Bioenergetics of the predatory lifestyle of Bdellovibrio bacteriovorus

革兰氏阴性菌细小芽孢杆菌有一种捕食性的生活方式：它附着在其他革兰氏阴性菌的周质中，并进入其周质，导致形成所谓的鞭毛体。它在宿主体内复制，最终导致猎物的裂解和少量蛭弧菌的释放。促成这种生活方式的分子途径非常复杂，对调节捕食过程的理解仍处于起步阶段。然而，细菌的捕食不仅在科学方面令人感兴趣(即仅对途径的理解)，而且可能被证明是作为抗生素的替代药物的一个有希望的医疗机会。关于医学应用的第一批研究已经完成，但在细菌菌可以商业化之前，更好地了解导致宿主裂解的过程是不可避免的。许多有趣的、迄今尚未探索的捕食问题之一是生物能量学方面。因此，阐明捕食者细胞膜上发生的分子(运输)过程将是拟议项目的主要目标。通过对细菌性芽孢杆菌基因组序列的初步筛选，鉴定出几种膜整合复合体，它们可能介导电子传递和伴随的离子传递、pH动态平衡、渗透适应以及化学渗透性的ATP合成。令人惊讶的是，生物信息学分析发现在ATP合成酶的c亚基中存在一个Na+结合基序，表明Na+是该细菌中ADP磷酸化的偶联离子。如果实验分析将证实这一发现，细菌芽孢杆菌可能是第一个已知的具有基于Na+的生物能量学的有氧原核生物。因此，一些选定的膜复合体(包括ATP合成酶及其偶联离子)的功能和它们在捕食中的作用应该用生化、遗传学和细胞生物学的方法来阐明。

The Gram-negative bacterium Bdellovibrio bacteriovorus has a predatory lifestyle: it attaches to and enters the periplasm of other Gram-negative bacteria, leading to the formation of a so-called bdelloplast. It replicates within the host, finally leading to lysis of the prey and the release of a small Bdellovibrio population. The molecular pathways that enable this lifestyle are very complex and the understanding of the processes mediating predation is still in its beginnings. However, predation of bacteria is not only intriguing in terms of scientific aspects (meaning the understanding of the pathways only), but might also prove to be a promising opportunity for medical treatments as an alternative to antibiotics. First studies concerning a medical application have already been performed, but before B. bacteriovorus can be used commercially, a better understanding of the processes leading to the lysis of the host is inevitable.One of many interesting and so far unexplored issues of predation is the bioenergetic aspect. Therefore, an elucidation of the molecular (transport) processes occurring at the cytoplasmic membrane of the predator shall be the main objective of the proposed project. A preliminary screen of the B. bacteriovorus genome sequence resulted in the identification of several membrane-integral complexes that might mediate electron transfer and concomitant ion transport, pH homeostasis, osmotic adaptation, as well as chemiosmotic ATP synthesis. Astonishingly, bioinformatic analysis revealed the presence of a Na+ binding motif in the c subunit of the ATP synthase, suggesting that Na+ is the coupling ion for ADP phosphorylation in this bacterium. If experimental analysis will confirm this finding, B. bacteriovorus might be the first known aerobic prokaryote with Na+-based bioenergetics. Therefore, the function of several selected membrane complexes (including the ATP synthase and its coupling ion) and their role in predation shall be elucidated using biochemical, genetic, and cell biological approaches.