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Appl. Environ. Microbiol. doi:10.1128/AEM.01736-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Proteome-based comparative analyses of growth stages reveal new cell-cycle dependent functions in the predatory bacterium Bdellovibrio bacteriovorus

Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel; Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel

^* To whom correspondence should be addressed. Email: jurkevi{at}agri.huji.ac.il.

	Abstract

Bdellovibrio and like organisms are obligate predators of bacteria, that are ubiquitously found in the environment. Most exhibit a peculiar dimorphic life-cycle during which free swimming attack phase (AP) cells search and invade bacterial prey cells. The invader develops in the prey as a filamentous polynucleoid-containing cell that finally splits into progeny cells. Therapeutic and biocontrol applications of Bdellovibrio in human and animal, and plant health, respectively, have been proposed but more knowledge on this peculiar cell cycle is needed to develop such applications. A proteomic approach was applied to study cell cycle dependent expression of the Bdellovibrio bacteriovorus' proteome in synchronous cultures of a facultative host-independent (HI) strain able to grow in the absence of prey. Two-dimensional gel electrophoresis, mass spectrometry and temporal expression of selected genes in predicted operons were analyzed. In total, about 21% of the in-silico predicted proteome was covered. One hundred and ninety six proteins were identified, including 63 hitherto unknown proteins and 140 life stage-dependent spots. Of those, 47 were differentially expressed, including chemotaxis, attachment, growth and replication-related, cell wall and regulatory proteins. Novel cell cycle-dependent adhesion, gliding, mechanosensing, signaling and hydrolytic functions were assigned. The HI model was further studied by comparing HI and wild-type AP-cells, revealing that proteins involved in DNA replication and signaling were deregulated in the former. A complementary analysis of the secreted proteome identified 59 polypeptides, including cell contact proteins and hydrolytic enzymes specific to predatory bacteria.