FIG 4.

Cellular distribution of the archaella in H. volcanii. (A) Transmission electron microscopy of the wild-type and ΔflaD H. volcanii cells in exponential growth phase. The four Roman numerals indicate the different archaellum distribution patterns that were observed for the wild-type (WT) cells as follows: I, archaella at one cell pole; II, elongated cell with archaella at both cell poles; II, constricting cell with archaella at both cell poles; IV, two cells, each with archaella at one pole. WT, wild type. Scale bar, 1 μm (B) Influence of FlaD on directional movement. The panels show results of assays of the motility of different H. volcanii strains on semisolid agar plates. (C) Intracellular distribution of FlaD-GFP in H. volcanii ΔflaD in the early log phase. The lower panels show closeup views of two different observed distribution patterns, and the numbers at the bottom represent percentages of the total population displaying the distribution (n, >1,000). Scale bars, 10 μm (upper panel) and 2 μm (lower panels). (D) Distribution of intracellular clusters. The cluster distances were plotted as a percentage of the total cell length. (E) Dependence of the number of observed intracellular FlaD foci on the cell length. The data were binned at 2-μm intervals. Error bars, SD. (F) Growth curve of a typical FlaD-GFP-expressing ΔflaD H. volcanii strain in CA media. Arrows indicate the time points at which the cells were analyzed as described in the panel G and H legends. (G) Intracellular distribution of GFP-CheW in H. volcanii ΔcheW in the growth phases as described in the panel F legend. The Roman numerals correspond to the time points indicated in the graph in panel F. (H) Distribution of the cells described in the panel G legend with the intracellular foci versus an equal level of cytoplasmic distribution. Orange, unipolar foci; red, bipolar foci; blue, signal evenly distributed in the cytoplasm. Error bars, SD. n, >1,000 per time point. Experiments were performed on at least 3 independent occasions.