Actin-based motility is used by various pathogens for dissemination within and between cells. Yet host factors restricting this process have not been identified. Septins are GTP-binding proteins that assemble as filaments and are essential for cell division. However, their role during interphase has remained elusive. Here, we report that septin assemblies are recruited to different bacteria that polymerize actin. We observed that intracytosolic Shigella either become compartmentalized in septin cage-like structures or form actin tails. Inactivation of septin caging increases the number of Shigella with actin tails and enhances cell-to-cell spread. TNF-α, a host cytokine produced upon Shigella infection, stimulates septin caging and restricts actin tail formation and cell-to-cell spread. Finally, we show that septin cages entrap bacteria targeted to autophagy. Together, these results reveal an unsuspected mechanism of host defense that restricts dissemination of invasive pathogens.

No abstract

Mitochondria are essential and highly dynamic organelles, constantly undergoing fusion and fission. We analyzed mitochondrial dynamics during infection with the human bacterial pathogen Listeria monocytogenes and show that this infection profoundly alters mitochondrial dynamics by causing transient mitochondrial network fragmentation. Mitochondrial fragmentation is specific to pathogenic Listeria monocytogenes, and it is not observed with the nonpathogenic Listeria innocua species or several other intracellular pathogens. Strikingly, the efficiency of Listeria infection is affected in cells where either mitochondrial fusion or fission has been altered by siRNA treatment, highlighting the relevance of mitochondrial dynamics for Listeria infection. We identified the secreted pore-forming toxin listeriolysin O as the bacterial factor mainly responsible for mitochondrial network disruption and mitochondrial function modulation. Together, our results suggest that the transient shutdown of mitochondrial function and dynamics represents a strategy used by Listeria at the onset of infection to interfere with cellular physiology.bacterial infection | calcium influx | bioenergetics

Clathrin assembles at bacterial adhesion sites and its phosphorylation is required for actin recruitment during bacterial infection.

We consider fluid wetting on a corrugated substrate using effective interfacial Hamiltonian theory and show that breaking the translational invariance along the wall can induce an unbending phase transition in addition to unbinding.Both first order and second order unbending transitions can occur at and out of coexistence. Results for systems with short-ranged and long-ranged forces establish that the unbending critical point is characterised by hyperuniversal scaling behaviour. We show that, at bulk coexistence, the adsorption at the unbending critical point is a universal multiple of the adsorption for the correspondent planar system.