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de Oliveira JL, Gómez I, Sánchez J, Soberón M, Polanczyk RA, Bravo A. Performance insights into spray-dryer microencapsulated Bacillus thuringiensis cry pesticidal proteins with gum arabic and maltodextrin for effective pest control. Appl Microbiol Biotechnol 2024; 108:181. [PMID: 38285209 PMCID: PMC10824793 DOI: 10.1007/s00253-023-12990-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/28/2023] [Accepted: 12/26/2023] [Indexed: 01/30/2024]
Abstract
Bacillus thuringiensis (Bt) produces crystals composed mainly of Cry pesticidal proteins with insecticidal activity against pests but are highly susceptible to degradation by abiotic factors. In this sense, encapsulation techniques are designed to improve their performance and lifetime. However, the effects of polymeric matrix encapsulation such as gum arabic and maltodextrin by spray-dryer in the mechanisms of action of Bt kurstaki and Bt aizawai are unknown. We analyzed crystal solubilization, protoxin activation, and receptor binding after microencapsulation and compared them with commercial non-encapsulated products. Microencapsulation did not alter protein crystal solubilization, providing 130 kDa (Cry1 protoxin) and 70 kDa (Cry2 protoxin). Activation with trypsin, chymotrypsin, and larval midgut juice was analyzed, showing that this step is highly efficient, and the protoxins were cleaved producing similar ~ 55 to 65 kDa activated proteins for both formulations. Binding assays with brush border membrane vesicles of Manduca sexta and Spodoptera frugiperda larvae provided a similar binding for both formulations. LC50 bioassays showed no significant differences between treatments but the microencapsulated treatment provided higher mortality against S. frugiperda when subjected to UV radiation. Microencapsulation did not affect the mechanism of action of Cry pesticidal proteins while enhancing protection against UV radiation. These data will contribute to the development of more efficient Bt biopesticide formulations. KEY POINTS: • Microencapsulation did not affect the mechanisms of action of Cry pesticidal proteins produced by Bt. • Microencapsulation provided protection against UV radiation for Bt-based biopesticides. • The study's findings can contribute to the development of more efficient Bt biopesticide formulations.
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Affiliation(s)
- Jhones Luiz de Oliveira
- Department of Agricultural Production Sciences, Faculty of Agronomy and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, São Paulo, 14884-900, Brazil
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Isabel Gómez
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Jorge Sánchez
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Mario Soberón
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Ricardo Antonio Polanczyk
- Department of Agricultural Production Sciences, Faculty of Agronomy and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, São Paulo, 14884-900, Brazil.
| | - Alejandra Bravo
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico.
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Länger ZM, Baur M, Korša A, Eirich J, Lindeza AS, Zanchi C, Finkemeier I, Kurtz J. Differential proteome profiling of bacterial culture supernatants reveals candidates for the induction of oral immune priming in the red flour beetle. Biol Lett 2023; 19:20230322. [PMID: 37909056 PMCID: PMC10618857 DOI: 10.1098/rsbl.2023.0322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/12/2023] [Indexed: 11/02/2023] Open
Abstract
Most organisms are host to symbionts and pathogens, which led to the evolution of immune strategies to prevent harm. Whilst the immune defences of vertebrates are classically divided into innate and adaptive, insects lack specialized cells involved in adaptive immunity, but have been shown to exhibit immune priming: the enhanced survival upon infection after a first exposure to the same pathogen or pathogen-derived components. An important piece of the puzzle are the pathogen-associated molecules that induce these immune priming responses. Here, we make use of the model system consisting of the red flour beetle (Tribolium castaneum) and its bacterial pathogen Bacillus thuringiensis, to compare the proteomes of culture supernatants of two closely related B. thuringiensis strains that either induce priming via the oral route, or not. Among the proteins that might be immunostimulatory to T. castaneum, we identify the Cry3Aa toxin, an important plasmid-encoded virulence factor of B. thuringiensis. In further priming-infection assays we test the relevance of Cry-carrying plasmids for immune priming. Our findings provide valuable insights for future studies to perform experiments on the mechanisms and evolution of immune priming.
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Affiliation(s)
- Zoe Marie Länger
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
| | - Moritz Baur
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
| | - Ana Korša
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
| | - Jürgen Eirich
- Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 7, 48149 Münster, Germany
| | - Ana Sofia Lindeza
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
| | - Caroline Zanchi
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
| | - Iris Finkemeier
- Institute of Plant Biology and Biotechnology, University of Münster, Schlossplatz 7, 48149 Münster, Germany
| | - Joachim Kurtz
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany
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Li X, Zhang Y, Zhan Y, Tian H, Yan B, Cai J. Utilization of a strong promoter combined with the knockout of protease genes to improve the yield of Vip3Aa in Bacillus thuringiensis BMB171. PEST MANAGEMENT SCIENCE 2023; 79:1713-1720. [PMID: 36622044 DOI: 10.1002/ps.7343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 12/15/2022] [Accepted: 01/09/2023] [Indexed: 06/17/2023]
Abstract
BACKGROUND Vip3Aa is an insecticidal protein secreted by some Bacillus thuringiensis strains during vegetative growth. It has excellent insecticidal activity, its mechanism of action is different from that of Cry protein, and it can delay the development of pest resistance. To date, Vip3Aa has been widely used in genetically modified Bt crops. However, the secretion of Vip3Aa by industrial production strains is usually very low. Moreover, most of the Vip3Aa in the medium is degraded by proteases, limiting its application as a biopesticide. RESULTS We report a novel constitutive strong promoter from B. thuringiensis, Prsi , which directs the abundant expression of vip3Aa in B. thuringiensis BMB171. Furthermore, to reduce the degradation of Vip3Aa caused by proteases, we constructed B. thuringiensis mutants in which different protease genes were knocked out. We found that the degradation of Vip3Aa was greatly inhibited and its yield was significantly improved in a mutant that lacked all three protease genes. CONCLUSION Our results provide a new strategy to enhance the production of Vip3Aa in B. thuringiensis and have reference value for the research and development of novel bioinsecticides. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Xuelian Li
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yanli Zhang
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yunda Zhan
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Hongwei Tian
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Bing Yan
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Jun Cai
- Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, China
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Yeak KYC, Tempelaars M, Wu JL, Westerveld W, Reder A, Michalik S, Dhople VM, Völker U, Pané-Farré J, Wells-Bennik MHJ, Abee T. SigB modulates expression of novel SigB regulon members via Bc1009 in non-stressed and heat-stressed cells revealing its alternative roles in Bacillus cereus. BMC Microbiol 2023; 23:37. [PMID: 36759782 PMCID: PMC9912610 DOI: 10.1186/s12866-023-02783-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 01/24/2023] [Indexed: 02/11/2023] Open
Abstract
BACKGROUND The Bacillus cereus Sigma B (SigB) dependent general stress response is activated via the two-component RsbKY system, which involves a phosphate transfer from RsbK to RsbY. It has been hypothesized that the Hpr-like phosphocarrier protein (Bc1009) encoded by bc1009 in the SigB gene cluster may play a role in this transfer, thereby acting as a regulator of SigB activation. Alternatively, Bc1009 may be involved in the activation of a subset of SigB regulon members. RESULTS We first investigated the potential role of bc1009 to act as a SigB regulator but ruled out this possibility as the deletion of bc1009 did not affect the expression of sigB and other SigB gene cluster members. The SigB-dependent functions of Bc1009 were further examined in B. cereus ATCC14579 via comparative proteome profiling (backed up by transcriptomics) of wt, Δbc1009 and ΔsigB deletion mutants under heat stress at 42 °C. This revealed 284 proteins displaying SigB-dependent alterations in protein expression levels in heat-stressed cells, including a subgroup of 138 proteins for which alterations were also Bc1009-dependent. Next to proteins with roles in stress defense, newly identified SigB and Bc1009-dependent proteins have roles in cell motility, signal transduction, transcription, cell wall biogenesis, and amino acid transport and metabolism. Analysis of lethal stress survival at 50 °C after pre-adaptation at 42 °C showed intermediate survival efficacy of Δbc1009 cells, highest survival of wt, and lowest survival of ΔsigB cells, respectively. Additional comparative proteome analysis of non-stressed wt and mutant cells at 30 °C revealed 96 proteins with SigB and Bc1009-dependent differences in levels: 51 were also identified under heat stress, and 45 showed significant differential expression at 30 °C. This includes proteins with roles in carbohydrate/ion transport and metabolism. Overlapping functions at 30 °C and 42 °C included proteins involved in motility, and ΔsigB and Δbc1009 cells showed reduced motility compared to wt cells in swimming assays at both temperatures. CONCLUSION Our results extend the B. cereus SigB regulon to > 300 members, with a novel role of SigB-dependent Bc1009 in the activation of a subregulon of > 180 members, conceivably via interactions with other transcriptional regulatory networks.
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Affiliation(s)
- Kah Yen Claire Yeak
- grid.419921.60000 0004 0588 7915NIZO, Kernhemseweg 2, PO Box 20, 6718 ZB Ede, The Netherlands ,grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Marcel Tempelaars
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Jia Lun Wu
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Wouter Westerveld
- grid.4818.50000 0001 0791 5666Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV Wageningen, The Netherlands
| | - Alexander Reder
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Stephan Michalik
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Vishnu M. Dhople
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Uwe Völker
- grid.5603.0Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Jan Pané-Farré
- grid.10253.350000 0004 1936 9756Center for Synthetic Microbiology (SYNMIKRO) & Department of Chemistry, Philipps-University Marburg, Karl-Von-Frisch-Strasse 14, 35043 Marburg, Germany
| | | | - Tjakko Abee
- Food Microbiology, Wageningen University and Research, PO Box 8129, 6700 EV, Wageningen, The Netherlands.
