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Pacheco S, Gómez I, Peláez-Aguilar AE, Verduzco-Rosas LA, García-Suárez R, do Nascimento NA, Rivera-Nájera LY, Cantón PE, Soberón M, Bravo A. Structural changes upon membrane insertion of the insecticidal pore-forming toxins produced by Bacillus thuringiensis. FRONTIERS IN INSECT SCIENCE 2023; 3:1188891. [PMID: 38469496 PMCID: PMC10926538 DOI: 10.3389/finsc.2023.1188891] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Accepted: 04/04/2023] [Indexed: 03/13/2024]
Abstract
Different Bacillus thuringiensis (Bt) strains produce a broad variety of pore-forming toxins (PFTs) that show toxicity against insects and other invertebrates. Some of these insecticidal PFT proteins have been used successfully worldwide to control diverse insect crop pests. There are several studies focused on describing the mechanism of action of these toxins that have helped to improve their performance and to cope with the resistance evolved by different insects against some of these proteins. However, crucial information that is still missing is the structure of pores formed by some of these PFTs, such as the three-domain crystal (Cry) proteins, which are the most commercially used Bt toxins in the biological control of insect pests. In recent years, progress has been made on the identification of the structural changes that certain Bt insecticidal PFT proteins undergo upon membrane insertion. In this review, we describe the models that have been proposed for the membrane insertion of Cry toxins. We also review the recently published structures of the vegetative insecticidal proteins (Vips; e.g. Vip3) and the insecticidal toxin complex (Tc) in the membrane-inserted state. Although different Bt PFTs show different primary sequences, there are some similarities in the three-dimensional structures of Vips and Cry proteins. In addition, all PFTs described here must undergo major structural rearrangements to pass from a soluble form to a membrane-inserted state. It is proposed that, despite their structural differences, all PFTs undergo major structural rearrangements producing an extended α-helix, which plays a fundamental role in perforating their target membrane, resulting in the formation of the membrane pore required for their insecticidal activity.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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2
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Hickey A, Pardo LM, Reen FJ, McGlacken GP. Pyrones Identified as LuxR Signal Molecules in Photorhabdus and Their Synthetic Analogues Can Alter Multicellular Phenotypic Behavior of Bacillus atropheaus. ACS OMEGA 2021; 6:33141-33148. [PMID: 34901665 PMCID: PMC8655920 DOI: 10.1021/acsomega.1c05508] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
Individual bacteria communicate by the release and interpretation of small molecules, a phenomenon known as quorum sensing (QS). We hypothesized that QS compounds extruded by Photorhabdus could be interpreted by Bacillus-a form of interspecies communication. We interrogate the structure-activity relationship within the recently discovered pyrone QS network and reveal the exquisite structural features required for targeted phenotypic behavior. The interruption of QS is an exciting, nonbiocidal approach to tackling infection, and understanding its nuances can only be achieved by studies such as this.
