Helical flagellation in Centipeda periodontii, a gram-negative, anaerobic bacillus from periodontitis lesions

The insertion pattern of flagellation of Centipeda periodontii was determined from electron micrographs of negatively stained cells treated with various detergents to remove their outer cell wall layer(s) selectively. The best results were obtained with 0.2% sodium dodecyl sulphate and a treatment time of 1-2 min. Detergent-treated cells displayed a unique helical pattern of flagellation which we designate as helicotrichous (Gk n. helix, helix + Gk n. thrix, hair). Flagella originated from an electron-dense region approximately 180 nm wide, which spiraled around the cell body. The length of the insertion path averaged 2.6 micron per 360 degrees turn; its periodicity was 2.5 micron. An average of 19 flagella were inserted per 1 micron length of the electron-dense region. The effects of cell division and branching on flagellation were also examined.