Most fungi are placed into Kingdom Fungi , and are more closely related to animals than to the plants. Fungal threads known as hyphae permeate rock, soil, crops, plant roots, algal cells, and human food stuffs. Fungi live in association with plant roots from nearly every plant group as mycorrhizae , which increase the nutrient uptake capabilities of the plants. Fungi form symbiotic associations with green algae and cyanobacteria to form nearly 15,000 different species of lichens . If it weren't for fungi, the forest floors of temparate regions would be meters deep with non-decayed wood.
Fungi are the major recyclers of carbon in many forest ecosystems.
Lichen associations between fungi and cyanobacteria, are important for nitrogen fixation in temparate forests. Fungi living inside plant stems as endophytes , produce chemicals that deter herbivores, providing a selective advantage for the plant that contain them. Devastating fungal disesases such as Chestnut Blight and Dutch Elm Disease have wiped out the dominant trees in entire forests. Wisconsin has had a large number of infections from Blastomycosis , a fungus that lives in damp soil, and seems to infect dogs in particular. Histoplasmosis can cause debilitating lung infections, and Pneumocystis is a virulent fungus that attacks people with whose immune systems have been compromised by the HIV virus or anti-rejection drugs.