Department of Biology

Unlike eukaryotes and archaea, which have multiple replication origins on their chromosomes, bacterial chromosomes usually contain a single replication origin.

In a recent paper published in Current Biology, researchers from the lab of Xindan Wang (an assistant professor in Indiana University College of Arts and Sciences’ Department of Biology) discussed their discovery of a dicentric linear bacterial chromosome with two replication origins. The chromosome resulted from the fusion of the circular and linear chromosomes in the plant pathogen, Agrobacterium tumefaciens.

The authors found that this stably-maintained fusion chromosome contains two active replication origins and requires two independent partitioning systems; however, independent segregation of two origins renders the dicentric chromosome broken when two origins on the same chromosome migrate to opposite poles. The team showed that site-specific recombinases XerC and XerD are required to resolve this situation, ensuring stable maintenance of this dicentric chromosome.

The study provides a natural comparative platform to examine a bacterial chromosome with multiple replication origins and a possible explanation for the fundamental difference in bacterial genome architecture relative to eukaryotes and archaea.

This work was a collaboration between the Wang lab and the lab of Clay Fuqua (a professor in the Department of Biology). The co-first authors of the paper are Qin Liao (a third-year Ph.D. student in the Genome, Cell, and Developmental Biology [GCDB] Graduate Program) and Zhongqing Ren (a fourth-year Ph.D. student in the GCDB program). Additional authors of the study include Emma Wiesler, a former IU undergraduate student, who has joined the IU Microbiology program and will start graduate school this fall. The study was funded by the National Institutes of Health and Indiana University.