Compilation and analysis of group II intron insertions in bacterial genomes: Evidence for retroelement behavior

Lixin Dai, Steven Zimmerly

Research output: Contribution to journalReview articlepeer-review

139 Scopus citations


Group II introns are novel genetic elements that have properties of both catalytic RNAs and retroelements. Initially identified in organellar genomes of plants and lower eukaryotes, group II introns are now being discovered in increasing numbers in bacterial genomes. Few of the newly sequenced bacterial introns are correctly identified or annotated by those who sequenced them. Here we have compiled and thoroughly analyzed group II introns and their fragments in bacterial DNA sequences reported to GenBank. Intron distribution in bacterial genomes differs markedly from the distribution in organellar genomes. Bacterial introns are not inserted into conserved genes, are often inserted outside of genes altogether and are frequently fragmented, suggesting a high rate of intron gain and loss. Some introns have multiple natural homing sites while others insert after transcriptional terminators. All bacterial group II introns identified to date encode reverse transcriptase open reading frames and are either active retroelements or derivatives of retroelements. Together, these observations suggest that group II introns in bacteria behave primarily as retroelements rather than as introns, and that the strategy for group II intron survival in bacteria is fundamentally different from intron survival in organelles.

Original languageEnglish (US)
Pages (from-to)1091-1102
Number of pages12
JournalNucleic acids research
Issue number5
StatePublished - Mar 1 2002
Externally publishedYes

ASJC Scopus subject areas

  • Genetics


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