Analyses of the F(420)s present in Methanococcus jannaschii have shown that these cells contain a series of gamma-glutamyl-linked F(420)s capped with a single, terminal alpha-linked L-glutamate. The predominant form of F(420) was designated as alpha-F(420)-3 and represented 86% of the F(420)s in these cells. Analyses of Methanosarcina thermophila, Methanosarcina barkeri, Methanobacterium thermoautotrophicum, Archaeoglobus fulgidus, and Mycobacterium smegmatis showed that they contained only gamma-glutamyl-linked F(420)s.