Bacterial toxic bullet kills competitors

Microbiologists have discovered a toxin that allows an infectious strain of bacteria to defeat its competitors.  

The new bullet-like toxin, discovered by Imperial College London scientists, is produced by Pseudomonas aeruginosa, a bacterium responsible for human diseases such as pneumonia and cystic fibrosis. 

The team investigated an understudied group of bacterial genes that encode proteins linked to P. aeruginosa‘s Type 6 secretion system (T6SS) – a molecular gun that delivers toxins to kill or supress rival bacteria.

Professor Alain Filloux from Imperial’s Department of Life Sciences and leader of the study said: “There is much more to learn about the exact role of T6SS in shaping the composition of bacterial communities in P. aeruginosa infections, which would eventually allow us to use our fundamental understanding of this system to tackle health-related problems."

One of these T6SS-related genes the team studied was found to encode a protein with an ability to degrade nucleic acids. This Tse7 protein can be delivered via the T6SS into a competitor cell, degrading their DNA and stopping their growth.

The researchers suggested that the newly discovered toxin may explain why samples of P. aeruginosa from specific infections are often dominated by a single strain.

The study also found that P. aeruginosa possesses a Tse7 immunity protein, which when introduced to victim cells protects them from Tse7 toxicity. Different P. aeruginosa strains were found to posses unique versions of this immunity protein, which were only protective against the toxin origination from the same strain. 

Imperial’s findings were published in Proceedings of the National Academy of Sciences.