Oral Presentation BacPath 13: Molecular Analysis of Bacterial Pathogens Conference 2015

Legionella longbeachae creates a replicative vacuole similar to Legionella pneumophila despite translocation of distinct effector repertoires (#16)

Rebecca E. Wood 1 , Patrice Newton 1 , Eleanor A. Latomanski 1 , Hayley J. Newton 1
  1. Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia

Legionella species are environmental bacteria and accidental human pathogens that can cause severe pneumonia termed Legionnaires’ disease. These bacteria utilise a Type IVB Dot/Icm secretion system to translocate effectors into the host cell. These effectors manipulate host cell trafficking pathways which enables the establishment of a replicative vacuole, the Legionella-containing vacuole (LCV). Our understanding of the development and dynamics of this vacuole is based on extensive analysis of Legionella pneumophila. However, little is known about the LCV of non-pneumophila species of Legionella. We have characterised the Legionella longbeachae replicative vacuole and demonstrated that, despite important genomic differences, during early infection the host Rab GTPase, Rab1, and the v-SNARE Sec22b are recruited to the longbeachae-LCV with similar dynamics to the recruitment of these host proteins to the pneumophila-LCV. We constructed a Dot/Icm deficient L. longbeachae strain by deleting dotB and demonstrated that this mutant was attenuated for intracellular growth in THP-1 macrophages. Using this mutant and a TEM-1 ß-lactamase reporter assay, we demonstrated the Dot/Icm-dependent translocation of a novel family of proteins, the Rab-like effectors (Rle). Immunofluorescent analysis confirmed that these proteins enter the host cell during infection, with RleA and RleC present on the longbeachae-LCV. Future work will explore the mechanism through which L. longbeachae recruits Rab1 and Sec22b to the LCV, and the roles of the Rles during infection.