Abstract

The ability ofSalmonellato survive and replicate within mammalian host cells involves the generation of a membranous compartment known as theSalmonella-containing vacuole (SCV).Salmonellaemploys a number of effector proteins that are injected into host cells for SCV formation using its type-3 secretion systems encoded in SPI-1 and SPI-2 (T3SS-1 and T3SS-2, respectively). Recently, we reported thatS. Typhimurium requires T3SS-1 and T3SS-2 to survive in the model amoebaDictyostelium discoideum. Despite these findings, the involved effector proteins have not been identified yet. Therefore, we evaluated the role of two majorS. Typhimurium effectors SopB and SifA duringD.discoideumintracellular niche formation. First, we established thatS. Typhimurium resides in a vacuolar compartment withinD.discoideum. Next, we isolated SCVs from amoebae infected with wild type or the Delta sopBand Delta sifAmutant strains ofS. Typhimurium, and we characterised the composition of this compartment by quantitative proteomics. This comparative analysis suggests thatS. Typhimurium requires SopB and SifA to modify the SCV proteome in order to generate a suitable intracellular niche inD.discoideum. Accordingly, we observed that SopB and SifA are needed for intracellular survival ofS. Typhimurium in this organism. Thus, our results provide insight into the mechanisms employed bySalmonellato survive intracellularly in phagocytic amoebae.