Portal de Periódicos da CAPES

Evidence for Acquisition of Legionella Type IV Secretion Substrates via Interdomain Horizontal Gene Transfer

2005; American Society for Microbiology; Volume: 187; Issue: 22 Linguagem: Inglês

10.1128/jb.187.22.7716-7726.2005

1098-5530

Karim Suwwan de Felipe, Sergey Pampou, Oliver S. Jovanovic, Christopher D. Pericone, Senna F. Ye, Sergey Kalachikov, Howard A. Shuman,

Bacterial biofilms and quorum sensing

ABSTRACT Intracellular pathogens exploit host cell functions to create a replication niche inside eukaryotic cells. The causative agent of Legionnaires' disease, the γ-proteobacterium Legionella pneumophila , resides and replicates within a modified vacuole of protozoan and mammalian cells. L. pneumophila translocates effector proteins into host cells through the Icm-Dot complex, a specialized type IVB secretion system that is required for intracellular growth. To find out if some effector proteins may have been acquired through interdomain horizontal gene transfer (HGT), we performed a bioinformatic screen that searched for eukaryotic motifs in all open reading frames of the L. pneumophila Philadelphia-1 genome. We found 44 uncharacterized genes with many distinct eukaryotic motifs. Most of these genes contain G+C biases compared to other L. pneumophila genes, supporting the theory that they were acquired through HGT. Furthermore, we found that several of them are expressed and up-regulated in stationary phase in an RpoS-dependent manner. In addition, at least seven of these gene products are translocated into host cells via the Icm-Dot complex, confirming their role in the intracellular environment. Reminiscent of the case with most Icm-Dot substrates, most of the strains containing mutations in these genes grew comparably to the parent strain intracellularly. Our findings suggest that in L. pneumophila , interdomain HGT may have been a major mechanism for the acquisition of determinants of infection.