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Updated: Jun 21, 2026
Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster
Published on: May 13, 2015
Drosophila embryos as model systems for monitoring bacterial infection in real time
Isabella Vlisidou1, Andrea J Dowling, Iwan R Evans
1Department of Biology and Biochemistry, University of Bath, Bath, United Kingdom.
Abstract:
Drosophila embryos are well studied developmental microcosms that have been used extensively as models for early development and more recently wound repair. Here we extend this work by looking at embryos as model systems for following bacterial infection in real time. We examine the behaviour of injected pathogenic (Photorhabdus asymbiotica) and non-pathogenic (Escherichia coli) bacteria and their interaction with embryonic hemocytes using time-lapse confocal microscopy. We find that embryonic hemocytes both recognise and phagocytose injected wild type, non-pathogenic E. coli in a Dscam independent manner, proving that embryonic hemocytes are phagocytically competent. In contrast, injection of bacterial cells of the insect pathogen Photorhabdus leads to a rapid 'freezing' phenotype of the hemocytes associated with significant rearrangement of the actin cytoskeleton. This freezing phenotype can be phenocopied by either injection of the purified insecticidal toxin Makes Caterpillars Floppy 1 (Mcf1) or by recombinant E. coli expressing the mcf1 gene. Mcf1 mediated hemocyte freezing is shibire dependent, suggesting that endocytosis is required for Mcf1 toxicity and can be modulated by dominant negative or constitutively active Rac expression, suggesting early and unexpected effects of Mcf1 on the actin cytoskeleton. Together these data show how Drosophila embryos can be used to track bacterial infection in real time and how mutant analysis can be used to genetically dissect the effects of specific bacterial virulence factors.
Insights
Drosophila embryos model real-time bacterial infection. Embryonic hemocytes phagocytose E. coli but freeze upon Photorhabdus infection due to the Mcf1 toxin affecting actin.
Area of Science:
- Developmental Biology
- Immunology
- Microbiology
Background:
- Drosophila embryos serve as established models for development and wound repair.
- Their utility is extended here to investigate bacterial infections in real-time.
Purpose of the Study:
- To utilize Drosophila embryos as a model system for observing bacterial infections and hemocyte interactions dynamically.
- To investigate the mechanisms underlying hemocyte responses to pathogenic and non-pathogenic bacteria.
Main Methods:
- Time-lapse confocal microscopy was employed to observe bacterial behavior and hemocyte interactions within Drosophila embryos.
- Pathogenic (Photorhabdus asymbiotica) and non-pathogenic (Escherichia coli) bacteria were injected into embryos.
- The effects of the insecticidal toxin Makes Caterpillars Floppy 1 (Mcf1) and its genetic manipulation were analyzed.
Main Results:
- Embryonic hemocytes demonstrated phagocytic competence, recognizing and engulfing non-pathogenic E. coli independently of Dscam.
- Pathogenic Photorhabdus bacteria induced a rapid hemocyte 'freezing' phenotype, linked to actin cytoskeleton rearrangement.
- This freezing was mimicked by Mcf1 toxin or recombinant E. coli expressing mcf1, dependent on shibire and modulated by Rac expression.
Conclusions:
- Drosophila embryos provide a powerful system for real-time tracking of bacterial infections.
- Hemocyte responses to bacterial virulence factors, like Mcf1, involve rapid cytoskeletal changes and endocytosis.
- Mutant analysis in this system can dissect the genetic basis of bacterial virulence factor effects.
