In bacteria, the dynamics of chromosome replication and segregation are tightly coordinated with cell-cycle progression and largely rely on specific spatiotemporal arrangement of the chromosome. Whereas these key processes are mostly investigated in species that divide by binary fission, they remain mysterious in bacteria producing larger number of descendants. Here, we establish the predatory bacterium Bdellovibrio bacteriovorus as a model to investigate the non-binary processing of a circular chromosome. We found that its single chromosome is highly compacted in a polarized nucleoid that excludes freely diffusing proteins during the non-proliferative stage of the cell cycle. A binary-like cycle of DNA replication and asymmetric segregation is followed by multiple asynchronous rounds of replication and progressive ParABS-dependent partitioning, uncoupled from cell division. Finally, we provide the first evidence for an on-off behavior of the ParB protein, which localizes at the centromere in a cell-cycle-regulated manner. Altogether, our findings support a model of complex chromosome choreography leading to the generation of variable, odd, or even numbers of offspring and highlight the adaptation of conserved mechanisms to achieve non-binary reproduction.

在细菌中，染色体复制和分离的动态与细胞周期进程密切协调，并且很大程度上依赖于染色体的特定时空排列。虽然这些关键过程主要在通过二元裂变分裂的物种中进行研究，但它们在产生大量后代的细菌中仍然是神秘的。在这里，我们建立了捕食性细菌Bdellovibrio bacteriovorus作为研究圆形染色体的非二元处理的模型。我们发现它的单个染色体在一个极化的类核中高度压缩，在细胞周期的非增殖阶段排除了自由扩散的蛋白质。DNA复制和不对称分离的二元循环之后是多轮异步复制和渐进式ParAB S-依赖分区，与细胞分裂无关。最后，我们为 ParB 蛋白的开关行为提供了第一个证据，它以细胞周期调节的方式定位于着丝粒。总而言之，我们的研究结果支持导致产生可变、奇数或偶数后代的复杂染色体编排模型，并强调了对保守机制的适应以实现非二元繁殖。