Structure and cell envelope associations of flagellar basal complexes of Vibrio cholerae and Campylobacter fetus

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Abstract
To isolate intact flagella with basal complexes from V. cholerae, a rhamnolipid hemolysin from Pseudomonas aeruginosa was used to disrupt the cell envelope and flagellar sheath. The nonionic detergent, Triton X-100, provided similar results for C. fetus. Each of these basal complexes possessed, in addition to the 4 classical rings, concentric membrane rings (CMR) similar to those found in Aquaspirillum serpens. Through the use of stereo imaging (which allows structures to be visualized in 3 dimensions) of thin sections of cells which were sequentially treated with a number of envelope perturbants (i.e., EDTA, lysozyme, Triton X-100, rhamnolipid hemolysin and sodium dodecyl sulfate), one progressively exposed the component parts of the basal organelles in V. cholerae and C. fetus. Since the action of these envelope perturbants has been well documented, it may be possible to determine the associations of the exposed portions of the flagellar basal complex and the layer of the cell envelope in which they would normally reside. In V. cholerae and C. fetus, the L ring is embedded in the outer membrane and the P ring is associated with the peptidoglycan. The CMR are bracketed by the L and P rings and are sandwiched between the outer membrane and the peptidoglycan. Elements of the S and M rings appear to be associated with the plasma membrane.