title: Effect of microaerophilic cell growth conditions on expression of the aerobic (cyoABCDE and cydAB) and anaerobic (narGHJI, frdABCD, and dmsABC) respiratory pathway genes in Escherichia coli.
abstract: Escherichia coli varies the synthesis of many of its respiratory enzymes in response to oxygen availability. These enzymes include cytochrome o oxidase (cyoABCDE) and cytochrome d oxidase (cydAB), used during aerobic cell growth, and a fumarate reductase (frdABCD), dimethyl sulfoxide/trimethylamine oxide reductase (dmsABC), and nitrate reductase (narGHJI), used during anaerobic respiratory conditions. To determine how different levels of oxygen affect the expression of each operon, strains containing cyo-lacZ, cyd-lacZ, frdA-lacZ, dmsA-lacZ, and narG-lacZ fusions were grown in continuous culture at various degrees of air saturation. The basal-level expression of the anaerobic respiratory genes, frdABCD, dmsABC, and narGHJI, occurred when the air saturation of the medium was above 20%; as the saturation was reduced to below 10% (ca. 2% oxygen), the expression rapidly increased and reached a maximal level at 0% air. In contrast, cyoABCDE gene expression was lowest under anaerobic conditions while cyd-lacZ expression was about 40% of its maximum level. When the oxygen level was raised into the microaerophilic range (ca. 7% air saturation) cyd-lacZ expression was maximal while cyo-lacZ expression was elevated by about fivefold. As the air level was raised to above 20% saturation, cyd-lacZ expression fell to a basal level while cyo-lacZ expression was increased to its maximum level. The role of the Fnr and ArcA regulatory proteins in this microaerophilic control of respiratory gene expression was documented: whereas Fnr function as an aerobic/anaerobic switch in the range of 0 to 10% air saturation, ArcA exerted its control in the 10 to 20% range. These two transcriptional regulators coordinate the hierarchial control of respiratory pathway gene expression in E. coli to ensure the optimal use of oxygen in the cell environment.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
authors.forename: C P
authors.initials: CP
authors.lastname: Tseng
authors.forename: J
authors.initials: J
authors.lastname: Albrecht
authors.forename: R P
authors.initials: RP
authors.lastname: Gunsalus
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000096:biosynthesis; D045222:Electron Transport Chain Complex Proteins; D003576:Electron Transport Complex IV / Q000096:biosynthesis; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D007506:Iron-Sulfur Proteins; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000096:biosynthesis; D010088:Oxidoreductases / Q000096:biosynthesis*; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010100:Oxygen / Q000494:pharmacology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012097:Repressor Proteins; D013385:Succinate Dehydrogenase / Q000096:biosynthesis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C041610:arcA protein, E coli; D010088:Oxidoreductases; D013385:Succinate Dehydrogenase; C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors; D009247:NADH, NADPH Oxidoreductases; D009565:Nitrate Reductases; D050901:Nitrate Reductase; C045664:dimethyl sulfoxide reductase; C040077:cytochrome bd terminal oxidase complex, E coli; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV; D010100:Oxygen