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首页> 外文期刊>Journal of bacteriology >Novel nuclear magnetic resonance spectroscopy methods demonstrate preferential carbon source utilization by Acinetobacter calcoaceticus.
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Novel nuclear magnetic resonance spectroscopy methods demonstrate preferential carbon source utilization by Acinetobacter calcoaceticus.

机译：新型核磁共振波谱方法证明钙乙酸不动杆菌优先利用碳源。

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Novel nuclear magnetic resonance spectroscopy techniques, designated metabolic observation, were used to study aromatic compound degradation by the soil bacterium Acinetobacter calcoaceticus. Bacteria which had been rendered spectroscopically invisible by growth with deuterated (2H) medium were used to inoculate cultures in which natural-abundance 1H hydrogen isotopes were provided solely by aromatic carbon sources in an otherwise 2H medium. Samples taken during the incubation of these cultures were analyzed by proton nuclear magnetic resonance spectroscopy, and proton signals were correlated with the corresponding aromatic compounds or their metabolic descendants. This approach allowed the identification and quantitation of metabolites which accumulated during growth. This in vivo metabolic monitoring facilitated studies of catabolism in the presence of multiple carbon sources, a topic about which relatively little is known. A. calcoaceticus initiates aromatic compound dissimilation by forming catechol or protocatechuate from a variety of substrates. Degradation proceeds via the beta-ketoadipate pathway, comprising two discrete branches that convert catechol or protocatechuate to tricarboxylic acid cycle intermediates. As shown below, when provided with several carbon sources simultaneously, all degraded via the beta-ketoadipate pathway, A. calcoaceticus preferentially degraded specific compounds. For example, benzoate, degraded via the catechol branch, was consumed in preference to p-hydroxybenzoate, degraded via the protocatechuate branch, when both compounds were present. To determine if this preference were governed by metabolites unique to catechol degradation, pathway mutants were constructed. Studies of these mutants indicated that the product of catechol ring cleavage, cis,cis-muconate, inhibited the utilization of p-hydroxybenzoate in the presence of benzoate. The accumulation of high levels of cis,cis-muconate also appeared to be toxic to the cells.
机译：使用新型核磁共振波谱技术（称为代谢观测）研究土壤细菌钙不动杆菌对芳香族化合物的降解作用。通过在氘化（2H）培养基中生长而在光谱上不可见的细菌用于接种培养物，在该培养物中，天然芳香的1H氢同位素仅由芳香族碳源提供，而在2H培养基中。通过质子核磁共振波谱分析在这些培养物的培养过程中采集的样品，并将质子信号与相应的芳族化合物或其代谢后代相关。这种方法可以鉴定和定量在生长过程中积累的代谢产物。这种体内代谢监测促进了在多种碳源存在下分解代谢的研究，而有关该主题的知识鲜为人知。钙乙酸曲霉通过从多种底物形成儿茶酚或原儿茶酸酯来引发芳香族化合物的异化作用。降解通过β-酮己二酸酯途径进行，该途径包括两个将儿茶酚或原儿茶酸酯转化为三羧酸循环中间体的离散分支。如下所示，当同时提供多个碳源时，所有的碳源都通过β-酮己二酸酯途径降解，A。calcoaceticus优先降解特定化合物。例如，当存在两种化合物时，通过邻苯二酚分支降解的苯甲酸酯优先于通过原儿茶酸分支降解的对羟基苯甲酸酯被消耗。为了确定这种偏好是否受儿茶酚降解所特有的代谢产物控制，构建了途径突变体。这些突变体的研究表明，在苯甲酸酯存在下，邻苯二酚环裂解产物顺式，顺式-粘康酸酯抑制了对羟基苯甲酸酯的利用。高水平的顺式，顺式-粘康酸酯的积累也似乎对细胞有毒。

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