chemotrophs
Most archaea are chemotrophs and derive their energy and nutrients from breaking down molecules in their environment. A few species of archaea are photosynthetic and capture the energy of sunlight. Unlike bacteria, which can be parasites and are known to cause a variety of diseases, there are no known archaea that act as parasites. Some archaea do live within other organisms. But these archea form mutualistic relationships with their host, where both the archaea and the host benefit. In other words, they assist the host in some way, for example by helping to digest food.