Influence of Water Activity on the Amount of Adenosine Triphosphate (ATP) of Bacteria by Bioluminescence

ATP levels of bacteria in Tryptic Soy Broth with 0.5 to 8.7% (w/w) NaCl (water activity, aw 0.997-0.945) were studied during 3-day incubation period at 25°C by the luciferin-luciferase bioluminescence reaction method. The amount of intracellular ATP per cell of Staphylococcus epidermidis, Escherichia coli and Vibrio parahaemolyticus ranged from 1.3 to 6.1×10-18 mol/cell in the stationary phase. ATP content of bacterial cells varied greatly with age. The changes in aw had little effect upon the amount of ATP.