Rapid Microbiology: the Use of Luminescence and Adenosine Triphosphate (ATP) for Enumerating Microbes and Checking Effectiveness of Biocides: Present Status and Future Prospects

Abstract

All living cells contain ATP and typically a bacterial cell contains about a femtogram (10-15g) of ATP. The enzyme firefly luciferase reacts specifically with ATP to produce a photon of light for each ATP molecule hydrolysed. It is possible to assay as little as 10-13gATP by measuring the light produced using a sensitive luminometer. The technique is suited for rapid enumeration of microbes in a range of samples. Once the ATP has been extracted from the microorganism the light producing reaction takes less than a minute to perform. Efforts are being made to improve the means by which ATP is extracted from a range of microbial cells and spores. Extractants must be effective and compatible with the firefly luciferase and not cause inhibition or colour quenching Most real samples also contain free ATP and some cellular somatic ATP (eg. from animal or plant cells) and methods need improvement for removal of this ATP prior to extraction and measurement of microbial ATP. Better specifications are also expected in the sensitivity of luminometers and available luciferase and accompanying reagents. Future improvements in the technology will allow the ATP luminescence technique to be used to enumerate at least some individual species of microorganisms.