Studies in Carotenogenesis. Some Observations on Carotenoid Synthesis in Two Varieties of Euglena gracilis.

Euglena gracilis v. bacillaris and E. gracilis v. fuscopunctata produce the same three carotenoids, β-carotene, lutein and neoxanthin in approximately the same relative amounts. Lutein is the major pigment and β-carotene represents about 10–15% of the total. The concentration of carotenoids in E. gracilis v. bacillaris is very high, reaching 700 mg./100 g. dry weight.
Streptomycin (0.02%, w/v) and darkness reduced growth of E. gracilis v. bacillaris by about 50% and carotenoid synthesis by about twenty times. Diphenylamine (1/70,000) reduced growth and carotenoid synthesis equally (about 50%). In no case was the synthesis of more saturated polyenes (the phytofluene series) stimulated.
The nature of the eye spot pigment is discussed.