乳酸乳球菌乳亚种双乙酰亚种的柠檬酸盐转运系统由酸胁迫诱导。
The citrate transport system of Lactococcus lactis subsp. lactis biovar diacetylactis is induced by acid stress.
作者信息
García-Quintáns N, Magni C, de Mendoza D, López P
机构信息
Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
出版信息
Appl Environ Microbiol. 1998 Mar;64(3):850-7. doi: 10.1128/AEM.64.3.850-857.1998.
Citrate transport in Lactococcus lactis subsp. lactis biovar diacetylactis is catalyzed by citrate permease P (CitP), which is encoded by the plasmidic citP gene. We have shown previously that citP is included in the citQRP operon, which is mainly transcribed from the P1 promoter in L. lactis subsp. lactis biovar diacetylactis. furthermore, transcription of citQRP and citrate transport are not induced by the presence of citrate in the growth medium. In this work, we analyzed the influence of the extracellular pH on the expression of citP. The citrate transport system is induced by natural acidification of the medium during cell growth and by a shift to media buffered at acidic pHs. This inducible response to acid stress takes place at the transcriptional level and seems to be due to increased utilization of the P1 promoter. Increased transcription correlates with increased synthesis of CitP and results in higher citrate transport activity catalyzed by the cells. Finally, this acid stress response seems to provide L. lactis subsp. lactis biovar diacetylactis with a selective advantage resulting from cometabolism of glucose and citrate at low pHs.
乳酸乳球菌乳亚种双乙酰亚种中的柠檬酸盐转运由柠檬酸盐通透酶P（CitP）催化，该酶由质粒上的citP基因编码。我们之前已经表明，citP包含在citQRP操纵子中，该操纵子主要从乳酸乳球菌乳亚种双乙酰亚种中的P1启动子转录。此外，生长培养基中柠檬酸盐的存在不会诱导citQRP的转录和柠檬酸盐转运。在这项工作中，我们分析了细胞外pH对citP表达的影响。柠檬酸盐转运系统在细胞生长过程中由培养基的自然酸化以及转移至酸性pH缓冲的培养基诱导。这种对酸胁迫的诱导反应发生在转录水平，似乎是由于P1启动子的利用率增加。转录增加与CitP合成增加相关，并导致细胞催化的柠檬酸盐转运活性更高。最后，这种酸胁迫反应似乎为乳酸乳球菌乳亚种双乙酰亚种提供了一种选择性优势，这种优势源于在低pH下葡萄糖和柠檬酸盐的共代谢。
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