Near Surface Swimming of Salmonella Typhimurium Explains Target-Site Selection and Cooperative Invasion

作者：Misselwitz Benjamin^*; Barrett Naomi; Kreibich Saskia; Vonaesch Pascale; Andritschke Daniel; Rout Samuel; Weidner Kerstin; Sormaz Milos; Songhet Pascal; Horvath Peter; Chabria Mamta; Vogel Viola; Spori Doris M; Jenny Patrick; Hardt Wolf Dietrich

来源：PLoS Pathogens, 2012, 8(7): e1002810.

DOI：10.1371/journal.ppat.1002810

Targeting of permissive entry sites is crucial for bacterial infection. The targeting mechanisms are incompletely understood. We have analyzed target-site selection by S. Typhimurium. This enteropathogenic bacterium employs adhesins (e. g. fim) and the type III secretion system 1 (TTSS-1) for host cell binding, the triggering of ruffles and invasion. Typically, S. Typhimurium invasion is focused on a subset of cells and multiple bacteria invade via the same ruffle. It has remained unclear how this is achieved. We have studied target-site selection in tissue culture by time lapse microscopy, movement pattern analysis and modeling. Flagellar motility (but not chemotaxis) was required for reaching the host cell surface in vitro. Subsequently, physical forces trapped the pathogen for similar to 1.5-3 s in "near surface swimming". This increased the local pathogen density and facilitated "scanning" of the host surface topology. We observed transient TTSS-1 and fim-independent "stopping" and irreversible TTSS-1-mediated docking, in particular at sites of prominent topology, i.e. the base of rounded-up cells and membrane ruffles. Our data indicate that target site selection and the cooperative infection of membrane ruffles are attributable to near surface swimming. This mechanism might be of general importance for understanding infection by flagellated bacteria.

• 出版日期2012-7