An Artificial microbe was a microorganism which was created by any process except natural ones (ie., biologically).

In 2369, Captain Benjamin Sisko, Lieutenant Commander Jadzia Dax, Chief Miles O'Brien and Doctor Julian Bashir encountered artificial microbes in the atmosphere of a moon in the Gamma Quadrant were an Ennis/Nol-Ennis penal colony was located. The artificial microbes regenerated those who had died on the moon, becoming a curse to the two warring factions. After Bashir had studied the artificial microbes aboard the USS Yangtzee Kiang he determined that once they had regenerated a lifeform from death, that lifeform could never live in any environment except on that moon without suffering immediate death. (DS9: "Battle Lines")