Figure 6.

NO₂ accumulation and nitrite reductase activity obtained with strains PA14, PA14ΔpaiI, and PA14ΔpaiI(pME-paiI). To determine the NO₂ concentration in the supernatants (A,B) and the NO₂ reductase activity (C,D), the cultures were grown under the same conditions as described in the legend to Figure 4. Depicted is mean ± SD, n = 3. Statistical analysis was performed using the unpaired student t-test (www.graphpad.com). ^***p < 0.001, ^**p < 0.01, ^*p < 0.05. (E,F) PaiI levels detected by Northern-blot analyses in total RNA isolated from the samples collected at the indicated times. For strains PA14ΔpaiI and PA14ΔpaiI (pME4510-1) only total RNA isolated at time 0 and 5 h were loaded onto the gel. 5S RNA levels determined by Northern-blotting served as a loading control.