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Affiliation(s)
- Aobha Hickey
- School
of Chemistry, Analytical and Biological Chemistry Research
Facility, School of Microbiology, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork T12 YN60, Ireland
| | - Leticia M. Pardo
- School
of Chemistry, Analytical and Biological Chemistry Research
Facility, School of Microbiology, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork T12 YN60, Ireland
| | - F. Jerry Reen
- School
of Chemistry, Analytical and Biological Chemistry Research
Facility, School of Microbiology, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork T12 YN60, Ireland
| | - Gerard P. McGlacken
- School
of Chemistry, Analytical and Biological Chemistry Research
Facility, School of Microbiology, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork T12 YN60, Ireland
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Dutta TK, Veeresh A, Mathur C, Phani V, Mandal A, Sagar D, Nebapure SM. The induced knockdown of GmCAD receptor protein encoding gene in Galleria mellonella decreased the insect susceptibility to a Photorhabdus akhurstii oral toxin. Virulence 2021; 12:2957-2971. [PMID: 34882066 PMCID: PMC8667893 DOI: 10.1080/21505594.2021.2006996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 10/12/2021] [Accepted: 11/11/2021] [Indexed: 12/02/2022] Open
Abstract
Photorhabdus bacteria secrete a repertoire of protein toxins that can kill the host insect. Among them, toxin complex (Tc) proteins have gained significant attention due to their wider conservation across the different bacterial genera. In our laboratory, a C-terminal domain of TcaB protein was characterized from P. akhurstii bacterium that conferred the potent oral insecticidal effect on Galleria mellonella. However, the role of insect gut receptors in the TcaB intoxication process was yet to be investigated. In the current study, we examined the transcription of candidate midgut receptors in TcaB-infected larvae and subsequently cloned a cadherin-like gene, GmCAD, from G. mellonella. GmCAD was highly transcribed in the fourth-instar larval stage and specifically in the midgut tissues. Our ligand blot and binding ELISA assays indicated that TcaB binds to the truncated peptides from the GmCAD transmembrane-proximal region with greater affinity than that from the transmembrane-distal region. Oral administration of bacterially expressed GmCAD dsRNA in G. mellonella severely attenuated the expression of target mRNA, which in turn alleviated the negative effect of TcaB on insect survival (TcaB-induced mortality in CAD dsRNA pretreated larvae reduced by 72-83% compared to control), implying the association of GmCAD in the TcaB intoxication process. Present findings form a basis of future research related to the insect gut receptor interactions with Photorhabdus toxins.
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Affiliation(s)
- Tushar K. Dutta
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Arudhimath Veeresh
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Chetna Mathur
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Victor Phani
- Department of Agricultural Entomology, College of Agriculture, Uttar Banga Krishi Viswavidyalaya, Dakshin Dinajpur, India
| | - Abhishek Mandal
- Division of Agricultural Chemicals, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Doddachowdappa Sagar
- Division of Entomology, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Suresh M. Nebapure
- Division of Entomology, ICAR-Indian Agricultural Research Institute, New Delhi, India
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Pacheco S, Gómez I, Chiñas M, Sánchez J, Soberón M, Bravo A. Whole Genome Sequencing Analysis of Bacillus thuringiensis GR007 Reveals Multiple Pesticidal Protein Genes. Front Microbiol 2021; 12:758314. [PMID: 34795652 PMCID: PMC8594373 DOI: 10.3389/fmicb.2021.758314] [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] [Received: 08/13/2021] [Accepted: 10/05/2021] [Indexed: 11/24/2022] Open
Abstract
Bacillus thuringiensis (Bt) are soil ubiquitous bacteria. They produce a great variability of insecticidal proteins, where certain of these toxins are used worldwide for pest control. Through their adaptation to diverse ecosystems, certain Bt strains have acquired genetic mobile elements by horizontal transfer, harboring genes that encode for different virulent factors and pesticidal proteins (PP). Genomic characterization of Bt strains provides a valuable source of PP with potential biotechnological applications for pest control. In this work, we have sequenced the complete genome of the bacterium Bt GR007 strain that is toxic to Spodoptera frugiperda and Manduca sexta larvae. Four replicons (one circular chromosome and three megaplasmids) were identified. The two largest megaplasmids (pGR340 and pGR157) contain multiple genes that codify for pesticidal proteins: 10 cry genes (cry1Ab, cry1Bb, cry1Da, cry1Fb, cry1Hb, cry1Id, cry1Ja, cry1Ka, cry1Nb, and cry2Ad), two vip genes (vip3Af and vip3Ag), two binary toxin genes (vpa2Ac and vpb1Ca), five genes that codify for insecticidal toxin components (Tc’s), and a truncated cry1Bd-like gene. In addition, genes that codify for several virulent factors were also found in this strain. Proteomic analysis of the parasporal crystals of GR007 revealed that they are composed of eight Cry proteins. Further cloning of these genes for their individual expression in Bt acrystalliferous strain, by means of their own intrinsic promoter showed expression of seven Cry proteins. These proteins display differential toxicity against M. sexta and S. frugiperda larvae, where Cry1Bb showed to be the most active protein against S. frugiperda larvae and Cry1Ka the most active protein against M. sexta larvae.
