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#bacterial chromosome

2 public questions tagged with this topic.

Microbial genetics

Bacterial chromosome is best described as

Bacterial chromosome represents highly compacted nucleoid rather than membrane-bound nucleus. Escherichia coli chromosome is single circular double-stranded DNA molecule approximately 4.6 megabases, negatively supercoiled by DNA gyrase and organized into looped domains by HU, IHF, and SMC proteins. Supercoiling facilitates replication, transcription, and compaction into cell volume. No free ends exist, conferring resistance to exonucleases and enabling rolling circle replication modes. Unlike eukaryotes, it lacks histone nucleosomes but shows hierarchical organization essential for rapid growt

Ref: NCBI Bookshelf, Bacterial Chromosome Structure; Griffiths, Chapter 6: Genome Organization

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Replication Basics

Bacterial chromosome is usually

Bacterial chromosomes possess single origin of replication oriC where DnaA-ATP binds DnaA boxes, unwinds DUE and recruits DnaB helicase with DnaC loader. Replication proceeds bidirectionally toward terminus region defined by Tus-Ter complexes. Because only one origin fires per chromosome per cell cycle, bacterial chromosome is monorepliconic. Some bacteria with secondary chromosomes or megaplasmids may appear multirepliconic but canonical E. coli remains model monoreplicon system. Regulation ensures initiation once per cycle via SeqA sequestration and DnaA inactivation, preventing over-replica

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 5: Bacterial Chromosome is Usually Monorepliconic

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