A large scale comparative genomic analysis reveals insertion sites for newly acquired genomic islands in bacterial genomes

BACKGROUND: Bacterial virulence enhancement and drug resistance are major threats to public health worldwide. Interestingly, newly acquired genomic islands (GIs) from horizontal transfer between different bacteria strains were found in Vibrio cholerae, Streptococcus suis, and Mycobacterium tuberculosis, which caused outbreak of epidemic diseases in recently years. RESULTS: Using a large-scale comparative genomic analysis of 1088 complete genomes from all available bacteria (1009) and Archaea (79), we found that newly acquired GIs are often anchored around switch sites of GC-skew (sGCS). After calculating correlations between relative genomic distances of genomic islands to sGCSs and the evolutionary distances of the genomic islands themselves, we found that newly acquired genomic islands are closer to sGCSs than the old ones, indicating that regions around sGCSs are hotspots for genomic island insertion. CONCLUSIONS: Based on our results, we believe that genomic regions near sGCSs are hotspots for horizontal transfer of genomic islands, which may significantly affect key properties of epidemic disease-causing pathogens, such as virulence and adaption to new environments.