Methanogenesis from acetamide occurs through a two-step reaction in methanogenic sludges. First, acetamide is transformed to acetate and ammonia, then, acetate is converted to methane. There is evidence that the first step is performed by an aerobic sporulating rod that co-exists in the same sludge with methanogens. This finding provides new perspectives for further technological developments in the field of waste-water treatment, on the basis of the establishment of controlled relationships between aerobes and strict anaerobes.