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Affiliation(s)
- Sabino Pacheco
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Isabel Gómez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Marcos Chiñas
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Jorge Sánchez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
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Identification of Diverse Toxin Complex Clusters and an eCIS Variant in Serratia proteamaculans Pathovars of the New Zealand Grass Grub ( Costelytra Giveni) and Manuka Beetle ( Pyronota Spp.) Larvae. Microbiol Spectr 2021; 9:e0112321. [PMID: 34668742 PMCID: PMC8528098 DOI: 10.1128/spectrum.01123-21] [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: 12/01/2022] Open
Abstract
The grass grub endemic to New Zealand, Costelytra giveni (Coleoptera: Scarabaeidae), and the manuka beetle, Pyronota festiva and P. setosa (Coleoptera: Scarabaeidae), are prevalent pest species. Through assessment of bacterial strains isolated from diseased cadavers of these insect species, 19 insect-active Serratia proteamaculans variants and a single Serratia entomophila strain were isolated. When independently bioassayed, these isolates differed in host range, the rate of disease progression, and 12-day mortality rates, which ranged from 60 to 100% of the challenged larvae. A Pyronota spp.-derived S. proteamaculans isolate caused a transient disease phenotype in challenged C. giveni larvae, whereby larvae appeared diseased before recovering to a healthy state. Genome sequence analysis revealed that all but two of the sequenced isolates contained a variant of the S. entomophila amber-disease-associated plasmid, pADAP. Each isolate also encoded one of seven distinct members of the toxin complex (Tc) family of insect-active toxins, five of which are newly described, or a member of the extracellular contractile injection (eCIS) machine family, with a new AfpX variant designated SpF. Targeted mutagenesis of each of the predicted Tc- or eCIS-encoding regions abolished or attenuated pathogenicity. Host-range testing showed that several of the S. proteamaculans Tc-encoding isolates affected both Pyronota and C. giveni species, with other isolates specific for either Pyronota spp. or C. giveni. The isolation of several distinct host-specific pathotypes of Serratia spp. may reflect pathogen-host speciation. IMPORTANCE New pathotypes of the insect pathogen Serratia, each with differing virulence attributes and host specificity toward larvae of the New Zealand manuka beetle and grass grub, have been identified. All of the Serratia proteamaculans isolates contained one of seven different insect-active toxin clusters or one of three eCIS variants. The diversity of these Serratia-encoded virulence clusters, resulting in differences in larval disease progression and host specificity in endemic scarab larvae, suggests speciation of these pathogens with their insect hosts. The differing virulence properties of these Serratia species may affect their potential infectivity and distribution among the insect populations. Based on their differing geographic isolation and pathotypes, several of these Serratia isolates, including the manuka beetle-active isolates, are likely to be more effective biopesticides in specific environments or could be used in combination for greater effect.
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Roderer D, Raunser S. Tc Toxin Complexes: Assembly, Membrane Permeation, and Protein Translocation. Annu Rev Microbiol 2019; 73:247-265. [DOI: 10.1146/annurev-micro-102215-095531] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tc toxin complexes are virulence factors of many bacteria, including insect and human pathogens. Tc toxins are composed of three subunits that act together to perforate the host membrane, similar to a syringe, and translocate toxic enzymes into the host cell. The reactions of the toxic enzymes lead to deterioration and ultimately death of the cell. We review recent high-resolution structural and functional data that explain the mechanism of action of this type of bacterial toxin at an unprecedented level of molecular detail. We focus on the steps that are necessary for toxin activation and membrane permeation. This is where the largest conformational transitions appear. Furthermore, we compare the architecture and function of Tc toxins with those of anthrax toxin and vertebrate teneurin.
