FIGURE 6.

Regulation model. The regulatory behaviors between LuxO, Qrr sRNAs, AphA, and OpaR were described previously in V. parahaemolyticus and closely related V. harveyi (Henke and Bassler, 2004; Tu et al., 2010; Rutherford et al., 2011; Sun et al., 2012; Zhang et al., 2012). AphA and OpaR are the two master QS regulators that operate at low cell density (LCD) and high cell density (HCD), respectively. The regulatory protein ToxR, which is expressed at LCD, coordinates with QS to repress T6SS1 expression from LCD to physiological HCD, resulting in high expression of T6SS1 at the mid-logarithmic growth phase.