Abstract: The protein response of bacterial enzymes involved in degradation of benzo(a)pyrene (BaP) by three bacteria (BZSY-1, BZSY-2 for Bacillus, BZSY-3 for Zooloea sp.) were examined under different conditions. The relationships between the degradation rate and enzyme activity were analyzed. Four enzymes (C12O, C23O, CAT and PPO) were detected upon using different concentrations of BaP. Among the four enzymes, the activity of C23O was the highest and that of PPO was the lowest. The activity of CAT was not correlated with the concentration of BaP. 〖After adding sodium succinate (co-metabolites), the activities of C12O and C23O were enhanced, whereas that of CAT was not changed, and the activity of PPO was still lower. Compared with the control, the activities of C12O, C23O and PPO were not affected when the concentration of TW80 was less than or equal to 1000 μg·mL^-1. When the concentration of TW80 was greater than 2000 μg·mL^-1, the activities of these three enzymes were inhibited by various degrees. Compared with BZSY-1, both BZSY-2 and BZSY-3 had higher BaP degradation rates and higher activities of the corresponding enzymes (especially C12O and C23O), which further supported the notion that the microbial degradation of BaP is an enzymatic reaction. C12O and C23O are the two key BaPdegrading enzymes in the three bacteria.

Key words: growing season, temperature sensitivity of autotrophic respiration, winter wheat growth stage, soil temperature