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首页> 外文期刊>Journal of bacteriology >CcpA-Dependent Carbohydrate Catabolite Repression Regulates Galactose Metabolism in Streptococcus oligofermentans
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CcpA-Dependent Carbohydrate Catabolite Repression Regulates Galactose Metabolism in Streptococcus oligofermentans

机译：CcpA依赖的碳水化合物分解代谢抑制调节低聚链球菌中​​的半乳糖代谢。

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Streptococcus oligofermentans is an oral commensal that inhibits the growth of the caries pathogen Streptococcus mutans by producing copious amounts of H2O2 and that grows faster than S. mutans on galactose. In this study, we identified a novel eight-gene galactose (gal) operon in S. oligofermentans that was comprised of lacABCD, lacX, and three genes encoding a galactose-specific transporter. Disruption of lacA caused more growth reduction on galactose than mutation of galK, a gene in the Leloir pathway, indicating that the principal role of this operon is in galactose metabolism. Diauxic growth was observed in cultures containing glucose and galactose, and a luciferase reporter fusion to the putative gal promoter demonstrated 12-fold repression of the operon expression by glucose but was induced by galactose, suggesting a carbon catabolite repression (CCR) control in galactose utilization. Interestingly, none of the single-gene mutations in the well-known CCR regulators ccpA and manL affected diauxic growth, although the operon expression was upregulated in these mutants in glucose. A double mutation of ccpA and manL eliminated glucose repression of galactose utilization, suggesting that these genes have parallel functions in regulating gal operon expression and mediating CCR. Electrophoretic mobility shift assays demonstrated binding of CcpA to the putative catabolite response element motif in the promoter regions of the gal operon and manL, suggesting that CcpA regulates CCR through direct regulation of the transcription of the gal operon and manL. This provides the first example of oral streptococci using two parallel CcpA-dependent CCR pathways in controlling carbohydrate metabolism.
机译：寡链球菌是一种口服代用品，可通过产生大量H 2 O 2 抑制龋病病原体变形链球菌的生长，并且在半乳糖上的生长速度比变形链球菌快。在这项研究中，我们在寡糖链球菌中鉴定了一种新型的八基因半乳糖（ gal ）操纵子，该操纵子由 lacABCD ， lacX 和编码半乳糖特异性转运蛋白的三个基因。 lacA 的破坏导致半乳糖的生长减少比Leloir途径中的基因 galK 的突变更多，这表明该操纵子的主要作用是半乳糖代谢。在含有葡萄糖和半乳糖的培养物中观察到双生生长，荧光素酶报告基因与假定的 gal 启动子融合显示葡萄糖对操纵子表达的抑制是12倍，但被半乳糖诱导，表明碳分解代谢物被抑制（CCR）控制半乳糖利用。有趣的是，尽管葡萄糖中的这些操纵子表达上调，但众所周知的CCR调节子 ccpA 和 manL 中的单基因突变均未影响双生生长。 ccpA 和 manL 的双重突变消除了半乳糖利用的葡萄糖抑制，表明这些基因在调节 gal 操纵子表达和介导CCR中具有平行功能。 。电泳迁移率迁移分析表明CcpA与 gal 操纵子和 manL 的启动子区域中假定的分解代谢物响应元件基序结合，这表明CcpA通过直接调控CCR来调节CCR。 gal 操纵子和 manL 的转录。这提供了使用两个平行的CcpA依赖性CCR途径控制碳水化合物代谢的口服链球菌的第一个例子。

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