A bacterial binary toxin system that kills both insects and aquatic crustaceans: Photorhabdus insect-related toxins A and B

Abstract

Photorhabdus insect-related toxins A and B (PirA and PirB) were first recognized as insecticidal toxins from Photorhabdus luminescens. However, subsequent studies showed that their homologs from Vibrio parahaemolyticus also play critical roles in the pathogenesis of acute hepatopancreatic necrosis disease (AHPND) in shrimps. Based on the structural features of the PirA/PirB toxins, it was suggested that they might function in the same way as a Bacillus thuringiensis Cry pore-forming toxin. However, unlike Cry toxins, studies on the PirA/PirB toxins are still scarce, and their cytotoxic mechanism remains to be clarified. In this review, based on our studies of V. parahaemolyticus PirAvp/PirBvp, we summarize the current understanding of the gene locations, expression control, activation, and cytotoxic mechanism of this type of toxin. Given the important role these toxins play in aquatic disease and their potential use in pest control applications, we also suggest further topics for research. We hope the information presented here will be helpful for future PirA/PirB studies.

Analyses ofXenorhabdus griffiniaegenomes reveal two distinct sub-species that display intra-species variation due to prophages

“…To better understand the toxic potential of the X. griffiniae bacteria, we mined the HGB2511, ID10, Kalro and TH1 genomes for toxin-domain-containing loci. Using a list of known toxins found in other Xenorhabdus [19, 68] we identified homologs of genes encoding the known insecticidal toxins Mcf “makes caterpillars floppy” and PirAB in each of the strains [108–110], along with proteins homologous to the MARTX toxin family (Table 3). Similar to X. innexi HGB1681, the MARTX proteins in HGB2511, ID10, Kalro and TH1 each lack four of the A repeats at the N -terminus of the protein (A Δ3-7), leaving nine repeats compared to the 14 found in X. nematophila 19061, X. bovienii SS-2004 (Jollieti), and Vibrio species [68, 111] (Fig.…”