Recent sequencing projects have characterized bacterial genomes that are organized onto elements of various sizes, shapes and numbers. Aside from its biological relevance and curiosity, this diversity calls into question the way that we define bacterial chromosomes.
Ochman, H. (2002, June 25). Bacterial evolution: Chromosome arithmetic and geometry. Current Biology. Cell Press. https://doi.org/10.1016/S0960-9822(02)00916-8