Figure 2.

Loss of DsbA1 and DsbA2 Disrupts the Function of the Type VI Secretion Machinery

(A) Immunoblot detection of Hcp1 and Ssp2 in the cellular and secreted fractions of wild-type (WT) or mutant (ΔtssE, ΔdsbA1, ΔdsbA2, and ΔdsbA1ΔdsbA2) strains of S. marcescens Db10. The ΔtssE mutant represents a T6SS-inactive control.

(B) Representative fluorescent microscopy images of the ΔdsbA1ΔdsbA2 mutant and the parental strain (WT) each expressing the TssB-mCherry reporter fusion together with uniform cytoplasmic GFP. From left to right: DIC image, mCherry channel (TssB-mCherry), and a false-colored merge of TssB-mCherry (red) with GFP (green).

(C–F) Recovery of target organisms E. coli MC4100 (C), P. fluorescens (D), Db10 Δssp4Δsip4 (E), or Db10 Δrhs2ΔrhsI2 (F), following co-culture with wild-type or mutant strains of S. marcescens Db10 as attackers. The Δssp4Δsip4 and Δrhs2ΔrhsI2 target strains are non-immune mutants of S. marcescens Db10 sensitive to Ssp4 and Rhs2, respectively.

(G) Recovery of P. fluorescens following co-culture with wild-type or mutant strains of S. marcescens Db10 carrying either the vector control (+VC, pSUPROM) or plasmids directing the expression of DsbA1 (+DsbA1, pSC1506) or DsbA2 (+DsbA2, pSC1507) in trans.

For (C)–(G), individual data points overlaid with mean ± SEM (n = 4) are shown, except (F) where n = 5.