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Affiliation(s)
- Daniel Roderer
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany;,
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany;,
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Ruan L, Crickmore N, Peng D, Sun M. Are nematodes a missing link in the confounded ecology of the entomopathogen Bacillus thuringiensis? Trends Microbiol 2015; 23:341-6. [DOI: 10.1016/j.tim.2015.02.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Revised: 01/29/2015] [Accepted: 02/25/2015] [Indexed: 01/23/2023]
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Blackburn MB, Martin PAW, Kuhar D, Farrar RR, Gundersen-Rindal DE. Crystalliferous Bacillus cereus group bacteria from a Maryland hardwood forest are dominated by psychrotolerant strains. Microbiologyopen 2014; 3:578-84. [PMID: 24985699 PMCID: PMC4287184 DOI: 10.1002/mbo3.189] [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] [Received: 02/21/2014] [Revised: 05/09/2014] [Accepted: 05/26/2014] [Indexed: 11/17/2022] Open
Abstract
Crystal-forming bacteria of the Bacillus cereus group were isolated from soil samples collected at different elevations within a mixed hardwood forest in central Maryland, and their phylogenetic relationships determined by multilocus sequence analysis. The vast majority of isolates obtained were associated with two phylogenetic groups known to be psychrotolerant, with very few isolates representing phylogenetic groups more typically associated with Bacillus thuringiensis. Isolates from the psychrotolerant groups were found to grow on solid media at 7°C. Isolates of 11 highly related, novel sequence types (STs) from the psychrotolerant group that includes Bacillus weihenstephanensis were generally found at higher elevations, and were not associated with soils near streams. Isolates of two related STs from the second psychrotolerant group were nearly always found at the bottoms of ravines near streams, in areas abundant in earthworm castings.
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Affiliation(s)
- Michael B Blackburn
- Invasive Insect Biocontrol and Behavior Laboratory, USDA/ARS, Beltsville, Maryland, 20705
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Castagnola A, Stock SP. Common Virulence Factors and Tissue Targets of Entomopathogenic Bacteria for Biological Control of Lepidopteran Pests. INSECTS 2014; 5:139-66. [PMID: 24634779 PMCID: PMC3952272 DOI: 10.3390/insects5010139] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 12/13/2013] [Accepted: 12/17/2013] [Indexed: 01/13/2023]
Abstract
This review focuses on common insecticidal virulence factors from entomopathogenic bacteria with special emphasis on two insect pathogenic bacteria Photorhabdus (Proteobacteria: Enterobacteriaceae) and Bacillus (Firmicutes: Bacillaceae). Insect pathogenic bacteria of diverse taxonomic groups and phylogenetic origin have been shown to have striking similarities in the virulence factors they produce. It has been suggested that the detection of phage elements surrounding toxin genes, horizontal and lateral gene transfer events, and plasmid shuffling occurrences may be some of the reasons that virulence factor genes have so many analogs throughout the bacterial kingdom. Comparison of virulence factors of Photorhabdus, and Bacillus, two bacteria with dissimilar life styles opens the possibility of re-examining newly discovered toxins for novel tissue targets. For example, nematodes residing in the hemolymph may release bacteria with virulence factors targeting neurons or neuromuscular junctions. The first section of this review focuses on toxins and their context in agriculture. The second describes the mode of action of toxins from common entomopathogens and the third draws comparisons between Gram positive and Gram negative bacteria. The fourth section reviews the implications of the nervous system in biocontrol.
