saprotrophic

Saprotrophic refers to organisms that feed on dead or decaying organic matter through extracellular digestion followed by uptake. They are heterotrophs that obtain their carbon and energy from litter, wood, dung, and other detritus rather than from photosynthesis. Saprotrophs occur in diverse groups, notably fungi and bacteria, and include many saprotrophic fungi in the phyla Basidiomycota and Ascomycota.

Saprotrophs secrete extracellular enzymes such as cellulases, hemicellulases, lignin-degrading enzymes (lignin peroxidases, manganese peroxidases), proteases, lipases, and amylases into the substrate. These enzymes break down complex polymers to smaller molecules that the organism can absorb through its cell walls. This enzymatic digestion enables the recycling of organic matter and the release of nutrients back to ecosystems.

They play a central role in nutrient cycling, soil structure, and carbon flux. They colonize leaf litter, the forest floor, decaying wood, and dung, and can form extensive networks of mycelium that explore substrates. In forests, saprotrophic fungi participate in the decomposition of lignin and cellulose, facilitating nutrient release for other organisms. Humans experience their influence in areas such as food spoilage, industrial enzyme production, and biotechnological applications.

They differ from parasitic organisms, which feed on living hosts, and from mutualists, which form beneficial associations with living organisms. Some organisms show flexible nutrition, acting as saprotrophs on dead material and as pathogens or mutualists in other contexts.