Thermal events accompanying the growth of K. aerogenes in batch culture in phosphate- and glucose-limited salts media were recorded using an LKB flow micro-calorimeter; changes in the cellular ATP content and growth parameters (biomass, CO2) were also measured. Calorimetric data is discussed in terms of the specific power output (P) and ATP data in terms of the ATP pool. Standard experimental and cultural conditions were established; at p = 0.95 the reproducibility of the heat output was 1%, and that of the ATP pool and other parameters was 3-4.5%. The specific power and ATP pool are similar indicators of metabolic activity; the P-t trace generally followed the course of the ATP profile. The values of P and the ATP pool increased rapidly at the start of the exponential growth phase; and on cessation of growth they decreased rapidly. During exponential growth under glucose-limitation the ATP profile oscillated about a mean value; the specific power remained nearly constant. The energy required for biosynthetic processes was calculated from mass and energy balances. Relative changes in this energy and the yield suggest that the biosynthetic energy is composed of the energy required for anabolism, for maintenance and for storage. Three different and distinct types of consecutive growth occurred under phosphate-limitation (glucose 60% in excess); mass and energy balances were established for each. The specific power output and cellular ATP profile decreased with decreasing availability of phosphate. It is apparent that cellular phosphate exists in two forms; free and fixed phosphate. The effect of increasing concentrations of sulphanilamide arid nalidixic acid (NA) on thermal and growth parameters was similar. NA exhibited a dual dose-related antibacterial potency; this is attributed to the change in its mode of action on RNA, DNA and protein synthesis. Changes in the P-t profiles were observed during the development of cellular resistance to NA.<p
