The microbiome is home to an estimated 100 trillion bacteria, existing as a dense colony of many different strains and species. Similar to all organisms, bacteria must also compete with one another for space and resources, engaging in "warfare" by releasing toxins to kill competitors. One of the many weapons bacteria use in this inevitable fight is the type VI secretion system (T6SS), which delivers toxic effectors into their enemies. The groups of Stefan Raunser from the Max Planck Institute of Molecular Physiology in Dortmund and John Whitney from McMaster University in Canada, have now together uncovered the high-resolution 3D structure of such an effector from Pseudomonas protegens by cryo-electron microscopy. The effector protein, called RhsA, has a toxic component that sits unlocked and ready to be fired within a molecular cocoon sealed by a cork-like structure. Their findings will not only help in understanding how the T6SS machinery works, but will also promote the future development of antibacterial treatments and plant protection strategies.