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Dimitriu T, Souissi W, Morwool P, Darby A, Crickmore N, Raymond B. Selecting for infectivity across metapopulations can increase virulence in the social microbe
Bacillus thuringiensis. Evol Appl 2023; 16:705-720. [PMID: 36969139 PMCID: PMC10033855 DOI: 10.1111/eva.13529] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 12/27/2022] [Indexed: 01/18/2023] Open
Abstract
Passage experiments that sequentially infect hosts with parasites have long been used to manipulate virulence. However, for many invertebrate pathogens, passage has been applied naively without a full theoretical understanding of how best to select for increased virulence and this has led to very mixed results. Understanding the evolution of virulence is complex because selection on parasites occurs across multiple spatial scales with potentially different conflicts operating on parasites with different life histories. For example, in social microbes, strong selection on replication rate within hosts can lead to cheating and loss of virulence, because investment in public goods virulence reduces replication rate. In this study, we tested how varying mutation supply and selection for infectivity or pathogen yield (population size in hosts) affected the evolution of virulence against resistant hosts in the specialist insect pathogen Bacillus thuringiensis, aiming to optimize methods for strain improvement against a difficult to kill insect target. We show that selection for infectivity using competition between subpopulations in a metapopulation prevents social cheating, acts to retain key virulence plasmids, and facilitates increased virulence. Increased virulence was associated with reduced efficiency of sporulation, and possible loss of function in putative regulatory genes but not with altered expression of the primary virulence factors. Selection in a metapopulation provides a broadly applicable tool for improving the efficacy of biocontrol agents. Moreover, a structured host population can facilitate artificial selection on infectivity, while selection on life-history traits such as faster replication or larger population sizes can reduce virulence in social microbes.
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Affiliation(s)
- Tatiana Dimitriu
- Centre for Ecology and Conservation University of Exeter Penryn UK
| | - Wided Souissi
- School of Life Sciences University of Sussex Brighton UK
| | - Peter Morwool
- Centre for Ecology and Conservation University of Exeter Penryn UK
| | - Alistair Darby
- Centre for Genomic Research, Institute of Integrative Biology University of Liverpool Liverpool UK
| | - Neil Crickmore
- School of Life Sciences University of Sussex Brighton UK
| | - Ben Raymond
- Centre for Ecology and Conservation University of Exeter Penryn UK
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Manoharan S, Taylor-Joyce G, Brooker TA, Hernández Rodríguez CS, Hapeshi A, Baldwin V, Baillie L, Oyston PCF, Waterfield NR. From cereus to anthrax and back again: Assessment of the temperature-dependent phenotypic switching in the "cross-over" strain Bacillus cereus G9241. Front Microbiol 2023; 14:1113562. [PMID: 36937299 PMCID: PMC10017872 DOI: 10.3389/fmicb.2023.1113562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 02/07/2023] [Indexed: 03/06/2023] Open
Abstract
Bacillus cereus G9241 was isolated from a Louisiana welder suffering from an anthrax-like infection. The organism carries two transcriptional regulators that have previously been proposed to be incompatible with each other in Bacillus anthracis: the pleiotropic transcriptional regulator PlcR found in most members of the Bacillus cereus group but truncated in all B. anthracis isolates, and the anthrax toxin regulator AtxA found in all B. anthracis strains and a few B. cereus sensu stricto strains. Here we report cytotoxic and hemolytic activity of cell free B. cereus G9241 culture supernatants cultured at 25°C to various eukaryotic cells. However, this is not observed at the mammalian infection relevant temperature 37°C, behaving much like the supernatants generated by B. anthracis. Using a combination of genetic and proteomic approaches to understand this unique phenotype, we identified several PlcR-regulated toxins to be secreted highly at 25°C compared to 37°C. Furthermore, results suggest that differential expression of the protease involved in processing the PlcR quorum sensing activator molecule PapR appears to be the limiting step for the production of PlcR-regulated toxins at 37°C, giving rise to the temperature-dependent hemolytic and cytotoxic activity of the culture supernatants. This study provides an insight on how B. cereus G9241 is able to "switch" between B. cereus and B. anthracis-like phenotypes in a temperature-dependent manner, potentially accommodating the activities of both PlcR and AtxA.
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Affiliation(s)
- Shathviga Manoharan
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Grace Taylor-Joyce
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Thomas A. Brooker
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | - Alexia Hapeshi
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | - Les Baillie
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | | | - Nicholas R. Waterfield
- Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom
- *Correspondence: Nicholas R. Waterfield,
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Expression of the Bacillus thuringiensis vip3A Insecticidal Toxin Gene Is Activated at the Onset of Stationary Phase by VipR, an Autoregulated Transcription Factor. Microbiol Spectr 2022; 10:e0120522. [PMID: 35727045 PMCID: PMC9430311 DOI: 10.1128/spectrum.01205-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The Vegetative insecticidal protein Vip3A is produced by some Bacillus thuringiensis strains from the mid-log growth phase to sporulation. Although Vip3A is important for the entomopathogenicity of B. thuringiensis, the vip3A gene regulation is unknown. In the B. thuringiensis serovar kurstaki HD1 strain, vip3A is carried by the pBMB299 plasmid, which is absent in the closely related strain B. thuringiensis kurstaki HD73. Using a transcriptional fusion between the vip3A promoter and lacZ, we observed that the HD73 strain is unable to express vip3A. This result suggests that a specific regulator is required for vip3A expression. Assuming that the regulator gene is located on the same plasmid as vip3A, we transferred pBMB299 from the HD1 strain to the HD73 strain. We found that Vip3A was produced in the HD73 strain containing pBMB299, suggesting that the regulator gene is located on this plasmid. Using this heterologous host and promoter-lacZ transcription fusions, we showed that a specific regulator, VipR, is essential to activate vip3A expression at the onset of stationary phase. We demonstrated that vipR transcription is positively autoregulated and the determination of the vipR and vip3A promoters pinpointed a putative VipR target upstream from the Sigma A-specific −10 region of these two promoters. Surprisingly, this conserved sequence was also found upstream of cry1I and cry2 genes. Finally, we showed that vip3A and vipR expression is increased drastically in a Δspo0A mutant unable to initiate sporulation. In conclusion, we have characterized a novel regulator involved in the entomopathogenic potency of B. thuringiensis through a sporulation-independent pathway. IMPORTANCE The insecticidal properties of Bacillus thuringiensis are due mainly to Cry toxins which form a crystalline inclusion during sporulation. However, other proteins participate in the pathogenicity of the bacterium, notably, the Vip3A toxins that are produced from vegetative growth to sporulation. The VipR regulator that activates vip3A gene expression at the onset of stationary phase is positively autoregulated, and an analysis of the promoter region of the vip3A and vipR genes reveals the presence of a highly conserved DNA sequence. This possible VipR target sequence is also found upstream of the cry2A and cry1I genes, suggesting that Cry toxins can be produced before the bacteria enter sporulation. Such a result could allow us to better understand the role of Cry and Vip3A toxins during the B. thuringiensis infectious cycle in insects, in addition to the primary role of the Cry toxins in the toxemia caused by ingestion of crystals.
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Tandem Mass Tag-Based Quantitative Proteomics and Virulence Phenotype of Hemolymph-Treated Bacillus thuringiensis kurstaki Cells Reveal New Insights on Bacterial Pathogenesis in Insects. Microbiol Spectr 2021; 9:e0060421. [PMID: 34704785 PMCID: PMC8549738 DOI: 10.1128/spectrum.00604-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The spore-forming bacterium Bacillus thuringiensis (Bt) of the Bacillus cereus group uses toxin-opened breaches at the insect midgut epithelium to infest the hemolymph, where it can rapidly propagate despite antimicrobial host defenses and induce host death by acute septicemia. The response of Bt to host hemolymph and the latter's role in bacterial pathogenesis is an area that needs clarification. Here, we report a proteomic analysis of the Bt kurstaki strain HD73 (Btk) hemolymph stimulon showing significant changes in 60 (34 up- and 26 downregulated) differentially accumulated proteins (DAPs). Gene ontology (GO) enrichment analysis revealed that DAPs were mainly related to glutamate metabolism, transketolase activity, and ATP-dependent transmembrane transport. KEGG analysis disclosed that DAPs were highly enriched in the biosynthesis of bacterial secondary metabolites, ansamycins. Interestingly, about 30% of all DAPs were in silico predicted as putative virulence factors. Further characterization of hemolymph effects on Btk showed enhanced autoaggregation in liquid cultures and biofilm formation in microtiter polystyrene plates. Hemolymph-exposed Btk cells were less immunogenic in mice, suggesting epitope masking of selected surface proteins. Bioassays with intrahemocoelically infected Bombyx mori larvae showed that hemolymph preexposure significantly increased Btk toxicity and reproduction within the insect (spore count per cadaver) at low inoculum doses, possibly due to 'virulence priming'. Collectively, our findings suggest that the Btk hemolymph stimulon could be partially responsible for bacterial survival and propagation within the hemolymph of infected insects, contributing to its remarkable success as an entomopathogen. All mass spectrometry data are available via ProteomeXchange with identifier PXD021830. IMPORTANCE After ingestion by a susceptible insect and damaging its midgut epithelium, the bacterium Bacillus thuringiensis (Bt) reaches the insect blood (hemolymph), where it propagates despite the host's antimicrobial defenses and induces insect death by acute septicemia. Although the hemolymph stage of the Bt toxic pathway is determinant for the infested insects' fate, the response of Bt to hemolymph and the latter's role in bacterial pathogenesis has been poorly explored. In this study, we identified the bacterial proteins differentially expressed by Bt after hemolymph exposure. We found that about 30% of hemolymph-regulated Bt proteins were potential virulence factors, including manganese superoxide dismutase, a described inhibitor of hemocyte respiratory burst. Additionally, contact with hemolymph enhanced Bt virulence phenotypes, such as cell aggregation and biofilm formation, altered bacterial immunogenicity, and increased Bt toxicity to intrahemocoelically injected insects.
