rqlH and rqlI are co-expressed and are not regulated by oxygen levels.

(A) A schematic of the rqlHI operon and surrounding genes, with the three primer sets used in (B) indicated. (B) RNA was isolated from F11 WT bacteria growing aerobically, and cDNA was made and used as template in PCRs using the three primer sets indicated in (A). Each primer set was used with a sample lacking reverse transcriptase (RT) as a control. Ladder band sizes are indicated at left. (C) F11 WT bacteria were grown either aerobically or microaerobically, RNA was isolated, and cDNA was made. Several primer sets were used in qRT-PCR reactions to measure levels of frdA, rqlH, rqlI, and rqlHI transcripts under the two oxygen conditions. All expression values were normalized to 16S rRNA. Bars indicate mean values ± SEM from three or more independent experiments performed in triplicate. *, P ≤ 0.05; as determined by Student’s t test.