Effect of the T6SS on motility. (A) Representative images of swimming motility of C. freundii CF74, CF74ΔT6SS, CF74ΔclpV, CF74Δvgr, and CF74Δhcp-2 and their complemented mutants [CF74ΔclpV(pBAD24-clpV), CF74Δhcp-2(pBAD24-hcp-2), and CF74Δvgr(pBAD24-vgr)]. Cells were inoculated with a toothpick from an overnight LB agar plate onto a swim plate (tryptone broth plus 0.3% agar) and photographed after 16 h of incubation at 30°C. The complemented mutants were induced with swim plates with 0.2% arabinose in the medium. (B to E) Quantification of the inhibition of the swimming motility halo by C. freundii CF74 mutants in swim plates. Statistical significance between the wild-type strain and mutants (CF74ΔT6SS, CF74ΔclpV, CF74Δvgr, and CF74Δhcp-2) was determined by a Mann-Whitney U test. *, P < 0.05; **, P < 0.01. pclpV, CF74ΔclpV(pBAD24-clpV); phcp-2, CF74Δhcp-2(pBAD24-hcp-2); pvgr, CF74Δvgr(pBAD24-vgr). The error bars indicate 1 standard deviation.