Mix ingredients, except yeast extract, sulfur and Na2S·9H2O, adjust pH to 6.5 with H2SO4, and autoclave under a N2 atmosphere. Separately autoclave yeast extract and peptone as 10% solutions under a N2 atmosphere. Steam sulfur for 3 hr on each of 3 successive days. Neutralize Na2S·9H2O as a 5% solution, and autoclave under a N2 atmosphere. Aseptically and anaerobically add the yeast extract and peptone solutions, and sulfur to the medium. Prior to inoculation, add the sterile Na2S·9H2O solution, and readjust pH to 6.5, if necessary.