CHARACTERIZATION OF TRANSLUCENT SEGMENTS OBSERVED IN AN SMBA MUTANT OF ESCHERICHIA-COLI

The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22 degrees C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrast microsco py at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22 degrees C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segmen t was observed in the wild-type cells in any of the media used. Electr on microscopic observation revealed that the translucent segments resu lted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane.