Respiratory quinone profiles were applied as tools for identifying different bacterial populations in the aerobic submerged biofilter along with the change of environment such as the temperature and the loading of hard-biodegradable chemicals. To begin with, a novel and simplified analytical operation of respiratory quinones was developed. A diversity in microbial population was observed in the film cultivated at the higher temperature. The change of microbial population in the course of acclimation to hard-biodegradable chemicals such as dimethylformamide(DMF, hereafter) was clarified on the basis of quinone profile.