Question:medium

Which bacterium possesses two circular chromosomes?

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The comma-shaped cholera bacterium famously has a divided (two-chromosome) genome.
Updated On: Jun 25, 2026
  • Escherichia coli
  • Vibrio cholerae
  • Mycobacterium tuberculosis
  • Mycoplasma genitalium
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The Correct Option is B

Solution and Explanation

Bacterial genomics usually means one circular chromosome, but a handful of organisms break this rule. The textbook answer for a two-chromosome genome is Vibrio cholerae.

V. cholerae packages its DNA into two circular replicons: a large chromosome (~3 Mb) holding the bulk of housekeeping and virulence genes, and a smaller second chromosome (~1 Mb) that evolved from an integrated megaplasmid but is now essential for viability. Both replicate in a coordinated fashion during cell division.

The remaining choices each have the conventional single circular chromosome: E. coli (with accessory plasmids), the slow-growing GC-rich M. tuberculosis, and the minimalist wall-less Mycoplasma genitalium.

\[\boxed{\text{Two circular chromosomes} \Rightarrow \textit{Vibrio cholerae}}\]
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