. The model is presented in a fully probabilistic discrete form for individual and small groups of spores and as a semicontinuous deterministic model for large spore populations. The same underlying algorithm applies to both isothermal and dynamic heat treatments. Its construction does not require the assumption of the activation and inactivation kinetics or knowledge of their biophysical and biochemical mechanisms. A simplified version of the semicontinuous model was used to simulate survival curves with the activation shoulder that are reminiscent of experimental curves reported in the literature. The model is not intended to replace current models to predict dynamic inactivation but only to offer a conceptual alternative to their interpretation. Nevertheless, by linking the survival curve's shape to probabilities of events at the individual spore level, the model explains, and can be used to simulate, the irregular activation and survival patterns of individual and small groups of spores, which might be involved in food poisoning and spoilage.
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89
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Caspers MPM, Schuren FHJ, van Zuijlen ACM, Brul S, Montijn RC, Abee T, Kort R. A mixed-species microarray for identification of food spoilage bacilli. Food Microbiol 2010; 28:245-51. [PMID: 21315980 DOI: 10.1016/j.fm.2010.03.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 03/12/2010] [Accepted: 03/16/2010] [Indexed: 11/19/2022]
Abstract
Failure of food preservation is frequently caused by thermostable spores of members of the Bacillaceae family, which show a wide spectrum of resistance to cleaning and preservation treatments. We constructed and validated a mixed-species genotyping array for 6 Bacillus species, including Bacillus subtilis, Bacillus licheniformis, Bacillus pumilus, Bacillus sporothermodurans, Bacillus cereus and Bacillus coagulans, and 4 Geobacillus species, including Geobacillus stearothermophilus, Geobacillus thermocatenulatus, Geobacillus toebii and Geobacillus sp., in order to track food spoilage isolates from ingredient to product. The discriminating power of the array was evaluated with sets of 42 reference and 20 test strains. Bacterial isolates contain a within-species-conserved core genome comprising 68-88% of the entire genome and a non-conserved accessory genome comprising 7-22%. The majority of the core genome markers do not hybridise between species, thus they allow for efficient discrimination at the species level. The accessory genome array markers provide high-resolution discrimination at the level of individual isolates from a single species. In conclusion, the reported mixed-species microarray contains discriminating markers that allow rapid and cost-effective typing of Bacillus food spoilage bacteria in a wide variety of food products.
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Affiliation(s)
- Martien P M Caspers
- TNO Quality of Life, Microbial Genomics Group, Utrechtseweg 48, 3704 HE Zeist, The Netherlands
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90
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The effect of calcium on the transcriptome of sporulating B. subtilis cells. Int J Food Microbiol 2009; 133:234-42. [PMID: 19552981 DOI: 10.1016/j.ijfoodmicro.2009.05.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 05/08/2009] [Accepted: 05/11/2009] [Indexed: 11/21/2022]
Abstract
Bacterial spores formed in the presence of high concentrations of minerals are a major problem in the food industry because of their extreme heat resistance. In order to enhance our insight in the molecular mechanisms underlying this phenomenon we have performed a detailed time-resolved analysis of the genome-wide transcriptome pattern of Bacillus subtilis sporulated both in the absence and presence of high calcium concentrations. The data was analysed in two ways. First, we determined the influence of the presence of high calcium levels during sporulation on the expression of gene groups as defined in Subtilist and KEGG pathways database. Second, we assessed the differential expression at the level of individual genes. When analysing groups and pathways, we found that those annotated as being involved in sporulation were significantly affected. Also, groups and pathways involved in flagella formation and biofilm matrix production were affected by the presence of calcium in the sporulation medium. When we analysed the behaviour of individual genes we found 305 genes influenced by calcium, including all known spore coat polysaccharide biosynthesis genes (10 induced and 1 repressed). A number of the calcium affected genes were also involved in biofilm formation. Minimal overlap with other stress outputs like sigma B activation and weak acid stress response was noted. Those genes that did overlap were unique to that combination which corroborates the notion that the cells sense these conditions differently.
