The assay of adenosine 5'-triphosphate extracted from salt-marsh microbiota

The light-emitting reaction of firefly luciferin and luciferase is a common ingredient in the quantification of adenosine triphosphate (ATP) extracted from the microbiota of environmental samples. Both portions of the light-emission phase of the luciferase reaction, the primary flash within 3 s of mixing and the secondary decay in the luminescence following the flash, have been used to quantify extracted ATP. However, the magnitude of the secondary phase is influenced by nucleotides other than ATP. The impact of this influence on the quantification of ATP was studied in samples collected from the water covering a salt marsh. Analysis by integration of the secondary decay portion of the emission yielded values of ATP per cubic metre that were consistently higher than those obtained by peak height analysis of the same extracts. Assays using the integration technology resulted in values that were up to 8 (mean = 3.6) times higher than corresponding values determined by peak height analysis in unfractionated samples (total microbial biomass) and up to 16 (mean = 4.8) times higher in water that had been prefiltered with a 1.0 micrometer filter (bacterial biomass).