Effect of ArcA and FNR on the expression of genes related to the oxygen regulation and the glycolysis pathway inEscherichia coli under microaerobic growth conditions

Abstract

Escherichia coli has several elaborate sensing mechanisms for response to the availability of oxygen and the presence of other electron acceptors. The adaptive responses are coordinated by a group of global regulators, which include the one-component Fnr protein, and the two-component Arc system. To quantitate the contribution of Arc and FNR dependent regulation under microaerobic conditions, the gene expression pattern of the fnr the arcA and arcB regulator genes, and the glycolysis related genes in a wild-type E. coli, an arcA mutant, an fnr mutant, and a double arcA, fnr mutant, in glucose limited cultures and different oxygen concentrations was studied in chemostat cultures at steady state using QRT-PCR. It was found that ArcA has a negative effect on fnr expression under microaerobic conditions. Moreover, the expression levels of the FNR regulated genes, yfiD and frdA, were higher in cultures of the arcA mutant strain compared to the wild-type. These imply that a higher level of the FNR regulator is in the activated form in cultures of the arcA mutant strain compared to the wild-type during the transition from aerobic to microanaerobic growth. The results also show that the highest expression level of aceE, pflB, and adhE were obtained in cultures of the arcA mutant strain under microaerobic growth while higher levels of ldhA expression were obtained in cultures of the arcA mutant strain and the arcA, fnr double mutant strain compared to the wild-type and the fnr mutant strain. While the highest expression of adhE and pflB in cultures of the arcA mutant strain can explain the previous report of high ethanol flux and flux through pyruvate formate lyase (PFL) in cultures of this strain, the higher level of ldhA expression was not sufficient to explain the trend in lactate fluxes. The results indicate that lower conversion of pyruvate to acetyl-CoA is the main reason for high fluxes through lactate dehydrogenase (LDH) in cultures of the arcA, fnr double mutant strain.

Metabolic Flux Analysis of Escherichia coli creB and arcA Mutants Reveals Shared Control of Carbon Catabolism under Microaerobic Growth Conditions

“…42% reduction in acetate synthesis [P Ͻ 0.01]), suggesting an additive effect of mutations in both ArcAB and CreBC on Pta-AckA fluxes. These results are in good agreement with the reported reduction of pta-ackA expression in a creC::kan mutant of E. coli DH5␣ (5), and in a ⌬arcA mutant of E. coli MG1655 (61). It is worth mentioning that conversion of Pyr to extracellular acetate is usually assumed to occur through the reactions catalyzed by PDH and/or Pfl, Pta, and AckA, but it may also arise from Pyr oxidase activity (PoxB) in one step.…”

Cross-Kingdom Comparison of Transcriptomic Adjustments to Low-Oxygen Stress Highlights Conserved and Plant-Specific Responses

“…The regulation of mRNAs encoding factors involved in low-oxygen sensing was consistent with published reports (i.e. induction of Sinorhizobium meliloti and Pseudomonas aeruginosa FixJ/FixK TFs [Green et al, 2009; OMCL8812], Mycobacterium tuberculosis DosR TF [Sherman et al, 2001; OMCL2741], fungal Hap1/Rox1 TFs that measure cellular heme [Hon et al, 2003;OMCL4393 and OMCL1263], and MGA2 that regulates fatty acid desaturase [Jiang et al, 2001;OMCL6345] and no induction in posttranscriptionally regulated TFs, including E. coli redox-sensing ArcA/ArcB system and FNR TFs [Shalel-Levanon et al, 2005;Malpica et al, 2006] and mammalian hypoxia-inducible factor1a-subunit [Bruick, 2003]; Supplemental Table S6). Plants lack orthologs of bacterial, yeast, and animal TFs associated with direct or indirect low-oxygen sensing (Bailey-Serres and Chang, 2005).…”

Role of RpoS in the Virulence of Citrobacter rodentium

“…A serial dilution of genomic DNA of C. rodentium was used as a standard for quantification. The rrsA gene, encoding the 16S RNA, was used as an endogenous control to normalize RNA quantity (12,47).…”