What makes a megaplasmid?

James P.J. Hall, João Botelho, Adrian Cazares, David A. Baltrus

Research output: Contribution to journalReview articlepeer-review

34 Scopus citations


Naturally occurring plasmids come in different sizes. The smallest are less than a kilobase of DNA, while the largest can be over three orders of magnitude larger. Historically, research has tended to focus on smaller plasmids that are usually easier to isolate, manipulate and sequence, but with improved genome assemblies made possible by long-read sequencing, there is increased appreciation that very large plasmids - known as megaplasmids - are widespread, diverse, complex, and often encode key traits in the biology of their host microorganisms. Why are megaplasmids so big? What other features come with large plasmid size that could affect bacterial ecology and evolution? Are megaplasmids 'just' big plasmids, or do they have distinct characteristics? In this perspective, we reflect on the distribution, diversity, biology, and gene content of megaplasmids, providing an overview to these large, yet often overlooked, mobile genetic elements. This article is part of the theme issue 'The secret lives of microbial mobile genetic elements'.

Original languageEnglish (US)
Article number20200472
JournalPhilosophical Transactions of the Royal Society B: Biological Sciences
Issue number1842
StatePublished - 2022


  • genome evolution
  • horizontal gene transfer
  • megaplasmid
  • mobile genetic element
  • pangenome
  • plasmid

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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