FIG. 2.

S. mutans luxS complements a frameshift mutation in E. coli DH5α. E. coli DH5α was transformed with an E. coli-S. mutans shuttle vector containing an intact copy of the S. mutans luxS gene (pLuxSm). This strain was examined for AI-2 production using the luminescence-based AI-2 reporter assay. V. harveyi strain BB170 (sensor 1⁻, sensor 2⁺) served as a positive control, while E. coli DH5α served as a negative control. Luminescence is expressed as fold induction relative to the background values.