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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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Wang J, Yu Q, Peng Q, Slamti L, Zhang R, Hou S, Lereclus D, Song F. Deletion of the novel gene mother cell lysis X results in Cry1Ac encapsulation in the Bacillus thuringiensis HD73. Front Microbiol 2022; 13:951830. [PMID: 36016772 PMCID: PMC9397120 DOI: 10.3389/fmicb.2022.951830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/14/2022] [Indexed: 11/13/2022] Open
Abstract
The novel protein MclX (mother cell lysis X) in Bacillus thuringiensis subsp. kurstaki strain HD73 (B. thuringiensis HD73) was characterized in this work. MclX has no known domain and its gene deletion in HD73 resulted in Cry1Ac encapsulation in the mother cell and did not influence Cry1Ac protein production or insecticidal activity. In vitro cell wall hydrolysis experiments showed that MclX cannot hydrolyze the cell wall. In mclX deletion mutants, the expression of cwlC (which encodes a key cell wall hydrolase) was significantly decreased, as shown by the β-galactosidase activity assay. MclX cannot directly bind to the cwlC promoter, based on the electrophoretic mobility shift assay (EMSA). The cwlC was reported to be regulated by σK and GerE. However, the transcriptional activities of sigK and gerE showed no difference between HD73 and the mclX deletion mutant. It is indicated that MclX influenced cwlC expression independently of σK or GerE, through a new pathway to regulate cwlC expression. mclX deletion could be a new approach for insecticidal protein encapsulation in Bacillus thuringiensis.
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Affiliation(s)
- Jiaojiao Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qingyue Yu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Leyla Slamti
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Ruibin Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China
| | - Shuo Hou
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Didier Lereclus
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- *Correspondence: Fuping Song,
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Luo Y, Su A, Yang J, Yu Q, Wang E, Yuan H. Production of 5-aminolevulinic acid from hydrolysates of cassava residue and fish waste by engineered Bacillus cereus PT1. Microb Biotechnol 2022; 16:381-391. [PMID: 35920136 PMCID: PMC9871517 DOI: 10.1111/1751-7915.14118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 06/28/2022] [Accepted: 07/01/2022] [Indexed: 01/27/2023] Open
Abstract
The economical production of 5-aminolevulinic acid (ALA) has recently received increasing attention for its extensive use in agriculture. In this study, a strain of Bacillus cereus PT1 could initially produce ALA at a titre of 251.72 mg/L by using a hydrolysate mixture of low-cost cassava residue and fish waste. The integration of endogenous hemA encoding glutamyl-tRNA reductase led to a 39.30% increase in ALA production. Moreover, improving cell permeability by deletion of the LytR-CpsA-Psr (LCP) family gene tagU led to a further increase of 59.73% in ALA production. Finally, the engineered strain B. cereus PT1-hemA-ΔtagU produced 2.62 g/L of ALA from the previously mentioned hydrolysate mixture in a 7-L bioreactor. In a pot experiment, foliar spray of the ALA produced by B. cereus PT1-hemA-ΔtagU from the hydrolysates increased salt tolerance of cucumber by improving chlorophyll content and catalase activity, while decreasing malondialdehyde content. Overall, this study demonstrated an economic way to produce ALA using a microbial platform and evidenced the potential of ALA in agricultural application.
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Affiliation(s)
- Ying Luo
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Anping Su
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Jinshui Yang
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Qijun Yu
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias BiológicasInstituto Politécnico NacionalMexico CityMexico
| | - Hongli Yuan
- State Key Laboratory of Agrobiotechnology and Key Laboratory of Soil Microbiology, Ministry of Agriculture, College of Biological SciencesChina Agricultural UniversityBeijingChina
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Chen H, Verplaetse E, Jauslin T, Cosson P, Slamti L, Lereclus D. The Fate of Bacteria of the Bacillus cereus Group in the Amoeba Environment. MICROBIAL ECOLOGY 2022; 83:1088-1104. [PMID: 34342700 DOI: 10.1007/s00248-021-01828-2] [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: 02/08/2021] [Accepted: 07/21/2021] [Indexed: 06/13/2023]
Abstract
The Bacillus cereus sensu lato group consists of several closely related species, including B. anthracis, B. cereus sensu stricto, and B. thuringiensis. Spores of these pathogenic bacteria are commonly found in the soil but evidence suggests that they are unable to grow in such a natural environment in the absence of nutrient input. Amoebas have been reported to be an amplifier for several species of pathogenic bacteria and their potential involvement to explain the large amount of B. thuringiensis and B. cereus spores in soil has been frequently proposed. Here, we studied the fate of Bacillus and amoebas when cultured together. We show that the virulence factors produced by B. thuringiensis and B. cereus do not affect the amoeba Acanthamoeba castellanii, which, on the contrary, can phagocytose and effectively digest vegetative Bacillus cells to grow and prevent the formation of cysts. Bacterial spores can germinate in the amoeba environment and the vegetative cells can then form chains or aggregates that appear to be less efficiently phagocyted by the amoeba. The use of transcriptional fusions between fluorescent reporter genes and stationary phase- and sporulation-specific promoters showed that the sporulation process occurs more efficiently in the presence of amoebas than in their absence. Moreover, our results showed the amoeba environment to promote spore germination and allow the bacteria to complete their developmental cycle. Overall, this study suggests that the amoeba-Bacillus interaction creates a virtuous circle in which each protagonist helps the other to develop.
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Affiliation(s)
- Haibo Chen
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
| | - Emilie Verplaetse
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
| | - Tania Jauslin
- Cell Physiology and Metabolism Dpt, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, CH-1211, Geneva 4, Switzerland
| | - Pierre Cosson
- Cell Physiology and Metabolism Dpt, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, CH-1211, Geneva 4, Switzerland
| | - Leyla Slamti
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France
| | - Didier Lereclus
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350, Jouy-en-Josas, France.
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The transcription factor CpcR determines cell fate by modulating the initiation of sporulation in Bacillus thuringiensis. Appl Environ Microbiol 2022; 88:e0237421. [PMID: 35108078 DOI: 10.1128/aem.02374-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus thuringiensis is a bacterium capable of differentiating into a spore, a dormant and highly resistant cellular form. During the sporulation process, this bacterium produces insecticidal toxins in the form of a crystal inclusion, usually in the sporulating cell. We previously reported that the B. thuringiensis LM1212 strain can differentiate into two distinct subpopulations of spore formers and crystal producers, and that this division of labour phenotype provides bacterium with a fitness advantage in competition with a typical B. thuringiensis strain. The transcription factor CpcR was characterized as the regulator responsible for this phenotype. Here, we examined how CpcR interacts with sporulation network to control the cell differentiation. We found sporulation process was inhibited prior to polar septum formation, and that Spo0A activity was impaired, in the presence of cpcR in LM1212 strain. Using bioinformatics and genetic tools, we identified a gene positively controlled by CpcR encoding a putative phosphatase of Spo0E family known to specifically dephosphorylate Spo0A-P. We showed that this protein (called Spo0E1) is a negative regulator of sporulation and that variations in spo0E1 expression can modulate the production of spores. Using fluorescent reporters to follow gene expression at the single-cell level, we correlated expression of cpcR and sporulation genes to the formation of the two differentiated subpopulations. IMPORTANCE Formation of spores is a paradigm for study of cell differentiation in prokaryotes. Sporulation initiation is governed by a gradual increase in the level and activity of the master regulator Spo0A. Spo0A is usually indirectly phosphorylated by a multicomponent phosphorelay and modulation of this phosphorelay system is a critical aspect of Bacillus physiology. Though we know this phosphorelay system is usually affected by two negative regulatory mechanisms: rap genes and spo0E family genes, the regulatory mechanisms controlling the transcription of these genes are poorly understood. Here, we reported the transcription factor CpcR positively regulates a spo0E family gene and variations in spo0E expression can modulate the production of spores in B. thuringiensis. This work emphasizes the diversity in modes of sporulation and illustrate the diversity in the strategies employed by bacteria to control this differentiation pathway and ensure their survival.
