PDF(Pubmed)
Abstract：
Lactic acid bacteria (LAB) present various benefits to humans; they play key roles in the fermentation of food and as probiotics. Acidic conditions are common to both LAB in the intestinal tract as well as fermented foods. Lactiplantibacillus plantarum is a facultative homofermentative bacterium, and lactic acid is the end metabolite of glycolysis. To characterize how L. plantarum responds to lactic acid, we investigated its transcriptome following treatment with hydrochloride (HCl) or dl-lactic acid at an early stage of growth. Bacterial growth was more attenuated in the presence of lactic acid than in the presence of HCl at the same pH range. Bacterial transcriptome analysis showed that the expression of 67 genes was significantly altered (log2FC > 2 or < 2). A total of 31 genes were up- or downregulated under both conditions: 19 genes in the presence of HCl and 17 genes in the presence of dl-lactic acid. The fatty acid synthesis-related genes were upregulated in both acidic conditions, whereas the lactate racemization-related gene (lar) was only upregulated following treatment with dl-lactic acid. In particular, lar expression increased following l-lactic acid treatment but did not increase following HCl or d-lactic acid treatment. Expression of lar and production of d-lactic acid were investigated with malic and acetic acid; the results revealed a higher expression of lar and production of d-lactic acid in the presence of malic acid than that in the presence of acetic acid.
摘要：
乳酸菌（LAB）对人类具有多种益处；它们在食物发酵和作为益生菌中起着关键作用。酸性条件对于肠道中的LAB以及发酵食品都是常见的。植物乳杆菌是兼性同型发酵细菌，乳酸是糖酵解的最终代谢产物。为了表征植物乳杆菌对乳酸的反应，我们研究了在生长早期用盐酸（HCl）或dl-乳酸处理后的转录组。在相同的pH范围内，乳酸存在下的细菌生长比HCl存在下的细菌生长减弱得多。细菌转录组分析显示67个基因的表达显著改变(log2FC>2或<2)。在两种条件下,总共31个基因上调或下调:在HCl存在下的19个基因和在dl-乳酸存在下的17个基因。脂肪酸合成相关基因在两种酸性条件下都上调,而乳酸消旋化相关基因（lar）仅在用dl-乳酸处理后上调。特别是,lar表达在l-乳酸处理后增加，但在HCl或d-乳酸处理后没有增加。用苹果酸和乙酸研究了lar的表达和d-乳酸的产生；结果表明，在苹果酸存在下，lar的表达和d-乳酸的产生高于在乙酸存在下的表达。
