Chern-Hsiung Lai

Ultrastructure of the flagellar basal body complex of Centipeda periodontii

The morphology and insertion of the flagellar basal body complex into the cell wall of Centipeda periodontii was studied by electron microscopy of both negatively and positively stained specimens. Freshly harvested cells were examined either after treatment with 0.2% sodium dodecyl sulfate (SDS) for 2 min and negatively stained with phosphotungstic acid, or after treatment according to standard electron microscopy procedures that included positive staining. Small numbers of flagella were dislocated from the cell body after treatment with SDS. The flagella demonstrated an unusual basal body structure: five rings were attached to a rod in a three-ringed (distal) and two-ringed (proximal) patterns; ring diameters produced a distinctive hourglass shape. The cell envelope was typical for gram-negative bacteria with a cytoplasmic membrane and an outer membrane separated by a peptidoglycan layer. Basal body length and cell wall width were in general agreement, approximately 29 nm. Cell wall width exceeded dimensions previously reported for Escherichia coli; this was attributed to an unusually thick peptidoglycan layer.