Flagella staining of P. vortex. Cells from cultures stained for flagella were viewed by transmission light microscopy. A. Cells swarming on MH agar (0.3% w/v) showing individual or bundles of flagella as dark threads. B. Cells swarming on MH agar (1.5% w/v). C. Non-motile cells from liquid culture lacking flagella. Scale bar (top right) is 3 μm.