Table 2. Concentration of PQS (μg/ml) and phz1 operon expression in an lasR mutant culture and a 1:1 lasR mutant: mvfR mutant culture.

	PQS, μg/ml	β-gal activity, MU*
lasR-	2.1 ± 0.1	63.6 ± 2.6
lasR- + mvfR-	5.2 ± 1.8	110.5 ± 4.3
Ratio†	5.0 ± 1.8	3.5 ± 0.2

Cultures were assayed at 8-hr sampling time, corresponding to OD₆₀₀ 4.3 to 4.5.

^*The lasR mutant carries a phzABC-lacZ fusion: Data correspond to averages of triplicates ± SD. MU, Miller units.

^†Ratios have been corrected by taking into account that the mixed culture contains 50% fewer lasR mutant cells than the lasR culture. mvfR mutant cells do not produce PQS.