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Tetreau G, Andreeva EA, Banneville AS, De Zitter E, Colletier JP. Can (We Make) Bacillus thuringiensis Crystallize More Than Its Toxins? Toxins (Basel) 2021; 13:toxins13070441. [PMID: 34206749 PMCID: PMC8309801 DOI: 10.3390/toxins13070441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/22/2021] [Accepted: 06/24/2021] [Indexed: 11/16/2022] Open
Abstract
The development of finely tuned and reliable crystallization processes to obtain crystalline formulations of proteins has received growing interest from different scientific fields, including toxinology and structural biology, as well as from industry, notably for biotechnological and medical applications. As a natural crystal-making bacterium, Bacillus thuringiensis (Bt) has evolved through millions of years to produce hundreds of highly structurally diverse pesticidal proteins as micrometer-sized crystals. The long-term stability of Bt protein crystals in aqueous environments and their specific and controlled dissolution are characteristics that are particularly sought after. In this article, we explore whether the crystallization machinery of Bt can be hijacked as a means to produce (micro)crystalline formulations of proteins for three different applications: (i) to develop new bioinsecticidal formulations based on rationally improved crystalline toxins, (ii) to functionalize crystals with specific characteristics for biotechnological and medical applications, and (iii) to produce microcrystals of custom proteins for structural biology. By developing the needs of these different fields to figure out if and how Bt could meet each specific requirement, we discuss the already published and/or patented attempts and provide guidelines for future investigations in some underexplored yet promising domains.
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10
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How Does Bacillus thuringiensis Crystallize Such a Large Diversity of Toxins? Toxins (Basel) 2021; 13:toxins13070443. [PMID: 34206796 PMCID: PMC8309854 DOI: 10.3390/toxins13070443] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/22/2021] [Accepted: 06/24/2021] [Indexed: 12/31/2022] Open
Abstract
Bacillus thuringiensis (Bt) is a natural crystal-making bacterium. Bt diversified into many subspecies that have evolved to produce crystals of hundreds of pesticidal proteins with radically different structures. Their crystalline form ensures stability and controlled release of these major virulence factors. They are responsible for the toxicity and host specificity of Bt, explaining its worldwide use as a biological insecticide. Most research has been devoted to understanding the mechanisms of toxicity of these toxins while the features driving their crystallization have long remained elusive, essentially due to technical limitations. The evolution of methods in structural biology, pushing back the limits in size of amenable protein crystals now allows access to be gained to structural information hidden within natural crystals of such toxins. In this review, we present the main parameters that have been identified as key drivers of toxin crystallization in Bt, notably in the light of recent discoveries driven by structural biology studies. Then, we develop how the future evolution of structural biology will hopefully unveil new mechanisms of Bt toxin crystallization, opening the door to their hijacking with the aim of developing a versatile in vivo crystallization platform of high academic and industrial interest.
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11
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Larvicidal Activities against Aedes aegypti of Supernatant and Pellet Fractions from Cultured Bacillus spp. Isolated from Amazonian Microenvironments. Trop Med Infect Dis 2021; 6:tropicalmed6020104. [PMID: 34204476 PMCID: PMC8293452 DOI: 10.3390/tropicalmed6020104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 05/30/2021] [Accepted: 06/13/2021] [Indexed: 11/16/2022] Open
Abstract
The Aedes aegypti mosquito is the primary vector of Dengue, Chikungunya and Zika causing major problems for public health, which requires new strategies for its control, like the use of entomopathogenic microorganisms. In this study, bacteria from various Amazonian environments were isolated and tested for their pathogenicity to A. aegypti larvae. Following thermal shock to select sporulated Bacillus spp., 77 bacterial strains were isolated. Molecular identification per 16S RNA sequences revealed that the assembled strains contained several species of the genus Bacillus and one species each of Brevibacillus, Klebsiella, Serratia, Achromobacter and Brevundimonas. Among the isolated Bacillus sp. strains, 19 showed larvicidal activity against A. aegypti. Two strains of Brevibacillus halotolerans also displayed larvicidal activity. For the first time, larvicidal activity against A. aegypti was identified for a strain of Brevibacillus halotolerans. Supernatant and pellet fractions of bacterial cultures were tested separately for larvicidal activities. Eight strains contained isolated fractions resulting in at least 50% mortality when tested at a concentration of 5 mg/mL. Further studies are needed to characterize the active larvicidal metabolites produced by these microorganisms and define their mechanisms of action.
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
Abstract
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.
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13
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Wang Z, Gan C, Wang J, Bravo A, Soberón M, Yang Q, Zhang J. Nutrient conditions determine the localization of Bacillus thuringiensis Vip3Aa protein in the mother cell compartment. Microb Biotechnol 2020; 14:551-560. [PMID: 33252200 PMCID: PMC7936315 DOI: 10.1111/1751-7915.13719] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/11/2020] [Accepted: 11/12/2020] [Indexed: 12/31/2022] Open
Abstract
Vip3Aa was first identified as a protein secreted during the vegetative growth phase of Bacillus thuringiensis (Bt) bacteria and which shows high insecticidal toxicity against lepidopteran insect pests (Estruch et al., 1996). Bt strains formulated as bio‐insecticides only had low amounts of Vip3Aa secreted to the medium. Here, we report that Vip3Aa proteins produced by three different Bt strains, including an industrial strain, were indeed not secreted to the culture solution when grown in sporulation medium, but were retained in the mother cell compartment. In order to further investigate the Vip3Aa secretion and location, we grew the strains in rich medium. We found that in rich medium, a fraction of Vip3Aa was secreted, suggesting that Vip3Aa secretion is nutrient‐dependent. Regardless of the growth conditions, we found that Vip3Aa retained in cell pellets exhibited high toxicity against Spodoptera frugiperda larvae. Hence, we speculate that the accumulation of Vip3Aa protein in the mother cell compartment under sporulation conditions could still be used as an efficient strategy for industrial production in commercial Bt strains.
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Affiliation(s)
- Zeyu Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Chunxia Gan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.,School of Plant Protection, Anhui Agricultural University, Hefei, 230036, China
| | - Jian Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62250, Mexico
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62250, Mexico
| | - Qing Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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Jessberger N, Dietrich R, Granum PE, Märtlbauer E. The Bacillus cereus Food Infection as Multifactorial Process. Toxins (Basel) 2020; 12:E701. [PMID: 33167492 PMCID: PMC7694497 DOI: 10.3390/toxins12110701] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 10/30/2020] [Accepted: 11/02/2020] [Indexed: 02/06/2023] Open
Abstract
The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.
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Affiliation(s)
- Nadja Jessberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
| | - Richard Dietrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
| | - Per Einar Granum
- Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, P.O. Box 5003 NMBU, 1432 Ås, Norway;
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764 Oberschleißheim, Germany; (R.D.); (E.M.)
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15
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Rap-Phr Systems from Plasmids pAW63 and pHT8-1 Act Together To Regulate Sporulation in the Bacillus thuringiensis Serovar kurstaki HD73 Strain. Appl Environ Microbiol 2020; 86:AEM.01238-20. [PMID: 32680861 DOI: 10.1128/aem.01238-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 07/13/2020] [Indexed: 02/07/2023] Open
Abstract
Bacillus thuringiensis is a Gram-positive spore-forming bacterium pathogenic to various insect species. This property is due to the Cry toxins encoded by plasmid genes and mostly produced during sporulation. B. thuringiensis contains a remarkable number of extrachromosomal DNA molecules and a great number of plasmid rap-phr genes. Rap-Phr quorum-sensing systems regulate different bacterial processes, notably the commitment to sporulation in Bacillus species. Rap proteins are quorum sensors acting as phosphatases on Spo0F, an intermediate of the sporulation phosphorelay, and are inhibited by Phr peptides that function as signaling molecules. In this study, we characterize the Rap63-Phr63 system encoded by the pAW63 plasmid from the B. thuringiensis serovar kurstaki HD73 strain. Rap63 has moderate activity on sporulation and is inhibited by the Phr63 peptide. The rap63-phr63 genes are cotranscribed, and the phr63 gene is also transcribed from a σH-specific promoter. We show that Rap63-Phr63 regulates sporulation together with the Rap8-Phr8 system harbored by plasmid pHT8_1 of the HD73 strain. Interestingly, the deletion of both phr63 and phr8 genes in the same strain has a greater negative effect on sporulation than the sum of the loss of each phr gene. Despite the similarities in the Phr8 and Phr63 sequences, there is no cross talk between the two systems. Our results suggest a synergism of these two Rap-Phr systems in the regulation of the sporulation of B. thuringiensis at the end of the infectious cycle in insects, thus pointing out the roles of the plasmids in the fitness of the bacterium.IMPORTANCE The life cycle of Bacillus thuringiensis in insect larvae is regulated by quorum-sensing systems of the RNPP family. After the toxemia caused by Cry insecticidal toxins, the sequential activation of these systems allows the bacterium to trigger first a state of virulence (regulated by PlcR-PapR) and then a necrotrophic lifestyle (regulated by NprR-NprX); ultimately, sporulation is controlled by the Rap-Phr systems. Our study describes a new rap-phr operon carried by a B. thuringiensis plasmid and shows that the Rap protein has a moderate effect on sporulation. However, this system, in combination with another plasmidic rap-phr operon, provides effective control of sporulation when the bacteria develop in the cadavers of infected insect larvae. Overall, this study highlights the important adaptive role of the plasmid Rap-Phr systems in the developmental fate of B. thuringiensis and its survival within its ecological niche.
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Xu L, Han G, Fan X, Lv J, Zhang X, Peng Q, Zhang J, Xu J, Song F. Characteristics of the sigK Deletion Mutant from Bacillus thuringiensis var. israelensis Strain Bt-59. Curr Microbiol 2020; 77:3422-3429. [PMID: 32770390 DOI: 10.1007/s00284-020-02150-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 07/28/2020] [Indexed: 11/26/2022]
Abstract
All major insecticidal genes of Bacillus thuringiensis var. israelensis (Bti) are controlled by the sporulation-specific sigma factor Sigma E (sigE), while sigE is negatively regulated by Sigma K (sigK). Therefore, knocking out sigK plays an important role in regulating the expression of insecticidal genes in Bti. A sigK deletion mutant of B. thuringiensis var. israelensis strain Bt-59, Bt59(ΔsigK), was constructed by homologous recombination and characterized. The sigK deletion resulted in no mature spores and delayed mother cell lysis from T25 to T60, while the genetically complemented strain, Bt59(HFsigK), had mother cell lysis at T25. Compared to Bt-59, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the expression of Cry4Aa2/4Ba1 and Cyt1Aa1 proteins in Bt59(ΔsigK) increased approximately 1.67 and 1.21 times, respectively. However, there was no significant change in Cry11Aa1 protein expression between the two strains. Bioassay results showed that the sigK deletion mutation slightly reduced the insecticidal activity of Bt-59 against Culex pipiens pallens and did not obviously affect activity against Aedes albopictus.