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Identification and Functional Characterization of Two Homologous SpoVS Proteins Involved in Sporulation of Bacillus thuringiensis. Microbiol Spectr 2021; 9:e0088121. [PMID: 34612699 PMCID: PMC8510167 DOI: 10.1128/spectrum.00881-21] [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
Sporulation is an important part of the life cycle of Bacillus thuringiensis and the basis for the production of parasporal crystals. This study identifies and characterizes two homologous spoVS genes (spoVS1 and spoVS2) in B. thuringiensis, both of whose expression is dependent on the σH factor. The disruption of spoVS1 and spoVS2 resulted in defective B. thuringiensis sporulation. Similar to Bacillus subtilis, B. thuringiensis strain HD(ΔspoVS1) mutants showed delayed formation of the polar septa, decreased sporulation efficiency, and blocked spore release. Different from B. subtilis, B. thuringiensis HD(ΔspoVS1) mutants had disporic septa and failed to complete engulfment in some cells. Moreover, HD(ΔspoVS2) mutants had delayed spore release. The effect of spoVS1 deletion on polar septum delay and sporulation efficiency could be compensated by spoVS2. β-Galactosidase activity analysis showed that the expression of pro-sigE and spoIIE decreased to different degrees in the HD(ΔspoVS1) and HD(ΔspoVS2) mutants. The different effects of the two mutations on the expression of sporulation genes led to decreases in Cry1Ac production of different levels. IMPORTANCE There is only one spoVS gene in B. subtilis, and its effects on sporulation have been reported. In this study, two homologous spoVS genes were found and identified in B. thuringiensis. The different effects on sporulation and parasporal crystal protein production in B. thuringiensis and their relationship were investigated. We found that these two homologous spoVS genes are highly conserved in the Bacillus cereus group, and therefore, the functional characterization of SpoVS is helpful to better understand the sporulation processes of members of the Bacillus cereus group.
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Attieh Z, Mouawad C, Rejasse A, Jehanno I, Perchat S, Hegna IK, Økstad OA, Kallassy Awad M, Sanchis-Borja V, El Chamy L. The fliK Gene Is Required for the Resistance of Bacillus thuringiensis to Antimicrobial Peptides and Virulence in Drosophila melanogaster. Front Microbiol 2020; 11:611220. [PMID: 33391240 PMCID: PMC7775485 DOI: 10.3389/fmicb.2020.611220] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/18/2020] [Indexed: 11/13/2022] Open
Abstract
Antimicrobial peptides (AMPs) are essential effectors of the host innate immune system and they represent promising molecules for the treatment of multidrug resistant microbes. A better understanding of microbial resistance to these defense peptides is thus prerequisite for the control of infectious diseases. Here, using a random mutagenesis approach, we identify the fliK gene, encoding an internal molecular ruler that controls flagella hook length, as an essential element for Bacillus thuringiensis resistance to AMPs in Drosophila. Unlike its parental strain, that is highly virulent to both wild-type and AMPs deficient mutant flies, the fliK deletion mutant is only lethal to the latter's. In agreement with its conserved function, the fliK mutant is non-flagellated and exhibits highly compromised motility. However, comparative analysis of the fliK mutant phenotype to that of a fla mutant, in which the genes encoding flagella proteins are interrupted, indicate that B. thuringiensis FliK-dependent resistance to AMPs is independent of flagella assembly. As a whole, our results identify FliK as an essential determinant for B. thuringiensis virulence in Drosophila and provide new insights on the mechanisms underlying bacteria resistance to AMPs.
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Affiliation(s)
- Zaynoun Attieh
- UR-EGP, Faculté des Sciences, Université Saint-Joseph de Beyrouth, Beirut, Lebanon
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Carine Mouawad
- UR-EGP, Faculté des Sciences, Université Saint-Joseph de Beyrouth, Beirut, Lebanon
| | - Agnès Rejasse
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Isabelle Jehanno
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Stéphane Perchat
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Ida K. Hegna
- Department of Pharmacy, Centre for Integrative Microbial Evolution (CIME), Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | - Ole A. Økstad
- Department of Pharmacy, Centre for Integrative Microbial Evolution (CIME), Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | | | - Vincent Sanchis-Borja
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Laure El Chamy
- UR-EGP, Faculté des Sciences, Université Saint-Joseph de Beyrouth, Beirut, Lebanon
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Quan M, Peng J, Zhu Z, Zhou P, Luo S, Xie J, Xia L, Sun Y, Ding X. Construction of a Conditionally Asporogenous Bacillus thuringiensis Recombinant Strain Overproducing Cry Protein by Deletion of the leuB Gene. Front Microbiol 2020; 11:1769. [PMID: 32849393 PMCID: PMC7396631 DOI: 10.3389/fmicb.2020.01769] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 07/06/2020] [Indexed: 11/13/2022] Open
Abstract
One of the common shortcomings with Bacillus thuringiensis (Bt) biopesticides in field application is their instability under UV irradiation. In Bt, the leuB gene encodes the 3-isopropylmalate dehydrogenase. In addition to its role in leucine biosynthesis, LeuB would be likely recruited to catalyze the dehydrogenation of malate in the final step of tricarboxylic acid cycle during sporulation. In this study, we constructed a Bt recombinant strain in which the gene leuB was deleted by using the markerless gene deletion system. The ΔleuB mutant strain showed a conditionally asporogenous phenotype while overproducing insecticidal crystal proteins and retaining its insecticidal activity well in both fermentation and LB media. Furthermore, the metabolic regulation mechanisms of LeuB was elucidated by iTRAQ-based quantitative proteomics approach. Evidences from proteomics data suggested that the inhibited supply of pyruvate (carbon source) was an important factor related to the conditionally asporogenous feature of the mutant. Consistently, the mutant regained its ability to sporulate in LB medium by adding 1% glucose or 1% sodium pyruvate. Taken together, our study demonstrated that deletion of the leuB gene resulted in delayed or completely blocked mother cell lysis, allowing the crystals encapsulated within cells, which makes this recombinant strain a good candidate for developing Bt preparations with better UV-stability.
