Table 1.
Strains used in this work.
Table 2.
List of genes and primer pairs for real-Time RT-PCR
Figure 1.
Aerobiosis scales aof MG1655 and the mutant strains.
The correlation between the percentage of oxygen in the input gas and the acetate production of the different strains was analyzed in bioreactor experiments. While MG1655 displays a linear inverse correlation with no longer detectable acetate production at about 4.5% oxygen in the input gas the mutant strains showed no linear correlations and acetate production was not completely abolished even at higher O2 input rates.
Figure 2.
Acetate und ethanol formation rates at different oxygen concentrations in glucose-limited cultures for the wild-type strain MG1655 (1a) and strain TBE029 (1b).
100% aerobiosis corresponds to the minimal oxygen concentration in glucose-limited cultures to prevent acetate formation in MG1655. TBE029: ΔnuoB.
Table 3.
Acetate l formation rates from glucose-limited chemostat cultures at different aerobiosis levels.
Figure 3.
Relative expression of genes coding for respiratory enzymes in E. coli MG1655 (2a) and mutant strain TBE029 (2b).
Transcription of NADH dehydrogenase I and II and of the cytochrome oxidases bo, bd-I and bd-II. The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression of the wild-type strain under anaerobic conditions. TBE029: ΔnuoB. ndh: NADH dehydrogenase II, nuoN: NADH dehydrogenase I, cyoA: subunit of cytochrome oxidase bo, cydA: subunit of cytochrome oxidase bd-I, appC: subunit of cytochrome oxidase bd-II.
Figure 4.
Relative expression of genes coding for enzymes of the TCA cycle in E. coli MG1655 (3a) and mutant strain TBE029 (3b).
Transcription of citrate synthase, 2-oxoglutarate dehydrogenase and succinate dehydrogenase. The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression of the wild-type strain under anaerobic conditions. TBE029: ΔnuoB. gltA: citrate synthase, sucA: subunit of 2-oxoglutarate dehydrogenase, sdhD: subunit of succinate dehydrogenase.
Figure 5.
Relative expression of genes coding for enzymes of acetate metabolism in E. coli MG1655 (4a) and mutant strain TBE029 (4b).
The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression under anaerobic conditions. aceA: isocitrate lyase, ackA: acetate kinase, poxB: pyruvate oxidase, acs: acetyl-CoA synthetase.
Figure 6.
ArcA phosphorylation in E. coli MG1655 and mutant strain TBE029 over the aerobiosis.
TBE029: ΔnuoB. A few data points do not seem to fit and might only be measuring inaccuracies. Nevertheless all values are displayed here as it is difficult to distinguish between measurement errors and variance in ArcA phosphorylation.
Figure 7.
Relative expression of genes coding for respiratory enzymes (6a) and TCA cycle enzymes (6b) in strain TBE031 (Cyt bo).
TBE031: ΔnuoB, ΔcydB, ΔappB. The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression of the wild-type strain under anaerobic conditions. ndh: NADH dehydrogenase II, cyoA: subunit of cytochrome oxidase bo, gltA: citrate synthase, sucA: subunit of 2-oxoglutarate dehydrogenase, sdhD: subunit of succinate dehydrogenase.
Figure 8.
ArcA phosphorylation in E. coli respiratory mutant strains over the aerobiosis.
TBE029: ΔnuoB; TBE031: ΔnuoB, ΔcydB, ΔappB; TBE032: ΔnuoB, ΔcydB, ΔcyoB; TBE042: ΔnuoB, ΔcyoB, ΔappB.
Table 4.
Ethanol formation rates from glucose-limited chemostat cultures at different aerobiosis levels.
Figure 9.
Relative expression of genes coding for respiratory enzymes (8a) and TCA cycle enzymes (8b) in strain TBE032 (Cyt bd-II).
TBE032: ΔnuoB, ΔcyoB, ΔcydB. The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression of the wild-type strain under anaerobic conditions. ndh: NADH dehydrogenase II, appC: subunit of cytochrome oxidase bd-II, gltA: citrate synthase, sucA: subunit of 2-oxoglutarate dehydrogenase, sdhD: subunit of succinate dehydrogenase.
Figure 10.
Relative expression of genes coding for respiratory enzymes (9a) and TCA cycle enzymes (9b) in strain TBE042 (Cyt bd-I).
TBE042: ΔnuoB, ΔcyoB, ΔappB. The transcription pattern was analyzed in cells from glucose-limited continuous cultures and normalized to the reference genes recA, rpoD and ybhC and to the expression of the wild-type strain under anaerobic conditions. ndh: NADH dehydrogenase II, cydA: subunit of cytochrome oxidase bd-I, gltA: citrate synthase, sucA: subunit of 2-oxoglutarate dehydrogenase, sdhD: subunit of succinate dehydrogenase.