FIG. 6.

Effect of Mg²⁺ concentration on luminescence. (A) Specific luminescence of V. fischeri strains ES114 (wild type), SLV16 (phoQ::mini-Tn5-ermR), JB22 (ES114 lacI^q-P_A1/34-luxC), and NL29 (SLV16 lacI^q-P_A1/34-luxC). (B) Specific luminescence of ES114 and SLV16 carrying the empty pVSV105 vector and SLV16 carrying pNL72, which contains the native phoQ allele. Both panels report data from cultures grown in FMM, which contains 55 mM magnesium (open bars), or FMM with low (0.03 mM) Mg²⁺ (gray bars). *, significant difference in luminescence for that strain grown in low-Mg²⁺ medium relative to normal FMM as determined with Student's t test (P ≤ 0.05).