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Affiliation(s)
- Meifang Quan
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China.,Key Laboratory of Molecular Epidemiology of Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
| | - Jinli Peng
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Zirong Zhu
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Pengji Zhou
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Sisi Luo
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Junyan Xie
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Liqiu Xia
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Yunjun Sun
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| | - Xuezhi Ding
- Hunan Provincial Key Laboratory of Microbial Molecular Biology, State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
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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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Lv J, Zhang X, Gao T, Cui T, Peng Q, Zhang J, Song F. Effect of the spoIIID mutation on mother cell lysis in Bacillus thuringiensis. Appl Microbiol Biotechnol 2019; 103:4103-4112. [PMID: 30953122 DOI: 10.1007/s00253-019-09722-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 02/19/2019] [Accepted: 02/23/2019] [Indexed: 11/28/2022]
Abstract
SpoIIID is a small, sequence-specific DNA-binding protein which can direct many genes' transcription and has an effect on spore formation in Bacillus subtilis. We investigated the role of SpoIIID in mother cell lysis in Bacillus thuringiensis. A β-galactosidase assay based on the promoter fusions with lacZ indicated that the sigK gene was positively regulated by SpoIIID and σK negatively regulated the expression of sigE. The spoIIID mutant strain exhibited no mother cell lysis in Schaeffer's sporulation medium (SSM) but did in ½ Luria-Bertani (LB) medium. cwlC is an essential hydrolase gene for mother cell lysis. Moreover, the expression of a PcwlC-lacZ fusion in spoIIID mutant was proved to be higher in ½ LB medium than in SSM. HD (ΔspoIIID)(ΔcwlC) mutant was obtained by knocking out the cwlC gene in HD(ΔspoIIID) and displayed no mother cell lysis in both SSM and ½ LB mediums. The deletion of spoIIID decreased the crystal protein production in HD73. The expression of Porf1cry8E and P5014 promoter fusions with lacZ gene in the acrystalliferous HD-(ΔspoIIID) mutant showed similar activity to that in the acrystalliferous HD73- strain before T7 and slightly higher than that in the acrystalliferous HD73- after T7. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that Cry1Ac production in HD-(ΔspoIIID) directed by the Porf1cry8E and P5014 promoters was at a similar level as that in HD73 wild strain. Altogether, these results suggested that the spoIIID mutant with Porf1cry8E or P5014 promoters could be an alternative delivery system for cry gene expression with no mature spore formation and medium-dependent mother cell lysis.
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Affiliation(s)
- 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
| | - Tantan Gao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Tingting Cui
- 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
| | - 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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Novel Cell Wall Hydrolase CwlC from Bacillus thuringiensis Is Essential for Mother Cell Lysis. Appl Environ Microbiol 2018; 84:AEM.02640-17. [PMID: 29374039 DOI: 10.1128/aem.02640-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 01/10/2018] [Indexed: 11/20/2022] Open
Abstract
In this study, a sporulation-specific gene (tentatively named cwlC) involved in mother cell lysis in Bacillus thuringiensis was characterized. The encoded CwlC protein consists of an N-terminal N-acetylmuramoyl-l-alanine amidase (MurNAc-LAA) domain and a C-terminal amidase02 domain. The recombinant histidine-tagged CwlC proteins purified from Escherichia coli were able to directly bind to and digest the B. thuringiensis cell wall. The CwlC point mutations at the two conserved glutamic acid residues (Glu-24 and Glu-140) shown to be critical for the catalytic activity in homologous amidases resulted in a complete loss of cell wall lytic activity, suggesting that CwlC is an N-acetylmuramoyl-l-alanine amidase. Results of transcriptional analyses indicated that cwlC is transcribed as a monocistronic unit and that its expression is dependent on sporulation sigma factor K (σK). Deletion of cwlC completely blocked mother cell lysis during sporulation without impacting the sporulation frequency, Cry1Ac protein production, and insecticidal activity. Taken together, our data suggest that CwlC is an essential cell wall hydrolase for B. thuringiensis mother cell lysis during sporulation. Engineered B. thuringiensis strains targeting cwlC, which allows the crystal inclusion to remain encapsulated in the mother cell at the end of sporulation, may have the potential to become more effective biological control agents in agricultural applications since the crystal inclusion remains encapsulated in the mother cell at the end of sporulation.IMPORTANCE Mother cell lysis has been well studied in Bacillus subtilis, which involves three distinct yet functionally complementary cell wall hydrolases. In this study, a novel cell wall hydrolase, CwlC, was investigated and found to be essential for mother cell lysis in Bacillus thuringiensis CwlC of B. thuringiensis only shows 9 and 21% sequence identity with known B. subtilis mother cell hydrolases CwlB and CwlC, respectively, suggesting that mechanisms of mother cell lysis may differ between B. subtilis and B. thuringiensis The cwlC gene deletion completely blocked the release of spores and crystals from the mother cell without affecting insecticidal activity. This may provide a new effective strategy for crystal encapsulation against UV light inactivation.
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12
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A strong promoter of a non-cry gene directs expression of the cry1Ac gene in Bacillus thuringiensis. Appl Microbiol Biotechnol 2018. [DOI: 10.1007/s00253-018-8836-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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13
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Kamar R, Réjasse A, Jéhanno I, Attieh Z, Courtin P, Chapot-Chartier MP, Nielsen-Leroux C, Lereclus D, El Chamy L, Kallassy M, Sanchis-Borja V. DltX of Bacillus thuringiensis Is Essential for D-Alanylation of Teichoic Acids and Resistance to Antimicrobial Response in Insects. Front Microbiol 2017; 8:1437. [PMID: 28824570 PMCID: PMC5541007 DOI: 10.3389/fmicb.2017.01437] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 07/14/2017] [Indexed: 11/13/2022] Open
Abstract
The dlt operon of Gram-positive bacteria is required for the incorporation of D-alanine esters into cell wall-associated teichoic acids (TAs). Addition of D-alanine to TAs reduces the negative charge of the cell envelope thereby preventing cationic antimicrobial peptides (CAMPs) from reaching their target of action on the bacterial surface. In most gram-positive bacteria, this operon consists of five genes dltXABCD but the involvement of the first ORF (dltX) encoding a small protein of unknown function, has never been investigated. The aim of this study was to establish whether this protein is involved in the D-alanylation process in Bacillus thuringiensis. We, therefore constructed an in frame deletion mutant of dltX, without affecting the expression of the other genes of the operon. The growth characteristics of the dltX mutant and those of the wild type strain were similar under standard in vitro conditions. However, disruption of dltX drastically impaired the resistance of B. thuringiensis to CAMPs and significantly attenuated its virulence in two insect species. Moreover, high-performance liquid chromatography studies showed that the dltX mutant was devoid of D-alanine, and electrophoretic mobility measurements indicated that the cells carried a higher negative surface charge. Scanning electron microscopy experiments showed morphological alterations of these mutant bacteria, suggesting that depletion of D-alanine from TAs affects cell wall structure. Our findings suggest that DltX is essential for the incorporation of D-alanyl esters into TAs. Therefore, DltX plays a direct role in the resistance to CAMPs, thus contributing to the survival of B. thuringiensis in insects. To our knowledge, this work is the first report examining the involvement of dltX in the D-alanylation of TAs.
