Abundance of integrons in halophilic bacteria

Abstract

Integrons are genetic platforms used for expressing open reading frames (ORFs) arranged in gene cassettes. Excision and integration of gene cassettes are controlled by their associated integron integrase (IntI). Using IntegronFinder software, we analyzed all complete halophilic genomes available in the HaloDom database, along with selected partial halophilic genomes. We identified 18 new complete bacterial integrons and 46 clusters of attC sites lacking a neighboring integron integrase (CALINs). Different classes of insertion sequences (ISs) were also identified within and near integrons and CALINs, with an abundance of IS1182 elements and different ISs that can presumably mobilize adjacent genomic structures. Different promoters of intI genes (PintI) showed nearby binding sites for arginine repressor (ArgR), raising the possibility that IntI expression and recombination activity are regulated by these proteins. Our findings revealed the existence of new integrons in halophilic bacteria with possible adaptive roles.