Fig. 5: Group I capsule-mediated T6SS shielding is a broad protection mechanism that can be horizontally-transferred.

a–c Horizontally acquired capsule biogenesis gene cluster confers protections to E. coli against T6SS attacks. a, b Capsule visualization and uronic acid quantification of the dog commensal E. coli strain Ec300. a CPS+ (Ec300; WT) and CPS− (Ec300ΔrfaH) E. coli bacteria were imaged after India Ink staining. Representative images are shown. Scale bar, 5 μm. b The production of uronic acid was quantified in Ec300, its CPS-minus mutant (ΔrfaH), and two laboratory reference E. coli strains as controls. c Encapsulated E. coli is protected from T6SS assaults by V. cholerae. WT (CPS+) and the capsule-minus (CPS−) Ec300 bacteria as well as two reference E. coli strains were cocultured with T6SS+ (WT; plain bars) or T6SS− (ΔvipA; stripped bars) V. cholerae. Their survival is indicated on the Y-axis. b, c Values are derived from three independent experiments and the bars represent the mean (±SD, as defined by the error bars). dl, detection limit, as indicated by the dashed line. Significant differences were determined using a two-sided Student’s t-test corrected for multiple comparisons. Only significant differences are indicated. ***p < 0.001. Source data underlying all panels are provided in the Source data file.