title: The main virulence determinant of Yersinia entomophaga MH96 is a broad-host-range toxin complex active against insects.
abstract: Through transposon mutagenesis and DNA sequence analysis, the main disease determinant of the entomopathogenic bacterium Yersinia entomophaga MH96 was localized to an ~32-kb pathogenicity island (PAI) designated PAI(Ye₉₆). Residing within PAI(Ye₉₆) are seven open reading frames that encode an insecticidal toxin complex (TC), comprising not only the readily recognized toxin complex A (TCA), TCB, and TCC components but also two chitinase proteins that form a composite TC molecule. The central TC gene-associated region (~19 kb) of PAI(Ye₉₆) was deleted from the Y. entomophaga MH96 genome, and a subsequent bioassay of the ΔTC derivative toward Costelytra zealandica larvae showed it to be innocuous. Virulence of the ΔTC mutant strain could be restored by the introduction of a clone containing the entire PAI(Ye₉₆) TC gene region. As much as 0.5 mg of the TC is released per 100 ml of Luria-Bertani broth at 25°C, while at 30 or 37°C, no TC could be detected in the culture supernatant. Filter-sterilized culture supernatants derived from Y. entomophaga MH96, but not from the ΔTC strain grown at temperatures of 25°C or less, were able to cause mortality. The 50% lethal doses (LD₅₀s) of the TC toward diamondback moth Plutella xylostella and C. zealandica larvae were defined as 30 ng and 50 ng, respectively, at 5 days after ingestion. Histological analysis of the effect of the TC toward P. xylostella larva showed that within 48 h after ingestion of the TC, there was a general dissolution of the larval midgut.
authors.affiliation: BioControl and BioSecurity, AgResearch, Lincoln Research Centre, Private Bag 4749, Christchurch 8140, Canterbury, New Zealand. mark.hurst@agresearch.co.nz
authors.forename: Mark R H
authors.initials: MR
authors.lastname: Hurst
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Jones
authors.forename: Tan
authors.initials: T
authors.lastname: Binglin
authors.forename: Lincoln A
authors.initials: LA
authors.lastname: Harper
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Jackson
authors.forename: Travis R
authors.initials: TR
authors.lastname: Glare
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000633:toxicity*; D001517:Coleoptera / Q000187:drug effects*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D041981:Gastrointestinal Tract / Q000473:pathology; D017353:Gene Deletion; D005816:Genetic Complementation Test; D044404:Genomic Islands; D006651:Histocytochemistry; D007814:Larva / Q000187:drug effects; D007915:Lepidoptera / Q000187:drug effects*; D007928:Lethal Dose 50; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D014774:Virulence; D037521:Virulence Factors / Q000633:toxicity*; D015007:Yersinia / Q000472:pathogenicity*
chemical_list: D001427:Bacterial Toxins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D037521:Virulence Factors