Biotin Liberation by the Lichen Alga Coccomyxa Sp. And by Chlorella Pyrenoidosa

The unicellular green alga Coccomyxa, a component of the lichen Peltigera aphthosa, liberated about 7.2mμg biotin per mg dry weight of cells into the culture medium during a growth period of 15–20 days. The corresponding figure for the free-living alga Chlorella pyrenoidosa was 0.45mμg of biotin. Chromatographic analysis indicated that this was free biotin and not a bound form of the vitamin. The biotin concentration of rinsed Coccomyxa cells was 1.88mμg per mg dry weight of cells, of which less than 0.01mμg was extractable by hot water. Cells of Chlorella contained 0.16mμg of biotin per mg dry weight, of which 0.11mμg was extractable by hot water. The biotin content of Coccomyxa, which was about 12 times that of Chlorella, is thus almost entirely in the bound form. The importance of biotin in the symbiotic interactions between the alga and the fungus in Peltigera is discussed.