Potential Virulence Role of theLegionella pneumophila ptsPOrtholog

Open Access
Publisher Website
Google Scholar
Abstract
We previously identified theLegionella pneumophila ptsP(phosphoenolpyruvate phosphotransferase) ortholog gene as a putative virulence factor in a study of signature-tagged mutagenesis using a guinea pig pneumonia model. In this study, we further defined the phenotypic properties ofL. pneumophila ptsPand its complete sequence. TheL. pneumophila ptsPwas 2,295 bases in length. Its deduced amino acid sequence had high similarity withptsPorthologs ofPseudomonas aeruginosa, Azotobacter vinelandii, andEscherichia coli, with nearly identical lengths. Here we show that while the mutant grew well in laboratory media, it was defective in both lung and spleen multiplication in guinea pigs. It grew slowly in guinea pig alveolar macrophages despite good uptake into the cells. Furthermore, there was minimal growth in a human alveolar epithelial cell line (A549). Transcomplementation of theL. pneumophila ptsPmutant almost completely rescued its growth in alveolar macrophages, in A549 cells, and in guinea pig lung and spleen. TheL. pneumophila ptsPmutant was capable of evasion of phagosome-lysosome fusion and resided in ribosome-studded phagosomes. Pore formation activity of the mutant was normal. TheL. pneumophila ptsPmutant expressed DotA and IcmX in apparently normal amounts, suggesting that theptsPmutation did not affectdotAandicmXregulation. In addition, the mutant was resistant to serum and neutrophil killing. Taken together, these findings show thatL. pneumophila ptsPis required for full in vivo virulence ofL. pneumophila, most probably by affecting intracellular growth.