Bioenergetics of the predatory lifestyle of Bdellovibrio bacteriovorus

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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.