Figure 4.

(A) Indirect downregulation of the mexGHI-opmD operon by Hfq during CCR (e.g., in the presence of succinate). The red bar indicates negative post-transcriptional regulation by Hfq/Crc of phzM (Sonnleitner and Bläsi, 2014), leading to moderate expression of the mexGHI-opmD operon (indicated by lean arrows and writing). (B) Increased synthesis of the mexGHI-opmD operon after relief of CCR (e.g., in the presence of mannitol). Titration of Hfq/Crc by CrcZ results in an increased synthesis of PhzM and hence in elevated levels of 5-Me-PCA and pyocyanin, which in turn results in activation of SoxR followed by transcriptional upregulation of the mexGHI-opmD operon (indicated by bold arrows and writing; Dietrich et al., 2006; Sakhtah et al., 2016). 5-Methyl-PCA efflux through MexGHI-OpmD (Sakhtah et al., 2016) protects the cells from the reactive compound. CM, cytoplasmic membrane.