GEOMETRY OF THE FLAGELLAR MOTOR IN THE CYTOPLASMIC MEMBRANE OF SALMONELLA-TYPHIMURIUM AS DETERMINED BY STEREO-PHOTOGRAMMETRY OF QUICK-FREEZE DEEP-ETCH REPLICA IMAGES

The precise geometry of the flagellar basal structure anchored in the cytoplasmic membrane was determined by digital stereo-photogrammetry o f the images captured by quick-freeze deep-etch replica electron micro scopy. In order to examine the structure on the periplasmic side of th e membrane, we analyzed the MS ring complexes of Salmonella typhimuriu m overproduced in the cytoplasmic membrane of Escherichia coli. The ro d, the S ring, and the shoulder of the M ring were exposed to the peri plasm. On the cytoplasmic side of the membrane, small bumps correspond ing to the cytoplasmic rod were discernible. We also examined the inta ct inner surface of the cells of polyhook mutant which was prepared by a new protocol and found the bell-shaped structure extending from the membrane towards the cytoplasm. It was identified as the C ring, sinc e it was located at the base of the polyhook. Various dimensions of th e MS ring complex and the C ring projecting from the membrane were det ermined by digital stereo-photogrammetry, and a three-dimensional mode l of the total basal structure is presented. (C) 1996 Academic Press L imited