title: Function and stationary-phase induction of periplasmic copper-zinc superoxide dismutase and catalase/peroxidase in Caulobacter crescentus.
abstract: Although cytosolic superoxide dismutases (SODs) are widely distributed among bacteria, only a small number of species contain a periplasmic SOD. One of these is Caulobacter crescentus, which has a copper-zinc SOD (CuZnSOD) in the periplasm and an iron SOD (FeSOD) in the cytosol. The function of periplasmic CuZnSOD was studied by characterizing a mutant of C. crescentus with an insertionally inactivated CuZnSOD gene. Wild-type and mutant strains showed identical tolerance to intracellular superoxide. However, in response to extracellular superoxide, the presence of periplasmic CuZnSOD increased survival by as much as 20-fold. This is the first demonstration that periplasmic SOD defends against external superoxide of environmental origin. This result has implications for those bacterial pathogens that contain a CuZnSOD. C. crescentus was shown to contain a single catalase/peroxidase which, like Escherichia coli KatG catalase/peroxidase, is present in both the periplasmic and cytoplasmic fractions. The growth stage dependence of C. crescentus catalase/peroxidase and SOD activity was studied. Although FeSOD activity was identical in exponential- and stationary-phase cultures, CuZnSOD was induced nearly 4-fold in stationary phase and the catalase/peroxidase was induced nearly 100-fold. Induction of antioxidant enzymes in the periplasm of C. crescentus appears to be an important attribute of the stationary-phase response and may be a useful tool for studying its regulation.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: S
authors.initials: S
authors.lastname: Schnell
authors.forename: H M
authors.initials: HM
authors.lastname: Steinman
mesh_terms: D002374:Catalase / Q000096:biosynthesis / Q000502:physiology; D002413:Cations, Divalent / Q000494:pharmacology; D016935:Caulobacter crescentus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D002451:Cell Compartmentation; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D004790:Enzyme Induction; D006861:Hydrogen Peroxide / Q000633:toxicity; D010269:Paraquat / Q000494:pharmacology; D009195:Peroxidase / Q000096:biosynthesis / Q000502:physiology*; D013482:Superoxide Dismutase / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D013481:Superoxides / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D002951:Citrates; D013481:Superoxides; D019343:Citric Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D010269:Paraquat