Аннотация:The bioluminescent luciferin-luciferase reaction is based on the oxidation of D-luciferin by oxygen in the presence of ATPand magnesium ions, catalyzed by firefly luciferase. The possibilities of using this reaction to study the influence of externaleffectors of a physical and chemical nature (temperature exposure, additions of drugs, membrane-active compounds, etc.) onliving cells (prokaryotes and eukaryotes) are considered. Examples of the use of test systems based on living cells producingthermostable firefly luciferase for monitoring cellular homeostasis are given. The study of the kinetics of changes in theconcentration of ATP and luciferase inside and outside cells made it possible to determine in dynamics the metabolic activity,cytotoxicity, and survival of cells under conditions of cellular stress, to study the processes of ATP synthesis/hydrolysis, andto evaluate the effectiveness of lytic agents in changing the permeability of the cell membrane.