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Affiliation(s)
- Rita Kamar
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France.,Laboratoire de Génétique de la Drosophile et Virulence Microbienne, Université Saint-JosephBeirut, Lebanon
| | - Agnès Réjasse
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France
| | - Isabelle Jéhanno
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France
| | - Zaynoun Attieh
- Laboratoire de Génétique de la Drosophile et Virulence Microbienne, Université Saint-JosephBeirut, Lebanon
| | - Pascal Courtin
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France
| | | | | | - Didier Lereclus
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France
| | - Laure El Chamy
- Laboratoire de Génétique de la Drosophile et Virulence Microbienne, Université Saint-JosephBeirut, Lebanon
| | - Mireille Kallassy
- Laboratoire de Génétique de la Drosophile et Virulence Microbienne, Université Saint-JosephBeirut, Lebanon
| | - Vincent Sanchis-Borja
- INRA, UMR1319 MicalisJouy-en-Josas, France.,AgroParisTech, UMR MicalisJouy-en-Josas, France
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14
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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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15
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Deng C, Peng Q, Song F, Lereclus D. Regulation of cry gene expression in Bacillus thuringiensis. Toxins (Basel) 2014; 6:2194-209. [PMID: 25055802 PMCID: PMC4113751 DOI: 10.3390/toxins6072194] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 07/11/2014] [Accepted: 07/15/2014] [Indexed: 02/02/2023] Open
Abstract
Bacillus thuringiensis differs from the closely related Bacillus cereus group species by its ability to produce crystalline inclusions. The production of these crystals mainly results from the expression of the cry genes, from the stability of their transcripts and from the synthesis, accumulation and crystallization of large amounts of insecticidal Cry proteins. This process normally coincides with sporulation and is regulated by various factors operating at the transcriptional, post-transcriptional, metabolic and post-translational levels.
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Affiliation(s)
- Chao Deng
- 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.
| | - 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.
| | - Didier Lereclus
- INRA, UMR1319 Micalis, La Minière, Guyancourt 78280, France.
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16
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Efficient production of Bacillus thuringiensis Cry1AMod toxins under regulation of cry3Aa promoter and single cysteine mutations in the protoxin region. Appl Environ Microbiol 2013; 79:6969-73. [PMID: 24014526 DOI: 10.1128/aem.02546-13] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus thuringiensis Cry1AbMod toxins are engineered versions of Cry1Ab that lack the amino-terminal end, including domain I helix α-1 and part of helix α-2. This deletion improves oligomerization of these toxins in solution in the absence of cadherin receptor and counters resistance to Cry1A toxins in different lepidopteran insects, suggesting that oligomerization plays a major role in their toxicity. However, Cry1AbMod toxins are toxic to Escherichia coli cells, since the cry1A promoter that drives its expression in B. thuringiensis has readthrough expression activity in E. coli, making difficult the construction of these CryMod toxins. In this work, we show that Cry1AbMod and Cry1AcMod toxins can be cloned efficiently under regulation of the cry3A promoter region to drive its expression in B. thuringiensis without expression in E. coli cells. However, p3A-Cry1Ab(c)Mod construction promotes the formation of Cry1AMod crystals in B. thuringiensis cells that were not soluble at pH 10.5 and showed no toxicity to Plutella xylostella larvae. Cysteine residues in the protoxin carboxyl-terminal end of Cry1A toxins have been shown to be involved in disulfide bond formation, which is important for crystallization. Six individual cysteine substitutions for serine residues were constructed in the carboxyl-terminal protoxin end of the p3A-Cry1AbMod construct and one in the carboxyl-terminal protoxin end of p3A-Cry1AcMod. Interestingly, p3A-Cry1AbMod C654S and C729S and p3A-Cry1AcMod C730S recover crystal solubility at pH 10.5 and toxicity to P. xylostella. These results show that combining the cry3A promoter expression system with single cysteine mutations is a useful system for efficient expression of Cry1AMod toxins in B. thuringiensis.
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Transcriptional regulation and characteristics of a novel N-acetylmuramoyl-L-alanine amidase gene involved in Bacillus thuringiensis mother cell lysis. J Bacteriol 2013; 195:2887-97. [PMID: 23603740 DOI: 10.1128/jb.00112-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Bacillus thuringiensis, a novel N-acetylmuramoyl-L-alanine amidase gene (named cwlB) was detected, and the CwlB protein was purified and characterized. Reverse transcription-PCR (RT-PCR) results indicated that cwlB and an upstream gene (named cwlA) formed one transcriptional unit. 5' rapid amplification of cDNA ends (5'-RACE)-PCR and transcriptional fusions with the lacZ gene indicated that transcription of the operon was directed by a promoter, P(cwlA), which is located upstream from the cwlA gene and that the transcription start site is a single 5'-end nucleotide residue T located 25 nucleotides (bp) upstream from the cwlA translational start codon. Moreover, the activity of P(cwlA) was controlled by σ(K). Morphological analysis suggested that the mutation of cwlB could delay spore release compared to the timing of spore release in the wild-type strain. Western blot assay demonstrated that purified CwlB bound to the B. thuringiensis cell wall. Observations with laser confocal microscopy and a green fluorescent protein-based reporter system demonstrated that the CwlB protein localizes to the cell envelope. All results suggest that the CwlB protein is involved in mother cell lysis in B. thuringiensis.
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18
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Liu G, Song L, Shu C, Wang P, Deng C, Peng Q, Lereclus D, Wang X, Huang D, Zhang J, Song F. Complete genome sequence of Bacillus thuringiensis subsp. kurstaki strain HD73. GENOME ANNOUNCEMENTS 2013; 1:e0008013. [PMID: 23516207 PMCID: PMC3622971 DOI: 10.1128/genomea.00080-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 02/14/2013] [Indexed: 11/26/2022]
Abstract
Bacillus thuringiensis is a Gram-positive bacterium that produces intracellular protein crystals toxic to a wide variety of insect larvae. We report the complete genome sequence of Bacillus thuringiensis subsp. kurstaki strain HD73 from the Centre OILB (Institut Pasteur, France), which belongs to serotype 3ab and is toxic to lepidopteran larvae.
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Affiliation(s)
- Guiming Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Lai Song
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Changlong Shu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Pinshu Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Chao Deng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Didier Lereclus
- INRA, UMR1319 Micalis, Génétique Microbienne et Environnement, La Minière, Guyancourt, France
| | - Xumin Wang
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Dafang Huang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
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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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20
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Weak transcription of the cry1Ac gene in nonsporulating Bacillus thuringiensis cells. Appl Environ Microbiol 2012; 78:6466-74. [PMID: 22773626 DOI: 10.1128/aem.01229-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cry1Ac gene of Bacillus thuringiensis subsp. kurstaki HD-73 (B. thuringiensis HD-73) is a typical example of a sporulation-dependent crystal gene and is controlled by sigma E and sigma K during sporulation. To monitor the production and accumulation of Cry1Ac at the cellular level, we developed a green fluorescent protein-based reporter system. The production of Cry1Ac was monitored in spo0A, sigE, and sigK mutants, and these mutants were able to express the Cry1Ac-green fluorescent protein fusion protein. In nonsporulating B. thuringiensis HD-73 cells, low-level expression of cry1Ac was also observed. Reverse transcription-PCR and Western blotting results confirmed that the cry1Ac promoter has low activity in nonsporulating B. thuringiensis cells. A beta-galactosidase assay demonstrated that the transcription of the cry1Ac gene during exponential and transition phases is positively regulated by Spo0A. Additional bioassay results indicated that spo0A and sigE mutants containing the cry1Ac-gfp fusion exhibited insecticidal activity against Plutella xylostella larvae.
