Diversity in kinetics of trichloroethylene-degrading activities exhibited by phenol-degrading bacteria

Whole-cell kinetics of phenol- and trichloroethylene (TCE)-degrading activi ties expressed by 13 phenol-degrading bacteria were analyzed. The K-s (appa rent affinity constant in Haldane's equation) values for TCE were unexpecte dly 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 p henol 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 sh owed high K-s values for TCE, and vice versa. A comparison of the K-s value s 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 thr ee types of bacteria. When bacteria were grown on phenol at the initial con centration of 2 mM, Comamonas testosteroni strain R5, a representative of l ow-K-s bacteria, completely degraded TCE at 3.8 muM, while strain P-8, a re presentative of high-K-s bacteria, did not. A mixed culture of these two ba cteria poorly degraded TCE under the same conditions, where P-8 outgrew R5. These results suggest that low-K-s bacteria should be selectively grown fo r effective bioremediation of TCE-contaminated groundwater.