No abstract

Bertrand-Hudson rule; the other exhibits activity resembling that of an extract made from Candida Utili. MATERIALS AND METHODS Organisms. Acetobacter suboxydans, no. 621, was obtained from the American Type Culture Collection, Washington, D.C. It was grown at 300 for 3 days in a yeast-water medium to which 0.3 % (w/v) of KH2PO4 and 2 % (w/v) of glycerol were added (pH about 5.5). The cultures (100 ml. of medium in 500ml. conicalflasks) were aerated by continuous shaking. Yeast water was prepared by boiling 1 lb. of baker's compressed yeast with 400 ml. of water for 30 min., allowing the yeast to settle overnight, filtering the supernatant through kieselguhr and making the volume up to 51. with water. Candida utilis (strain Y 90/77) was obtained through the courtesy of the Northern Regional Research Laboratories, Department of Agriculture, U.S.A. The stock culture was maintained on malt-agar slopes. For experiments the organism was transferred either to the glucose-containing basal medium of Schultz & Atkin (1947) or to a medium having the following composition: 2-0 g. of KH2P04, 0-25 g. of anhydrous CaCl2, 0.5 g. of MgSO4,7H20, 4.5 g. of (NH4)2SO4, 20 g. of mannitol and tap water to 1 1. The cultures were incubated at 30°for 2 days and continuously shaken. Cell-free extracts. The cells ofA. 8uboxydans were harvested and washed three times with water by centrifuging. Washed cells (5-10 g.) were suspended in sufficient 001M-Na2HPO4 solution to make a total volume of 25 ml., and disrupted by treating for 40 min. in a Raytheon 9 kcyc./sec. sonic disintegrator. The cup assembly of the apparatus was set up in a cold room at 2-3°and the internal temperature of the cup kept at 0-1°by circulation of ice-water (1.5 1./min.). The extract was clarified by centrifuging at 20000 g for 30 min. in a centrifuge operating at-5°, and dialysed against water for 12 hr. at 20. The extracts were clear red-brown solutions, * This buffer was made by mixing appropriate volumes of 0-2M aminotrishydroxymethylmethane (tris) solution and 0'1M succinic acid solution.