Penaud S, Fernandez A, Boudebbouze S, Ehrlich S D, Maguin E, van de Guchte M
Génétique Microbienne, INRA-CRJ, 78352 Jouy en Josas cedex, France.
Appl Environ Microbiol. 2006 Dec;72(12):7445-54. doi: 10.1128/AEM.01109-06. Epub 2006 Sep 22.
Lactobacillus bulgaricus is a lactic acid bacteria (LAB) that, through the production of lactic acid, gradually acidifies its environment during growth. In the course of this process, L. bulgaricus acquires an improved tolerance to acidity. A survey of the recently established genome sequence shows that this bacterium possesses few of the pH control functions that have been described in other LAB and raises the question of what other mechanisms could be involved in its adaptation to the decreasing environmental pH. In some bacteria other than LAB, ion transport systems have been implicated in acid adaptation. We therefore studied the expression of this type of transport system during acid adaptation in L. bulgaricus by reverse transcription and real-time quantitative PCR and mapped transcription start sites. Intriguingly, the most significantly induced were three ATPases carrying the CPX signature of heavy-metal transporters. Protein homology and the presence of a conserved sequence motif in the promoter regions of the genes encoding these proteins strongly suggest that they are involved in copper homeostasis. Induction of this system is thought to assist in avoiding indirect damage that could result from medium acidification.
保加利亚乳杆菌是一种乳酸菌,在生长过程中,它通过产生乳酸逐渐酸化其环境。在此过程中,保加利亚乳杆菌对酸度的耐受性得到提高。对最近确定的基因组序列的一项研究表明,这种细菌拥有在其他乳酸菌中所描述的少数pH控制功能,这就提出了一个问题,即它适应环境pH值下降还可能涉及哪些其他机制。在乳酸菌以外的一些细菌中,离子转运系统与酸适应有关。因此,我们通过逆转录和实时定量PCR研究了保加利亚乳杆菌在酸适应过程中这类转运系统的表达,并绘制了转录起始位点。有趣的是,诱导最显著的是三种带有重金属转运蛋白CPX特征的ATP酶。蛋白质同源性以及编码这些蛋白质的基因启动子区域中保守序列基序的存在强烈表明它们参与铜稳态。该系统的诱导被认为有助于避免因培养基酸化而可能导致的间接损伤。