Bacterial defenses against natural antibiotics promote collateral resilience to clinical antibiotics

To characterize the defense mechanisms P. aeruginosa has evolved in response to its most toxic phenazine, pyocyanin, we performed a genome-wide transposon sequencing (TnSeq) screen in which the mutant library was exposed to PYO under carbon starvation in order to maximize PYO toxicity, and genes for which transposon mutants were significantly enriched or depleted were identified. Overall design: Assessment of transposon mutant frequency per gene in a pooled library of approximately 145,000 random Tn5 transposon insertion mutants, following exposure to 100 µM pyocyanin for 26 hours in the absence of a carbon source, or to the same conditions without pyocyanin. The experiment was performed with two biological replicates.