A Novel Secreted Protein Toxin from the Insect Pathogenic Bacterium Xenorhabdus nematophila

• Published in: The Journal of biological chemistry Vol. 279; no. 15; pp. 14595 - 14601
• Main Authors: Brown, Susan E., Cao, Anh T., Hines, Eric R., Akhurst, Raymond J., East, Peter D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.04.2004; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Biological Assay; Blotting, Western; Cosmids; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Escherichia coli - metabolism; Galleria mellonella; Gene Library; Helicoverpa armigera; Insecta - microbiology; Larva - microbiology; Molecular Sequence Data; Photorhabdus - metabolism; Recombinant Proteins - chemistry; Software; Time Factors; Toxins, Biological - chemistry; Xenorhabdus - metabolism; Xenorhabdus nematophila
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M309859200

The bacterium Xenorhabdus nematophila is an insect pathogen that produces several proteins that enable it to kill insects. Screening of a cosmid library constructed from X. nematophila strain A24 identified a gene that encoded a novel protein that was toxic to insects. The 42-kDa protein encoded by the toxin gene was expressed and purified from a recombinant system, and was shown to kill the larvae of insects such as Galleria mellonella and Helicoverpa armigera when injected at doses of around 30–40 ng/g larvae. Sequencing and bioinformatic analysis suggested that the toxin was a novel protein, and that it was likely to be part of a genomic island involved in pathogenicity. When the native bacteria were grown under laboratory conditions, a soluble form of the 42-kDa toxin was secreted only by bacteria in the phase II state. Preliminary histological analysis of larvae injected with recombinant protein suggested that the toxin primarily acted on the midgut of the insect. Finally, some of the common strategies used by the bacterial pathogens of insects, animals, and plants are discussed.