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| The fly, the amoeba, and the worm |
Robet Koch formulated in 1890 the Koch´s postulates as general guidelines that should be followed to identify pathogens causing diseases. One century later, Stanley Falkow established the molecular version of Koch's postulates to guide, this time, the identification of microbial genes encoding virulence factors. A key point of the molecular postulates is to test the virulence of the microorganism with the inactivated candidate virulence gene in an appropriate animal model. However, this is not always possible. Suitable animals models are lacking for many diseases such as brucellosis, typhoid and leprosy. And the models for tuberculosis and cholera do not reflect the biology of human infections. In addition, large scale analysis of virulence are costs prohibited due to the high number of animals that should be infected to get statistically significant results. And, last but not least, there are important ethical concerns on the use of vertebrate animals models (including mice and rats) for research. In the case of plant pathogens ethical concerns are not an issue, however the logistics behind a virulence experiment in plants represent a challenge (space, biosafety regulations, possibility of spreading in nature of genetically modified organisms,...).
To solve these issues, some years ago new models to test virulence were introduced: Drosophila melanogaster (the fruit-fly), Dyctiostelium discoideum (the social amoeba) and Caenorhabditis elegans (the soil nematode). With general skepticism, it was assumed that the same virulence factors important for virulence in humans/plants could play a role in the interplay with these surrogate hosts. Indeed, this has been case, and these three amigos (no offense for the actors, I like the movie) have made outstanding contributions to the microbial pathonegesis field.
To solve these issues, some years ago new models to test virulence were introduced: Drosophila melanogaster (the fruit-fly), Dyctiostelium discoideum (the social amoeba) and Caenorhabditis elegans (the soil nematode). With general skepticism, it was assumed that the same virulence factors important for virulence in humans/plants could play a role in the interplay with these surrogate hosts. Indeed, this has been case, and these three amigos (no offense for the actors, I like the movie) have made outstanding contributions to the microbial pathonegesis field.
