Bacteria signalling using pheromones. Computer artwork showing bacteria (round, white) on the skin releasing chemical messages known as pheromones (green), to communicate with each other. Bacteria release these chemicals in response to stimuli in their environment. The chemicals messages regulate the metabolism of other bacteria of the same species so as to increase the chance of the colony's survival. For example, some pheromones induce the bacteria to exchange DNA (deoxyribonucleic acid) present in plasmids, rings of genetic material floating in the cytoplasm. Such exchange can increase the bacteria's resistance to antibiotic substances.