title: Characterization of a spontaneous avirulent mutant of Legionella pneumophila Serogroup 6: evidence of DotA and flagellin involvement in the loss of virulence.
abstract: The pathogenesis of Legionella pneumophila mainly resides in its ability to inhibit the phagosome-lysosome fusion, which normally prevents the killing of the host cells. In order to characterize the molecular alterations that occurred in a spontaneous avirulent mutant of Legionella pneumophila serogroup 6, named Vir-, we investigated the ability of the mutant to adhere to and multiply in the WI26VA4 alveolar epithelial cell line and in human macrophages, when compared to its parental strain, Vir+. We also determined the colocalization of bacteria with LAMP-1 to gain an insight into the phagosome-lysosome fusion process. Additionally, we determined the flagellin expression and dotA nucleotide sequencing. We observed a lack of expression of flagellin and an in-frame mutation in the dotA. gene. The data obtained strongly suggest the loss of virulence of the mutant could probably be due to the absence of flagellin and the dysfunctional type IV secretion System, resulting from the DotA protein being severely compromised.
authors.affiliation: Department of Infectious, Parasitic and Immune-Mediated Diseases, 00161 Rome, Italy. maria.scaturro@iss.i
authors.forename: Maria
authors.initials: M
authors.lastname: Scaturro
authors.forename: Stefania
authors.initials: S
authors.lastname: Meschini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Arancia
authors.forename: Fontana
authors.initials: F
authors.lastname: Stefano
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Ricci
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D002448:Cell Adhesion; D002460:Cell Line; D002478:Cells, Cultured; D015169:Colony Count, Microbial; D004847:Epithelial Cells / Q000382:microbiology; D005408:Flagellin / Q000096:biosynthesis*; D015870:Gene Expression; D006801:Humans; D016952:Legionella pneumophila / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D008247:Lysosomes / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D009154:Mutation; D010588:Phagosomes / Q000382:microbiology; D017422:Sequence Analysis, DNA; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C440002:DotA protein, Legionella pneumophila; D008565:Membrane Proteins; D037521:Virulence Factors; D005408:Flagellin; C067138:flaA protein, bacteria