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Affiliation(s)
- Linghuan Xu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
- Department of Applied Microbiology, Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou, 225007, China
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225002, China
| | - Guangjie Han
- Department of Applied Microbiology, Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou, 225007, China
| | - Xintong Fan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Jing Lv
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Xin Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Jian Xu
- Department of Applied Microbiology, Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou, 225007, China.
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225002, China.
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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Abstract
The Bacillus cereus group includes several Bacillus species with closely related phylogeny. The most well-studied members of the group, B. anthracis, B. cereus, and B. thuringiensis, are known for their pathogenic potential. Here, we present the historical rationale for speciation and discuss shared and unique features of these bacteria. Aspects of cell morphology and physiology, and genome sequence similarity and gene synteny support close evolutionary relationships for these three species. For many strains, distinct differences in virulence factor synthesis provide facile means for species assignment. B. anthracis is the causative agent of anthrax. Some B. cereus strains are commonly recognized as food poisoning agents, but strains can also cause localized wound and eye infections as well as systemic disease. Certain B. thuringiensis strains are entomopathogens and have been commercialized for use as biopesticides, while some strains have been reported to cause infection in immunocompromised individuals. In this article we compare and contrast B. anthracis, B. cereus, and B. thuringiensis, including ecology, cell structure and development, virulence attributes, gene regulation and genetic exchange systems, and experimental models of disease.
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18
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Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis. Parasit Vectors 2018; 11:121. [PMID: 29499735 PMCID: PMC5834902 DOI: 10.1186/s13071-018-2741-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 02/23/2018] [Indexed: 12/11/2022] Open
Abstract
Background Insect microbiota is a dynamic microbial community that can actively participate in defense against pathogens. Bacillus thuringiensis (Bt) is a natural entomopathogen widely used as a bioinsecticide for pest control. Although Bt’s mode of action has been extensively studied, whether the presence of microbiota is mandatory for Bt to effectively kill the insect is still under debate. An association between a higher tolerance and a modified microbiota was already evidenced but a critical point remained to be solved: is the modified microbiota a cause or a consequence of a higher tolerance to Bt? Methods In this study we focused on the mosquito species Aedes aegypti, as no work has been performed on Diptera on this topic to date, and on B. thuringiensis israelensis (Bti), which is used worldwide for mosquito control. To avoid using antibiotics to cure bacterial microbiota, mosquito larvae were exposed to an hourly increasing dose of Bti during 25 hours to separate the most susceptible larvae dying quickly from more tolerant individuals, with longer survival. Results Denaturing gradient gel electrophoresis (DGGE) fingerprinting revealed that mosquito larval bacterial microbiota was strongly affected by Bti infection after only a few hours of exposure. Bacterial microbiota from the most tolerant larvae showed the lowest diversity but the highest inter-individual differences. The proportion of Bti in the host tissue was reduced in the most tolerant larvae as compared to the most susceptible ones, suggesting an active control of Bti infection by the host. Conclusions Here we show that a modified microbiota is associated with a higher tolerance of mosquitoes to Bti, but that it is rather a consequence of Bti infection than the cause of the higher tolerance. This study paves the way to future investigations aiming at unraveling the role of host immunity, inter-species bacterial competition and kinetics of host colonization by Bti that could be at the basis of the phenotype observed in this study. Electronic supplementary material The online version of this article (10.1186/s13071-018-2741-8) contains supplementary material, which is available to authorized users.
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19
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Rampersaud R, Lewis EL, LaRocca TJ, Ratner AJ. Environmental pH modulates inerolysin activity via post-binding blockade. Sci Rep 2018; 8:1542. [PMID: 29367601 PMCID: PMC5784117 DOI: 10.1038/s41598-018-19994-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 01/11/2018] [Indexed: 11/29/2022] Open
Abstract
The cholesterol dependent cytolysins (CDCs) are a family of pore-forming toxins produced by a wide range of bacteria. Some CDCs are important virulence factors for their cognate organisms, but their activity must be tightly regulated to ensure they operate at appropriate times and within the appropriate subcellular compartments. pH-dependent activity has been described for several CDCs, but the mechanism of such regulation has been studied in depth only for listeriolysin O (LLO), which senses environmental pH through a triad of acidic residues that mediate protein unfolding. Here we present data supporting a distinct mechanism for pH-dependence for inerolysin (INY), the CDC produced by Lactobacillus iners. Inerolysin (INY) has an acidic pH optimum with loss of activity at neutral pH. INY pH-dependence is characterized by reversible loss of pore formation with preservation of membrane binding. Fluorescent membrane probe assays indicated that INY insertion into host cell membranes, but not oligomerization, was defective at neutral pH. These data support the existence of a newly appreciated form of CDC pH-dependence functioning at a late stage of pore formation.
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Affiliation(s)
- Ryan Rampersaud
- College of Physicians & Surgeons, Columbia University, New York, NY, USA.,Department of Psychiatry, University of California, San Francisco, CA, USA
| | - Emma L Lewis
- College of Physicians & Surgeons, Columbia University, New York, NY, USA.,Perelman School of Medicine, University of Pennsylvania, Pennsylvania, PA, USA
| | - Timothy J LaRocca
- College of Physicians & Surgeons, Columbia University, New York, NY, USA.,Department of Basic & Clinical Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, USA
| | - Adam J Ratner
- College of Physicians & Surgeons, Columbia University, New York, NY, USA. .,Department of Pediatrics, New York University School of Medicine, New York, NY, USA. .,Department of Microbiology, New York University School of Medicine, New York, NY, USA.
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20
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Perchat S, Talagas A, Poncet S, Lazar N, Li de la Sierra-Gallay I, Gohar M, Lereclus D, Nessler S. How Quorum Sensing Connects Sporulation to Necrotrophism in Bacillus thuringiensis. PLoS Pathog 2016; 12:e1005779. [PMID: 27483473 PMCID: PMC4970707 DOI: 10.1371/journal.ppat.1005779] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 06/29/2016] [Indexed: 11/28/2022] Open
Abstract
Bacteria use quorum sensing to coordinate adaptation properties, cell fate or commitment to sporulation. The infectious cycle of Bacillus thuringiensis in the insect host is a powerful model to investigate the role of quorum sensing in natural conditions. It is tuned by communication systems regulators belonging to the RNPP family and directly regulated by re-internalized signaling peptides. One such RNPP regulator, NprR, acts in the presence of its cognate signaling peptide NprX as a transcription factor, regulating a set of genes involved in the survival of these bacteria in the insect cadaver. Here, we demonstrate that, in the absence of NprX and independently of its transcriptional activator function, NprR negatively controls sporulation. NprR inhibits expression of Spo0A-regulated genes by preventing the KinA-dependent phosphorylation of the phosphotransferase Spo0F, thus delaying initiation of the sporulation process. This NprR function displays striking similarities with the Rap proteins, which also belong to the RNPP family, but are devoid of DNA-binding domain and indirectly control gene expression via protein-protein interactions in Bacilli. Conservation of the Rap residues directly interacting with Spo0F further suggests a common inhibition of the sporulation phosphorelay. The crystal structure of apo NprR confirms that NprR displays a highly flexible Rap-like structure. We propose a molecular regulatory mechanism in which key residues of the bifunctional regulator NprR are directly and alternatively involved in its two functions. NprX binding switches NprR from a dimeric inhibitor of sporulation to a tetrameric transcriptional activator involved in the necrotrophic lifestyle of B. thuringiensis. NprR thus tightly coordinates sporulation and necrotrophism, ensuring survival and dissemination of the bacteria during host infection. Bacillus thuringiensis is an entomopathogenic bacterium used worldwide as biopesticide. Its life cycle in insect larvae, which includes virulence, necrotrophism and sporulation, is regulated by cell-cell communication systems involving sensor proteins directly regulated by re-internalized peptide pheromones. After toxaemia caused by pore-forming Cry toxins, the PlcR sensor activates the production of virulence factors leading to insect death. B. thuringiensis then shifts to a necrotrophic lifestyle preceding sporulation. Previously, we showed that this process is regulated by the sensor NprR, which, in the presence of its cognate signaling peptide NprX, adopts a tetrameric conformation allowing its binding to specific DNA sequences and transcription of genes involved in survival of the bacteria in insect cadavers. Here, we demonstrate that, in the absence of NprX, NprR is a dimer, which negatively controls sporulation, independently of its transcription factor activity. We show that NprR prevents the phosphorylation of the phosphoprotein Spo0F and inhibits the phosphorylation cascade regulating sporulation. This demonstrates that NprX binding switches the bifunctional sensor NprR from a dimeric sporulation inhibitor to a tetrameric transcription factor. By establishing a close coordination between cell density, necrotrophism and sporulation, this communication system benefits a pathogenic bacterium feeding on death matter like B. thuringiensis. NprR is found in all strains of the B. cereus group, including B. anthracis and B. cereus involved in food poisoning. Our results may provide new insights for controlling the development and the survival of these undesirable bacteria.
