Fig. 8.

Model for the consequences and cellular adaptive responses at various stages of SRP depletion in bacteria. A, Immediate cellular responses to SRP depletion (<7 generations), which primarily involves the heat shock response (magenta), down-regulation of TCA cycle and the respiratory chain (cyan), coupled with compromised pmf which likely leads to down-regulation of chemotaxis/motility and reduced expression of pmf-dependent transporters. B, Cellular stress responses and proteome changes at late stages of SRP depletion (≥9 generations), including: reduced levels of TCA cycle and respiratory chain components (cyan) coupled with severe dissipation of the pmf, which leads to activation of ArcB/A signaling (brown) and induction of the phage shock response (purple); a second spike of cytoplasmic chaperones and protease induction (magenta); reduced levels of transporters (orange and yellow); impaired localization of periplasmic chaperones that leads to envelope stress and the induction of DegP and DegQ (dark blue); defects in chromosome segregation and cell division that leads to filamentous morphology (coral).