Modular Lipoprotein Toxins Transferred by Outer Membrane Exchange Target Discrete Cell Entry Pathways

Many bacterial species use diverse systems to deliver bacteriocins or toxins to neighboring competing cells. These systems are often selective in targeting cells that are related to themselves and therefore compete in the same niches for resources. How these systems specifically identify target cells and deliver toxins to particular cellular compartments is a fundamental question. This study uses the model social bacterium Myxococcus xanthus to unravel how its kin discrimination system, called outer membrane exchange, works. Along with the TraA polymorphic cell surface receptor that identifies related individuals with compatible receptors, this work discovered a new protein, called TraC, that functions in this discrimination system. Additionally, genetic screens identified host factors that are proposed to be involved in the cytoplasmic entry of lipoprotein toxins from the OM. This work complements and broadens our mechanistic understanding of how bacteria use transport systems to discriminate against related foes to build clonal populations.