Adenosine triphosphate measurement in soil: an improved method

An improved method for measuring the adenosine 5'-triphosphate (ATP) content of soil is described, in which a purified rather than a crude luciferase preparation is used. Light produced during the reaction between luciferase and ATP is measured with a liquid scintillation spectrometer. Calibration curves by the modified method are linear. Guanosine 5'-triphosphate (GTP) increased light output with the crude but not with the purified luciferase, presumably because the crude preparation contained enzymes that converted GTP to ATP. The ATP contents of 9 soils were, on average, 24% lower when measured using the purified preparation of luciferase than when measured using the crude preparation. However the amount of GTP needed to account for the difference was unreasonably large and other ATP-synthesizing processes must have contributed to the extra ATP measured with the crude luciferase. Conditions for using a luminometer for measuring light output in the ATP assay procedure, in place of a liquid scintillation spectrometer, are also described.