title: Bacterial defense against aging: role of the Escherichia coli ArcA regulator in gene expression, readjusted energy flux and survival during stasis.
abstract: Using two-dimensional gel electrophoresis and N-terminal amino acid sequencing analysis, we demonstrate that a mutant of the global regulatory protein ArcA fails to decrease the synthesis of the TCA cycle enzymes malate dehydrogenase, isocitrate dehydrogenase, lipoamide dehydrogenase E3 and succinate dehydrogenase in response to stasis, while the increased production of the glycolysis enzymes phosphoglycerate mutase and pyruvate kinase is unaffected. Microcalorimetric and respiratory measurements show that the continued production of TCA cycle enzymes in the (delta)arcA mutant is manifested as an elevated rate of respiration and total metabolic activity during starvation. The (delta)arcA mutant is severely impaired in surviving prolonged periods of exogenous carbon starvation, a phenotype that can be alleviated by overproducing the superoxide dismutase SodA. In addition, flow cytometry demonstrates that starving (delta)arcA mutant cells, in contrast to wild-type cells, fail to perform reductive division, remain large and contain multiple chromosomal copies. We suggest that the ArcA-dependent reduced production of electron donors and the decreased level and activity of the aerobic respiratory apparatus during growth arrest is an integral part of a defense system aimed at avoiding the damaging effects of oxygen radicals and controlling the rate of utilization of endogenous reserves.
authors.affiliation: Department of General and Marine Microbiology, Lundberg Laboratory, Göteborg University, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Nyström
authors.forename: C
authors.initials: C
authors.lastname: Larsson
authors.forename: L
authors.initials: L
authors.lastname: Gustafsson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D002455:Cell Division; D002952:Citric Acid Cycle; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis; D006801:Humans; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000096:biosynthesis
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; C041610:arcA protein, E coli; D013482:Superoxide Dismutase; D005947:Glucose; D010100:Oxygen