Methanobacterium lacus (la9cus. L. gen. n. lacus of a lake, indicating the site of isolation).Cells are non-motile, long (2–15 mm) rods that usually grow as filaments. Cells stain Gram-negative, autofluoresce under ultraviolet light (l420) and are resistant to lysis in 0.1% (w/v) SDS or distilled water