Fig. 2.

Intoxication by Ssp6 causes inhibition of bacterial growth. a Growth in liquid LB media of E. coli MG1655 carrying empty vector control (VC, pBAD18-Kn) or plasmids directing the expression of Ssp6 fused with an N-terminal OmpA signal peptide (sp-Ssp6), either alone or with Sip6. To induce gene expression, 0.2% l-arabinose was added as indicated. To remove induction, the cells were washed and resuspended in fresh LB only (‘recovered’) at the ‘wash’ timepoint; control cells were resuspended in fresh LB + 0.2% l-arabinose. Points show mean +/− SEM (n = 3 biological replicates). b Example images showing Ssp6-mediated growth inhibition as observed by time-lapse fluorescence microscopy. A Ssp6-susceptible target strain of S. marcescens Db10, Δssp6Δsip6 expressing cytoplasmic GFP (green), was co-cultured with wild type (WT) or mutant (Δssp6 or ΔtssE) attacker strains expressing cytoplasmic mCherry (red) for 3 h. Scale bar 2 μm. c Quantification of time-lapse experiments. The total number of attacker cells and total number of target cells in at least ten microcolonies per experiment was counted at t = 0 h and 3 h and used to calculate fold increase in attacker and target cell numbers during the co-culture. Bars show mean +/− SEM, with individual data points superimposed (n = 3 independent experiments). Source data are provided as a Source Data file.