Fig. 1

SPI-1 T3SS-dependent secretion of SaEsxA and SaEsxB fusing with different secretion tags. SaEsxA and SaEsxB were fused with N-terminal secretion tags, and were expressed with cognate chaperones under PsicA promoter. 6 × his tag at C-terminus was used for detection (a). Secretion assays were conducted for SaEsxA (b) and SaEsxB (c) to identify the optimal secretion tag/chaperone pairs. And the secretion of SipA-SaEsxA (d) and SipA-SaEsxB (e) from S. Typhimurium strain ML21 and isogenic ΔinvA mutant was compared. For bacterial cell lysates, an equivalent of 200 μL bacterial culture was used for SDS-PAGE. And for “1× secretion”, an equivalent of 13 μL culture was used and exposure time of western blot extended to 1 min. For “secretion TCA”, secreted proteins were further 20-fold concentrated by TCA precipitation, and an equivalent of 400 μL culture was used