FIG. 3.

PQS effect on denitrifying enzyme activities and NO₃⁻ respiratory chain. NAR (A), NIR (B), NOR (C), and NADH-dependent NAR (D) activities were measured in cells cultured for 6 h (mid-logarithmic phase). PQS was added at a final concentration of 50 μM for the culture medium or the reaction mixture. Bar 1, PAO1; bar 2, ΔpqsA mutant cultured without added PQS; bar 3, ΔpqsA mutant cultured with PQS; bar 4, PQS added to the reaction mixture with cell fractions collected from a ΔpqsA mutant cultured without added PQS. More than three independent experiments were carried out, and the data represented are means ± standard deviations of triplicate assays.