title: Characterization of a catalase gene from Aeromonas veronii, the digestive-tract symbiont of the medicinal leech.
abstract: The catalase gene katA of the medicinal leech symbiont Aeromonas veronii bv. sobria was cloned, sequenced, and functionally characterized. Southern hybridization, using an A. veronii katA-specific hybridization probe, suggested the presence of a single gene copy in many Aeromonas species. A. veronii katA consisted of 1446 nt encoding a protein with a high degree of similarity to the small-subunit group III bacterial catalases. A catalase-null mutant (JG186) was constructed through gene-replacement mutagenesis. In the parent strain (HM21R), catalase activity was only detected in extracts of cells grown to early exponential phase following H(2)O(2) induction, in which the ability to induce activity was inversely related to optical density. In contrast, induced JG186 cells were very sensitive to oxidative stress, with survival being affected even at low H(2)O(2) concentrations. In contrast to the findings of previous reports of other symbiotic systems, the catalase mutant was not defective in its ability to competitively colonize or persist within its host, in both co-inoculation and sole-colonization assays. This body of evidence suggests either that oxidative stress, in the form of H(2)O(2) exposure, is not encountered by the microbial partner under the examined symbiotic conditions or that compensatory mechanisms exist. The data suggest that although many colonization factors reoccur, each symbiotic system has also evolved specific mechanisms that affect symbiont-host dynamics.
authors.affiliation: Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA.
authors.forename: Rita V M
authors.initials: RVM
authors.lastname: Rio
authors.affiliation: Institute for Infectious Diseases, University of Berne, Friedbühlstr. 51, CH-3010 Berne, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Anderegg
authors.affiliation: Institute for Infectious Diseases, University of Berne, Friedbühlstr. 51, CH-3010 Berne, Switzerland.|Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA.
authors.forename: Joerg
authors.initials: J
authors.lastname: Graf
mesh_terms: D000333:Aeromonas / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D026501:Blotting, Southwestern; D002374:Catalase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D041981:Gastrointestinal Tract / Q000382:microbiology; D017353:Gene Deletion; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D007865:Leeches / Q000382:microbiology* / Q000502:physiology; D050296:Microbial Viability; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006861:Hydrogen Peroxide; D002374:Catalase