ABSTRACTBdellovibrio bacteriovorusis a small Gram-negative, obligate predatory bacterium that is largely found in wet, aerobic environments (e.g., soil). This bacterium attacks and invades other Gram-negative bacteria, including animal and plant pathogens. The intriguing life cycle ofB. bacteriovorusconsists of two phases: a free-living nonreplicative attack phase, in which the predatory bacterium searches for its prey, and a reproductive phase, in whichB. bacteriovorusdegrades a host’s macromolecules and reuses them for its own growth and chromosome replication. Although the cell biology of this predatory bacterium has gained considerable interest in recent years, we know almost nothing about the dynamics of its chromosome replication. Here, we performed a real-time investigation into the subcellular localization of the replisome(s) in single cells ofB. bacteriovorus. Our results show that inB. bacteriovorus, chromosome replication takes place only during the reproductive phase and exhibits a novel spatiotemporal arrangement of replisomes. The replication process starts at the invasive pole of the predatory bacterium inside the prey cell and proceeds until several copies of the chromosome have been completely synthesized. Chromosome replication is not coincident with the predator cell division, and it terminates shortly before synchronous predator filament septation occurs. In addition, we demonstrate that if thisB. bacteriovoruslife cycle fails in some cells ofEscherichia coli, they can instead use second prey cells to complete their life cycle.IMPORTANCENew strategies are needed to combat multidrug-resistant bacterial infections. Application of the predatory bacteriumBdellovibrio bacteriovorus, which kills other bacteria, including pathogens, is considered promising for combating bacterial infections. TheB. bacteriovoruslife cycle consists of two phases, a free-living, invasive attack phase and an intracellular reproductive phase, in which this predatory bacterium degrades the host’s macromolecules and reuses them for its own growth. To understand the use ofB. bacteriovorusas a “living antibiotic,” it is first necessary to dissect its life cycle, including chromosome replication. Here, we present a real-time investigation into subcellular localization of chromosome replication in a single cell ofB. bacteriovorus. This process initiates at the invasion pole ofB. bacteriovorusand proceeds until several copies of the chromosome have been completely synthesized. Interestingly, we demonstrate that some cells ofB. bacteriovorusrequire two prey cells sequentially to complete their life cycle.
Cloacal Gram-Negative Microbiota in Free-Living Grass Snake Natrix natrix from Poland
