saprobe

A saprobe, also called a saprotroph, is an organism that obtains nutrients from dead or decaying organic matter rather than from a living host. Saprobic organisms play a central role in decomposition and nutrient cycling, breaking down complex materials into simpler compounds that can be reused in ecosystems.

Most saprobes secrete extracellular enzymes to degrade their food sources. In fungi, these enzymes include cellulases, ligninases, and proteases, which allow breakdown of cellulose, lignin, proteins, and other polymers. Bacteria and some other microorganisms use similar enzymatic strategies to access organic matter. Many saprobes are aerobic, but some can survive in low-oxygen conditions or switch to facultative anaerobic metabolism when needed.

Ecologically, saprobes contribute to soil formation, organic matter turnover, and the release of minerals, supporting plant growth and ecosystem productivity. They are essential for carbon cycling, humus formation, and the restoration of nutrients after the death of organisms. In forests, wood-decaying fungi and litter-decomposing microorganisms are prominent saprobes.

Examples of saprobes include various fungi such as white-rot and brown-rot basidiomycetes that decompose wood, as well as saprotrophic molds and yeasts. Bacteria such as Bacillus species and Streptomyces also function as saprobes in soils and other habitats. Some organisms can be facultative saprobes, feeding on dead matter under certain conditions but capable of pathogenic or symbiotic lifestyles when living hosts or resources are available.

The term saprobe emphasizes an ecological role rather than a fixed lifestyle, and in microbiology it is often preferred to the older term saprophyte.