Compost Critters Actinomycetes - medium temperature colonizers. Actinomycetes produce the grayish cobwebby growths throughout the compost that give a pleasing, earthy smell, like the forest floor.
Actinomycetes usually colonize the compost after the thermophilic bacteria have been active.
Fungi Fungi are like simple plants that lack chlorophyll, the green pigment that allows most plants to convert sunlight into carbohydrate. Instead, most fungi obtain nutrients from dead plant matter. Therefore, Fungi are important decomposers in the natural world. Fungi are most active in the later stages of the compost pile, where they finish the decomposition of materials partially decomposed by bacteria. This may mean that the compost is ready for use, or it may also indicate that the compost pile is not decomposing properly and not becoming hot.