The technique for ATP bioluminescent cell detection was first described in the 1960s by NASA scientists who were interested in clinical applications as well as for determining if life existed on other planets. The technique makes use of the fact that all living cells contain ATP, which is a universal energy donor for metabolic reactions. However, after cell death, the ATP content decreases sharply, allowing the intracellular ATP concentration to serve as a measure of biomass and cell viability.
The level of ATP in a cell remains relatively constant; thus, the light produced during the luciferase-luciferin-catalyzed reaction is directly related to the number of metabolically active cells present in the assay. Assuming that the ATP content of an average bacterial cell is about 1–10 amol, theoretically even single cells should be detectable using this method.
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