Methanogenic bacteria are members of a newly described, third primary kingdom of organisms, the archaebacteria. One of the many characteristics that seperate the methanogens from all other organisms, including other archaebacteria, is their ability to produce methane. The production of methane requires a number of novel coenzymes or cofactors; these include methanopterin and component B. This research is directed at establishing the routes used by these organisms for the biosyntheses of these important coenzymes. Methanopterin appears to represent the first reported example of a structurally modified folic acid. Since this modified folic acid is present in the methanogenic archaebacteria, there is the possibility that other modified C1 carriers are to be found in other archaebacterial species. Studies on one species of Sulfolobus, a thermophilic archaebacteria, have indeed shown it to contain a C1 carrier different in structure from methanopterin and from any known folic acid. In this research, the structure of this C1 carrier will be determined and it will be compared with those of folic acid and methanopterin in the hope that their structures may shed some light on how the biosyntheses of these different C1 carriers have evolved in the different groups of organisms.//