Phage lysates are reservoirs of biologically active quorum sensing signals

PQS persists in a bioactive state in Pseudomonas aeruginosa phage lysates for at least one year, while 3OC12-HSL and C4-HSL are rapidly degraded.

• Why it matters: Phage lysates are commonly filtered and used without purification, so host metabolites may carry over; the consequences for quorum-sensing signaling have been unclear.
• What they did: The study tracked quorum-sensing molecule stability in lysates and showed PQS protection comes from association with outer membrane vesicles. It also tested lysate effects by measuring pyocyanin induction and mortality in a Galleria mellonella infection model.
• The result: PQS-containing lysates increased pyocyanin and mortality, implying lysates can transfer biologically active signals; importantly, PQS-free lysates also trigger PQS-system activation, separating phage-induced signaling from PQS carryover.

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