. capable of anaerobic growth on methane have not been cultivated so far, and the biochemical pathway of the anaerobic oxidation of methane (AOM) re- mains speculative. Analyses of depth profiles and. michaelis@geowiss.uni-hamburg.de R EPORTS www.sciencemag.org SCIENCE VOL 297 9 AUGUST 2002 1013 methane. The methane seeping from the mi- crobial structures and from nearby sediment pockmarks is of biogenic origin, as. structure of about 1 m height. The surface of the structure consists of gray- black microbial mat; the interior of the massive mat is pink. The greenish-gray inner part of the structure consists of