Lichens are a symbiosis of at least two quite different organisms. The partnership always involves a fungus, which lives with one or more partners which are capable of photosynthesis. The photobiont partner may be a green alga and/or a cyanobacterium. 
Behind the scenes
- Lichens have also been used to make dyes, perfumes, and herbal medicines. Some lichen produce natural antibiotics that kill bacteria. Humans have used these compounds as natural antibiotics. Extracts from many Usnea species were used to treat wounds in Russia in the mid-twentieth century.
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