Fig. 3.
Colony morphology and piliation of T. thermophilus HB27 strains. A, the effects of the overexpression of various PilF proteins in T. thermophilus HB27. Strains containing a plasmid expressing the indicated PilF allele were incubated on 1.6% Thermus medium plates for 3 days at 70 °C under humid conditions. Scale bar represents 5 mm. B, precipitation of the overexpressed PilF proteins in T. thermophilus HB27. After a 6-h incubation at 70 °C and an initial A600 of 0.6, the cells were transferred to 2-ml tubes containing PBS buffer and subjected to gravity sedimentation at 4 °C for 1 day. C, images of T. thermophilus HB27 strains overexpressing the various PilF proteins. Cells from 2-day cultures on agar plates of the indicated strains were directly transferred to a grid and stained with 2% uranyl acetate for transmission electron microscopy. Approximately 20 cells of each strain were analyzed for piliation. Bar, 0.1 μm.