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91
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Kau JH, Sun DS, Huang HH, Wong MS, Lin HC, Chang HH. Role of visible light-activated photocatalyst on the reduction of anthrax spore-induced mortality in mice. PLoS One 2009; 4:e4167. [PMID: 19132100 PMCID: PMC2613519 DOI: 10.1371/journal.pone.0004167] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 12/07/2008] [Indexed: 11/28/2022] Open
Abstract
Background Photocatalysis of titanium dioxide (TiO2) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis. Methodology/Principal Findings Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components. Conclusion/Significance Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host.
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Affiliation(s)
- Jyh-Hwa Kau
- Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan
| | - Der-Shan Sun
- Institute of Molecular Biology and Human Genetics, Tzu-Chi University, Hualien, Taiwan
- Institute of Medical Science, Tzu-Chi University, Hualien, Taiwan
| | - Hsin-Hsien Huang
- Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan
| | - Ming-Show Wong
- Department of Materials Science and Engineering, National Dong-Hwa University, Hualien, Taiwan, Republic of China
| | - Hung-Chi Lin
- Institute of Preventive Medicine, National Defense Medical Center, Taipei, Taiwan
| | - Hsin-Hou Chang
- Institute of Molecular Biology and Human Genetics, Tzu-Chi University, Hualien, Taiwan
- Institute of Medical Science, Tzu-Chi University, Hualien, Taiwan
- * E-mail:
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92
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Xu H, He X, Gou J, Lee HY, Ahn J. Kinetic evaluation of physiological heterogeneity in bacterial spores during thermal inactivation. J GEN APPL MICROBIOL 2009; 55:295-9. [DOI: 10.2323/jgam.55.295] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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93
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Kort R, Keijser BJ, Caspers MPM, Schuren FH, Montijn R. Transcriptional activity around bacterial cell death reveals molecular biomarkers for cell viability. BMC Genomics 2008; 9:590. [PMID: 19061518 PMCID: PMC2648990 DOI: 10.1186/1471-2164-9-590] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 12/06/2008] [Indexed: 11/29/2022] Open
Abstract
Background In bacteriology, the ability to grow in selective media and to form colonies on nutrient agar plates is routinely used as a retrospective criterion for the detection of living bacteria. However, the utilization of indicators for bacterial viability-such as the presence of specific transcripts or membrane integrity-would overcome bias introduced by cultivation and reduces the time span of analysis from initiation to read out. Therefore, we investigated the correlation between transcriptional activity, membrane integrity and cultivation-based viability in the Gram-positive model bacterium Bacillus subtilis. Results We present microbiological, cytological and molecular analyses of the physiological response to lethal heat stress under accurately defined conditions through systematic sampling of bacteria from a single culture exposed to gradually increasing temperatures. We identified a coherent transcriptional program including known heat shock responses as well as the rapid expression of a small number of sporulation and competence genes, the latter only known to be active in the stationary growth phase. Conclusion The observed coordinated gene expression continued even after cell death, in other words after all bacteria permanently lost their ability to reproduce. Transcription of a very limited number of genes correlated with cell viability under the applied killing regime. The transcripts of the expressed genes in living bacteria – but silent in dead bacteria-include those of essential genes encoding chaperones of the protein folding machinery and can serve as molecular biomarkers for bacterial cell viability.
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Affiliation(s)
- Remco Kort
- TNO Quality of Life, Business Unit Food and Biotechnology Innovations, Microbial Genomics Group, Utrechtseweg 48, Zeist, The Netherlands.
