FIG 5.

Proposed model of ODS. At low cell density, the ds operon is weakly expressed. When the cell density increases and host OA is present, the DS enzymes start to produce oxylipins. Subsequently, the oxylipins enter the cells through OdsT and bind OdsR, which in turn induces the ds operon. Induced DS enzymes cross the inner membrane through the Sec secretory pathway to reach the periplasm. Then, the enzymes cross the outer membrane via Xcp T2SS. This causes a sudden accumulation of extracellular DS enzymes and therefore of oxylipins, which further activates the ODS and induces the effector genes. The as-yet-undetermined parts of the model, i.e., the sec pathway and the transcriptional activator(s) of the effector genes, are marked with a question mark.