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Affiliation(s)
- Stéphane Perchat
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Antoine Talagas
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Sandrine Poncet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Noureddine Lazar
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Inès Li de la Sierra-Gallay
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Michel Gohar
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Didier Lereclus
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
- * E-mail: (DL); (SN)
| | - Sylvie Nessler
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
- * E-mail: (DL); (SN)
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Verplaetse E, Slamti L, Gohar M, Lereclus D. Two distinct pathways lead Bacillus thuringiensis to commit to sporulation in biofilm. Res Microbiol 2016; 168:388-393. [PMID: 27106256 DOI: 10.1016/j.resmic.2016.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 03/21/2016] [Accepted: 03/30/2016] [Indexed: 10/21/2022]
Abstract
The spore-forming bacterium Bacillus thuringiensis is an efficient biofilm producer, responsible for persistent contamination of industrial food processing systems. B. thuringiensis biofilms are highly heterogeneous bacterial structures in which three distinct cell types controlled by quorum sensing regulators were identified: PlcR-controlled virulent cells, NprR-dependent necrotrophic cells and cells committed to sporulation, a differentiation process controlled by Rap phosphatases and Spo0A-P. Interestingly, a cell lineage study revealed that, in LB medium or in insect larvae, only necrotrophic cells became spores. Here we analyzed cellular differentiation undertaken by cells growing in biofilm in a medium optimized for sporulation. No virulent cells were identified; surprisingly, two distinct routes could lead to differentiation as a spore in this growth condition: the NprR-dependent route, followed by the majority of cells, and the newly identified NprR-independent route, which is followed by 20% of sporulating cells.
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Affiliation(s)
- Emilie Verplaetse
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | - Leyla Slamti
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | - Michel Gohar
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | - Didier Lereclus
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
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22
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Slamti L, Lemy C, Henry C, Guillot A, Huillet E, Lereclus D. CodY Regulates the Activity of the Virulence Quorum Sensor PlcR by Controlling the Import of the Signaling Peptide PapR in Bacillus thuringiensis. Front Microbiol 2016; 6:1501. [PMID: 26779156 PMCID: PMC4701985 DOI: 10.3389/fmicb.2015.01501] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 12/14/2015] [Indexed: 01/17/2023] Open
Abstract
In Gram-positive bacteria, cell–cell communication mainly relies on cytoplasmic sensors of the RNPP family. Activity of these regulators depends on their binding to secreted signaling peptides that are imported into the cell. These quorum sensing regulators control important biological functions in bacteria of the Bacillus cereus group, such as virulence and necrotrophism. The RNPP quorum sensor PlcR, in complex with its cognate signaling peptide PapR, is the main regulator of virulence in B. cereus and Bacillus thuringiensis (Bt). Recent reports have shown that the global stationary phase regulator CodY, involved in adaptation to nutritional limitation, is required for the expression of virulence genes belonging to the PlcR regulon. However, the mechanism underlying this regulation was not described. Using genetics and proteomics approaches, we showed that CodY regulates the expression of the virulence genes through the import of PapR. We report that CodY positively controls the production of the proteins that compose the oligopeptide permease OppABCDF, and of several other Opp-like proteins. It was previously shown that the pore components of this oligopeptide permease, OppBCDF, were required for the import of PapR. However, the role of OppA, the substrate-binding protein (SBP), was not investigated. Here, we demonstrated that OppA is not the only SBP involved in the recognition of PapR, and that several other OppA-like proteins can allow the import of this peptide. Altogether, these data complete our model of quorum sensing during the lifecycle of Bt and indicate that RNPPs integrate environmental conditions, as well as cell density, to coordinate the behavior of the bacteria throughout growth.
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Affiliation(s)
- Leyla Slamti
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
| | - Christelle Lemy
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
| | - Céline Henry
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
| | - Alain Guillot
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
| | - Eugénie Huillet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
| | - Didier Lereclus
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay Jouy-en-Josas, France
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23
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Rice AJ, Woo JK, Khan A, Szypulinski MZ, Johnson ME, Lee H, Lee H. Over-expression, purification, and confirmation of Bacillus anthracis transcriptional regulator NprR. Protein Expr Purif 2015; 125:83-9. [PMID: 26344899 DOI: 10.1016/j.pep.2015.08.030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 08/28/2015] [Accepted: 08/31/2015] [Indexed: 12/21/2022]
Abstract
Quorum sensing (QS) has been recognized as an important biological phenomenon in which bacterial cells communicate and coordinate their gene expression and cellular processes with respect to population density. Bacillus anthracis is the etiological agent of fatal pulmonary anthrax infections, and the NprR/NprX QS system may be involved in its pathogenesis. NprR, renamed as aqsR for anthrax quorum sensing Regulator, is a transcriptional regulator that may control the expression of genes required for proliferation and survival. Currently, there is no protocol reported to over-express and purify B. anthracis AqsR. In this study, we describe cloning, purification, and confirmation of functional full-length B. anthracis AqsR protein. The AqsR gene was cloned into the pQE-30 vector with an HRV 3C protease recognition site between AqsR and the N-terminal His6-tag in order to yield near native AqsR after the His-tag cleavage, leaving only two additional amino acid residues at the N-terminus.
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Affiliation(s)
- Amy J Rice
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA; Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA
| | - Jerry K Woo
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA
| | - Attiya Khan
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA
| | - Michael Z Szypulinski
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA
| | - Michael E Johnson
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA; Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA
| | - Hyunwoo Lee
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA; Department of Biopharmaceutical Sciences, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA.
| | - Hyun Lee
- Center for Pharmaceutical Biotechnology, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA; Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 900 S. Ashland, IL 60607, USA.
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Monnet V, Gardan R. Quorum-sensing regulators in Gram-positive bacteria: 'cherchez le peptide'. Mol Microbiol 2015; 97:181-4. [PMID: 25988215 DOI: 10.1111/mmi.13060] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2015] [Indexed: 12/29/2022]
Abstract
Gram-positive bacteria can regulate gene expression at the population level via a mechanism known as quorum sensing. Oligopeptides serve as the signaling molecules; they are secreted and then are either detected at the bacterial surface by two-component systems or reinternalized via an oligopeptide transport system. In the latter case, imported peptides interact with cognate regulators (phosphatases or transcriptional regulators) that modulate the expression of target genes. These regulators help control crucial functions such as virulence, persistence, conjugation and competence and have been reported in bacilli, enterococci and streptococci. They form the rapidly growing RRNPP group. In this issue of Molecular Microbiology, Hoover et al. (2015) highlight the group's importance: they have identified a new family of regulators, Tprs (Transcription factor regulated by a Phr peptide), which work with internalized Phr-like peptides. The mechanisms underlying the expression of the genes that encode these internalized peptides are poorly documented. However, Hoover et al. (2015) have provided a new insight: an environmental molecule, glucose, can inhibit expression of the Phr-like peptide gene via catabolic repression. This previously undescribed regulatory pathway, controlling the production of a bacteriocin, might influence Streptococcus pneumonia's fitness in the nasopharynx, where galactose is present.
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Affiliation(s)
- V Monnet
- UMR1319 MICALIS, INRA, Jouy en Josas, France.,UMR MICALIS, AgroParistech, Jouy en Josas, France
| | - R Gardan
- UMR1319 MICALIS, INRA, Jouy en Josas, France.,UMR MICALIS, AgroParistech, Jouy en Josas, France
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Jeßberger N, Krey VM, Rademacher C, Böhm ME, Mohr AK, Ehling-Schulz M, Scherer S, Märtlbauer E. From genome to toxicity: a combinatory approach highlights the complexity of enterotoxin production in Bacillus cereus. Front Microbiol 2015; 6:560. [PMID: 26113843 PMCID: PMC4462024 DOI: 10.3389/fmicb.2015.00560] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 05/21/2015] [Indexed: 01/30/2023] Open
Abstract
In recent years Bacillus cereus has gained increasing importance as a food poisoning pathogen. It is the eponymous member of the B. cereus sensu lato group that consists of eight closely related species showing impressive diversity of their pathogenicity. The high variability of cytotoxicity and the complex regulatory network of enterotoxin expression have complicated efforts to predict the toxic potential of new B. cereus isolates. In this study, comprehensive analyses of enterotoxin gene sequences, transcription, toxin secretion and cytotoxicity were performed. For the first time, these parameters were compared in a whole set of B. cereus strains representing isolates of different origin (food or food poisoning outbreaks) and of different toxic potential (enteropathogenic and apathogenic) to elucidate potential starting points of strain-specific differential toxicity. While toxin gene sequences were highly conserved and did not allow for differentiation between high and low toxicity strains, comparison of nheB and hblD enterotoxin gene transcription and Nhe and Hbl protein titers revealed not only strain-specific differences but also incongruence between toxin gene transcripts and toxin protein levels. With one exception all strains showed comparable capability of protein secretion and so far, no secretion patterns specific for high and low toxicity strains were identified. These results indicate that enterotoxin expression is more complex than expected, possibly involving the orchestrated interplay of different transcriptional regulator proteins, as well as posttranscriptional and posttranslational regulatory mechanisms plus additional influences of environmental conditions.
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Affiliation(s)
- Nadja Jeßberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
| | - Viktoria M Krey
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Corinna Rademacher
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine Vienna Vienna, Austria
| | - Maria-Elisabeth Böhm
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Ann-Katrin Mohr
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Department of Pathobiology, Institute of Microbiology, University of Veterinary Medicine Vienna Vienna, Austria
| | - Siegfried Scherer
- Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung, Wissenschaftszentrum Weihenstephan, Technische Universität München Freising, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München Oberschleißheim, Germany
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Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection. mBio 2015; 6:e00138-15. [PMID: 25922389 PMCID: PMC4436061 DOI: 10.1128/mbio.00138-15] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Bacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment. Bt is an entomopathogen found ubiquitously in the environment and is a widely used biopesticide. Studies performed at the population level suggest that the infection process of Bt includes three successive steps (virulence, necrotrophism, and sporulation) controlled by different regulators. This study aimed to determine how these phenotypes are activated at the cellular level and if they are switched on in all cells. We used an insect model of infection and biofilms to decipher the cellular differentiation of this bacterium under naturalistic conditions. Our study reveals the connection and lineage existing among virulent, necrotrophic, and sporulating cells. It also shows that the complex conditions encountered in biofilms and during infection generate great heterogeneity inside the population, which might reflect a bet-hedging strategy to ameliorate survival. These data generate new insights into the role of regulatory networks in the adaptation of a pathogen to its host.
