Abstract
Genomic Islands (GIs) are DNA regions acquired through horizontal gene transfer that encode advantageous traits for bacteria. Many GIs harbor genes that encode the molecular machinery required for their excision from the bacterial chromosome. Notably, the excision/integration dynamics of GIs may modulate the virulence of some pathogens. Here, we report a novel family of GIs found in plant and animal Enterobacteriaceae pathogens that share genes with those found in ROD21, a pathogenicity island whose excision is involved in the virulence of Salmonella enterica serovar Enteritidis. In these GIs we identified a conserved set of genes that includes an excision/integration module, suggesting that they are excisable. Indeed, we found that GIs within carbapenem-resistant Klebsiella pneumoniae ST258 KP35 and enteropathogenic Escherichia coli O127:H6 E2348/69 are excised from the bacterial genome. In addition to putative virulence factors, these GIs encode conjugative transfer-related proteins and short and full-length homologues of the global transcriptional regulator H-NS. Phylogenetic analyses suggest that the identified GIs likely originated in phytopathogenic bacteria. Taken together, our findings indicate that these GIs are excisable and may play a role in bacterial interactions with their hosts.
Highlights
Genomic Islands (GIs) are horizontally transferred DNA segments integrated into bacterial chromosomes[1]
We found that Region of Difference 21 (ROD21)-like GIs are a novel group of genomic islands encoded by members of Enterobacteriaceae, including plant and animal pathogenic strains
Given their presence in this bacterial family, we have designated these GIs as the Enterobacteriaceae-associated ROD21-like genomic islands (EARL GIs)
Summary
Genomic Islands (GIs) are horizontally transferred DNA segments integrated into bacterial chromosomes[1]. Many GIs contain an excision/ integration module that includes an integrase gene, usually belonging to the tyrosine recombinase family[1,11] and a Recombination Directionality Factor (RDF), which is a small protein of approximately 60–180 amino acids[12]. We found and analyzed different genomic islands within pathogenic and non pathogenic Enterobacteriaceae that share a conserved syntenic core with ROD21 These GIs share conserved genes encoding the excision/integration processes of the islands and the majority share genes encoding putative proteins that are likely involved in conjugal transfer. Phylogenetic analysis revealed that these islands represent a novel family of GIs present among animal- and plant-pathogenic members of the Enterobacteriaceae family
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