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首页> 美国卫生研究院文献>Applied and Environmental Microbiology >Saturable Energy-Dependent Uptake of Phenanthrene in Aqueous Phase by Mycobacterium sp. Strain RJGII-135
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Saturable Energy-Dependent Uptake of Phenanthrene in Aqueous Phase by Mycobacterium sp. Strain RJGII-135

机译：分枝杆菌对水相中菲的能量依赖吸收。菌株RJGII-135

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The mechanism of uptake of phenanthrene by Mycobacterium sp. strain RJGII-135, a polycyclic hydrocarbon-degrading bacterium, was examined with cultures grown on phenanthrene (induced for phenanthrene metabolism) and acetate (uninduced). Washed cells were suspended in aqueous solutions of [9-14C]phenanthrene, and then the cells were collected by filtration. Low-level steady-state 14C concentrations in uninduced cells were achieved within the first 15 s of incubation. This immediate uptake did not show saturation kinetics and was not susceptible to inhibitors of active transport, cyanide and carbonyl cyanide m-chlorophenylhydrazone. These results indicated that phenanthrene enters rapidly into the cells by passive diffusion. However, induced cells showed cumulative uptake over several minutes. The initial uptake rates followed saturation kinetics, with an apparent affinity constant (Kt) of 26 ± 3 nM (mean ± standard deviation). Uptake of phenanthrene by induced cells was strongly inhibited by the inhibitors. Analysis of cell-associated 14C-labeled compounds revealed that the concurrent metabolism during uptake was rapid and was not saturated at the substrate concentrations tested, suggesting that the saturable uptake observed reflects membrane transport rather than intracellular metabolism. These results were consistent with the presence of a saturable, energy-dependent mechanism for transport of phenanthrene in induced cells. Moreover, the kinetic data for the cumulative uptake suggested that phenanthrene is specifically bound by induced cells, based on its saturation with an apparent dissociation constant (Kd) of 41 ± 21 nM (mean ± standard deviation). Given the low values of Kt and Kd, Mycobacterium sp. strain RJGII-135 may use a high-affinity transport system(s) to take up phenanthrene from the aqueous phase.
机译：分枝杆菌对菲的吸收机理用在菲（诱导的菲代谢）和乙酸盐（未诱导）上生长的培养物检查了多环烃降解细菌RJGII-135菌株。将洗涤的细胞悬浮在[9- 14 C]菲的水溶液中，然后通过过滤收集细胞。在孵育的前15 s内，未诱导细胞中的低水平稳态 14 C浓度达到。这种立即摄取没有显示出饱和动力学，并且不易受活性传递抑制剂氰化物和羰基氰化物间氯苯基hydr的影响。这些结果表明菲通过被动扩散迅速进入细胞。但是，诱导的细胞在几分钟内显示出累积摄取。初始吸收速率遵循饱和动力学，其表观亲和常数（Kt）为26±3 nM（均值±标准偏差）。抑制剂强烈抑制了诱导细胞吸收菲。细胞相关的 14 C标记化合物的分析表明，摄取期间的并发代谢迅速，并且在测试的底物浓度下未达到饱和，这表明所观察到的饱和摄取反映了膜转运而不是细胞内代谢。这些结果与在诱导的细胞中菲转运的饱和，依赖能量的机制的存在是一致的。此外，累积摄取的动力学数据表明，菲以饱和状态为基础，其表观解离常数（Kd）为41±21 nM（均值±标准偏差），因此被诱导的细胞特异性结合。由于Kt和Kd值较低，因此分枝杆菌RJGII-135菌株可使用高亲和力转运系统从水相吸收菲。

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