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Abstract
Plasmid-encoded virulence factors are important in the pathogenesis of diseases caused by spore-forming bacteria. Unlike many other bacteria, the most common virulence factors encoded by plasmids in Clostridium and Bacillus species are protein toxins. Clostridium perfringens causes several histotoxic and enterotoxin diseases in both humans and animals and produces a broad range of toxins, including many pore-forming toxins such as C. perfringens enterotoxin, epsilon-toxin, beta-toxin, and NetB. Genetic studies have led to the determination of the role of these toxins in disease pathogenesis. The genes for these toxins are generally carried on large conjugative plasmids that have common core replication, maintenance, and conjugation regions. There is considerable functional information available about the unique tcp conjugation locus carried by these plasmids, but less is known about plasmid maintenance. The latter is intriguing because many C. perfringens isolates stably maintain up to four different, but closely related, toxin plasmids. Toxin genes may also be plasmid-encoded in the neurotoxic clostridia. The tetanus toxin gene is located on a plasmid in Clostridium tetani, but the botulinum toxin genes may be chromosomal, plasmid-determined, or located on bacteriophages in Clostridium botulinum. In Bacillus anthracis it is well established that virulence is plasmid determined, with anthrax toxin genes located on pXO1 and capsule genes on a separate plasmid, pXO2. Orthologs of these plasmids are also found in other members of the Bacillus cereus group such as B. cereus and Bacillus thuringiensis. In B. thuringiensis these plasmids may carry genes encoding one or more insecticidal toxins.
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Maciel H, Zingaretti S, Maciel G. Comparative analysis of the amino acid sequence of the Cry protein of Bacillus thuringiensis codify the toxic protein to insects of the orders Lepidoptera, Diptera and Lepidoptera/ Diptera. BMC Proc 2014. [PMCID: PMC4210762 DOI: 10.1186/1753-6561-8-s4-p120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
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Bi Y, Zhang Y, Shu C, Crickmore N, Wang Q, Du L, Song F, Zhang J. Genomic sequencing identifies novel Bacillus thuringiensis Vip1/Vip2 binary and Cry8 toxins that have high toxicity to Scarabaeoidea larvae. Appl Microbiol Biotechnol 2014; 99:753-60. [PMID: 25081556 DOI: 10.1007/s00253-014-5966-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 11/26/2022]
Abstract
The Bacillus thuringiensis strain HBF-18 (CGMCC 2070), which has previously been shown to encode the cry8Ga toxin gene, is active against both Holotrichia oblita and Holotrichia parallela. Recombinant Cry8Ga however is only weakly toxic to these insect pests suggesting the involvement of additional toxins in the native strain. We report that through the use of Illumina sequencing three additional, and novel, genes, namely vip1Ad1, vip2Ag1, and cry8-like, were identified in this strain. Although no protein corresponding to these genes could be identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the HBF-18 proteome, reverse transcription (RT)-PCR indicated that all three genes were transcribed in the native strain. The two vip genes were cloned and expressed and, as with other Vip1/2 toxins, appeared to function as a binary toxin and showed strong activity against H. oblita, H. parallela and Anomala corpulenta. This is the first report to demonstrate that the Vip1/Vip2 binary toxin is active against these Scarabaeoidea larvae. The cry8-like gene appeared to be a C-terminally truncated form of a typical cry8 gene and was not expressed in our usual recombinant Bt expression system. When however the missing C-terminal region was replaced with the corresponding sequence from cry8Ea, the resulting hybrid expressed well and the toxin was active against the three test insects.
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Affiliation(s)
- Yang Bi
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
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Slamti L, Perchat S, Huillet E, Lereclus D. Quorum sensing in Bacillus thuringiensis is required for completion of a full infectious cycle in the insect. Toxins (Basel) 2014; 6:2239-55. [PMID: 25089349 PMCID: PMC4147580 DOI: 10.3390/toxins6082239] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 07/10/2014] [Accepted: 07/15/2014] [Indexed: 11/16/2022] Open
Abstract
Bacterial cell-cell communication or quorum sensing (QS) is a biological process commonly described as allowing bacteria belonging to a same pherotype to coordinate gene expression to cell density. In Gram-positive bacteria, cell-cell communication mainly relies on cytoplasmic sensors regulated by secreted and re-imported signaling peptides. The Bacillus quorum sensors Rap, NprR, and PlcR were previously identified as the first members of a new protein family called RNPP. Except for the Rap proteins, these RNPP regulators are transcription factors that directly regulate gene expression. QS regulates important biological functions in bacteria of the Bacillus cereus group. PlcR was first characterized as the main regulator of virulence in B. thuringiensis and B. cereus. More recently, the PlcR-like regulator PlcRa was characterized for its role in cysteine metabolism and in resistance to oxidative stress. The NprR regulator controls the necrotrophic properties allowing the bacteria to survive in the infected host. The Rap proteins negatively affect sporulation via their interaction with a phosphorelay protein involved in the activation of Spo0A, the master regulator of this differentiation pathway. In this review we aim at providing a complete picture of the QS systems that are sequentially activated during the lifecycle of B. cereus and B. thuringiensis in an insect model of infection.
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Affiliation(s)
- Leyla Slamti
- INRA, Unité MICALIS UMR-1319, La Minière, 78280 Guyancourt, France.
| | - Stéphane Perchat
- INRA, Unité MICALIS UMR-1319, La Minière, 78280 Guyancourt, France.
| | - Eugénie Huillet
- INRA, Unité MICALIS UMR-1319, La Minière, 78280 Guyancourt, France.
| | - Didier Lereclus
- INRA, Unité MICALIS UMR-1319, La Minière, 78280 Guyancourt, France.
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Lozano Goné AM, Dinorín Téllez Girón J, Jiménez Montejo FE, Hidalgo-Lara ME, López y López VE. Behavior of Transition State Regulator AbrB in Batch Cultures of Bacillus thuringiensis. Curr Microbiol 2014; 69:725-32. [DOI: 10.1007/s00284-014-0650-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/20/2014] [Indexed: 10/25/2022]
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Porcar M, Déleclusse A, Ibarra JE, Juárez-Pérez V. Early transcription of Bacillus thuringiensis cry genes in strains active on Lepidopteran species and the role of gene content on their expression. Antonie van Leeuwenhoek 2014; 105:1007-15. [PMID: 24691997 DOI: 10.1007/s10482-014-0160-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 03/22/2014] [Indexed: 11/28/2022]
Abstract
Six strains of Bacillus thuringiensis previously selected as highly toxic against Manduca sexta and Plutella xylostella were analyzed by PCR screening in order to identify the cry genes active on Lepidoptera. According to their gene content and insecticidal potency, these strains were cultured and aliquots taken at different pre- and post-sporulation times. Total RNA was extracted and used as template in RT-PCR analyses directed to identify mRNAs of the previously identified cry genes. Results showed transcription of genes cry1A, cry1E, cry1I, and cry2 even before the onset of sporulation. However, this early transcription did not lead to an appreciable parasporal protein synthesis until t5-t9, as deduced from SDS-PAGE profiles. As for cry1I gene, the corresponding protein was not detected, as expected, but cry1I mRNAs were present at least until t5. Interestingly, strains expressing four cry genes from the end of the log phase onwards exhibited kinetics characterized by a very long transition phase, whereas the strain expressing only one cry gene showed a very short transition phase. Strains expressing three genes showed an intermediate profile. These results indicate that the transcription of B. thuringiensis cry1 and cry2 genes in natural strains can start several hours before massive crystal synthesis occurs and that this translation is probably competing with transcriptional regulators required for the sporulation onset.
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Affiliation(s)
- Manuel Porcar
- Institut Pasteur, 25 rue du Dr. Roux, 75724, Paris Cedex 15, France
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Ghosh N, Goel AK, Alam SI. Exoproteome analysis of a novel strain of Bacillus cereus implicated in disease resembling cutaneous anthrax. INFECTION GENETICS AND EVOLUTION 2014; 22:1-11. [PMID: 24412723 DOI: 10.1016/j.meegid.2013.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 11/06/2013] [Accepted: 12/11/2013] [Indexed: 12/15/2022]
Abstract
Bacillus cereus belongs to B. cereus sensu lato group, shared by six other related species including Bacillus anthracis. B. anthracis is the causative agent for serious illness affecting a wide range of animals as well as humans and is a category A Biological and Toxin Warfare (BTW) agent. Recent studies indicate that a Bacillus species other than B. anthracis can cause anthrax-like disease and role of anthrax virulence plasmids (pXO1 and pXO2) on the pathogenicity of B. cereus has been documented. B. cereus strain TF5 was isolated from the tissue fluid of cutaneous anthrax-like skin lesions of a human patient from an anthrax endemic area in India. The strain harboured a PA gene, however, presence of pXO1 or pXO2-like plasmids could not be ascertained using reported primers. Abundant exoproteome of the strain in the early stationary phase was elucidated using a 2-DE MS approach and compared with that from a reference B. cereus strain. Analysis of proteins showing qualitative and quantitative differences between the two strains indicated an altered regulatory mechanism and putative role of S-layer protein and sphingomyelinase in the pathogenesis of strain TF5. Phylogenetic analysis of the S-layer protein indicated close affiliation of the strain with anthracis-like B. cereus strains such as B. cereus var. anthracis strain CI; whereas sphingomyelinase exhibited specific relationship with all the strains of B. anthracis apart from that with anthracis-like B. cereus strains.
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Affiliation(s)
- Neha Ghosh
- Biotechnology Division, Defence Research and Development Establishment, Gwalior 474002, India.
| | - Ajay Kumar Goel
- Biotechnology Division, Defence Research and Development Establishment, Gwalior 474002, India.
| | - Syed Imteyaz Alam
- Biotechnology Division, Defence Research and Development Establishment, Gwalior 474002, India.
