FIG 4.

Twitching motility of cells of the T. thermophilus HB27 wild type (A), the pilF::kat insertion mutant (B), and the ΔpilF deletion mutant (C). The cells were inoculated on minimal medium containing 1% BSA and cultivated for 72 h at 64°C under a water-saturated atmosphere. Agar and cells were stained with Coomassie blue. The cells and the Coomassie dye were removed, and the twitching zone corresponding to the noncolored agar region was determined. The pictures were inverted. Experiments were done in triplicate and gave identical results. Bars = 0.5 cm.