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21
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Identification of the promoter in the intergenic region between orf1 and cry8Ea1 controlled by sigma H factor. Appl Environ Microbiol 2012; 78:4164-8. [PMID: 22504821 DOI: 10.1128/aem.00622-12] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus thuringiensis Cry8Ea toxin is specifically toxic to larvae of the Asian cockchafer, Holotrichia parallela. Here we investigated the mechanism of transcriptional regulation of the cry8Ea1 gene. Reverse transcription-PCR (RT-PCR) results indicated that cry8Ea1 and an upstream gene (orf1) were cotranscribed. Transcriptional fusions with the lacZ gene demonstrated that transcription of the cry8Ea1 gene started from two promoters: P(orf1), which is located upstream of the orf1 gene, and P(cry8E), located in the intergenic region mapping between orf1 and cry8Ea1. Of the known, similar orf1-cry operons, this is the first report of the existence of a promoter in the intergenic region between the orf1 and cry genes. The transcriptional activity of P(orf1) was found during sporulation in B. thuringiensis subsp. kurstaki HD-73 and was almost abolished in the sigE mutant, while the transcriptional activity of P(cry8E) was detected after the end of the exponential phase in HD-73 and was considerably lower in the sigH mutant. The transcription start sites generated by the two cry8Ea1 promoters were determined by the 5' -SMARTer rapid amplification of cDNA ends (RACE) method. The -35 and -10 regions of P(orf1) and P(cry8E) showed high sequence similarity with the σ(E) and σ(H) promoters, respectively. These results indicated that P(orf1) is controlled by the σ(E) factor and P(cry8E) by the σ(H) factor.
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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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Buasri W, Panbangred W. Large crystal toxin formation in chromosomally engineered Bacillus thuringiensis subsp. aizawai due to σE accumulation. Appl Environ Microbiol 2012; 78:1682-91. [PMID: 22267677 PMCID: PMC3298149 DOI: 10.1128/aem.06505-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 01/02/2012] [Indexed: 11/20/2022] Open
Abstract
Seven distinct Bacillus thuringiensis subsp. aizawai integrants were constructed that carried the chitinase (chiBlA) gene from B. licheniformis under the control of the cry11Aa promoter and terminator with and without p19 and p20 genes. The toxicity of B. thuringiensis subsp. aizawai integrants against second-instar Spodoptera litura larvae was increased 1.8- to 4.6-fold compared to that of the wild-type strain (BTA1). Surprisingly, the enhanced toxicity in some strains of B. thuringiensis subsp. aizawai integrants (BtaP19CS, BtaP19CSter, and BtaCAT) correlated with an increase in toxin formation. To investigate the role of these genes in toxin production, the expression profiles of the toxin genes, cry1Aa and chiBlA, as well as their transcriptional regulators (sigK and sigE), were analyzed by quantitative real-time RT-PCR (qPCR) from BTA1, BtaP19CS, and BtaCAT. Expression levels of cry1Aa in these two integrants increased about 2- to 3-fold compared to those of BTA1. The expression of the transcription factor sigK also was prolonged in the integrants compared to that of the wild type; however, sigE expression was unchanged. Western blot analysis of σ(E) and σ(K) showed the prolonged accumulation of σ(E) in the integrants compared to that of BTA1, resulting in the increased synthesis of pro-σ(K) up to T(17) after the onset of sporulation in both BtaP19CS and BtaCAT compared to that of T(13) in BTA1. The results from qPCR indicate clearly that the cry1Aa promoter activity was influenced most strongly by σ(E), whereas cry11Aa depended mostly on σ(K). These results on large-crystal toxin formation with enhanced toxicity should provide useful information for the generation of strains with improved insecticidal activity.
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Affiliation(s)
- Wasin Buasri
- Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand
- Center of Excellence for Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok, Thailand
| | - Watanalai Panbangred
- Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand
- Center of Excellence for Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok, Thailand
- Mahidol University and Osaka University Collaborative Research Center of Bioscience and Biotechnology (MU-OU: CRC), Faculty of Science, Mahidol University, Bangkok, Thailand
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Pérez-García G, Basurto-Ríos R, Ibarra JE. Potential effect of a putative sigma(H)-driven promoter on the over expression of the Cry1Ac toxin of Bacillus thuringiensis. J Invertebr Pathol 2010; 104:140-6. [PMID: 20223249 DOI: 10.1016/j.jip.2010.02.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Accepted: 02/25/2010] [Indexed: 11/16/2022]
Abstract
Sequence analysis of the upstream region of the cry1Ac gene in the HD-73 strain of B. thuringiensis showed a putative sigma(H)-like promoter. The potential regulating role of this sequence was tested by transforming an acrystaliferous mutant of the HD-73 strain with three different constructs: (1) a construct consisting of the sigma(H)-, sigma(E)- and sigma(K)-like promoters, the 0A box, and the cry1Ac coding sequence (EK0AH); (2) a derivative construct that lacked the sigma(H)-promoter (EK0A); and (3) a second derivative construct that lacked the sigma(H)-promoter and the 0A box (EK). Crystals from the recombinant and the wild-type (Bt HD-73) strains were measured by transmission electron microscopy. Statistically significant differences in crystal size were detected between all the transformed and the wild-type strains, with averages of 1.54, 1.31, 1.05, and 0.95microm for the EK0AH, EK0A, HD-73, and EK constructs, respectively. SDS-PAGE analyses of the EK0AH construct corroborated a higher expression level of the cry1Ac gene than that of the EK0A construct, as well as the lower expression of the EK construct. Interestingly, RT-PCR analyses indicated that the recombinant strain carrying the construct EK0AH started the transcription of the cry gene earlier than the Bt HD-73 strain, as observed when a kinetics study was carried out, which may explain the larger crystals and the higher expression of the construct with the putative sigma(H)-like promoter, along with the vector's high copy number.
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Affiliation(s)
- Germán Pérez-García
- Departamento de Biotecnología y Bioquímica, CINVESTAV-Irapuato, 36500 Irapuato, Mexico.
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Fedhila S, Daou N, Lereclus D, Nielsen-LeRoux C. Identification ofBacillus cereusinternalin and other candidate virulence genes specifically induced during oral infection in insects. Mol Microbiol 2006; 62:339-55. [PMID: 16978259 DOI: 10.1111/j.1365-2958.2006.05362.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Bacillus cereus is an opportunistic bacterium frequently associated with food-borne infections causing gastroenteritis. We developed an in vivo expression technology (IVET), with an insect host, for identification of the B. cereus genes specifically expressed during infection. This IVET-based approach uses site-specific recombinase TnpI to identify transient promoter activation. We constructed a genomic library of B. cereus ATCC14579 by cloning DNA fragments upstream from tnpI. The library was screened in vivo by oral infection of the insect Galleria mellonella. We selected 100 clones from dead larvae. Sequencing of the inserts followed by a second screen for specific in vivo induction led to the identification of 20 in vivo-induced genes (ivi genes). They belonged to several different functional classes: regulation, metabolism, DNA repair and replication, cell division, transport, virulence and adaptation. A strongly induced gene, ivi29, was further analysed. It encodes an internalin-like protein with four distinct domains: an N-terminal signal peptide for export, a NEAT domain thought to be involved in iron transport, a leucine-rich repeat domain that may interact with host cells, and a C-terminal SLH domain presumably binding the protein to the peptidoglycan. As suggested by a Fur box in the promoter, transcriptional analysis showed ivi29 expression to be repressed by iron, suggesting that expression was induced in vivo due to iron deprivation in the host. This iron-regulated, leucine-rich surface protein was designated IlsA. Disruption of ilsA reduced the virulence of the bacteria to the insect larvae indicating its role in the overall pathogenesis of B. cereus.