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Sastalla I, Fattah R, Coppage N, Nandy P, Crown D, Pomerantsev AP, Leppla SH. The Bacillus cereus Hbl and Nhe tripartite enterotoxin components assemble sequentially on the surface of target cells and are not interchangeable. PLoS One 2013; 8:e76955. [PMID: 24204713 PMCID: PMC3799921 DOI: 10.1371/journal.pone.0076955] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/28/2013] [Indexed: 02/06/2023] Open
Abstract
Bacillus cereus is a spore-forming, Gram-positive bacterium commonly associated with outbreaks of food poisoning. It is also known as an opportunistic pathogen causing clinical infections such as bacteremia, meningitis, pneumonia, and gas gangrene-like cutaneous infections, mostly in immunocompromised patients. B. cereus secretes a plethora of toxins of which four are associated with the symptoms of food poisoning. Two of these, the non-hemolytic enterotoxin Nhe and the hemolysin BL (Hbl) toxin, are predicted to be structurally similar and are unique in that they require the combined action of three toxin proteins to induce cell lysis. Despite their dominant role in disease, the molecular mechanism of their toxic function is still poorly understood. We report here that B. cereus strain ATCC 10876 harbors not only genes encoding Nhe, but also two copies of the hbl genes. We identified Hbl as the major secreted toxin responsible for inducing rapid cell lysis both in cultured cells and in an intraperitoneal mouse toxicity model. Antibody neutralization and deletion of Hbl-encoding genes resulted in significant reductions of cytotoxic activity. Microscopy studies with Chinese Hamster Ovary cells furthermore showed that pore formation by both Hbl and Nhe occurs through a stepwise, sequential binding of toxin components to the cell surface and to each other. This begins with binding of Hbl-B or NheC to the eukaryotic membrane, and is followed by the recruitment of Hbl-L1 or NheB, respectively, followed by the corresponding third protein. Lastly, toxin component complementation studies indicate that although Hbl and Nhe can be expressed simultaneously and are predicted to be structurally similar, they are incompatible and cannot complement each other.
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Affiliation(s)
- Inka Sastalla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Rasem Fattah
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Nicole Coppage
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Poulomi Nandy
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Devorah Crown
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Andrei P. Pomerantsev
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
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Oltuszak-Walczak E, Walczak P. PCR detection of cytK gene in Bacillus cereus group strains isolated from food samples. J Microbiol Methods 2013; 95:295-301. [PMID: 24060693 DOI: 10.1016/j.mimet.2013.09.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 10/26/2022]
Abstract
A method for detection of the cytotoxin K cytK structural gene and its active promoter preceded by the PlcR-binding box, controlling the expression level of this enterotoxin, was developed. The method was applied for the purpose of the analysis of 47 bacterial strains belonging to the Bacillus cereus group isolated from different food products. It was found that the majority of the analyzed strains carried the fully functional cytK gene with its PlcR regulated promoter. The cytK gene was not detected in four emetic strains of Bacillus cereus carrying the cesB gene and potentially producing an emetic toxin - cereulide. The cytotoxin K gene was detected in 4 isolates classified as Bacillus mycoides and one reference strain B. mycoides PCM 2024. The promoter region and the N-terminal part of the cytK gene from two strains of B. mycoides (5D and 19E) showed similarities to the corresponding sequences of Bacillus cereus W23 and Bacillus thuringiensis HD-789, respectively. It was shown for the first time that the cytK gene promoter region from strains 5D and 19E of Bacillus mycoides had a similar arrangement to the corresponding sequence of Bacillus cereus ATCC 14579. The presence of the cytK gene in Bacillus mycoides shows that this species, widely recognized as nonpathogenic, may pose potential biohazard to human beings.
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Affiliation(s)
- Elzbieta Oltuszak-Walczak
- Institute of Fermentation Technology and Microbiology, Lodz University of Technology, 90-924 Lodz, Wolczanska 171/173, Poland
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Dubois T, Perchat S, Verplaetse E, Gominet M, Lemy C, Aumont-Nicaise M, Grenha R, Nessler S, Lereclus D. Activity of the Bacillus thuringiensis NprR-NprX cell-cell communication system is co-ordinated to the physiological stage through a complex transcriptional regulation. Mol Microbiol 2013; 88:48-63. [PMID: 23388036 DOI: 10.1111/mmi.12168] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2013] [Indexed: 12/01/2022]
Abstract
NprR is a quorum sensor of the RNPP family found in bacteria of the Bacillus cereus group. In association with its cognate peptide NprX, NprR controls the expression of genes essential for survival and sporulation of Bacillus thuringiensis during its necrotrophic development in insects. Here, we report that the nprR-nprX genes are not autoregulated and are co-transcribed from a σ(A) -dependent promoter (PA ) located upstream from nprR. The transcription from PA starts at the onset of the stationary phase and is controlled by two transcriptional regulators: CodY and PlcR. The nutritional repressor CodY represses nprR-nprX transcription during the exponential growth phase and the quorum sensor PlcR activates nprR-nprX transcription at the onset of stationary phase. We show that nprX is also transcribed independently of nprR from two promoters, PH and PE , dependent on the sporulation-specific sigma factors, σ(H) and σ(E) respectively. Both promoters ensure nprX transcription during late stationary phase while transcription from PA has decreased. These results show that the activity of the NprR-NprX quorum sensing system is tightly co-ordinated to the physiological stage throughout the developmental process of the Bacillus.
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Affiliation(s)
- Thomas Dubois
- INRA, UMR1319 Micalis, La Minière, F-78280, Guyancourt, France
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Rutherford ST, Bassler BL. Bacterial quorum sensing: its role in virulence and possibilities for its control. Cold Spring Harb Perspect Med 2012; 2:2/11/a012427. [PMID: 23125205 DOI: 10.1101/cshperspect.a012427] [Citation(s) in RCA: 1094] [Impact Index Per Article: 91.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Quorum sensing is a process of cell-cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly. This process enables bacteria to express energetically expensive processes as a collective only when the impact of those processes on the environment or on a host will be maximized. Among the many traits controlled by quorum sensing is the expression of virulence factors by pathogenic bacteria. Here we review the quorum-sensing circuits of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, and Vibrio cholerae. We outline these canonical quorum-sensing mechanisms and how each uniquely controls virulence factor production. Additionally, we examine recent efforts to inhibit quorum sensing in these pathogens with the goal of designing novel antimicrobial therapeutics.
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Affiliation(s)
- Steven T Rutherford
- Department of Molecular Biology, Princeton University, New Jersey 08544, USA
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Necrotrophism is a quorum-sensing-regulated lifestyle in Bacillus thuringiensis. PLoS Pathog 2012; 8:e1002629. [PMID: 22511867 PMCID: PMC3325205 DOI: 10.1371/journal.ppat.1002629] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/22/2012] [Indexed: 11/19/2022] Open
Abstract
How pathogenic bacteria infect and kill their host is currently widely investigated. In comparison, the fate of pathogens after the death of their host receives less attention. We studied Bacillus thuringiensis (Bt) infection of an insect host, and show that NprR, a quorum sensor, is active after death of the insect and allows Bt to survive in the cadavers as vegetative cells. Transcriptomic analysis revealed that NprR regulates at least 41 genes, including many encoding degradative enzymes or proteins involved in the synthesis of a nonribosomal peptide named kurstakin. These degradative enzymes are essential in vitro to degrade several substrates and are specifically expressed after host death suggesting that Bt has an active necrotrophic lifestyle in the cadaver. We show that kurstakin is essential for Bt survival during necrotrophic development. It is required for swarming mobility and biofilm formation, presumably through a pore forming activity. A nprR deficient mutant does not develop necrotrophically and does not sporulate efficiently in the cadaver. We report that necrotrophism is a highly regulated mechanism essential for the Bt infectious cycle, contributing to spore spreading.
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Gong Y, Li M, Xu D, Wang H, He J, Wu D, Chen D, Qiu N, Bao Q, Sun M, Yu Z. Comparative proteomic analysis revealed metabolic changes and the translational regulation of Cry protein synthesis in Bacillus thuringiensis. J Proteomics 2012; 75:1235-46. [DOI: 10.1016/j.jprot.2011.10.037] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 10/29/2011] [Accepted: 10/31/2011] [Indexed: 01/15/2023]
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Perchat S, Dubois T, Zouhir S, Gominet M, Poncet S, Lemy C, Aumont-Nicaise M, Deutscher J, Gohar M, Nessler S, Lereclus D. A cell-cell communication system regulates protease production during sporulation in bacteria of the Bacillus cereus group. Mol Microbiol 2011; 82:619-33. [PMID: 21958299 DOI: 10.1111/j.1365-2958.2011.07839.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In sporulating Bacillus, major processes like virulence gene expression and sporulation are regulated by communication systems involving signalling peptides and regulators of the RNPP family. We investigated the role of one such regulator, NprR, in bacteria of the Bacillus cereus group. We show that NprR is a transcriptional regulator whose activity depends on the NprX signalling peptide. In association with NprX, NprR activates the transcription of an extracellular protease gene (nprA) during the first stage of the sporulation process. The transcription start site of the nprA gene has been identified and the minimal region necessary for full activation has been characterized by promoter mutagenesis. We demonstrate that the NprX peptide is secreted, processed and then reimported within the bacterial cell. Once inside the cell, the mature form of NprX, presumably the SKPDIVG heptapeptide, directly binds to NprR allowing nprA transcription. Alignment of available NprR sequences from different species of the B. cereus group defines seven NprR clusters associated with seven NprX heptapeptide classes. This cell-cell communication system was found to be strain-specific with a possible cross-talk between some pherotypes. The phylogenic relationship between NprR and NprX suggests a coevolution of the regulatory protein and its signalling peptide.
