Bacteria and fungi, such as actinomycetes, saprophytes and protozoa. They can use different carbohydrates, including sugar, starch, organic acids, cellulose, hemicellulose and so on as energy sources. The best carbon sources are glucose, maltose, dextrin, starch and glycerol, followed by sucrose, xylose, raffinose, alcohol and organic acids. Among the organic acids, acetic acid, lactic acid, citric acid, succinic acid and malic acid are easy to use, while oxalic acid, tartaric acid and hippuric acid are difficult to use. Some actinomycetes can also use chitin, hydrocarbons, tannins and even rubber.
Heterotrophs: Small invertebrates such as dung beetles and earthworms. They crush plant residues and accelerate the decomposition and transformation of organic matter under the action of microorganisms. In addition, these soil animals can also be decomposed in the body, transforming organic matter into inorganic salts for plants to absorb and utilize again. There are also medium and large scavengers, such as vultures.