Whole-cell kinetics of phenol- and trichloroethylene (TCE)-degrading activities expressed by 13 phenol-degrading bacteria were analyzed. The K-s (apparent affinity constant in Haldane's equation) values for TCE were unexpectedly diverse, ranging from 11 muM to over 800 muM. The V-max/K-s values for phenol were three orders of magnitude higher than the values for TCE in all bacteria analyzed, suggesting that these bacteria preferentially degrade phenol rather than TCE. A positive correlation between K-s for phenol and K-s for TCE was found, i.e., bacteria exhibiting high Kh values for phenol showed high K-s values for TCE, and vice versa. A comparison of the K-s values allowed grouping of these bacteria into three types, i.e., low-, moderate- and high-K-s types. Pseudo-first-order degradation-rate constants for TCE at 3.8 muM were found to be adequate to rapidly discriminate among the three types of bacteria. When bacteria were grown on phenol at the initial concentration of 2 mM, Comamonas testosteroni strain R5, a representative of low-K-s bacteria, completely degraded TCE at 3.8 muM, while strain P-8, a representative of high-K-s bacteria, did not. A mixed culture of these two bacteria poorly degraded TCE under the same conditions, where P-8 outgrew R5. These results suggest that low-K-s bacteria should be selectively grown for effective bioremediation of TCE-contaminated groundwater.