decay of organic matter

decay of organic matter or putrefaction, process whereby heterotrophic organisms, including some bacteria, fungi, saprophytic plants, and lower animals, utilize the remains of once-living tissue as a source of nutrition. The polysaccharides, lipids, nucleic acids, and proteins of dead tissue are broken down into smaller organic molecules, often by enzymes that are secreted into the external environment by the bacteria and fungi that are involved; the breakdown products are then readily absorbed by the heterotrophs and are used both as a source of building blocks for the synthesis of their own polysaccharides, lipids, nucleic acids, and proteins, and as a source of chemical energy, obtained either by fermentation (in an anaerobic environment) or respiration (in the presence of oxygen). Often during the process of putrefaction, trace elements and nitrogen are released into the environment in forms suitable for uptake by higher plants; this is the basis for the use of decayed organic matter as fertilizer. The disagreeable odor produced as putrefaction takes place is caused by the formation of certain gases, including ammonia and hydrogen sulfide, and certain volatile amines, including putrescine and cadaverine, two products of the breakdown of protein by microorganisms.

decay (di-kay) n. (in bacteriology) the decomposition of organic matter due to microbial action.

de·cay / diˈkā/ • v. [intr.] (of organic matter) rot or decompose through the action of bacteria and fungi: [as adj.] (decayed) a decayed cabbage leaf | [as adj.] (decaying) the odor of decaying fish. ∎  [tr.] cause to rot or decompose: the fungus will decay soft timber. ∎  (of a building or area) fall into disrepair; deteriorate. ∎  decline in quality, power, or vigor: moral authority was decaying. ∎  Physics (of a radioactive substance, particle, etc.) undergo change to a different form by emitting radiation. ∎ technical (of a physical quantity) undergo a gradual decrease. • n. the state or process of rotting or decomposition. ∎  structural or physical deterioration: the old barn fell into decay. ∎  rotten matter or tissue: fluoride heals small spots of decay. ∎  the process of declining in quality, power, or vigor: moral decay. ∎  Physics the change of a radioactive substance, particle, etc., into another by the emission of radiation. ∎ technical gradual decrease in the magnitude of a physical quantity. ORIGIN: late Middle English: from Old French decair, based on Latin decidere ‘fall down or off,’ from de- ‘from’ + cadere ‘fall.’