BACTERIAL CALORIMETRY I. GENERAL CONSIDERATIONS. DESCRIPTION OF DIFFERENTIAL MICROCALORIMETER

Abstract

The author describes modifications of the differential microcalorimeter of A. V. Hill, which adapt it to the study of heat produced by growing bacteria. The chief changes are addition of an inner vessel which can be filled with the required amount of culture fluid and sterilized. Other minor changes permit insertion of the thermocouples without contaminating the media, mechanical stirring in place of stirring by air bubbles, and a tube for introduction of inoculum and withdrawal of small samples. Data from calibrations are presented, showing that the apparatus is sufficiently sensitive and accurate to measure production of approximately 6 gm. calories per hr. with an error of [plus or minus]1.88%, and liberation of 23.68 gm. calories per hr. with an error [plus or minus]3.33%, in a vessel and fluid having a heat capacity equivalent to 125 cc. of water. Heat production by cultures of bacteria is within these limits in most of the media employed and it is estimated that the error in measurements within this range is approximately [plus or minus]3%.