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Affiliation(s)
- Sinda Fedhila
- Unité Génétique Microbienne et Environnement, Institut National de la Recherche Agronomique, La Minière, 78285 Guyancourt cedex, France
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Hajaij-Ellouze M, Fedhila S, Lereclus D, Nielsen-LeRoux C. The enhancin-like metalloprotease from the Bacillus cereus group is regulated by the pleiotropic transcriptional activator PlcR but is not essential for larvicidal activity. FEMS Microbiol Lett 2006; 260:9-16. [PMID: 16790012 DOI: 10.1111/j.1574-6968.2006.00289.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bacillus cereus group bacteria produce virulence factors. Many of these are regulated by the pleiotropic transcriptional activator PlcR, which is implicated in insect virulence. In silico analysis of the B. cereus strain ATCC14579 genome showed an enhancin-like gene preceded by a typical PlcR binding sequence. The gene is predicted to encode a polypeptide showing 23-25% identity with enhancins from several baculoviruses and 31% with that of Yersinia pestis. Viral enhancin acts after oral infection and degrades the peritrophic matrix of various Lepidopteran larvae. To rule out a possible implication of Bacillus enhancin in insect virulence, we sequenced the enhancin gene from the Bacillus thuringiensis 407-crystal minus strain and investigated its gene regulation and larvicidal activity. A typical metalloprotease zinc-binding domain (HEIAH) was detected and the gene was named mpbE (metalloprotease bacillus enhancin). An mpbE'-lacZ transcriptional fusion demonstrated that mpbE belongs to the PlcR regulon. The mpbE mutant was fed to Galleria mellonella larvae, and no significant reduction in virulence was observed. However, this may not exclude MpbE from a role in pathogenesis.
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Affiliation(s)
- Myriam Hajaij-Ellouze
- Unité Génétique Microbienne et Environnement, I.N.R.A., La Minière, Guyancourt, France
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Bouillaut L, Ramarao N, Buisson C, Gilois N, Gohar M, Lereclus D, Nielsen-Leroux C. FlhA influences Bacillus thuringiensis PlcR-regulated gene transcription, protein production, and virulence. Appl Environ Microbiol 2006; 71:8903-10. [PMID: 16332888 PMCID: PMC1317475 DOI: 10.1128/aem.71.12.8903-8910.2005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus thuringiensis and Bacillus cereus are closely related. B. thuringiensis is well known for its entomopathogenic properties, principally due to the synthesis of plasmid-encoded crystal toxins. B. cereus appears to be an emerging opportunistic human pathogen. B. thuringiensis and B. cereus produce many putative virulence factors which are positively controlled by the pleiotropic transcriptional regulator PlcR. The inactivation of plcR decreases but does not abolish virulence, indicating that additional factors like flagella may contribute to pathogenicity. Therefore, we further analyzed a mutant (B. thuringiensis 407 Cry(-) DeltaflhA) previously described as being defective in flagellar apparatus assembly and in motility as well as in the production of hemolysin BL and phospholipases. A large picture of secreted proteins was obtained by two-dimensional electrophoresis analysis, which revealed that flagellar proteins are not secreted and that production of several virulence-associated factors is reduced in the flhA mutant. Moreover, we quantified the effect of FlhA on plcA and hblC gene transcription. The results show that the flhA mutation results in a significant reduction of plcA and hblC transcription. These results indicate that the transcription of several PlcR-regulated virulence factors is coordinated with the flagellar apparatus. Consistently, the flhA mutant also shows a strong decrease in cytotoxicity towards HeLa cells and in virulence against Galleria mellonella larvae following oral and intrahemocoelic inoculation. The decrease in virulence may be due to both a lack of flagella and a lower production of secreted factors. Hence, FlhA appears to be an essential virulence factor with a pleiotropic role.
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Affiliation(s)
- Laurent Bouillaut
- Unité Génétique Microbienne et Environnement, INRA, La Minière, 78285 Guyancourt Cedex, France
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Espinasse S, Gohar M, Lereclus D, Sanchis V. An extracytoplasmic-function sigma factor is involved in a pathway controlling beta-exotoxin I production in Bacillus thuringiensis subsp. thuringiensis strain 407-1. J Bacteriol 2004; 186:3108-16. [PMID: 15126472 PMCID: PMC400614 DOI: 10.1128/jb.186.10.3108-3116.2004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Beta-exotoxin I is an insecticidal nucleotide analogue secreted by various Bacillus thuringiensis strains. In this report, we describe the characterization and transcriptional analysis of a gene cluster, designated sigW-ecfX-ecfY, that is essential for beta-exotoxin I production in B. thuringiensis subsp. thuringiensis strain 407-1. In this strain, the disruption of the sigW cluster resulted in nontoxic culture supernatants. sigW encodes a protein of 177 residues that is 97 and 94% identical to two putative RNA polymerase extracytoplasmic-function-type sigma factors from Bacillus anthracis strain Ames and Bacillus cereus strain ATCC 14579, respectively. It is also 50, 30, and 26% identical to SigW from Clostridium perfringens and SigW and SigX from Bacillus subtilis, respectively. EcfX, encoded by the gene following sigW, significantly repressed the expression of sigW when both genes were overtranscribed, suggesting that it could be the anti-sigma factor of SigW. Following the loss of its curable cry plasmid, strain 407 became unable to synthesize crystal toxins, in contrast to the mutant strain 407-1(Cry-)(Pig+), which overproduced this molecule in the absence of this plasmid. Transcriptional analysis of sigW indicated that this gene was expressed during the stationary phase and only in the 407-1(Cry-)(Pig+) mutant. This suggests that in the wild type-407(Cry+) strain, beta-exotoxin I was produced from determinants located on a cry gene-bearing plasmid and that sigW is able to induce beta-exotoxin I production in B. thuringiensis in the absence of cry gene-bearing plasmids. Although the signal responsible for this activation is unknown, these results indicate that beta-exotoxin I production in B. thuringiensis can be restored or induced via an alternative pathway that requires sigW expression.
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Affiliation(s)
- Sylvain Espinasse
- Unité Génétique Microbienne et Environnement, INRA La Minière, 78285 Guyancourt, France
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Fedhila S, Gohar M, Slamti L, Nel P, Lereclus D. The Bacillus thuringiensis PlcR-regulated gene inhA2 is necessary, but not sufficient, for virulence. J Bacteriol 2003; 185:2820-5. [PMID: 12700261 PMCID: PMC154399 DOI: 10.1128/jb.185.9.2820-2825.2003] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously reported that Bacillus thuringiensis strain 407 Cry 32(-) secretes a zinc-requiring metalloprotease, InhA2, that is essential for virulence in orally infected insects. Analysis of the inhA2-lacZ transcriptional fusion showed that inhA2 expression is repressed in a PlcR(-) background. Using DNase I footprinting experiments, we demonstrated that PlcR activates inhA2 transcription directly by binding to a DNA sequence showing a one-residue mismatch with the previously reported PlcR box. It was previously reported that PlcR is essential for B. thuringiensis virulence in oral infection by contributing to the synergistic properties of the spores on the insecticidal activity of the Cry1C protein. We used complementation experiments to investigate whether the PlcR(-) phenotype was due to the absence of InhA2. The results indicated that overexpression of inhA2 in the (Delta)plcR strain did not restore the wild-type phenotype. However, virulence was fully restored in the (Delta)inhA2 complemented mutant. Thus, inhA2 is the first example of a PlcR-regulated gene found to be directly involved in virulence. However, it is not sufficient for pathogenicity when the other members of the PlcR regulon are lacking. This suggests that InhA2 may act in concert with other PlcR-regulated gene products to provide virulence.
