The bacterial chromosome
Start with the big picture
Most bacterial chromosomes are single, circular, double-stranded DNA molecules compacted in the nucleoid, although some bacteria, including Borrelia, have linear chromosomes. Their genes are often arranged in operons, supporting coordinated expression, while sigma factors and regulons help adjust gene activity. Replication begins at OriC and proceeds in both directions; DNA gyrase and topoisomerase IV contribute to chromosome management. Bacteria can also acquire or rearrange genetic material through transformation, conjugation, transduction, recombination, and mobile elements. Plasmids replicate independently of the chromosome, though some can integrate as episomes. Together, these features explain how chromosome structure, gene regulation, and genome flexibility support bacterial function and adaptation.
What you'll learn
- Describe typical bacterial chromosome organization and recognize the linear-chromosome exception.
- Outline the roles of OriC, DNA polymerase III, and topoisomerases in replication and chromosome maintenance.
- Explain how operons, sigma factors, and regulons contribute to bacterial gene regulation.
- Distinguish plasmids from chromosomes and identify mechanisms of horizontal gene transfer.
- Describe how mobile genetic elements and acquired DNA can contribute to genomic change.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
