PhoPQ is an upstream regulator of quorum sensing in small colony variant subpopulations of Pseudomonas aeruginosa

Deleting lasR and altering rhlI in Pseudomonas aeruginosa increases small-colony formation over time, and transcriptomes link this switching to PhoPQ regulation in small-colony variants.

• Why it matters: Hospital-associated P. aeruginosa adapts by forming small-colony subpopulations under stress, but how quorum-sensing mutations reshape that subpopulation via upstream regulators is unclear.
• What they did: The study tested quorum-sensing mutant backgrounds for time-dependent small-colony formation and performed transcriptome analyses comparing isogenic small versus large colony variants, focusing on PhoPQ and rhlR regulation.
• The result: In small-colony variants, unphosphorylated PhoP represses rhlR, and de-repression of quorum sensing is linked to virulence factor production and the small-colony phenotype in these mutant backgrounds.

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