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Affiliation(s)
- Sinda Fedhila
- Unité Génétique Microbienne et Environnement, Institut National de la Recherche Agronomique, La Minière, 78285 Guyancourt Cedex, France.
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Espinasse S, Gohar M, Lereclus D, Sanchis V. An ABC transporter from Bacillus thuringiensis is essential for beta-exotoxin I production. J Bacteriol 2002; 184:5848-54. [PMID: 12374817 PMCID: PMC135382 DOI: 10.1128/jb.184.21.5848-5854.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
beta-Exotoxin I is a nonspecific insecticidal metabolite secreted by some Bacillus thuringiensis strains. Several studies of B. thuringiensis strains that have lost the capacity to produce beta-exotoxin I have suggested that there is a strong correlation between high levels of beta-exotoxin I production and the ability to synthesize crystal proteins. In this study, we showed that a mutant strain, B. thuringiensis 407-1(Cry(-))(Pig(+)), with no crystal gene, produced considerable amounts of beta-exotoxin I together with a soluble brown melanin pigment. Therefore, beta-exotoxin I production can take place after a strain has lost the plasmids bearing the cry genes, which suggests that these curable plasmids probably contain determinants involved in the regulation of beta-exotoxin I production. Using a mini-Tn10 transposon, we constructed a library of strain 407-1(Cry(-))(Pig(+)) mutants. We screened for nonpigmented mutants with impaired beta-exotoxin I production and identified a genetic locus harboring two genes (berA and berB) essential for beta-exotoxin I production. The deduced amino acid sequence of the berA gene displayed significant similarity to the ATP-binding domains of the DRI (drug resistance and immunity) family of ATP-binding cassette (ABC) proteins involved in drug resistance and immunity to bacteriocins and lantibiotics. The berB gene encodes a protein with six putative transmembrane helices, which probably constitutes the integral membrane component of the transporter. The demonstration that berAB is required for beta-exotoxin I production and/or resistance in B. thuringiensis adds an adenine nucleotide analog to the wide range of substrates of the superfamily of ABC proteins. We suggest that berAB confers beta-exotoxin I immunity in B. thuringiensis, through active efflux of the molecule.
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Affiliation(s)
- Sylvain Espinasse
- Unité de Recherches de Lutte Biologique, INRA La Minière, 78285 Guyancourt, France
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31
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Slamti L, Lereclus D. A cell-cell signaling peptide activates the PlcR virulence regulon in bacteria of the Bacillus cereus group. EMBO J 2002; 21:4550-9. [PMID: 12198157 PMCID: PMC126190 DOI: 10.1093/emboj/cdf450] [Citation(s) in RCA: 223] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
PlcR is a pleiotropic regulator that activates the expression of genes encoding various virulence factors, such as phospholipases C, proteases and hemolysins, in Bacillus thuringiensis and Bacillus cereus. Here we show that the activation mechanism is under the control of a small peptide: PapR. The papR gene belongs to the PlcR regulon and is located 70 bp downstream from plcR. It encodes a 48-amino-acid peptide. Disruption of the papR gene abolished expression of the PlcR regulon, resulting in a large decrease in hemolysis and virulence in insect larvae. We demonstrated that the PapR polypeptide was secreted, then reimported via the oligopeptide permease Opp. Once inside the cell, a processed form of PapR, presumably a pentapeptide, activated the PlcR regulon by allowing PlcR to bind to its DNA target. This activating mechanism was found to be strain specific, with this specificity determined by the first residue of the penta peptide.
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Affiliation(s)
- Leyla Slamti
- Unité de Biochimie Microbienne, CNRS (URA2172), Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris cedex and Unité de Lutte Biologique, INRA, La Minière, 78285 Guyancourt cedex, France Corresponding author e-mail:
| | - Didier Lereclus
- Unité de Biochimie Microbienne, CNRS (URA2172), Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris cedex and Unité de Lutte Biologique, INRA, La Minière, 78285 Guyancourt cedex, France Corresponding author e-mail:
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32
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Fedhila S, Nel P, Lereclus D. The InhA2 metalloprotease of Bacillus thuringiensis strain 407 is required for pathogenicity in insects infected via the oral route. J Bacteriol 2002; 184:3296-304. [PMID: 12029046 PMCID: PMC135110 DOI: 10.1128/jb.184.12.3296-3304.2002] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The entomopathogenic bacterium Bacillus thuringiensis is known to secrete a zinc metalloprotease (InhA) that specifically cleaves antibacterial peptides produced by insect hosts. We identified a second copy of the inhA gene, named inhA2, in B. thuringiensis strain 407 Cry(-). The inhA2 gene encodes a putative polypeptide showing 66.2% overall identity with the InhA protein and harboring the zinc-binding domain (HEXXH), which is characteristic of the zinc-requiring metalloproteases. We used a transcriptional inhA2'-lacZ fusion to show that inhA2 expression is induced at the onset of the stationary phase and is overexpressed in a Spo0A minus background. The presence of a reverse Spo0A box in the promoter region of inhA2 suggests that Spo0A directly regulates the transcription of inhA2. To determine the role of the InhA and InhA2 metalloproteases in pathogenesis, we used allelic exchange to isolate single and double mutant strains for the two genes. Spores and vegetative cells of the mutant strains were as virulent as those of the parental strain in immunized Bombyx mori larvae infected by the intrahemocoelic route. Exponential phase cells of all the strains displayed the same in vitro potential for colonizing the vaccinated hemocoel. We investigated the synergistic effect of the mutant strain spores on the toxicity of Cry1C proteins against Galleria mellonella larvae infected via the oral pathway. The spores of DeltainhA2 mutant strain were ineffective in providing synergism whereas those of the DeltainhA mutant strain were not. These results indicate that the B. thuringiensis InhA2 zinc metalloprotease has a vital role in virulence when the host is infected via the oral route.
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Affiliation(s)
- Sinda Fedhila
- Unité de Recherches de Lutte Biologique, Institut National de la Recherche Agronomique, La Minière, 78285 Guyancourt Cedex, France.
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Komano T, Takabe S, Sakai H. Transcription of the insecticidal crystal protein genes of Bacillus thuringiensis. BIOTECHNOLOGY ANNUAL REVIEW 2000; 5:131-54. [PMID: 10874999 DOI: 10.1016/s1387-2656(00)05034-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Production of a large amount of insecticidal crystal proteins encoded on large plasmids is largely dependent upon the mother cell, Bacillus thuringiensis (B. thuringiensis, also Bt), specific transcription systems attributable to sporulation. In the middle stages of sporulation, cry4A is most actively transcribed from the promoter cry4A-P1. The proximal transcriptional start point of cry4A, which is under the control of the promoter P1, is used in Bacillus subtilis (B. subtilis) in the middle stage of sporulation. The nucleotide sequence that determines the cry4A-P1 promoter is homologous to the consensus sequence for the promoter of sigma E-specific genes in B. subtilis, and to those promoters of the insecticidal protein genes that are efficiently transcribed in vitro with the RNA polymerase E sigma 35 isolated from B. thuringiensis. The sigma factor sigma 35 of B. thuringiensis is highly homologous and functionally equivalent to sigma E of B. subtilis. These results suggest that the cry4A transcription from P1 is under the control of sigma E in B. subtilis, and under the control of sigma 35 in B. thuringiensis.
