An increased level of alternative sigma factor RpoS partially suppresses drug hypersensitivity associated with inactivation of the multidrug resistance pump AcrAB in Escherichia coli.

Constitutive expression of stationary phase alternative sigma factor RpoS in Escherichia coli during the exponential phase was found to partially suppress drug sensitivity associated with an acrAB mutation that inactivates the major multidrug resistance pump, suggesting that Rpos might significantly contribute to multidrug resistance, underscoring yet another role for this important stress-related transcription factor.