Natures wonders: bacterial toxin warfare weapons (Introduction)

by David Turell , Monday, September 21, 2020, 20:14 (1522 days ago) @ David Turell

Still finding new ones:

https://phys.org/news/2020-09-family-toxins-bacterial-competition.html

"The novel family's founding member is the protein Tlde1 (type VI L,D-transpeptidase effector 1), which attacks bacterial cell wall precursors. It is secreted via the type VI secretion system or T6SS. Targeted bacteria continue growing but because their cell walls are weakened they eventually die as cell contents leak owing to osmotic pressure and lysis.

"'This family of toxins has a hitherto undescribed mechanism. While other anti-bacterial toxins secreted by the same system destroy the already formed cell walls of target bacteria, this one acts on precursors so that they're weak or cannot form at all," said Ethel Bayer-Santos,...

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"This co-expression neutralized the toxic effect and the bacteria survived, confirming that the proteins in question are indeed a toxin and an immune protein respectively.

"In evolutionary terms, T6SS is related to the apparatus of bacteriophages, viruses that infect bacteria. It comprises 13 structural proteins that are assembled into a weapon resembling a spear or harpoon with a sharp tip inside a retractable cytoplasmic sheath. The attacking cell ejects the harpoon full of toxic proteins from the sheath into the target cell.

"Bioinformatics analysis showed that members of the Tlde1 family are present in several species of bacterium and that the family probably evolved from bacterial enzymes with a key role in cell wall synthesis. The next step in the project is an effort to understand by structural biology how an enzyme that had this role has ended up doing the opposite."

Comment: I wonder how chance evolution found these specific poisons which are not dangerous to their hosts?