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Ceuppens S, Rajkovic A, Heyndrickx M, Tsilia V, Van De Wiele T, Boon N, Uyttendaele M. Regulation of toxin production by Bacillus cereus and its food safety implications. Crit Rev Microbiol 2011; 37:188-213. [PMID: 21417966 DOI: 10.3109/1040841x.2011.558832] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Toxin expression is of utmost importance for the food-borne pathogen B. cereus, both in food poisoning and non-gastrointestinal host infections as well as in interbacterial competition. Therefore it is no surprise that the toxin gene expression is tightly regulated by various internal and environmental signals. An overview of the current knowledge regarding emetic and diarrheal toxin transcription and expression is presented in this review. The food safety aspects and management tools such as temperature control, food preservatives and modified atmosphere packaging are discussed specifically for B. cereus emetic and diarrheal toxin production.
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Affiliation(s)
- Siele Ceuppens
- Ghent University, Faculty of Bioscience Engineering, Laboratory of Food Microbiology and Food Preservation, Ghent, Belgium
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Abee T, Kovács AT, Kuipers OP, van der Veen S. Biofilm formation and dispersal in Gram-positive bacteria. Curr Opin Biotechnol 2010; 22:172-9. [PMID: 21109420 DOI: 10.1016/j.copbio.2010.10.016] [Citation(s) in RCA: 173] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/26/2010] [Accepted: 10/26/2010] [Indexed: 11/25/2022]
Abstract
Biofilms are structured communities of bacteria, which are adhered to a surface and embedded in a self-produced matrix of extracellular polymeric substances. Since biofilms are very resistant to antimicrobial agents, they are at the basis of a range of problems, including quality and safety issues in food industry. Recently, major advances have been made in elucidating the different structural components of the biofilm matrix, the regulatory pathways involved in biofilm formation, and signaling molecules involved in biofilm formation and dispersal, which provide opportunities for prevention and control of these biofilms in the food industry.
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Affiliation(s)
- Tjakko Abee
- Top Institute Food and Nutrition, Nieuwe Kanaal 9A, 6709 PA Wageningen, The Netherlands.
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43
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Potential of the melanophore pigment response for detection of bacterial toxicity. Appl Environ Microbiol 2010; 76:8243-6. [PMID: 20952639 DOI: 10.1128/aem.01241-10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Chromatophore cells have been investigated as potential biodetectors for function-based detection of chemically and biologically toxic substances. Oncorhynchus tshawytscha (chinook salmon) melanophores, a chromatophore cell type containing brown pigment, rapidly detect the salmonid pathogens Aeromonas salmonicida, Yersinia ruckeri, and Flavobacterium psychrophilum and the human pathogen Bacillus cereus.
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Fouet A. AtxA, a Bacillus anthracis global virulence regulator. Res Microbiol 2010; 161:735-42. [PMID: 20863885 DOI: 10.1016/j.resmic.2010.09.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 07/20/2010] [Indexed: 11/30/2022]
Abstract
Fifteen years ago, AtxA was isolated as a toxin gene activator and five years later it was shown to be a Bacillus anthracis master regulator. AtxA controls the expression of more than a hundred genes belonging to all genetic elements, the chromosome and both virulence plasmids, including those encoding the major virulence factors. AtxA can activate or repress gene expression. The mechanism by which AtxA exerts its control is unknown; it is indirect on some genes but may be direct on others. The expression of many AtxA-controlled genes is induced by the presence of bicarbonate/CO(2). AtxA links the metabolic state and virulence gene expression.
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Affiliation(s)
- Agnès Fouet
- Institut Pasteur, Toxines et Pathogénie Bactérienne, Département de Microbiologie, 28 rue du Dr Roux, 75724 Paris cedex 15, France.
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Production, secretion and biological activity of Bacillus cereus enterotoxins. Toxins (Basel) 2010; 2:1690-703. [PMID: 22069656 PMCID: PMC3153264 DOI: 10.3390/toxins2071690] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 06/14/2010] [Accepted: 06/28/2010] [Indexed: 11/17/2022] Open
Abstract
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.
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Raymond B, Johnston PR, Nielsen-LeRoux C, Lereclus D, Crickmore N. Bacillus thuringiensis: an impotent pathogen? Trends Microbiol 2010; 18:189-94. [DOI: 10.1016/j.tim.2010.02.006] [Citation(s) in RCA: 249] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 02/18/2010] [Accepted: 02/24/2010] [Indexed: 11/17/2022]
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Pang JC, Chen ML, Ho YC, Yang CY, Tzeng CC, Kao SS, Tsen HY. Effect of fermentation conditions on the enterotoxigenicity, cytotoxicity and pesticidal activity of Bacillus thuringiensis strains isolated in Taiwan. BIORESOURCE TECHNOLOGY 2010; 101:1871-1876. [PMID: 19880313 DOI: 10.1016/j.biortech.2009.09.090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 09/29/2009] [Accepted: 09/30/2009] [Indexed: 05/28/2023]
Abstract
A total of 75 Bacillus thuringiensis strains, among them 62 of Taiwan's microbiota, were screened for their enterotoxin genes, hemolysin BL activity and cytotoxicity. All the strains harbored enterotoxin genes and were cytotoxic to the cultivated Chinese hamster ovary (CHO) cells. The hemolysin BL and cytotoxicity titers of the B. thuringiensis culture in casitone yeast sucrose (CYS) broth were lower than those in brain heart infusion (BHI) broth, and when the B. thuringiensis strains were cultivated in CYS broth for 5 days, no cytotoxicity was detected. The spores and crystal toxins collected from 40 isolates showed high levels of insecticidal activity against Plutella xylostella. All strains exhibiting low cytotoxicity also had low pesticidal activity. Our study demonstrated that it is difficult to find B. thuringiensis strains that are both effective against insect targets and do not produce enterotoxins or cytotoxic effects in CHO cells. However, it is possible to avoid or reduce unwanted properties, but not the insecticidal activity, of some B. thuringiensis preparations by alteration of culture media and conditions.
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Affiliation(s)
- Jen-Chieh Pang
- Department of Biotechnology, Van-Nung University, Chung-Li, Taoyuan County 320, Taiwan, ROC
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The InhA metalloproteases of Bacillus cereus contribute concomitantly to virulence. J Bacteriol 2010; 192:286-94. [PMID: 19837797 DOI: 10.1128/jb.00264-09] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The virulence of Bacillus cereus requires that bacteria have the capacity to colonize their host, degrade specific tissues, and circumvent the host immune system. To study this aspect of pathogenesis, we focused on three metalloproteases, InhA1, InhA2, and InhA3, which share more than 66% identity. The expression of these metalloprotease genes was assessed by transcriptional fusions with a lacZ reporter gene. The expression profiles suggest a complementary time course of InhA production. Indeed, the genes are simultaneously expressed but are oppositely controlled during stationary phase. We constructed single and multiple inhA mutants and assessed the bacterial locations of the proteins as well as their individual or additive roles in macrophage escape and toxicity, antibacterial-peptide cleavage, and virulence. InhA1, a major component of the spore exosporium, is the only InhA metalloprotease involved in bacterial escape from macrophages. A mutant lacking inhA1, inhA2, and inhA3 shows a strong decrease in the level of virulence for insects. Taken together, these results show that the InhA metalloproteases of B. cereus are important virulence factors that may allow the bacteria to counteract the host immune system.
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Characterization of the sporulation initiation pathway of Clostridium difficile and its role in toxin production. J Bacteriol 2009; 191:7296-305. [PMID: 19783633 DOI: 10.1128/jb.00882-09] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Clostridium difficile is responsible for significant mortality and morbidity in the hospitalized elderly. C. difficile spores are infectious and are a major factor contributing to nosocomial transmission. The Spo0A response regulator is the master regulator for sporulation initiation and can influence many other cellular processes. Using the ClosTron gene knockout system, we inactivated genes encoding Spo0A and a putative sporulation-associated sensor histidine kinase in C. difficile. Inactivation of spo0A resulted in an asporogeneous phenotype, whereas inactivation of the kinase reduced C. difficile sporulation capacity by 3.5-fold, suggesting that this kinase also has a role in sporulation initiation. Furthermore, inactivation of either spo0A or the kinase resulted in a marked defect in C. difficile toxin production. Therefore, Spo0A and the signaling pathway that modulates its activity appear to be involved in regulation of toxin synthesis in C. difficile. In addition, Spo0A was directly phosphorylated by a putative sporulation-associated kinase, supporting the hypothesis that sporulation initiation in C. difficile is controlled by a two-component signal transduction system rather than a multicomponent phosphorelay. The implications of these findings for C. difficile sporulation, virulence, and transmission are discussed.
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Pomerantsev AP, Pomerantseva OM, Camp AS, Mukkamala R, Goldman S, Leppla SH. PapR peptide maturation: role of the NprB protease in Bacillus cereus 569 PlcR/PapR global gene regulation. ACTA ACUST UNITED AC 2009; 55:361-77. [PMID: 19159431 DOI: 10.1111/j.1574-695x.2008.00521.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The global transcriptional regulator PlcR controls gene expression in Bacillus cereus and Bacillus thuringiensis. Activity of PlcR is regulated by PapR, the product of an ORF located immediately downstream of plcR. To be active in B. cereus, PapR must be secreted and then processed to the mature peptide by an unknown protease. This peptide is transported by an oligopeptide permease into the cell, where it activates PlcR. In this study, we show that the neutral protease B (NprB) secreted by B. cereus 569 is required for extracellular PapR maturation. Purified recombinant NprB processed the synthetic PapR propeptide to produce a set of peptides derived from the C-terminal domain of PapR. Supplementation of growth media with synthetic PapR-derived C-terminal 5-, 7-, 8- and 27-amino acid (aa) peptides caused activation of intracellular PlcR in a PapR-deficient strain of B. cereus 569 while only the 5- and 7-aa peptides activated PlcR in a nprB mutant. The maximum activity was found for the 7-mer peptide. However, even the 7-mer peptide could not activate PlcR with a C-terminal truncation of as few as 6 aa. This indicates that interactions of the C-terminal regions of both PlcR and PapR are important in transcriptional activation of the B. cereus 569 PlcR regulon.
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Affiliation(s)
- Andrei P Pomerantsev
- Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-3202, USA
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