FIG 1.

(A) Confirmation of acid-sensitive phenotype. ISS1 transposon mutants that displayed an initial acid-sensitive phenotype were further verified by spotting of 5.0 μl from a 10-fold dilution series, with a starting optical density (A₆₀₀) of 2.0 made in 0.85% NaCl, onto THY agar plates at pH 5.5 or 7.0. Experiments were repeated at least three times, and the relevant areas of the representative plates are shown. UA159 is the wild-type strain, while 3S3F, 7A5G, and 61B11C are independent mutants. (B) Genetic organization of the SMU.745-SMU.747 region of S. mutans UA159. Locations of ISS1 insertion are shown with inverted triangles. The lollipop indicates putative transcription termination. Plasmids used for promoter analysis are indicated. (C) Plasmids used for construction of the deletion mutants and complementation are shown. Arrows indicate gene orientation.