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.
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.
Tseng
C P
CP
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
Albrecht
J
J
Gunsalus
R P
RP
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
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