Glycerol Is Metabolized in a Complex and Strain-Dependent Manner in Enterococcus faecalis
Glycerol Is Metabolized in a Complex and Strain-Dependent Manner in Enterococcus faecalis
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DOI：
10.1128/jb.00959-09
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发表时间：
2010-02-01
影响因子：
3.2
通讯作者：
Hartke, Axel
中科院分区：
文献类型：
--
作者：
Bizzini, Alain;Zhao, Chen;Hartke, Axel
粪肠球菌具有两条甘油异化途径。甘油可以先被甘油激酶磷酸化，然后被甘油-3-磷酸氧化酶氧化(glpK途径)，或者首先被甘油脱氢酶氧化，然后被二羟丙酮激酶磷酸化(dhak途径)。这两条途径都会导致二羟丙酮磷酸的形成，这是糖酵解的中间产物。假设glpK途径在好氧过程中运行，而Dhak途径在厌氧条件下运行。因为这还没有通过遗传研究进行分析，所以我们构建了在这两个途径上都受到影响的菌株JH2-2的突变株。对这些突变体在好氧和厌氧条件下在甘油上的生长进行了监测。与前一个模型相反，结果强烈表明粪肠球菌JH2-2株在氧气存在下，甘油被两条途径同时分解。根据前一个模型，甘油在厌氧条件下通过DHAK途径代谢。不同粪肠球菌菌株的比较表明，在甘油上的生长行为具有令人印象深刻的多样性。BLAST搜索和实时逆转录聚合酶链式反应的分析表明，这种多样性不是基于不同的基因含量，而是基于基因表达的差异。在好氧条件下，一些菌株优先使用glpK途径，而另一些菌株可能只使用Dhak途径。我们的结果表明，粪肠球菌不能仅用一种有氧甘油分解代谢模型来表示。
Enterococcus faecalis is equipped with two pathways of glycerol dissimilation. Glycerol can either first be phosphorylated by glycerol kinase and then oxidized by glycerol-3-phosphate oxidase (the glpK pathway) or first be oxidized by glycerol dehydrogenase and then phosphorylated by dihydroxyacetone kinase (the dhaK pathway). Both pathways lead to the formation of dihydroxyacetone phosphate, an intermediate of glycolysis. It was assumed that the glpK pathway operates during aerobiosis and that the dhaK pathway operates under anaerobic conditions. Because this had not been analyzed by a genetic study, we constructed mutants of strain JH2-2 affected in both pathways. The growth of these mutants on glycerol under aerobic and anaerobic conditions was monitored. In contrast to the former model, results strongly suggest that glycerol is catabolized simultaneously by both pathways in the E. faecalis JH2-2 strain in the presence of oxygen. In accordance with the former model, glycerol is metabolized by the dhaK pathway under anaerobic conditions. Comparison of different E. faecalis isolates revealed an impressive diversity of growth behaviors on glycerol. Analysis by BLAST searching and real-time reverse transcriptase PCR revealed that this diversity is based not on different gene contents but rather on differences in gene expression. Some strains used preferentially the glpK pathway whereas others probably exclusively the dhaK pathway under aerobic conditions. Our results demonstrate that the species E. faecalis cannot be represented by only one model of aerobic glycerol catabolism.