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Affiliation(s)
- T Komano
- Department of Genetic Engineering, Faculty of Biology-oriented Science and Technology, Kinki University, Wakayama, Japan.
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Lereclus D, Agaisse H, Grandvalet C, Salamitou S, Gominet M. Regulation of toxin and virulence gene transcription in Bacillus thuringiensis. Int J Med Microbiol 2000; 290:295-9. [PMID: 11111901 DOI: 10.1016/s1438-4221(00)80024-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022] Open
Abstract
Bacillus thuringiensis is a spore-forming bacterium well known for its insecticidal properties and its ability to produce a crystal inclusion during sporulation. The specific activity of B. thuringiensis against insect larvae is due to the crystal proteins (Cry proteins). Two different transcriptional mechanisms (dependent and independent of sporulation) are responsible for cry gene transcription during the stationary phase. In addition to these specific insecticidal toxins, B. thuringiensis produces potential virulence factors including haemolysins, degradative enzymes and enterotoxins. A pleiotropic regulator (PlcR) that activates the transcription of various genes encoding such extracellular proteins has been identified. Its expression at the onset of the stationary phase is dependent on the growth medium and is controlled by the transition state regulator, SpoOA.
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Affiliation(s)
- D Lereclus
- Unité de Biochimie Microbienne, Centre National de la Recherche Scientifique URA 2172, Institut Pasteur, Paris, France.
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35
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Sedlak M, Walter T, Aronson A. Regulation by overlapping promoters of the rate of synthesis and deposition into crystalline inclusions of Bacillus thuringiensis delta-endotoxins. J Bacteriol 2000; 182:734-41. [PMID: 10633108 PMCID: PMC94337 DOI: 10.1128/jb.182.3.734-741.2000] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During sporulation, Bacillus thuringiensis produces intracellular, crystalline inclusions comprised of a mixture of protoxins active on insect larvae. A major class of these protoxin genes, designated cry1, is transcribed from two overlapping promoters (BtI and BtII) utilizing RNA polymerase containing sporulation sigma factors sigma(E) and sigma(K), respectively. Fusions of these promoters to lacZ were constructed in order to analyze transcription patterns. Mutations within the -10 region of the BtII promoter (within the spacer region of the BtI promoter) which departed from the consensus -10 sequence for either sigma(E) or sigma(K) resulted in inactivation of transcription from BtII and a fivefold stimulation of transcription from BtI. In contrast, transcription from both promoters was inhibited with a change to the sigma(E) consensus. One of the "promoter-up" mutations was fused to the cry1Ac1 gene, and enhanced transcription was confirmed by Northern blotting. There was an increase in the accumulation of Cry1Ac antigen at early but not later times in sporulation in the mutant. This shift was due to the rapid turnover of much of the excessively accumulated protoxin at the early times as measured by pulse-chase labeling. As a result of the turnover and the inactivation of the BtII promoter, the mutant produced smaller inclusions which contained two- to threefold-less protoxin than inclusions from the wild type. Promoter overlap is a mechanism for modulating protoxin synthesis, thus ensuring the efficient packaging of these protoxins into inclusions.
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Affiliation(s)
- M Sedlak
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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36
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Sanchis V, Gohar M, Chaufaux J, Arantes O, Meier A, Agaisse H, Cayley J, Lereclus D. Development and field performance of a broad-spectrum nonviable asporogenic recombinant strain of Bacillus thuringiensis with greater potency and UV resistance. Appl Environ Microbiol 1999; 65:4032-9. [PMID: 10473413 PMCID: PMC99738 DOI: 10.1128/aem.65.9.4032-4039.1999] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The main problems with Bacillus thuringiensis products for pest control are their often narrow activity spectrum, high sensitivity to UV degradation, and low cost effectiveness (high potency required). We constructed a sporulation-deficient SigK(-) B. thuringiensis strain that expressed a chimeric cry1C/Ab gene, the product of which had high activity against various lepidopteran pests, including Spodoptera littoralis (Egyptian cotton leaf worm) and Spodoptera exigua (lesser [beet] armyworm), which are not readily controlled by other Cry delta-endotoxins. The SigK(-) host strain carried the cry1Ac gene, the product of which is highly active against the larvae of the major pests Ostrinia nubilalis (European corn borer) and Heliothis virescens (tobacco budworm). This new strain had greater potency and a broader activity spectrum than the parent strain. The crystals produced by the asporogenic strain remained encapsulated within the cells, which protected them from UV degradation. The cry1C/Ab gene was introduced into the B. thuringiensis host via a site-specific recombination vector so that unwanted DNA was eliminated. Therefore, the final construct contained no sequences of non-B. thuringiensis origin. As the recombinant strain is a mutant blocked at late sporulation, it does not produce viable spores and therefore cannot compete with wild-type B. thuringiensis strains in the environment. It is thus a very safe biopesticide. In field trials, this new recombinant strain protected cabbage and broccoli against a pest complex under natural infestation conditions.
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Affiliation(s)
- V Sanchis
- Unité de Biochimie Microbienne, Institut Pasteur, Centre National de Recherche Scientifique, Paris, France.
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Schnepf E, Crickmore N, Van Rie J, Lereclus D, Baum J, Feitelson J, Zeigler DR, Dean DH. Bacillus thuringiensis and its pesticidal crystal proteins. Microbiol Mol Biol Rev 1998; 62:775-806. [PMID: 9729609 PMCID: PMC98934 DOI: 10.1128/mmbr.62.3.775-806.1998] [Citation(s) in RCA: 1690] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism's pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.
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Affiliation(s)
- E Schnepf
- Mycogen Corp., San Diego, California 92121, USA
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38
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Zhang J, Schairer HU, Schnetter W, Lereclus D, Agaisse H. Bacillus popilliae cry18Aa operon is transcribed by sigmaE and sigmaK forms of RNA polymerase from a single initiation site. Nucleic Acids Res 1998; 26:1288-93. [PMID: 9469839 PMCID: PMC147395 DOI: 10.1093/nar/26.5.1288] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bacillus popilliae is an obligate pathogen for larvae of the insect family Scarabaeidae (Coleoptera). It forms parasporal crystals upon sporulation. The gene cry18Aa coding for the parasporal crystal protein and an upstream open reading frame, orf1, were previously isolated from B.popilliae. Here we report an analysis of cry18Aa transcription in Bacillus thuringiensis. The only transcriptional start site of cry18Aa was found 29 bp upstream of the open reading frame orf1, suggesting that orf1 and cry18Aa are transcribed as an operon. lacZ fusion to the cry18Aa promoter was used to follow the time-course of cry18Aa transcription in wild type B.thuringiensis and in various B.thuringiensis sporulation-deficient mutants (spo0A, sigE or sigK). In wild type B.thuringiensis, the cry18Aa promoter was activated 2 h after the end of exponential growth and the expression lasted to the late sporulation phase. The results of promoter activity in Spo+or Spo-backgrounds together with the results of primer extension experiments suggest that the transcription from this promoter can be driven by both sigmaE and sigmaK types of RNA polymerase at a single start site. The promoter region of cry18Aa operon fits the consensus sequences of both sigmaE and sigmaK dependent promoters of Bacillus.
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Affiliation(s)
- J Zhang
- Zentrum für Molekularbiologie Heidelberg and Zoologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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Sanchis V, Chaufaux J, Lereclus D. Amélioration biotechnologique de Bacillus thuringiensis: les enjeux et les risques. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0924-4204(97)86395-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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