Bacterial Group II Intron Genomic Neighborhoods Reflect Survival Strategies: Hiding and Hijacking.

Group II (gII) introns are mobile retroelements that can spread to new DNA sites through retrotransposition, which can be influenced by a variety of host factors. To determine if these host factors bear any relationship to the genomic location of gII introns, we developed a bioinformatic pipeline wherein we focused on the genomic neighborhoods of bacterial gII introns within their native contexts and sought to determine global relationships between introns and their surrounding genes. We found that, although gII introns inhabit diverse regions, these neighborhoods are often functionally enriched for genes that could promote gII intron retention or proliferation. On one hand, we observe that gII introns are frequently found hiding in mobile elements or after transcription terminators. On the other hand, gII introns are enriched in locations in which they could hijack host functions for their movement, potentially timing expression of the intron with genes that produce favorable conditions for retrotransposition. Thus, we propose that gII intron distributions have been shaped by relationships with their surrounding genomic neighbors.