Related Experiment Video
Updated: Aug 17, 2026
The Insect Galleria mellonella as a Powerful Infection Model to Investigate Bacterial Pathogenesis
Published on: December 11, 2012
A single Photorhabdus gene, makes caterpillars floppy (mcf), allows Escherichia coli to persist within and kill
P J Daborn1, N Waterfield, C P Silva
1Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom.
Abstract:
Photorhabdus luminescens, a bacterium with alternate pathogenic and symbiotic phases of its lifestyle, represents a source of novel genes associated with both virulence and symbiosis. This entomopathogen lives in a "symbiosis of pathogens" with nematodes that invade insects. Thus the bacteria are symbiotic with entomopathogenic nematodes but become pathogenic on release from the nematode into the insect blood system. Within the insect, the bacteria need to both avoid the peptide- and cellular- (hemocyte) mediated immune response and also to kill the host, which then acts as a reservoir for bacterial and nematode reproduction. However, the mechanisms whereby Photorhabdus evades the insect immune system and kills the host are unclear. Here we show that a single large Photorhabdus gene, makes caterpillars floppy (mcf), is sufficient to allow Esherichia coli both to persist within and kill an insect. The predicted high molecular weight Mcf toxin has little similarity to other known protein sequences but carries a BH3 domain and triggers apoptosis in both insect hemocytes and the midgut epithelium.
Insights
Photorhabdus luminescens bacteria use the makes caterpillars floppy (mcf) gene to evade insect immunity and cause disease. This single gene, when transferred to E. coli, enables it to persist in and kill insects by triggering apoptosis.
Area of Science:
- Microbiology
- Insect Pathology
- Molecular Biology
Background:
- Photorhabdus luminescens exhibits a dual lifestyle, acting symbiotically with nematodes and pathologically within insects.
- Understanding how P. luminescens evades insect immune responses and induces host mortality is crucial for identifying novel virulence factors.
- The bacterium's interaction with insect hemocytes and midgut epithelium highlights key targets for immune evasion and pathogenesis.
Purpose of the Study:
- To investigate the role of the Photorhabdus luminescens makes caterpillars floppy (mcf) gene in insect pathogenesis.
- To determine if the mcf gene alone is sufficient to confer virulence and persistence in a foreign bacterial host.
- To elucidate the mechanism by which the Mcf toxin affects insect cells.
Main Methods:
- Gene transfer of Photorhabdus luminescens mcf into Escherichia coli.
- Assessment of E. coli survival and pathogenicity within insect hosts.
- Analysis of Mcf toxin's effect on insect hemocytes and midgut epithelial cells, including apoptosis assays.
Main Results:
- A single gene, makes caterpillars floppy (mcf), from Photorhabdus luminescens, was sufficient to enable Escherichia coli to persist within and kill an insect.
- The Mcf toxin, a high molecular weight protein, shares little similarity with known proteins but contains a BH3 domain.
- Mcf toxin was shown to induce apoptosis in both insect hemocytes and the midgut epithelium.
Conclusions:
- The makes caterpillars floppy (mcf) gene is a potent virulence factor of Photorhabdus luminescens, capable of inducing apoptosis and host death.
- The Mcf toxin represents a novel class of insecticidal toxins with potential applications in pest control.
- This study identifies a key mechanism by which P. luminescens overcomes insect defenses and establishes infection.
Related Concept Videos
01:27Chemotaxis in E. coli
01:23Stringent Response in E. coli