Drosophila as a model host for Pseudomonas aeruginosa infection

Using the fruit fly Drosophila melanogaster as model host, we have identifi ed mutants of the bacterium Pseudomonas aeruginosa with reduced virulence. Strikingly, all strains strongly impaired in fly killing also lacked twitch ing motility; most such strains had a mutation in pilGHIJKL chpABCDE, a gen e cluster known to be required for twitching motility and potentially encod ing a signal transduction system. The pil chp genes appear to control the e xpression of additional virulence factors, however, since the mild-type fly -killing phenotype of a subset of mutants isolated on the basis of their co mpact colony morphology indicated that twitching motility itself was not re quired for full virulence in the fly.