Weiss A A, Murphy S D, Silver S
J Bacteriol. 1977 Oct;132(1):197-208. doi: 10.1128/jb.132.1.197-208.1977.
Penicillinase plasmids of Staphylococcus aureus often contain genes conferring resistance to inorganic mercury (Hg(2+)) and the organomercurial phenylmercury acetate. The mechanism of resistance was found to be the enzymatic hydrolysis of the organomercurial phenylmercury to benzene plus inorganic ionic mercury, which was then enzymatically reduced to metallic mercury (Hg(0)). The Hg(0) was rapidly volatilized from the medium into the atmosphere. After the mercurial was degraded and the mercury was volatilized, the resistant cells were able to grow. These plasmids also conferred the ability to volatilize mercury from thimerosal, although the plasmid-bearing strains were equally as thimerosal sensitive as the S. aureus without plasmids. None of the plasmids conferred the ability to volatilize mercury from several other organomercurials, however: methylmercury, ethylmercury, p-hydroxymercuribenzoate, merbromin, and fluorescein mercuric acetate. (Organomercurial resistance-conferring plasmids of Escherichia coli and Pseudomonas aeruginosa that we have been studying confer the ability to degrade two or three of these organomercurials.) Although mercury was not volatilized from p-hydroxymercuribenzoate or fluorescein mercuric acetate, the plasmid-bearing strains were resistant to these organomercurials. The ability to volatilize mercury from Hg(2+) and phenylmercury was inducible. The range of inducers included Hg(2+), phenylmercury, and several organomercurials that were not substrates for the degradation system. Mercury-sensitive mutants have been isolated from the parental plasmids pI258 and pII147. Thirty-one such mercury-sensitive strains fall into three classes: (i) mercury-sensitive strains totally devoid of the phenylmercury hydrolase and Hg(2+) reductase activities; (ii) mutants with normal hydrolase levels and no detectable reductase; and (iii) mutants with essentially normal hydrolase levels and low and variable (5 to 25%) levels of reductase activities. The mercury-sensitive strains were also sensitive to phenylmercury, including those with the potential for hydrolase activity.
金黄色葡萄球菌的青霉素酶质粒通常含有赋予对无机汞（Hg(2+)）和有机汞醋酸苯汞抗性的基因。研究发现，抗性机制是有机汞醋酸苯汞通过酶促水解生成苯和无机离子汞，然后无机离子汞再被酶促还原为金属汞（Hg(0)）。Hg(0)迅速从培养基挥发到大气中。汞化合物降解且汞挥发后，抗性细胞能够生长。这些质粒还赋予了从硫柳汞中挥发汞的能力，不过携带质粒的菌株与不含质粒的金黄色葡萄球菌对硫柳汞的敏感性相同。然而，这些质粒均未赋予从其他几种有机汞化合物中挥发汞的能力，这些有机汞化合物包括甲基汞、乙基汞、对羟基汞苯甲酸、红汞和荧光素汞醋酸盐。（我们一直在研究的大肠杆菌和铜绿假单胞菌的赋予有机汞抗性的质粒能够降解其中两三种有机汞化合物。）尽管汞不会从对羟基汞苯甲酸或荧光素汞醋酸盐中挥发，但携带质粒的菌株对这些有机汞化合物具有抗性。从Hg(2+)和醋酸苯汞中挥发汞的能力是可诱导的。诱导剂范围包括Hg(2+)、醋酸苯汞以及几种不是降解系统底物的有机汞化合物。已从亲本质粒pI258和pII147中分离出汞敏感突变体。31个这样的汞敏感菌株分为三类：（i）完全没有醋酸苯汞水解酶和Hg(2+)还原酶活性的汞敏感菌株；（ii）水解酶水平正常但未检测到还原酶的突变体；（iii）水解酶水平基本正常但还原酶活性水平较低且变化不定（5%至25%）的突变体。汞敏感菌株对醋酸苯汞也敏感，包括那些具有水解酶活性潜力的菌株。
