Microcalorimetry studies of energy changes during the growth of Klebsiella aerogenes in simple salts/glucose media: inhibition by nalidixic acid.

The addition of nalidixic acid (NA) to exponentially growing cells of Klebsiella aerogenes in simple salts/glucose media has a marked effect on the thermal and other growth parameters of the cells. Mass and energy balances have been established for normal and inhibited growth. The decrease, with increasing NA concentration, of energy allocated to biomass and the increase in that wasted is discussed in terms of the energy stored in macromolecular species by the cells under conditions of stress. The enthalpy of production of cellular material, and the enthalpy of metabolism of glucose become more negative with increasing inhibition. A dual-dose response of NA was observed; at low concentrations the potency was greater than at high concentrations.