Dynamic remodeling of the endosomal system during formation of Salmonella-induced filaments by intracellular Salmonella enterica

The infection by Salmonella enterica results in the massive remodeling of the endosomal system of eukaryotic host cells. One unique consequence is the formation of long tubular endosomal compartments, so-called Salmonella-induced filaments (SIF). Formation of SIF requires the function of type III secretion system and is a requirement of efficient intracellular proliferation of Salmonella. Using high-resolution live cell imaging approaches and electron microscopy, we report for the first time the highly dynamic characteristics of SIF and their ultrastructural properties. In the early phase of infection (4-5 h), SIF display highly dynamic properties in various types of host cells. SIF extend, branch and contract rapidly, and a stabilized network of SIF is formed later (>or=8 h after infection). The velocities of SIF extension and contraction in the different phases of infection were quantified. Our observations lead to novel models for the modification of host cell transport processes by virulence factors of intracellular Salmonella.