Hu Nan, Zhao Bin
State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.
FEMS Microbiol Lett. 2007 Feb;267(1):17-22. doi: 10.1111/j.1574-6968.2006.00505.x. Epub 2006 Dec 8.
A cadmium-resistant bacterium Pseudomonas putida CD2 was isolated from sewage sludge samples. Strain CD2 exhibited high maximal tolerant concentrations (MTC) for a large spectrum of divalent metals. Screening a library obtained using Tn5-B21 insertion mutagenesis resulted in identification of 12 mutants with a substantial decrease in resistance to 3 mM cadmium. The DNA sequences of the contiguous region from the Tn5 insertion sites were determined by inverse PCR. Six genes involved in cadmium resistance were identified. These genes were from three gene clusters: czcCBA1, cadA2R and colRS. The homologs of the first two gene clusters were predicted to be metal efflux systems, whereas the products of colRS, ColR and ColS, were thought to be a two-component signal transduction (TCST) system. In this study, we have demonstrated that ColRS also function in regulating multi-metal resistance using genetic complementation.
从污水污泥样本中分离出了一株耐镉细菌恶臭假单胞菌CD2。菌株CD2对多种二价金属表现出较高的最大耐受浓度（MTC）。对使用Tn5 - B21插入诱变获得的文库进行筛选，鉴定出12个对3 mM镉抗性大幅降低的突变体。通过反向PCR确定了Tn5插入位点相邻区域的DNA序列。鉴定出6个与镉抗性相关的基因。这些基因来自三个基因簇：czcCBA1、cadA2R和colRS。前两个基因簇的同源物预计为金属外排系统，而colRS的产物ColR和ColS被认为是一个双组分信号转导（TCST）系统。在本研究中，我们通过基因互补证明了ColRS在调节多金属抗性中也发挥作用。
