Dynamic response of catabolic pathways to autoacidification in Lactococcus lactis:: transcript profiling and stability in relation to metabolic and energetic constraints
Dynamic response of catabolic pathways to autoacidification in Lactococcus lactis:: transcript profiling and stability in relation to metabolic and energetic constraints
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DOI：
10.1046/j.1365-2958.2002.03086.x
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发表时间：
2002-08-01
影响因子：
3.6
通讯作者：
Cocaign-Bousquet, M
中科院分区：
文献类型：
--
作者：
Even, S;Lindley, ND;Cocaign-Bousquet, M
通过整合代谢和能量参数生理研究中的分子数据（细胞转录物浓度，mRNA周转率），以全局方式研究了乳酸乳球菌中中心代谢途径对自酸化（有机酸发酵产物的积累）的动态响应。与有机酸积累相关的pH值降低大大改变了细胞的生理状态。细胞质酸化导致酶活性的抑制，因此，减少通过糖酵解和生化能量合成率下降的分解代谢通量。这种能量产生的减少以及对抗细胞质酸化的能量消耗增加导致生物质合成的能量限制。在这些条件下，比生长速率逐渐降低，生长最终停止，尽管在没有生长的情况下保持了减少的分解代谢通量。对这种现象的细胞反应是维持分解代谢基因的mRNA的显著水平，包括基因的持续转录，并且在某些情况下，增加转录物稳定性。因此，翻译保持，和细胞内的某些酶的浓度增加，部分补偿的抑制活性引起的pH值降低。当分解代谢活动停止后，长期暴露于应力诱导的静止期，内源性RNA catenase观察。
The dynamic response of the central metabolic pathways to autoacidification (accumulation of organic acid fermentation products) in Lactococcus lactis was investigated in a global manner by integrating molecular data (cellular transcript concentrations, mRNA turnover) within physiological investigations of metabolic and energetic parameters. The decrease in pH associated with the accumulation of organic acids modified the physiological state of the cell considerably. Cytoplasmic acidification led to inhibition of enzyme activities and, consequently, to a diminished catabolic flux through glycolysis and a decreased rate of biochemical energy synthesis. This decrease in energy production together with the increased energy expenditure to counter cytoplasmic acidification led to energetic limitations for biomass synthesis. In these conditions, the specific growth rate decreased progressively, and growth ultimately stopped, although a diminished catabolic flux was maintained in the absence of growth. The cellular response to this phenomenon was to maintain significant levels of mRNA of catabolic genes, involving both continued transcription of the genes and also, in certain cases, an increase in transcript stability. Thus, translation was maintained, and intracellular concentration of certain enzymes increased, partially compensating for the inhibition of activity provoked by the diminished pH. When catabolic activity ceased after prolonged exposure to stress-induced stationary phase, endogenous RNA catabolism was observed.