MICROBIOLOGY: New Host for Old Pathogen

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Science  22 Mar 2002:
Vol. 295, Issue 5563, pp. 2179d
DOI: 10.1126/science.295.5563.2179d

The free-living amoeba Dictyostelium discoideum grazes on bacteria. Pukatzki et al. have developed a variant system in which, as food for the amoebae, they substitute the opportunistic bacterial pathogen Pseudomonas aeruginosa, notorious for colonizing the lungs of cystic fibrosis patients. On bacterial lawns, amoebae can feed on avirulent mutants of P. aeruginosa; a mutation in the bacterial lasR gene, which encodes a transcriptional activator of quorum-sensing genes (a pathway that produces virulence factors only when the pathogen is present in high numbers), converts the bacteria into fodder for the amoebae. If the mutation is complemented, then virulence is restored, and the amoebae fall prey to the bacteria. Likewise, mutations in the type III secretion system for cytotoxin render the bacteria vulnerable to the amoebae. This system could offer a convenient model for investigating bacterial virulence mechanisms, not least because D. discoideum is haploid and genetically tractable and its genome is being sequenced. – CA

Proc. Natl. Acad. Sci. U.S.A. 99, 3159 (2002).

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