Futamata H, Harayama S, Watanabe K
Marine Biotechnology Institute, Kamaishi Laboratories, Iwate, Japan.
Appl Microbiol Biotechnol. 2001 Mar;55(2):248-53. doi: 10.1007/s002530000500.
Whole-cell kinetics of phenol- and trichloroethylene (TCE)-degrading activities expressed by 13 phenol-degrading bacteria were analyzed. The Ks (apparent affinity constant in Haldane's equation) values for TCE were unexpectedly diverse, ranging from 11 microM to over 800 microM. The Vmax/Ks 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 Ks for phenol and Ks for TCE was found, i.e., bacteria exhibiting high Ks values for phenol showed high Ks values for TCE, and vice versa. A comparison of the Ks values allowed grouping of these bacteria into three types, i.e., low-, moderate- and high-Ks types. Pseudo-first-order degradation-rate constants for TCE at 3.8 microM 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-Ks bacteria, completely degraded TCE at 3.8 microM, while strain P-8, a representative of high-Ks 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-Ks bacteria should be selectively grown for effective bioremediation of TCE-contaminated groundwater.
分析了13株苯酚降解菌所表达的苯酚和三氯乙烯（TCE）降解活性的全细胞动力学。TCE的Ks（Haldane方程中的表观亲和常数）值出人意料地多样，范围从11μM到超过800μM。在所有分析的细菌中，苯酚的Vmax/Ks值比TCE的值高三个数量级，这表明这些细菌优先降解苯酚而非TCE。发现苯酚的Ks值与TCE的Ks值之间存在正相关，即对苯酚表现出高Ks值的细菌对TCE也表现出高Ks值，反之亦然。通过比较Ks值可将这些细菌分为三种类型，即低Ks型、中Ks型和高Ks型。发现3.8μM的TCE的拟一级降解速率常数足以快速区分这三种类型的细菌。当细菌在初始浓度为2 mM的苯酚上生长时，低Ks细菌的代表菌株睾酮丛毛单胞菌R5能完全降解3.8μM的TCE，而高Ks细菌的代表菌株P-8则不能。在相同条件下，这两种细菌的混合培养物对TCE的降解效果很差，其中P-8的生长超过了R5。这些结果表明，为有效生物修复受TCE污染的地下水，应选择性培养低Ks细菌。
