Decomposing organic material
Saprobionts gain nutrients by digesting dead organisms and organic waste outside their cells. Common saprobionts include fungi and bacteria.
By acting on dead material, saprobionts return elements such as nitrogen and phosphorus to the surrounding environment so that they can enter nutrient cycles again.
Extracellular digestion
Secretion
Digestive enzymes are released from the saprobiont onto material outside its cells.
Digestion
The enzymes break organic substances into smaller soluble substances in the surroundings.
Absorption
The saprobiont then takes up some of the soluble products for use in its cells.
A proportion of the digestion products remains outside the saprobiont. This can leave mineral ions in the soil, where they are available for plant uptake.
Key outcome: elements are moved out of organic remains and into the surroundings, allowing mineral nutrients to become available to producers again.
Role in ammonification
When saprobionts act on nitrogen-containing remains and waste, ammonia is produced. This contribution to nitrogen recycling is known as ammonification.
Exam Tip: Link decomposition to nutrient availability. Explain that extracellular digestion can leave mineral ions in the surroundings where other organisms can take them up.