Single-celled Kamikazes Spearhead Bacterial Infection
Published:30 Jan.2024    Source:Max Planck Institute of Molecular Physiology
You suddenly feel sick -- pathogenic bacteria have managed to colonize and spread in your body! The weapons they use for their invasion are harmful toxins that target the host's defense mechanisms and vital cell functions. Before these deadly toxins can attack host cells, bacteria must first export them from their production site -- the cytoplasm -- using dedicated secretion systems. The group of Stefan Raunser, Director at the Max Planck Institute of Molecular Physiology, has now elucidated a so-far enigmatic, exceptional secretion mechanism, that allows the release of the gigantic Tc toxins. In a kind of kamikaze attack, a small group of so-called "soldier" bacteria, packed to the brim with toxins, release their deadly cargo by exploding in the host. Targeting such subpopulations in medical therapies could be a promising treatment strategy for diseases triggered by bacteria that are becoming increasingly resistant to antibiotics.
 
Once a pathogenic bacterium has entered its host, it turns on a series of defense and attack mechanisms to spread, invade and colonize deeper tissues and organs. This includes the secretion of an array of toxic proteins that subvert the host's cellular defenses. In gram-negative bacteria, which can trigger severe infections and are becoming increasingly resistant to antibiotics, toxic proteins face the challenge of crossing several cellular barriers -- belonging to both the bacteria and the host -- to finally reach their destination. To this end, bacteria have developed a number of specialized secretion systems.
 

Some can secrete a variety of toxins and are found in almost all bacteria, while others have been identified in only few bacteria. The machinery for the secretion of many smaller toxins has already been established. Not so for larger ones, like the Tc toxins produced by the notorious Yersinia bacteria, which also include pathogens that cause plague and tuberculosis.