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首页> 外文期刊>Applied Microbiology >Acid Stress-Mediated Metabolic Shift in Lactobacillus sanfranciscensis LSCE1
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Acid Stress-Mediated Metabolic Shift in Lactobacillus sanfranciscensis LSCE1

机译：酸应激介导的Sanfranciscensis乳酸杆菌LSCE1的代谢转变

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Lactobacillus sanfranciscensis LSCE1 was selected as a target organism originating from recurrently refreshed sourdough to study the metabolic rerouting associated with the acid stress exposure during sourdough fermentation. In particular, the acid stress induced a metabolic shift toward overproduction of 3-methylbutanoic and 2-methylbutanoic acids accompanied by reduced sugar consumption and primary carbohydrate metabolite production. The fate of labeled leucine, the role of different nutrients and precursors, and the expression of the genes involved in branched-chain amino acid (BCAA) catabolism were evaluated at pH 3.6 and 5.8. The novel application of the program XCMS to the solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) data allowed accurate separation and quantification of 2-methylbutanoic and 3-methylbutanoic acids, generally reported as a cumulative datum. The metabolites coming from BCAA catabolism increased up to seven times under acid stress. The gene expression analysis confirmed that some genes associated with BCAA catabolism were overexpressed under acid conditions. The experiment with labeled leucine showed that 2-methylbutanoic acid originated also from leucine. While the overproduction of 3-methylbutanoic acid under acid stress can be attributed to the need to maintain redox balance, the rationale for the production of 2-methylbutanoic acid from leucine can be found in a newly proposed biosynthesis pathway leading to 2-methylbutanoic acid and 3 mol of ATP per mol of leucine. Leucine catabolism to 3-methylbutanoic and 2-methylbutanoic acids suggests that the switch from sugar to amino acid catabolism supports growth in L. sanfranciscensis in restricted environments such as sourdough characterized by acid stress and recurrent carbon starvation.
机译：选择旧金山乳杆菌LSCE1作为源于反复刷新的酵母的目标生物，以研究与酵母发酵过程中暴露于酸胁迫相关的代谢重新路由。特别地，酸胁迫诱导了向过度产生3-甲基丁酸和2-甲基丁酸的代谢转变，伴随着糖消耗的减少和初级碳水化合物代谢产物的产生。在pH 3.6和5.8下，评估了标记的亮氨酸的命运，不同养分和前体的作用以及支链氨基酸（BCAA）分解代谢中相关基因的表达。 XCMS程序在固相微萃取-气相色谱-质谱（SPME-GC-MS）数据上的新颖应用使得可以准确地分离和定量2-甲基丁酸和3-甲基丁酸（通常以累积数据形式报告）。在酸性胁迫下，来自BCAA分解代谢的代谢产物增加了多达7倍。基因表达分析证实了一些与BCAA分解代谢相关的基因在酸性条件下过表达。标记亮氨酸的实验表明2-甲基丁酸也源自亮氨酸。虽然在酸性胁迫下3-甲基丁酸的过量生产可以归因于维持氧化还原平衡的需要，但可以在新提出的生物合成途径中找到由亮氨酸生产2-甲基丁酸的基本原理，从而导致2-甲基丁酸和每摩尔亮氨酸3摩尔ATP。亮氨酸分解为3-甲基丁酸和2-甲基丁酸的代谢表明，从糖分解为氨基酸的分解代谢支持了L. sanfranciscensis在受限环境中的生长，例如以酸胁迫为特征的酸面团和经常性的碳饥饿。

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