An organism that obtains energy from the chemical breakdown of dead organisms or animal or plant wastes. Decomposers, most of which are bacteria and fungi, secrete enzymes onto dead matter and then absorb the breakdown products (see saprotroph). Many decomposers (e.g. nitrifying bacteria) are specialized to break down organic materials that are difficult for other organisms to digest. Decomposers fulfil a vital role in the ecosystem, returning the constituents of organic matter to the environment in inorganic form so that they can again be assimilated by plants. Compare detritivore. See also carbon cycle; nitrogen cycle.