Cell-cycle progress in obligate predatory bacteria is dependent upon sequential sensing of prey recognition and prey quality cues.
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.
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;
Or
O
Rotem
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel;
Zohar
Z
Pasternak
Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel;
Eyal
E
Shimoni
Institute of Plant Sciences, Agricultural Research Organization, Bet Dagan 50250, Israel;
Eduard
E
Belausov
Flow Cytometry Unit, Department of Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel;
Ziv
Z
Porat
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
Shmuel
S
Pietrokovski
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; edouard.jurkevitch@mail.huji.ac.il.
Edouard
E
Jurkevitch
D000818:Animals; D018407:Bacterial Physiological Phenomena; D002453:Cell Cycle; D011235:Predatory Behavior
Bdellovibrio bacteriovorus; bacterial cell cycle; bacterial physiology; microbial ecology; predatory bacteria