Lipopolysaccharide structure impacts the entry kinetics of bacterial outer membrane vesicles into host cells

Outer membrane vesicles are nano-sized microvesicles shed from the outer membrane of gram-negative bacteria and play important roles in immune priming and disease pathogenesis. however,our current mechanistic understanding of vesicle—host cell interactions is limited by a lack of methods to study the rapid kinetics of vesicle entry and cargo delivery to host cells. here,we describe a highly sensitive method to study the kinetics of vesicle entry into host cells in real-time using a genetically encoded,vesicle-targeted probe. we found that the route of vesicular uptake,and thus entry kinetics and efficiency,are shaped by bacterial cell wall composition. the presence of lipopolysaccharide o antigen enables vesicles to bypass clathrin-mediated endocytosis,which enhances both their entry rate and efficiency into host cells. collectively,our findings highlight the composition of the bacterial cell wall as a major determinant of secretion-independent delivery of virulence factors during gram-negative infections. © 2017 o’donoghue et al.