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Affiliation(s)
- Anaïs Castagnola
- Center for Insect Science, University of Arizona, 1007 E. Lowell Street, Tucson, AZ 85721, USA; E-Mail:
| | - S. Patricia Stock
- Department of Entomology, University of Arizona, 1140 E. South Campus Dr., Tucson, AZ 85721, USA
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Phylogenetic distribution of phenotypic traits in Bacillus thuringiensis determined by multilocus sequence analysis. PLoS One 2013; 8:e66061. [PMID: 23762464 PMCID: PMC3677866 DOI: 10.1371/journal.pone.0066061] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 05/03/2013] [Indexed: 01/24/2023] Open
Abstract
Diverse isolates from a world-wide collection of Bacillus thuringiensis were classified based on phenotypic profiles resulting from six biochemical tests; production of amylase (T), lecithinase (L), urease (U), acid from sucrose (S) and salicin (A), and the hydrolysis of esculin (E). Eighty two isolates representing the 15 most common phenotypic profiles were subjected to phylogenetic analysis by multilocus sequence typing; these were found to be distributed among 19 sequence types, 8 of which were novel. Approximately 70% of the isolates belonged to sequence types corresponding to the classical B. thuringiensis varieties kurstaki (20 isolates), finitimus (15 isolates), morrisoni (11 isolates) and israelensis (11 isolates). Generally, there was little apparent correlation between phenotypic traits and phylogenetic position, and phenotypic variation was often substantial within a sequence type. Isolates of the sequence type corresponding to kurstaki displayed the greatest apparent phenotypic variation with 6 of the 15 phenotypic profiles represented. Despite the phenotypic variation often observed within a given sequence type, certain phenotypes appeared highly correlated with particular sequence types. Isolates with the phenotypic profiles TLUAE and LSAE were found to be exclusively associated with sequence types associated with varieties kurstaki and finitimus, respectively, and 7 of 8 TS isolates were found to be associated with the morrisoni sequence type. Our results suggest that the B. thuringiensis varieties israelensis and kurstaki represent the most abundant varieties of Bt in soil.
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11
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Genome sequence of Paenibacillus alvei DSM 29, a secondary invader during European foulbrood outbreaks. J Bacteriol 2013; 194:6365. [PMID: 23105091 DOI: 10.1128/jb.01698-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paenibacillus alvei is known as a secondary invader during European foulbrood of honeybees. Here, we announce the 6.83-Mb draft genome sequence of P. alvei type strain DSM 29. Putative genes encoding an antimicrobial peptide, a binary toxin, a mosquitocidal toxin, alveolysin, and different polyketides and nonribosomal peptides were identified.
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Kupferschmied P, Maurhofer M, Keel C. Promise for plant pest control: root-associated pseudomonads with insecticidal activities. FRONTIERS IN PLANT SCIENCE 2013; 4:287. [PMID: 23914197 PMCID: PMC3728486 DOI: 10.3389/fpls.2013.00287] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 07/12/2013] [Indexed: 05/20/2023]
Abstract
Insects are an important and probably the most challenging pest to control in agriculture, in particular when they feed on belowground parts of plants. The application of synthetic pesticides is problematic owing to side effects on the environment, concerns for public health and the rapid development of resistance. Entomopathogenic bacteria, notably Bacillus thuringiensis and Photorhabdus/Xenorhabdus species, are promising alternatives to chemical insecticides, for they are able to efficiently kill insects and are considered to be environmentally sound and harmless to mammals. However, they have the handicap of showing limited environmental persistence or of depending on a nematode vector for insect infection. Intriguingly, certain strains of plant root-colonizing Pseudomonas bacteria display insect pathogenicity and thus could be formulated to extend the present range of bioinsecticides for protection of plants against root-feeding insects. These entomopathogenic pseudomonads belong to a group of plant-beneficial rhizobacteria that have the remarkable ability to suppress soil-borne plant pathogens, promote plant growth, and induce systemic plant defenses. Here we review for the first time the current knowledge about the occurrence and the molecular basis of insecticidal activity in pseudomonads with an emphasis on plant-beneficial and prominent pathogenic species. We discuss how this fascinating Pseudomonas trait may be exploited for novel root-based approaches to insect control in an integrated pest management framework.
