The Photorhabdus asymbiotica virulence cassettes deliver protein effectors directly into target eukaryotic cells.

Isabella Vlisidou,Joseph Rj Healey,Guowei Yang,Alexia Hapeshi,Katie Smart,Nicholas R Waterfield

doi:10.7554/elife.46259

Isabella Vlisidou, Joseph Rj Healey + Show 4 more

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https://doi.org/10.7554/elife.46259

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Abstract

Photorhabdus is a highly effective insect pathogen and symbiont of insecticidal nematodes. To exert its potent insecticidal effects, it elaborates a myriad of toxins and small molecule effectors. Among these, the Photorhabdus Virulence Cassettes (PVCs) represent an elegant self-contained delivery mechanism for diverse protein toxins. Importantly, these self-contained nanosyringes overcome host cell membrane barriers, and act independently, at a distance from the bacteria itself. In this study, we demonstrate that Pnf, a PVC needle complex associated toxin, is a Rho-GTPase, which acts via deamidation and transglutamination to disrupt the cytoskeleton. TEM and Western blots have shown a physical association between Pnf and its cognate PVC delivery mechanism. We demonstrate that for Pnf to exert its effect, translocation across the cell membrane is absolutely essential.

Highlights

Bacteria belonging to the Enterobacteriaceae genus Photorhabdus exist in a symbiotic partnership with entomopathogenic Heterorhabditis sp. nematodes
The PVCpnf operon belongs to class I, which has 16 structural genes and three translationally coupled gene blocks, and is of the type typically seen in non-Photorhabdus genera
An example of the method we have adopted is as follows; [Pa ATCC43949 PVCpnf], where Pa ATCC43949 is species and strain, in this case Photorhabdus asymbiotica strain ATCC43949 and PVCpnf is the specific operon within that genome with the suffix referring to one of the tightly linked effectors, in this case the pnf effector gene

Summary

Introduction

Bacteria belonging to the Enterobacteriaceae genus Photorhabdus exist in a symbiotic partnership with entomopathogenic Heterorhabditis sp. nematodes. Bacteria belonging to the Enterobacteriaceae genus Photorhabdus exist in a symbiotic partnership with entomopathogenic Heterorhabditis sp. Insect tissues are subsequently bio-converted into a dense soup of Photorhabdus bacteria, which provide a food source to support the replication of the nematode. As food resources are depleted Photorhabdus re-associates with infective juvenile nematodes, and together they emerge from the insect cadaver able to re-infect a new host (Ciche et al, 2008; Somvanshi et al, 2012). In addition to the normal insect life cycle, P. asymbiotica is the etiological agent of a serious human infection termed Photorhabdosis, which is associated with severe ulcerated skin lesions both at the initial infection foci and later at disseminated distal sites (Gerrard et al, 2004; Gerrard et al, 2006; Gerrard et al, 2003a; Gerrard et al, 2003b)

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