The most important type involved in bioremediation, however, are the fungi living on decaying organic matter, called saprophytes. They are most abundant during the initial stages in decomposition of organic matter. The addition of organic matter in soil results in an immediate increase in fungi. During early stages of decomposition, organic matter is seen to be permeated with hyphae. As organic matter is decomposed, fungi decrease.
All fungi are aerobic, and all decomposition carried out by fungi is oxidative in nature.
However, a fungus can have hyphae in anaerobic environments if some of the organism is in an aerobic environment. Fungi can also survive and grow in environments with a high osmotic pressure that would kill or inhibit other microorganisms if the hyphae live partly in and partly outside of areas of high osmotic potential. Using the same mechanism, they can live and grow in fuels such as gasoline, kerosene, and diesel. The growth of fungi in aviation fuel is quite dangerous because the mycelium can block filters and tubing, preventing the flow of fuel to the engines. They can also foul hydraulic lines.