title: Identification and characterization of genes, encoding the 3-hydroxybutyrate dehydrogenase and a putative lipase, in an avirulent spontaneous Legionella pneumophila serogroup 6 mutant.
abstract: Legionella pneumophila is a pathogen widespread in aquatic environment, able to multiply both within amoebae and human macrophages. The aim of this study was to identify genes differently expressed in a spontaneous avirulent Legionella pneumophila serogroup 6 mutant, named Vir-, respect the parental strain (Vir+), and to determine their role in the loss of virulence. Protein profiles revealed some differences in Vir- proteomic maps, and among the identified proteins the undetectable 3-hydroxybutyrate dehydrogenase (BdhA) and a down-produced lipase. Both Legionella enzymes were studied before and were here further characterized at genetic level. A significant down-regulation of both genes was observed in Vir- at the transcriptional level, but the use of defined mutants demonstrated that they did not affect the intracellular multiplication. A mutant (MS1) showed an accumulation of poly-3-hydroxybutyrate (PHB) granules suggesting a role of bdhA gene in its degradation process. The lipase deduced amino acid sequence revealed a catalytic triad, typical of the 'lipase box' characteristic of PHB de-polymerase enzymes, that let us suppose a possible involvement of lipase in the PHB granule degradation process. Our results revealed unexpected alterations in secondary metabolic pathways possibly linking the loss of virulence to Legionella lack of energy sources.
authors.affiliation: Department of Infectious Parasitic Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Scaturro
authors.forename: Cristina
authors.initials: C
authors.lastname: Barello
authors.forename: Melania De
authors.initials: MD
authors.lastname: Giusti
authors.forename: Stefano
authors.initials: S
authors.lastname: Fontana
authors.forename: Federica
authors.initials: F
authors.lastname: Pinci
authors.forename: Maria Gabriella
authors.initials: MG
authors.lastname: Giuffrida
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Ricci
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D015536:Down-Regulation; D004734:Energy Metabolism / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D006884:Hydroxybutyrate Dehydrogenase / Q000235:genetics*; D006885:Hydroxybutyrates / Q000378:metabolism*; D016952:Legionella pneumophila / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D008049:Lipase / Q000235:genetics*; D008969:Molecular Sequence Data; D011091:Polyesters / Q000378:metabolism*; D000091402:Prohibitins; D040901:Proteomics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics; D065288:Serogroup; D000094122:Polyhydroxybutyrates
chemical_list: D001426:Bacterial Proteins; D006884:Hydroxybutyrate Dehydrogenase; D006885:Hydroxybutyrates; D008049:Lipase; D011091:Polyesters; D000091402:Prohibitins; C000717328:PHB protein, human; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates
keywords: Legionella; bdhA; ketone compounds; lipase; proteome