Table 1.
Bacterial strains and plasmids used in this study.
Table 2.
PCR oligonucleotide primers used for amplification of pilT1 and pilT2.
Figure 1.
Axenic growth curve of B. bacteriovorus 109JA and pilT mutants.
Growth in PY medium over a 42 h period. Results shown are an average of 20 replicates repeated in triplicate. Error bars represent standard error.
Figure 2.
Effect of mutations in pilT genes on predation by B. bacteriovorus on E. coli.
The decrease in prey cell optical density was used to assess predator growth. Results shown are an average of 20 replicates repeated in triplicate. Controls included: HM Buffer alone, E. coli ML35 prey cells alone and the wild type strain 109JA. Error bars represent standard error.
Table 3.
Presence of type IV pili on the surface of cells as assessed by electron microscopy and immunofluorescence microscopy.
Figure 3.
Biofilms of E. coli CO1 were pre-formed for 48 h in 96-well microtiter plates. Predator cultures containing either B. bacteriovorus 109JA or a pilT mutant were added and the plates incubated for a further 24 h. Residual biofilm cells were stained with crystal violet and the optical density at 600 nm (OD600) determined (*p<0.005). To exclude secreted factors contributing to the decrease in remaining biofilm, a 0.45 µm filtrate of a B. bacteriovorus 109JA culture used as a control. The percent biofilm remaining relative to the 109JA filtrate is shown on the secondary axis. Data presented were an average of 12-wells per replicate repeated in triplicate. Statistical significance was measured using a 1-way ANOVA with a Bonferonni corrected post-hoc Students T-test, *p<0.005.
Figure 4.
Scanning electron microscopy of predation on pre-formed biofilms of E. coli.
(A) Biofilms of E. coli CO1 (arrows) were formed for 48 h on polyvinyl chloride plastic coverslips. Predator cultures (arrowheads) of (B) B. bacteriovorus 109JA, (C) ΔpilT1, (D) ΔpilT2 (E) ΔpilT1pilT2 were added for a further 24 h.