Figure 1.

Schematic representation of the two types of QS systems involving AIP in Gram-positive bacteria. The steps common to the two systems are on the right. The middle panel represents the extracellular-acting AIP-dependent mechanism. The left panel represents the intracellular-acting AIP-dependent mechanism. This study will focus on QS systems relying on the peptides indicated in the purple box. Black arrows represent a positive effect. Black blunt lines represent a negative effect. Purple lines indicate the circuit followed by the AIP. RR, response regulator.