A population of *Pseudomonas aeruginosa* expresses an efflux pump conferring resistance to a beta-lactam antibiotic. Which event most likely allows the bacteria to thrive, despite increasing antibiotic concentration?

💡 Explanation

A mutation enhancing efflux pump activity allows the bacteria to thrive because it directly increases the rate at which the antibiotic is expelled, therefore decreasing its intracellular concentration. This provides a selective advantage under antibiotic pressure, rather than other defensive mechanisms.

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