Cytochrome oxidase in cells of the genus Brucella

Few quantitative data exist on the cytochrome oxidase activity of bacteria although studies (Nishibe, 1926; Loele, 1929; Yamagutchi, 1935) of the distributionof bacterial oxidasehave shown that approximately one-third of the bacteria ex-amined were capable of oxidizing para-phenyl-enediamine or its derivatives. Colorimetric deter-mination of the oxidized dye has served for the approximation of bacterial cytochrome oxidase activity, but intracellular decoloration of the dye (Battelli and Stern, 1912) and the complexity of the reaction (Clark et al., 1926) produce results too inaccurate for quantitative studies. The meas-urement of oxygen uptake has not been rigor-ously pursued and developed for use with bacte-ria. Yamagutchi (1935) most nearly approached quantitative technique by determining the oxygen uptake of several bacterial species on the basis of dry cell weight; no study of conditions for maxi-mum activity of intact cells was recorded, and the oxygen uptake of a single mass of cells did not permit correction for autoxidation of p-phenyl-enediamine in the presence of cells. Data do not appear to exist on the oxygen uptake of a given number of viable bacterial cells in the presence of p-phenylenediamine. When investigation with the Keilin and Hartree manometric method (1938) for the measurement of cytochrome oxidase activity showed that a small, but definite, oxygen consumption occurred with cells of the genus Brucella, experiments were conducted to determine if conditions could be established that would increase the oxygen uptake to permit quantitative determination of p-phenyl-enediamine oxidase activity in relatively few cells. The cytochrome oxidase activity of 109 viable cells of the 3 Brucella species was determined under the conditions selected. An attempt was made to study the cytochrome oxidase activity of disintegrated cells and cells of increased per