GENOME OF AN "INSECTICIDAL" BACTERIUM DECODED
New approaches for the fight against insects and microbes
The genome of Photorhabdus luminescens, an insect-pathogenic bacterium living in symbiosis with a nematode (a worm), has just been fully sequenced by a team working at the Institut Pasteur (associated with the CNRS, the French National Scientific Research Centre). Their analysis, published in Nature Biotechnology (E. Duchaud et al., November 2003), was carried out in collaboration with INRA-Université de Montpellier II, other teams from the CNRS and from the Institut Pasteur, and the Company Bayer CropScience. It reveals a whole variety of genes coding for entomopathogenic toxins, which may be of use in the fight against insect pests. Moreover, the bacterium carries a large number of genes coding for the biosynthesis of antibiotics and fungicides, which are potential sources of spin-offs for the treatment of infectious diseases.
The teams, co-ordinated by Frank Kunst and Philippe Glaser (Institut Pasteur-CNRS), heads of the Genomics of Microbial Pathogens Laboratory at the Institut Pasteur, have sequenced and analysed the Photorhabdus luminescens genome, a circular chromosome containing a total of 4839 protein-coding genes.
The Photorhabdus luminescens bacterium, first classified by a team headed by Noël Boemare (INRA-Unversité), lives in the digestive tract of a nematode worm. When the worm attacks insect larvae, it makes small lesions which allow the bacterium to penetrate into the haemolymph of the insect. Then it secretes a large set of virulence factors, which rapidly lead to the death of the victim. Photorhabdus luminescens is thus capable of destroying a large variety of insects, carried by its vector.
It is therefore not astonishing that the researchers have identified the genes of toxins capable of killing a wide range of insects. However, it should be emphasized that no bacterial genome sequenced to date had revealed so many entomopathogenic toxin genes. Moreover, the researchers have verified experimentally the toxicity of some of these proteins, which have proved lethal to mosquitoes, among others. These discoveries are therefore all the more interesting for research concerning the fight against insects that are harmful to agriculture or human health.
The bioconversion of the body of the victim by the bacterial enzymes allows the bacterium to multiply as the worm reproduces, and to colonize the nematode before it leaves the body of the insect. The Photorhabdus luminescens bacterium also has to defend the body of the insect against other competing bacteria. For this purpose, the bacterium secretes substances to destroy other bacteria or fungi. The researchers have in fact identified a whole range of genes coding for the biosynthesis of antibiotics and fungicides. They may help in the development of new resources in the fight against infectious diseases.
Therefore, Photorhabdus luminescens offers, in the light of its genome, new approaches for the fight against microbes and insects.
The researchers also discovered numerous genes that will make it possible to reach a better understanding of the symbiosis between this bacterium and its nematode host. Such knowledge may become useful for employing this "tandem" in the biological control of insects.
This project was partially
funded by the "Après-séquençage des génomes"
(Post-sequencing of Genome) grant from the French Ministry of the Economy, Finance
- "The Photorhabdus
luminescens genome reveals a biotechnological weapon to fight microbes and insect
pests", Nature Biotechnology, November 2003.
Eric Duchaud (1), Christophe Rusniok (1), Lionel Frangeul (2), Carmen Buchrieser (1), Alain Givaudan (5), Séad Taourit (1), Stéphanie Bocs (6), Caroline Boursaux-Eude (2), Michael Chandler (7), Jean-François Charles (3), Elie Dassa (4), Richard Derose (8), Sylviane Derzelle (3), Georges Freyssinet (8), Sophie Gaudriault (5), Claudine Médigue (6), Anne Lanois (5), Kerrie Powell (9), Patricia Siguier (7), Rachel Vincent (5), Vincent Wingate (9), Mohamed Zouine (1), Philippe Glaser (1), Noël Boemare (5), Antoine Danchin (3) et Frank Kunst (1)
1. Laboratoire de Génomique
des Microorganismes Pathogènes (Genomics of Microbial Pathogens Laboratory),
Institut Pasteur, Paris
2. Genopole, Plate-Forme Intégration et Analyse génomiques (Genome Analysis and Integration Platform), Institut Pasteur, Paris
3. Unité de Génétique des Génomes Bactériens (Genetics of Bacterial Genomes Unit), Institut Pasteur, Paris
4. Unité de Programmation Moléculaire et Toxicologie Génétique (Molecular Programming and Genetic Toxicology Unit), Institut Pasteur, Paris
5. Laboratoire EMIP (Microbial Ecology and Host-Pathogen Interaction Laboratory), Université Montpellier II, INRA (UMR 1133), Montpellier
6. Atelier de Génomique Comparative (Comparative Genomics Unit), Génoscope/CNRS-UMR 80 30, Evry
7. Laboratoire de Microbiologie et de Génétique Moléculaire (Microbiology and Molecular Genetics Laboratory), CNRS, Toulouse
8. Bayer CropScience, Evry
9. Bayer CropScience, NC 277709, USA
- Frank Kunst :
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- Noël Boemare, INRA:
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