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94
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Smelt J, Bos A, Kort R, Brul S. Modelling the effect of sub(lethal) heat treatment of Bacillus subtilis spores on germination rate and outgrowth to exponentially growing vegetative cells. Int J Food Microbiol 2008; 128:34-40. [DOI: 10.1016/j.ijfoodmicro.2008.08.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 08/29/2008] [Accepted: 08/29/2008] [Indexed: 10/21/2022]
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95
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Li Q, Dasgupta PK, Temkin H. A time-gated fluorescence detector using a tuning fork chopper. Anal Chim Acta 2008; 616:63-8. [DOI: 10.1016/j.aca.2008.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 03/28/2008] [Accepted: 04/03/2008] [Indexed: 11/24/2022]
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96
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Li Q, Dasgupta PK, Temkins HK. Airborne bacterial spore counts by terbium-enhanced luminescence detection: pitfalls and real values. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:2799-2804. [PMID: 18497126 DOI: 10.1021/es702472t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Bacterial spore determination by terbium(III)-dipicolinate luminescence has been reported by several investigators. We collected spore samples with a cyclone and extracted dipicolinic acid (DPA) in-line with hot aqueous dodecylamine, added Tb(III) in a continuous-flow system and detected the Tb(III)-DPA with a gated liquid core waveguide fluorescence detector with a flashlamp excitation source. The absolute limit of detection (LOD) for the system was equivalent to 540 B. subtilis spores (for a 1.8 m3 sample volume (t = 2 h, Q = 15 L/min), concentration LOD is 0.3 spores/L air). Extant literature suggests that, from office to home settings, viable spore concentrations range from 0.1 to 10 spores/L; however, these data have never been validated. Previously reported semiautomated instrumentation had an LOD of 50 spores/L. The present system was tested at five different location settings in Lubbock, Texas. The apparent bacterial spore concentrations ranged from 9 to 700 spores/L and only occasionally exhibited the same trend as the simultaneously monitored total optical particle counts in the > or = 0.5 microm size fraction. However, because the apparent spore counts sometimes were very large relative to the 0.5+ microm size particle counts, we investigated potential positive interferences. We show that aromatic acids are very likely large interferents. This interference typically constitutes approximately 70% of the signal and can be as high as 95%. It can be completely removed by prewashing the particles.
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Affiliation(s)
- Qingyang Li
- Department of Chemistry and Biochemistry and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409-1061, USA
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97
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Oomes SJCM, van Zuijlen ACM, Hehenkamp JO, Witsenboer H, van der Vossen JMBM, Brul S. The characterisation of Bacillus spores occurring in the manufacturing of (low acid) canned products. Int J Food Microbiol 2007; 120:85-94. [PMID: 17644202 DOI: 10.1016/j.ijfoodmicro.2007.06.013] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 02/11/2007] [Indexed: 10/23/2022]
Abstract
Spore-forming bacteria can be a problem in the food industry, especially in the canning industry. Spores present in ingredients or present in the processing environment severely challenge the preservation process since their thermal resistance may be very high. We therefore asked the question which bacterial spore formers are found in a typical soup manufacturing plant, where they originate from and what the thermal resistance of their spores is. To answer these questions molecular techniques for bacterial species and strain identification were used as well as a protocol for the assessment of spore heat stress resistance based on the Kooiman method. The data indicate the existence and physiological cause of the high thermal resistance of spores of many of the occurring species. In particular it shows that ingredients used in soup manufacturing are a rich source of high thermal resistant spores and that sporulation in the presence of ingredients rich in divalent metal ions exerts a strong influence on spore heat resistance. It was also indicated that Bacillus spores may well be able to germinate and resporulate during manufacturing i.e. through growth and sporulation in line. Both these spores and those originating from the ingredients were able to survive certain thermal processing settings. Species identity was confirmed using fatty acid analysis, 16SrRNA gene sequencing and DNA-DNA hybridisation. Finally, molecular typing experiments using Ribotyping and AFLP analysis show that strains within the various Bacillus species can be clustered according to the thermal resistance properties of their spores. AFLP performed slightly better than Ribotyping. The data proofed to be useful for the generation of strain specific probes. Protocols to validate these probes in routine identification and innovation aimed at tailor made heat processing in soup manufacturing have been formulated.
