At asphalt volcanoes in the Gulf of Mexico that spew oil, gas and tar, mussels and sponges live in symbiosis with bacteria providing them with food. Scientists from the Max Planck Institute for Marine Microbiology and colleagues from the USA have now discovered deep-sea animals living in symbiosis with bacteria that use oil as an energy source and appear to thrive on short-chained alkanes in the oil. According to the researchers, bacteria closely related to the symbionts, which bloomed during the Deepwater Horizon oil spill, used this ability to degrade the oil in the sea.