Summary: Mutants of the gliding bacterium that are incapable of movement are called truly nonmotile (TNM) to distinguish them from other mutants that are motile but produce nonspreading colonies. All TNM mutants are pleiotropic, being nonmotile, unable to digest chitin, resistant to all phages that infect wild-type cells, nonadherent and having less hydrophobic surfaces than do wild-type cells. In this study, we tested the idea that the TNM pleiotropy is the result of blocking cell surface movement, rather than of loss or alteration of a specific cell surface component. Motility of wild-type cells was blocked by addition of chemicals, and treated cells were compared with untreated cells for their ability to adhere to spheroidal hydroxyapatite (SHA) beads and to adsorb phages, two characteristics used as an index of the TNM pleiotropy. All the chemicals tested that blocked motility also reduced phage adsorption and adherence to SHA to approximately the same extent seen with TNM mutants. The chemicals tested (carbonyl cyanide -chlorophenylhydrazone, cyanide, azide and photoactivated eosin Y and rose bengal) were sufficiently different from each other to reduce the possibility that each chemical inhibited phage adsorption and cell adherence by similar secondary effects, independent of their effects on motility. It was also shown that the pleiotropy of TNM mutants is not caused by their inability to maintain a membrane potential. The results are compatible with the conclusion that the TNM pleiotropy is manifested whenever cell movement is stopped, whether by mutation or by use of chemical inhibitors, and they are inconsistent with the idea that all TNM mutants are pleiotropic because they all carry a lesion in the same gene that codes for expression of surface components required for all characteristics affected. The reason that stopping motility influences several seemingly unrelated properties is not known but is probably related to adaptations required for the organism to interact with its environment through a cell surface covered with a slime that is normally kept in motion by components of the machinery of gliding motility.


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