An inducible tellurite-resistance operon in Proteus mirabilis
An inducible tellurite-resistance operon in Proteus mirabilis
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DOI：
10.1099/mic.0.25981-0
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发表时间：
2003-05-01
期刊：
影响因子：
2.8
通讯作者：
Hoffman, PS
中科院分区：
文献类型：
--
作者：
Toptchieva, A;Sisson, G;Hoffman, PS
碲酸盐抗性(Te-r)在自然界中广泛存在，奇异变形杆菌对碲酸盐的天然抗性是由于肠道细菌中发现的质粒携带的TER基因的染色体同源所致。在Tn5/acZ产生的突变体中发现了奇异P.mirabilis ter基因座(TerZABCDE)，其中一个突变在TERC中含有一个插入片段。奇异P.mirabilis tec突变体对碲酸盐(Te-S)的敏感性增加，并与teRC互补，恢复了高水平的Te-r。引物延伸分析显示，Terz的上游只有一个单一的转录起始点，但只有在亚碲酸盐存在的情况下生长的细菌获得的RNA。Northern印迹和逆转录聚合酶链式反应(RT-PCR)分析证实，TER操纵子可被亚碲酸盐诱导，在较小程度上可被过氧化氢和甲基紫精(百草枯)等氧化胁迫诱导剂诱导。在TER启动子区域以及-35六聚体上游类似于OxyR结合序列的基序中发现了正向和反向重复序列。最后，位于orf3和terz之间的390bp的基因间启动子区与其他已发表的TER序列没有DNA序列同源性，而terZABCDE基因的DNA序列同源性为73-85%。在所有奇异变形杆菌和普通变形杆菌的临床分离株中都存在TER操纵子，推测该操纵子适用于摩根氏杆菌和普罗维登西亚细菌。基于对高水平Ter的筛查和初步的PCR分析。因此，染色体上可诱导的碲酸盐抗性操纵子似乎是变形杆菌属的共同特征。
Tellurite resistance (Te-r) is widespread in nature and it is shown here that the natural resistance of Proteus mirabilis to tellurite is due to a chromosomally located orthologue of plasmid-borne ter genes found in enteric bacteria. The P. mirabilis ter locus (terZABCDE) was identified in a screen of Tn5/acZ-generated mutants of which one contained an insertion in terC. The P. mirabilis terC mutant displayed increased susceptibility to tellurite (Te-s) and complementation with terC carried on a multicopy plasmid restored high-level Te-r. Primer extension analysis revealed a single transcriptional start site upstream of terZ, but only with RNA harvested from bacteria grown in the presence of tellurite. Northern blotting and reverse transcriptase-PCR (RT-PCR) analyses confirmed that the ter operon was inducible by tellurite and to a lesser extent by oxidative stress inducers such as hydrogen peroxide and methyl viologen (paraquat). Direct and inverted repeat sequences were identified in the ter promoter region as well as motifs upstream of the -35 hexamer that resembled OxyR-binding sequences. Finally, the 390 bp intergenic promoter region located between orf3 and terZ showed no DNA sequence identity with any other published ter sequences, whereas terZABCDE genes exhibited 73-85 % DNA sequence identity. The ter operon was present in all clinical isolates of P. mirabilis and Proteus vulgaris tested and is inferred for Morganella and Providencia sop. based on screening for high level Ter and preliminary PCR analysis. Thus, a chromosomally located inducible tellurite resistance operon appears to be a common feature of the genus Proteus.