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Predictions based on a general model of surface components involved in gliding motility of Cytophaga johnsonae along with characteristics of previously isolated nonspreading mutants of C. johnsonae led us to suspect that isolation of such mutants could be accomplished by selecting for nonadherent or nonhydrophobic mutants. Accordingly, conditions were devised to select for mutants that failed to attach to cheesecloth suspended in growth media and for mutants that failed to adhere to n-hexadecane droplets. Populations of cells obtained from both selection procedures were screened for mutants producing nonspreading colonies. Both techniques resulted in enrichment for nonspreading mutants that were classified by previously established criteria as MNS (motile nonspreading), CNS (conditional nonspreading) or TNM (truly nonmotile). When assayed for adherence and hydrophobicity, all TNM mutants were nonadherent and nonhydrophobic, compared with wild-type cells. Most mutants of the other two classes were unchanged with respect to these properties. Results from subjecting cells of four other strains of gliding bacteria to selection by the same procedures indicate that the methods will be broadly applicable for isolating nonspreading mutants of gliding bacteria. Abbreviations: EC, enriched cytophaga medium; PB, phosphate buffer (5 mM, pH 7-1); AI, adhesion index; HI, hydrophobicity index ; CNS, conditional nonspreading mutants; MNS, motile nonspreading mutants; TNM, truly nonmotile mutants. 0001-2132 0 1985 SGM

Two strains of bacteria that produce slender appendages (pseudostalks) from their lateral surfaces were studied using the electron microscope. The pseudostalks were shown to be extensions of the cytoplasm and peripheral membranes of the cell proper. Both strains of bacteria produce holdfasts at the poles of the cells by the means of which attachment can take place. The pseudostalks are not involved in the attachment of cells. No specialized intracytoplasmic structures are present at the point of juncture of pseudostalk and cell. A discussion of the possible functions of the pseudostalks, based on the electron microscope findings, is presented.

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