A free-living aspartate-fermenting Campylobacter spec. was shown to utilize hydrogen produced in mixed culture by Clostridium cochlearium from glutamate. Resting cells of Campylobacter were shown to reduce aspartate, fumarate and malate as well as nitrate, nitrite, hydroxylamine, sulphite, thiosulphate and elemental sulphur with molecular hydrogen. Growth of Campylobacter spec. was demonstrated with formate as electron donor and nitrate, thiosulphate, elemental sulphur or oxygen as electron acceptor in the presence of acetate as carbon source.