Instead of going to all the trouble of launching a weapon, why not just turn yourself into the weapon? Porphyromonas gingivalis like this one use yet another secretion system, the type IX secretion system (T9SS), to secrete proteins called gingipains to the cell surface, where they are anchored to the outer membrane. Gingipains are peptidases, enzymes that chop up other proteins. In their lifestyle as human oral pathogens, the cells use gingipains to block host immune system signals and digest host biomolecules for food, causing the tissue damage of periodontitis.
In Chapter 6 you saw another T9SS with a very different function, in the gliding motility of Flavobacterium johnsoniae. In that case, instead of gingipains, the machine secretes adhesive filaments which are also anchored to the cell surface.
