Novel transcriptional regulators of Legionella pneumophila that affect replication in Acanthamoeba castellanii.
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.
Lebeau
Ilya
I
Laboratory of Bacteriology, Rega Instituut, Katholieke Universiteit Leuven, Minderbroedersstraat 10, 3000 Leuven, Belgium.
Lammertyn
Elke
E
De Buck
Emmy
E
Maes
Liesbeth
L
Geukens
Nick
N
Van Mellaert
Lieve
L
Anné
Jozef
J
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
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