Isolation and characterization of nonspreading mutants of the gliding bacterium Cytophaga johnsonae.

Three approaches were taken to isolate a total of 153 nonspreading mutants derived from our laboratory strain of Cytophaga johnsonae, UW101, or from its auxotrophic derivative, UW10538. Characterization of 109 of these mutants led to their placement in five general categories: (i) motile, nonspreading (MNS) mutants whose cells are motile to various degrees but whose colonies fail to spread on agar gels under any conditions of incubation; (ii) conditional nonspreading (CNS) mutants with motile cells whose colonies require more moisture to spread on agar gels than do those of wild-type cells; (iii) filamentous conditional motility (FCM) mutants whose cells grow as nonmotile filaments or as motile cells with wild-type morphology, depending on conditions of incubation; (iv) short, tumbling, nonspreading (STN) mutants with short cells that tumble constantly; and (v) truly nonmotile (TNM) mutants whose cells never move and whose colonies never spread under any conditions tested. All TNM mutants exhibited a remarkable pleiotropy not seen in the other four classes of mutants: all were resistant to 39 phages to which wild-type cells are sensitive, and all were unable to digest chitin, which is digested by wild-type cells. The correlation between ability to move and phage sensitivity was strengthened further by showing that 150 additional TNM mutants derived from UW101 and 43 TNM mutants derived from 29 independent isolates of C. johnsonae were resistant to all phages to which their parents were sensitive. Furthermore, motile revertants of TNM mutants became phage sensitive, and temperature-sensitive mutants were motile and phage sensitive at 25 degrees C and nonmotile and phage resistant at 32 degrees C. Evidence supports the conclusion that any mutation rendering cells truly nonmotile invariably alters cell surface-associated properties such as phage sensitivity and chitin digestion merely as a consequence of changing a moving cell surface to a static surface.