A luminescence measurement of the luxAB-genes-marked strain (Pseudomonas fluoreseens X16L2) was carried out in liquid culture and soil microcosms.The curves of luminescence kinetics of X16L2 in the liquid culture and soils were similar.The time reaching stable luminescence was about 7 nun after the luciferase substrate (n-decanal) was added.The results also showed that the bioluminescence could reflect the biomass of X16L2 in liquid culture,and the light output of X16L2 was closely related to not only the number.of viable cells but also the cell physiological activity.Soil conditions and native microorganisms had great effects on the survival of the introduced strain,including the number of viable cells and light output as well as the potential luminescence of X16L2.This study also demonstrated that luminometry could not only in situ detect the physiological activity of lux-genes-marked strain in the samples,but also measure its population indirectly.This method was a rapid and economical technique with high stability and sensitivity,and strong selectivity for tracking and recovering target microorganisms released to the environments.