FtsK acts upstream of FtsWI and is required for constriction initiation. (A) Representative phase-contrast images of strains during depletion of FtsK_C or FtsK_FL in either WT or ftsW**I* backgrounds. Cells were grown in the presence of 0.3% xylose (top row, ftsK induced) or 0.2% glucose (bottom row, FtsK or FtsK_C depleted) with images taken at 6 and 20 h after depletion. FtsK_C depletion, EG2996. FtsK_FL depletion in WT, EG3332. FtsK_FL depletion in ftsW**I*, EG3333. (B) Spot dilutions of strains with xylose-inducible ftsK expression in the WT or ftsW**I* background, in the absence or presence of native ftsK. Plates contain either 0.2% glucose (−Inducer) or 0.3% xylose (+Inducer). Row 1, EG3299. Row 2, EG3300. Row 3, EG3332. Row 4, EG3333. (C) Growth curves of strains dependent on xylose for ftsK expression (same as A). Solid lines indicate growth in the presence of 0.3% xylose. Dashed lines indicate growth in the presence of 0.2% glucose. FtsK_C depletion, EG2996. FtsK_FL depletion in WT, EG3332. FtsK_FL depletion in ftsW**I*, EG3333. Points are the mean of three technical replicates at that timepoint, error bars are SEM. Shown is a representative replicate of a biological triplicate.