Extra cytoplasmic function σ factor activation

The bacterial cell envelope is essential for cell viability and is a target for numerous antibiotics and host immune defenses. Thus bacteria must sense and respond to damage to the cell envelope. Many bacteria utilize alternative sigma factors such as extracytoplasmic function (ECF) sigma factors to respond to cell envelope stress. Although ECF sigma factors are utilized by both Gram negative and Gram positive bacteria to respond to cell envelope stress, the mechanisms of sensing differ. In this review, we examine the events and proteins that are required for activation of two model extracytoplasmic function sigma factors, sigma(E) in E. coli and sigma(w) in B. subtilis.