[2] Extraction of adenosine triphosphate from microbial and somatic cells

This chapter discusses the extraction of adenosine triphosphate (ATP) from microbial and somatic cells. There are many reasons for extracting and measuring ATP from cells, but they may be placed into one of two main categories: (1) the level of endogenous ATP in a cell may be used as an index of energy status, and it is therefore useful in metabolic and physiological studies; (2) estimates of cell numbers in microbial and tissue cultures may be obtained after assuming that the ATP per cell remains at a fairly constant (within a factor of five) and known value under defined conditions. Thus, by measuring total ATP in a sample of culture, cell numbers may be rapidly obtained. This is the basis of rapid microbiology using the ATP-firefly luminescence technique. The chapter discusses the properties of the ideal extractant: (1) it should penetrate the cell wall and membrane more or less instantaneously; (2) it should extract ATP more or less instantaneously; and (3) it should instantaneously and irreversibly inactivate all enzymes that use ATP as a substrate or produce ATP from other substrates.