These micro-biological organisms allow alien races to understand each other's speech. They "colonize at the base of the brain" and allow one to understand alien speech. The microbes can be injected, and go to work almost instantly. ("Premiere") It is notable that there is, potentially, at least one alien species, the Kalish, who cannot tolerate translator microbes. When Crichton first met Sikozu, who was a Kalish bioloid, had to learn English before she could understand what he was saying. His translator microbes allowed him to understand her.