Activation of the Yersinia type III secretion system induces large-scale spatial reorganization of chromosomal and virulence plasmid DNA

The type III secretion system (T3SS) is used by Gram-negative bacteria, including important pathogens, to manipulate eukaryotic cells by injecting effector proteins. Type III secretion and bacterial physiology are tightly interconnected. Notably, secreting cells undergo a secretion-associated growth inhibition in the T3SS model organisms Yersinia, Salmonella, and Shigella. In Yersinia, T3SS genes are encoded on the plasmid of Yersinia virulence (pYV), whose copy number increases upon induction of T3SS secretion. In this study, we characterize the link between T3SS activity and subcellular organization by localizing and quantifying pYV and chromosomal DNA in Yersinia enterocolitica. In secreting bacteria, pYV plasmids move toward the membrane and poles. We find no evidence for the transertion (coupled transcription, translation, and translocation) of a candidate effector, but we do find a striking relocation of chromosomal DNA to mid-cell. These findings reveal that T3SS activation coincides with large-scale reorganization of the bacterial nucleoid and plasmid DNA.