AUTHOR=Makowski Łukasz , Donczew Rafał , Weigel Christoph , Zawilak-Pawlik Anna , Zakrzewska-Czerwińska Jolanta 

TITLE=Initiation of Chromosomal Replication in Predatory Bacterium Bdellovibrio bacteriovorus

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01898

DOI=10.3389/fmicb.2016.01898

ISSN=1664-302X

ABSTRACT=<p><italic>Bdellovibrio bacteriovorus</italic> is a small Gram-negative predatory bacterium that attacks other Gram-negative bacteria, including many animal, human, and plant pathogens. This bacterium exhibits a peculiar biphasic life cycle during which two different types of cells are produced: non-replicating highly motile cells (the free-living phase) and replicating cells (the intracellular-growth phase). The process of chromosomal replication in <italic>B. bacteriovorus</italic> must therefore be temporally and spatially regulated to ensure that it is coordinated with cell differentiation and cell cycle progression. Recently, <italic>B. bacteriovorus</italic> has received considerable research interest due to its intriguing life cycle and great potential as a prospective antimicrobial agent. Although, we know that chromosomal replication in bacteria is mainly regulated at the initiation step, no data exists about this process in <italic>B. bacteriovorus</italic>. We report the first characterization of key elements of initiation of chromosomal replication – DnaA protein and <italic>oriC</italic> region from the predatory bacterium, <italic>B. bacteriovorus</italic>. <italic>In vitro</italic> studies using different approaches demonstrate that the <italic>B. bacteriovorus oriC</italic> (Bd<italic>oriC</italic>) is specifically bound and unwound by the DnaA protein. Sequence comparison of the DnaA-binding sites enabled us to propose a consensus sequence for the <italic>B. bacteriovorus</italic> DnaA box [5′-NN(A/T)TCCACA-3′]. Surprisingly, <italic>in vitro</italic> analysis revealed that Bd<italic>oriC</italic> is also bound and unwound by the host DnaA proteins (relatively distantly related from <italic>B. bacteriovorus</italic>). We compared the architecture of the DnaA–<italic>oriC</italic> complexes (orisomes) in homologous (<italic>oriC</italic> and DnaA from <italic>B. bacteriovorus</italic>) and heterologous (Bd<italic>oriC</italic> and DnaA from prey, <italic>Escherichia coli</italic> or <italic>Pseudomonas aeruginosa</italic>) systems. This work provides important new entry points toward improving our understanding of the initiation of chromosomal replication in this predatory bacterium.</p>