Ochrombel Ines, Ott Lisa, Krämer Reinhard, Burkovski Andreas, Marin Kay
Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany.
Biochim Biophys Acta. 2011 Apr;1807(4):444-50. doi: 10.1016/j.bbabio.2011.01.008. Epub 2011 Feb 2.
Metal ion uptake is crucial for all living cells and an essential part of cellular bioenergetic homeostasis. In this study the uptake and the impact of the most abundant internal cation, potassium, were investigated in Actinobacteria, a group of high G+C Gram-positives with a number of prominent biotechnologically and medically important members. Genome analyses revealed a variety of different potassium uptake systems in this monophyletic group ranging from potassium channels common in virtually all Actinobacteria to different active carriers that were present predominantly in pathogenic members able to cope with various stress conditions. By applying Corynebacterium glutamicum as model system we provide experimental evidence that under optimal conditions a potassium channel is sufficient in bacteria for the maintenance of internal pH and membrane potential ensuring survival of cells under stress conditions. Under potassium limitation, however, viability of C. glutamicum was increased under acidic stress or during desiccation when a functional KtrAB potassium transporter from the pathogen Corynebacterium jeikeium was heterologously expressed. We provide experimental evidence that the KtrAB mediated enhanced potassium accumulation improved maintenance of internal pH and membrane potential. The results indicate that the occurrence of active potassium transport systems correlates with an improved potassium-dependent bioenergetic homeostasis and survival of bacterial cells under stress conditions.
金属离子摄取对所有活细胞都至关重要，是细胞生物能量稳态的重要组成部分。在本研究中，我们调查了放线菌中最丰富的内部阳离子钾的摄取及其影响。放线菌是一类高G+C革兰氏阳性菌，其中有许多在生物技术和医学上具有重要意义的突出成员。基因组分析揭示了这一单系类群中存在多种不同的钾摄取系统，从几乎所有放线菌中常见的钾通道到主要存在于能够应对各种应激条件的致病成员中的不同活性载体。通过将谷氨酸棒杆菌作为模型系统，我们提供了实验证据，即在最佳条件下，细菌中的钾通道足以维持内部pH值和膜电位，确保细胞在应激条件下存活。然而，在钾限制条件下，当来自病原菌杰氏棒杆菌的功能性KtrAB钾转运蛋白异源表达时，谷氨酸棒杆菌在酸性应激或干燥过程中的活力会增加。我们提供了实验证据，表明KtrAB介导的钾积累增强改善了内部pH值和膜电位的维持。结果表明，活性钾转运系统的出现与应激条件下细菌细胞中依赖钾的生物能量稳态改善和存活相关。
