Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.
Curr Microbiol. 2010 Sep;61(3):163-8. doi: 10.1007/s00284-010-9590-9. Epub 2010 Jan 29.
Acidophilic bacterium, Acidiphilium symbioticum H8, is resistant to high levels of several heavy metals, hydrophobic agents, and organic solvents. The approximately 9.6 kb plasmid pASH8, was purified, digested with HindIII, and sub-cloned in pUC19 at the respective site. Three different fragment size clones were achieved. The clones were completely sequenced and analyzed. The first clone encodes for a single putative open reading frame (ORF), which showed significant homology to several rusticyaninA1 proteins. The second clone encodes for a 43-kDa protein, which has conserved domain homology with several outer envelop TolC proteins. The clone with pASH8 tolC gene can functionally complement an Escherichia coli tolC mutant strain, making it resistant to several toxic hydrophobic agents, earlier for which it was sensitive. The tolC gene was found to be essential for imparting resistance to the clone toward these toxic hydrophobic agents. The third clone encodes for a putative 318-aa AcrA (acriflavine resistance protein A) protein and the clone was resistance to plasmid curing dye acriflavine. The clone also has a truncated ORF, which showed significant homology to cation-efflux pump AcrB. This study is the first to report a multi-drug efflux system to be encoded on a plasmid of any Acidiphilium strain.
嗜酸菌（Acidiphilium symbioticum H8）能够耐受多种重金属、疏水性物质和有机溶剂的高水平影响。大约 9.6kb 的质粒 pASH8 经 HindIII 消化并在 pUC19 相应位点亚克隆。得到了三个不同大小的片段克隆。对克隆进行了完全测序和分析。第一个克隆编码一个单一的假定开放阅读框（ORF），该 ORF 与几种锈色蛋白 A1 蛋白具有显著同源性。第二个克隆编码一个 43kDa 的蛋白质，它与几种外膜 TolC 蛋白具有保守结构域同源性。具有 pASH8 tolC 基因的克隆能够在功能上互补大肠杆菌 tolC 突变株，使其能够耐受几种以前敏感的有毒疏水性物质。tolC 基因对于赋予该克隆对这些有毒疏水性物质的抗性是必需的。第三个克隆编码一个假定的 318-氨基酸 AcrA（吖啶黄素抗性蛋白 A）蛋白，该克隆对质粒去垢剂吖啶黄素具有抗性。该克隆还具有一个截断的 ORF，与阳离子外排泵 AcrB 具有显著同源性。这项研究首次报道了任何嗜酸菌菌株的质粒上编码的多药外排系统。
