Effects of iron deficiency and of zinc deficiency on the composition of Mycobacterium smegmatis.

hydroxybutyrate and DPN+ and the amounts of DPNH formed were measured. Phosphate buffer was used at pH 7 and tris buffer at the fnore alkaline pH values. Controls containing all reagents except P-hydroxybutyrate or acetoacetate showed no significant changes in extinction. The results of 14 individual measurements showed good agreement (Table 1). The mean value for K was 1-42 + 0 19 (S.D.) X 10-9. From this value and the Eo for the DPN+-DPNH system of 0320 v at pH 7 0 and 250 (Burton, 1957), Eo for the ,Bhydroxybutyrate system is calculated to be 0266 v. This figure is much less negative than that calculated by Burton (1957) and slightly less negative than those arrived at (for 380) by Green et al. and Hoff-Jorgensen. For a full discussion of any error in Burton's figure for Eo of the DPN system see Clark (1960); the figure of -0-320 v may be a little too high. The above K value is very similar to that recently obtained at 32° by Doudoroff, Merrick & Contopoulou (1961), using a preparation of f-hydroxybutyric dehydrogenase from Rhodospirillum rubirum (1-3 x 10-9).