The entry of Salmonella in a distinct tight compartment revealed at high temporal and ultrastructural resolution

Abstract Salmonella enterica induces membrane ruffling and genesis of macropinosomes during its interactions with epithelial cells. This is achieved through the type three secretion system‐1 (T3SS‐1), which first mediates bacterial attachment to host cells and then injects bacterial effector proteins to alter host behavior. Next, Salmonella enters into the targeted cell within an early membrane‐bound compartment that matures into a slow growing, replicative niche called the Salmonella Containing Vacuole (SCV). Alternatively, the pathogen disrupts the membrane of the early compartment and replicate at high rate in the cytosol. Here, we show that the in situ formed macropinosomes, which have been previously postulated to be relevant for the step of Salmonella entry, are key contributors for the formation of the mature intracellular niche of Salmonella. We first clarify the primary mode of T3SS‐1 induced Salmonella entry into epithelial cells by combining classical fluorescent microscopy with cutting edge large volume electron microscopy. We observed that Salmonella, similarly to Shigella, enters epithelial cells inside tight vacuoles rather than in large macropinosomes. We next apply this technology to visualize rupturing Salmonella containing compartments, and we use extended time‐lapse microscopy to establish early markers that define which Salmonella will eventually hyper replicate. We show that at later infection stages, SCVs harboring replicating Salmonella have ...
Source: Cellular Microbiology - Category: Microbiology Authors: Tags: RESEARCH ARTICLE Source Type: research