Table 1.

Relative expression of ribonucleotide reductase (RNR) genes based on real-time PCR.

	Differential expression (fold-change)
	nrdA	nrdJa	nrdD
Planktonic anaerobic vs. Planktonic aerobic	2.1 ± 0.4	85.2 ± 5.0	110.6 ± 19.2
Biofilm aerobic vs. Planktonic aerobic	13.1 ± 6.2	1500 ± 150	128.2 ± 5.1
Biofilm aerobic vs. Planktonic anaerobic	2.4 ± 1.0	51.6 ± 7.3	-12.3 ± 1.6

Fold change in Pseudomonas aeruginosa PAO1 nrdA, nrdJa, and nrdD transcription determined using real time PCR from 16-h-old planktonic cells grown aerobically or anaerobically and 4-day-old cells growing in biofilms. “Biofilm aerobic” refers to biofilms grown under initially aerobic conditions. The gap gene was used as an internal standard. The results shown represent the average of three independent experiments ± standard deviation.