Honors College Thesis


A Genome-Wide, Phenotypic Screen for Genes Regulating Quorum Sensing in Pseudomonas aeruginosa Public Deposited

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  • The opportunistic pathogen Pseudomonas aeruginosa possesses two LuxR-LuxI type quorum-sensing systems that use diffusible acyl-homoserine lactone molecules to autoinduce and coordinate expression of multiple virulence factors. We conducted a highthroughput screen for mutants deficient in skim-milk proteolysis—a quorum-sensing dependent phenotype—using a nonredundant transposon-insertion library representing most nonessential genes in P. aeruginosa strain PA14. Of 75 mutants with decreased skim-milk proteolysis, a mutant with a transposon insertion in gidA grew sufficiently and displayed significant deficiencies in three other quorum-controlled phenotypes—LasA staphylolytic activity, pyocyanin production, and rhamnolipid production. These deficiencies were restored by complementation. Moreover, overexpression of gidA in PA14 wild-type cells led to a significant increase in pyocyanin production. The gidA gene, which has already been identified in other bacteria as a regulator of virulence, encodes an enzyme involved in tRNA modification that promotes codon-anticodon interaction. Thus, gidA may play an important role as a posttranscriptional super regulator of virulence, and additional investigation may show a new means to interfere with P. aeruginosa virulence.
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