Rotem Or, Pasternak Zohar, Shimoni Eyal, Belausov Eduard, Porat Ziv, Pietrokovski Shmuel, Jurkevitch Edouard
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel; The Otto Warburg Minerva Center for Agricultural Biotechnology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel;
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel;
Proc Natl Acad Sci U S A. 2015 Nov 3;112(44):E6028-37. doi: 10.1073/pnas.1515749112. Epub 2015 Oct 20.
Predators feed on prey to acquire the nutrients necessary to sustain their survival, growth, and replication. In Bdellovibrio bacteriovorus, an obligate predator of Gram-negative bacteria, cell growth and replication are tied to a shift from a motile, free-living phase of search and attack to a sessile, intracellular phase of growth and replication during which a single prey cell is consumed. Engagement and sustenance of growth are achieved through the sensing of two unidentified prey-derived cues. We developed a novel ex vivo cultivation system for B. bacteriovorus composed of prey ghost cells that are recognized and invaded by the predator. By manipulating their content, we demonstrated that an early cue is located in the prey envelope and a late cue is found within the prey soluble fraction. These spatially and temporally separated cues elicit discrete and combinatory regulatory effects on gene transcription. Together, they delimit a poorly characterized transitory phase between the attack phase and the growth phase, during which the bdelloplast (the invaded prey cell) is constructed. This transitory phase constitutes a checkpoint in which the late cue presumably acts as a determinant of the prey's nutritional value before the predator commits. These regulatory adaptations to a unique bacterial lifestyle have not been reported previously.
捕食者以猎物为食，获取维持其生存、生长和繁殖所需的营养物质。在革兰氏阴性菌的专性捕食者——蛭弧菌中，细胞生长和繁殖与从游动的、自由生活的搜索和攻击阶段转变为固着的、细胞内生长和繁殖阶段相关联，在此期间单个猎物细胞被消耗。生长的启动和维持是通过感知两种未知的源自猎物的信号来实现的。我们开发了一种用于蛭弧菌的新型体外培养系统，该系统由被捕食者识别和入侵的猎物空壳细胞组成。通过操纵它们的内容物，我们证明早期信号位于猎物包膜中，晚期信号存在于猎物可溶部分中。这些在空间和时间上分离的信号对基因转录产生离散和组合的调节作用。它们共同界定了攻击阶段和生长阶段之间一个特征不明的过渡阶段，在此期间蛭弧体（被入侵的猎物细胞）形成。这个过渡阶段构成一个检查点，在此期间晚期信号可能在捕食者行动之前作为猎物营养价值的决定因素。这些对独特细菌生活方式的调节适应以前尚未见报道。
