Saprotrofe

Saprotroph is a term used in biology to describe organisms that obtain nutrients from dead or decaying organic matter. In some languages the term saprotrofe is used as a cognate. Saprotrophs perform decomposition by breaking down complex organic polymers into smaller molecules from which they absorb nutrients.

Most saprotrophs are fungi and bacteria, though some protists and certain invertebrates can participate. Fungi commonly secrete extracellular enzymes such as cellulases, ligninases, and proteases to digest material outside their cells, then take up the resulting sugars, amino acids, and other compounds. Bacteria carry out similar extracellular digestion and absorption. This mode of nutrition is described as saprotrophic or saprobic and is distinct from symbiotic parasitism on living hosts.

Ecologically, saprotrophs are central to nutrient cycling and soil formation. They decompose leaf litter, dead wood, and other organic residues, releasing inorganic nutrients that plants can reuse and contributing to the formation of humus. Rates of decomposition depend on substrate quality, moisture, temperature, and the activity of saprotrophic communities.

Common habitats include forest soils, leaf litter, decaying wood, compost, and marine or freshwater sediments. In forests, wood-decay fungi such as white-rot and brown-rot species are well known saprotrophs.

Humans employ saprotrophs in composting and bioremediation; understanding their activity improves waste management and soil fertility.