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Affiliation(s)
- Peter Kupferschmied
- Department of Fundamental Microbiology, University of LausanneLausanne, Switzerland
| | - Monika Maurhofer
- Plant Pathology, Institute of Integrative Biology, Swiss Federal Institute of Technology ZurichZurich, Switzerland
| | - Christoph Keel
- Department of Fundamental Microbiology, University of LausanneLausanne, Switzerland
- *Correspondence: Christoph Keel, Department of Fundamental Microbiology, University of Lausanne, Biophore Building, CH-1015 Lausanne, Switzerland e-mail:
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Marshall SDG, Hares MC, Jones SA, Harper LA, Vernon JR, Harland DP, Jackson TA, Hurst MRH. Histopathological effects of the Yen-Tc toxin complex from Yersinia entomophaga MH96 (Enterobacteriaceae) on the Costelytra zealandica (Coleoptera: Scarabaeidae) larval midgut. Appl Environ Microbiol 2012; 78:4835-47. [PMID: 22544254 PMCID: PMC3416359 DOI: 10.1128/aem.00431-12] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Accepted: 04/21/2012] [Indexed: 12/11/2022] Open
Abstract
Yersinia entomophaga MH96, which was originally isolated from the New Zealand grass grub, Costelytra zealandica, produces an orally active proteinaceous toxin complex (Yen-Tc), and this toxin is responsible for mortality in a range of insect species, mainly within the Coleoptera and Lepidoptera. The genes encoding Yen-Tc are members of the toxin complex (Tc) family, with orthologs identified in several other bacterial species. As the mechanism of Yen-Tc activity remains unknown, a histopathological examination of C. zealandica larvae was undertaken in conjunction with cultured cells to identify the effects of Yen-Tc and to distinguish the contributions that its individual subunit components make upon intoxication. A progressive series of events that led to the deterioration of the midgut epithelium was observed. Additionally, experiments using a cell culture assay system were carried out to determine the cellular effects of intoxication on cells after topical application and the transient expression of Yen-Tc and its individual components. While observations were broadly consistent with those previously reported for other Tc family members, some differences were noted. In particular, the distinct stepwise disintegration of the midgut shared features associated with both apoptosis and necrotic programmed cell death pathways. Second, we observed, for the first time, a contribution of toxicity from two chitinases associated with the Yen-Tc complex. Our findings were suggestive of the activities encoded within the subunit components of Yen-Tc targeting different sites along putative programmed cell death pathways. Given the observed broad host range for Yen-Tc, these targeted loci are likely to be widely shared among insects.
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Affiliation(s)
- Sean D G Marshall
- AgResearch, Innovative Farm Systems, Lincoln Research Centre, Christchurch, New Zealand.
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Nielsen-LeRoux C, Gaudriault S, Ramarao N, Lereclus D, Givaudan A. How the insect pathogen bacteria Bacillus thuringiensis and Xenorhabdus/Photorhabdus occupy their hosts. Curr Opin Microbiol 2012; 15:220-31. [PMID: 22633889 DOI: 10.1016/j.mib.2012.04.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/26/2012] [Accepted: 04/27/2012] [Indexed: 10/28/2022]
Abstract
Insects are the largest group of animals on earth. Like mammals, virus, fungi, bacteria and parasites infect them. Several tissue barriers and defense mechanisms are common for vertebrates and invertebrates. Therefore some insects, notably the fly Drosophila and the caterpillar Galleria mellonella, have been used as models to study host-pathogen interactions for several insect and mammal pathogens. They are excellent tools to identify pathogen determinants and host tissue cell responses. We focus here on the comparison of effectors used by two different groups of bacterial insect pathogens to accomplish the infection process in their lepidopteran larval host: Bacillus thuringiensis and the nematode-associated bacteria, Photorhabdus and Xenorhabdus. The comparison reveals similarities in function and expression profiles for some genes, which suggest that such factors are conserved during evolution in order to attack the tissue encountered during the infection process.
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Affiliation(s)
- Christina Nielsen-LeRoux
- INRA, UMR1319, Micalis, Génétique microbienne et Environnement, La Minière, F-78280 Guyancourt, France.
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