FIG 4.

Schematic description of the cooperative-dormancy model (A) versus the unique-dormancy model (B). (A) It is possible that there is a single spectrum of dormant phenotypes with a network of different signals triggering entry and exit from this dormant phenotype (pale red and green arrows). This could happen through an interconnected system in which TA modules (red arrow) interact with the stringent response (blue arrow), which results in a distinctive dormant phenotype (black cells). Dormant cells may be resuscitated by resuscitation-promoting factor, nutrients (green arrow), the degradation of toxin modules, or other signals (orange) stimulating cells to restart growth. (B) It is also possible that there is only one growth phenotype and that, depending on the signal, cells switch by independent mechanisms to separate dormant phenotypes. TA modules (red arrow) could generate one distinctive kind of dormant cell, and these cells will resuscitate only when toxin modules are removed from the cell (green arrows). Growing cells could respond to environmental signals through the stringent response (blue arrow) to enter a distinct form of dormancy. These cells will resuscitate when the appropriate stimulus, for example, resuscitation-promoting factor, or nutrients (orange arrow) are present.