title: Novel transcriptional regulators of Legionella pneumophila that affect replication in Acanthamoeba castellanii.
abstract: Legionella pneumophila is commonly found in freshwater environments and is able to invade and replicate within amoebae and ciliated protozoa. Moreover, this bacterium is also able to replicate within human alveolar macrophages causing a severe form of pneumonia, designated Legionnaires' disease. L. pneumophila pathogenesis is not yet completely understood, but the genes responsible for infection and intracellular replication are becoming known. Nonetheless, knowledge as to how these genes are controlled is still very limited. The partially sequenced genome of L. pneumophila was searched for open reading frames encoding proteins with sequence similarity to members of the LuxR family of transcriptional regulators. These were designated LpnR1, LpnR2, LpnR3, and LpnR4. Although these proteins could not be identified as true LuxR proteins, they do act as regulators, as illustrated in this report. LpnR1 negatively affected rpoS expression, whereas LpnR2 and LpnR3 positively affected flagellin expression. Furthermore, LpnR2 proved to be necessary for efficient invasion of Acanthamoeba castellanii and LpnR3 for intracellular replication in this protozoan host. LpnR4 was recently identified as LetA.
authors.affiliation: Laboratory of Bacteriology, Rega Instituut, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium.
authors.forename: Ilya
authors.initials: I
authors.lastname: Lebeau
authors.forename: Elke
authors.initials: E
authors.lastname: Lammertyn
authors.forename: Emmy
authors.initials: E
authors.lastname: De Buck
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Maes
authors.forename: Nick
authors.initials: N
authors.lastname: Geukens
authors.forename: Lieve
authors.initials: L
authors.lastname: Van Mellaert
authors.forename: Jozef
authors.initials: J
authors.lastname: Anné
mesh_terms: D000048:Acanthamoeba / Q000382:microbiology*; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D005408:Flagellin / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D016952:Legionella pneumophila / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D007877:Legionnaires' Disease / Q000209:etiology; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic; D020298:U937 Cells; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C068355:CcdA protein, Bacteria; D004269:DNA, Bacterial; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; D005408:Flagellin; C067138:flaA protein, bacteria