7-methylpterin derivatives in extracts of methanogens characterized by a relatively low methanopterin content.

Cofactor extracts of five hydrogenotrophic methanogenic bacteria which contain relatively low amounts of methanopterin were screened for the presence of 7-methylpterin derivatives. Extracts of Methanospirillum hungatei, Methanobrevibacter smithii and Methanoplanus endosymbiosus were found to contain 7-methylpterin and methanopterin. These compounds were absent in extracts of Methanogenium thermophilicum and Methanogenium tatii. An unidentified methanopterin-like compound was detected in extracts of these two species and of Msp. hungatei, while a 7-methylpterin-like compound was found in extracts of Mp. endosymbiosus. A possible physiological role of the latter two compounds is discussed.