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Affiliation(s)
- S J C M Oomes
- Unilever Food and Health Reseach Institute, Department of Advanced Food Microbiology, Unilever Research and Development Vlaardingen, Olivier van Noortlaan 120, 3133AT Vlaardingen, The Netherlands
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98
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Fichtel J, Köster J, Rullkötter J, Sass H. Spore dipicolinic acid contents used for estimating the number of endospores in sediments. FEMS Microbiol Ecol 2007; 61:522-32. [PMID: 17623026 DOI: 10.1111/j.1574-6941.2007.00354.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Endospores are heat-resistant bacterial resting stages that can remain viable for long periods of time and may thus accumulate in sediments as a function of sediment age. The number of spores in sediments has only rarely been quantified, because of methodological problems, and consequently little is known about the quantitative contribution of endospores to the total number of prokaryotic cells. We here report on a protocol to determine the number of endospores in sediments and cultures. The method is based on the fluorimetric determination of dipicolinic acid (DPA), a spore core-specific compound, after reaction with terbium chloride. The concentration of DPA in natural samples is converted into endospore numbers using endospore-forming pure cultures as standards. Quenching of the fluorescence by sediment constituents and background fluorescence due to humic substances hampered direct determination of DPA in sediments. To overcome those interferences, DPA was extracted using ethyl acetate prior to fluorimetric measurements of DPA concentrations. The first results indicated that endospore numbers obtained with this method are orders of magnitude higher than numbers obtained by cultivation after pasteurization. In one of the explored sediment cores, endospores accounted for 3% of all stainable prokaryotic cells.
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Affiliation(s)
- Jörg Fichtel
- Institut für Chemie und Biologie des Meeres (ICBM), Carl von Ossietzky Universität Oldenburg, Carl-von-Ossietzky-Strasse 9-11, Oldenburg, Germany
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99
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Keijser BJF, Ter Beek A, Rauwerda H, Schuren F, Montijn R, van der Spek H, Brul S. Analysis of temporal gene expression during Bacillus subtilis spore germination and outgrowth. J Bacteriol 2007; 189:3624-34. [PMID: 17322312 PMCID: PMC1855883 DOI: 10.1128/jb.01736-06] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis forms dormant spores upon nutrient depletion. Under favorable environmental conditions, the spore breaks its dormancy and resumes growth in a process called spore germination and outgrowth. To elucidate the physiological processes that occur during the transition of the dormant spore to an actively growing vegetative cell, we studied this process in a time-dependent manner by a combination of microscopy, analysis of extracellular metabolites, and a genome-wide analysis of transcription. The results indicate the presence of abundant levels of late sporulation transcripts in dormant spores. In addition, the results suggest the existence of a complex and well-regulated spore outgrowth program, involving the temporal expression of at least 30% of the B. subtilis genome.
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Affiliation(s)
- Bart J F Keijser
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
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100
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Chen D, Huang SS, Li YQ. Real-Time Detection of Kinetic Germination and Heterogeneity of SingleBacillusSpores by Laser Tweezers Raman Spectroscopy. Anal Chem 2006; 78:6936-41. [PMID: 17007517 DOI: 10.1021/ac061090e] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Germination is the process by which a dormant spore returns to its vegetative state when exposed to suitable conditions. We report on the real-time detection of kinetic germination and heterogeneity of single Bacillus thuringiensis spores in an aqueous solution by monitoring the calcium dipicolinate (CaDPA) biomarker with laser tweezers Raman spectroscopy (LTRS). A single B. thuringiensis spore was optically trapped in a focused laser beam, and its Raman spectra were recorded sequentially in time after exposure to a nutrient-rich medium, so that the CaDPA amount inside the trapped spore was monitored during the dynamic germination process. The CaDPA content in an individual spore was observed to remain almost constant in the first period and then decrease very rapidly due to its release into the medium (within approximately 2 min). The time-to-germination (t(germ)), defined as the time required for the CaDPA band intensity to decrease to the midpoint from its initial value, was found to be stochastic for individual spores with a typical value of approximately 30 min under the experimental conditions. The distribution of the time-to-germination was measured from a time lapse measurement of a population of spores. The results demonstrated that LTRS can be used to noninvasively detect the kinetic germination process at the single-cell level and explore cellular heterogeneity.
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Affiliation(s)
- De Chen
- Department of Physics, East Carolina University, Greenville, North Carolina 27858-4353, USA
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