@McTag,
I'll admit McTag it's a stretch but "they" dangles just a little so if we're wondering for instance how one bacterium could poison another then we might assume you have reference to "an entirely different apparatus used by certain bacteria that they [the toxins] are attacking, to inject toxins into other bacteria," it being unclear whether the "certain" bacterium suffers either one
In other words, an apparatus used by certain bacterium under attack by toxins is used in return to infect (or at least inject) other bacteria, perhaps using a different agent
It's like saying, an entirely new and different airplane used by the Germans comes under attack by Armenians and French using poison gas, it counterattacks these forces by the same means