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The literature concerning the effect of immune serum upon the activities of microorganisms has been fully reviewed and discussed by Sevag (1945). Sevag and Miller (1948) recently reported that the agglutination of typhoid organisms does not inhibit oxygen upta4e by the cells, whereas lysed cells show an immediate increased rate of oxygen consumption followed by a marked decrease. The work herein reported consisted of a series of experiments to determine whether combination of agglutinins with the cells of a number of Salmonella species had any effect on their respiratory activity. Cells for studies were obtained by culturing the organism on glycerol thiosulfate agar. Sufficient growth occurred in 24 hours to yield a heavy suspension of cells suitable for use either as antigens or for enzyme studies. Cells were suspended in a balanced salts-buffer solution (Harris and Gainey, 1944) and washed twice by centrifuging, after which they were suspended in a concentration of approximately 100 times the turbidity of MacFarland nephelometer tube no. 1, and cooled to 3 C. Normal adult rabbits were immunized by a series of intravenous injections of heat-killed cultures. The immune serum was obtained by centrifugation following clotting of blood removed by cardio-puncture. All tests were conducted the same day the rabbits were bled. Agglutination tests to determine the antibody titer followved the usual procedure for tube tests. Oxygen utilization was measured in the Warburg microrespirometer at 37 C, following the usual technique of Dixon (1934). Twentieth molar glucose, buffered at pH 7.0 with phosphate salts, was used as the respiration substrate in all experiments. Cells grown and harvested in the manner described were quite active physiologically and exhibited little or no endogenous respiration. The methylene blue reduction tests followed the Thunberg technique as described by Quastel and Whetham (1925). Visual judgment of the complete reduction of the dye was taken as the end point. Although this method is subject to error, significant differences in the rate of reduction of the methylene blue can be observed. In measuring oxygen uptake by microorganisms with the manometric method, the formation of hydrogen gas by the cells may lead to significant errors. However, in no instance in this investigation was a positive gaseous pressure recorded during an experimental period of 2" hours when nitrogen replaced the air in the respiration flasks and alkali was present to absorb carbon dixoide. Hence it may be assumed that no appreciable volume of hydrogen was liberated by the

The Respiration of Salmonella in the Presence of Agglutinating Serum