FIGURE 7.

Potential mechanisms of stringent response-mediated CT production during anaerobic TMAO respiration in V. cholerae. Anaerobic TMAO respiration stimulates the production of ppGpp in V. cholerae. RelV probably plays a dominant role in ppGpp biosynthesis under this particular condition. Reactive oxygen species (ROS), specifically generated during anaerobic TMAO respiration (11) or pH increase due to the action of TMAO reductase (see “Discussion”), can be considered as contributing factors to the induction of stringent response. DksA protein in conjunction with its cofactor ppGpp is required for the CT production, and DksA/ppGpp inhibits the anaerobic growth of V. cholerae. CT production is only active when stringent response-mediated growth inhibition occurs.