A. Hcp release assay. HA-tagged Hcp (HcpHA) release was assessed by separating cells (C) and cell-free culture supernatant (S) fractions from 109 wild-type (WT), ΔtssM cells or ΔtssM cells carrying the AHT-inducible FLAG-tagged tssM-borne plasmid (tssM+) treated (bulgecin) or not (NT) with bulgecin A prior to tssM gene induction. Proteins were separated by 12.5%-acrylamide SDS-PAGE and the periplasmic TolB protein (control for cell lysis), HcpHA and FLTssM were immunodetected using anti-TolB (middle panel), anti-HA (lower panel) and anti-FLAG (upper panel) antibodies. Molecular weight markers (in kDa) are indicated on the left. The experiment was performed in duplicate and a representative result is shown. 