Regulation,Excision And Horizontal Transfer Of Genomic Islands GIsul2 In Bacteria

BackgroundHorizontal gene transfer(HGT),is a common mechanism for the exchange of genetic information between bacterial species,which contributes to the diversification and adaptation of microorganisms.Mobile genetic elements(MGEs),the drivers of HGT,are segments of DNA that encode enzymes and other proteins that mediate the movement of DNA within genomes(intracellular mobility)or between bacterial cells(intercellular mobility).Genomic island is an important MGE in bacteria.Mobile genomic islands are able to integrate into the chromosome of the host,from which they get excised under favorable conditions and are then transferred to a new host via transformation,conjugation or transduction.Genomic islands have a variety of biological function,such as antibiotic resistance,pathogenicity,xenobiotic degradation and heavy metal resistance.Genomic island not only helps microorganisms adapt to the external environment,but also can cause widespread transmission of variable genes among different species of bacteria.GIsul2,a genomic island carrying the sul2 sulphonamide resistance gene and the small mobile ISCR2 element was found in the Enterobacter cloacae,Acinetobacter baumannii and Shigella flexneri.In this article,We have conducted in-depth studies on regulation,excision and horizontal transfer of GIsul2 genomic island in bacteria.ObjectivesIn this paper,we study the transfer and regulation mechanism of the GIsul2genomic island and explore the effect of GIsul2 genomic island on the spread of bacterial drug resistance genes.We try to elucidate the pathogenicity,drug resistance,and spread of pathogenic bacteria through horizontal gene transfer and epigenomics.Finally,to provide a new theoretical basis for solving bacterial drug resistance.Methods1 GIsul2 genomic island with a size of 15 kb is obtained by molecular cloning and PCR template is Shigella flexneri 515752 To construct the donor plasmid pKD46-GIsul2 and related knockout plasmids,and to construct the receptor plasmid pKF18-GMP800.3 The donor and receptor plasmids are transformed into E.coli competent DH5?(recA~-).4 To construct the‘mini'mobile plasmid by molecular cloning and to study the interaction of related factors in the double plasmids system.5 To purify the P4-like integrase by using the His bind purification kit and explore function of the P4-like integrase.Results1.GIsul2 genomic island and ISCR2 element are transferred the donor to the receptor.2.P4-like integrase and DRs are necessary to GIsul2 genomic island and ISCR2element.3.The regulatory factors fitA and Alpa can regulate the transfer frequency and transfer form of the GIsul2 genomic island and ISCR2 element.4.The transfer of‘mini'mobile plasmid is mediated by P4-like integrase and DRs though the tests of double plasmid system.5.There are cofactor-binding target sequences at the border of the genomic island.6.P4-like integrase make DNA untwisting and specifically bind to DR sequences.Conclusions1.P4-like integrase and DRs are necessary to GIsul2 genomic island and ISCR2element.The cofactor can regulate the transfer frequency and transfer form of the GIsul2 genomic island.2.P4-like integrase binds to DR sequences and transfers from the host genome through specific site recombination.There are cofactor-binding sites around the DR sequences,and the DNA target sequences have low homologous,and the secondary structure of cofactor-binding sites has a higher degree of similarity.It is speculated that the complex secondary structure enables the P4-like integrase to more accurately recognize and bind DR sequences.