Events occurring during introgression of an antibiotic resistance gene in mutator populations of Acinetobacter baylyi

Abstract

Natural transformation is recognaized as a major horizontal gene transfer mecahnism which impacts the genetic adaptaion , diversity and evolution of prokaryotes. Natural ransformation is uptake of extracellular DNA and its integration in a host genome. The fact that species take up foregin nucleotide sequences is believed to be followed by elimination of non-adventageous DNA sequence since bacterial genome do not grow in size.Transfer of gene from one species into the gene pool of another by backcrossing of hybid transformants with one parents is defined as intrgression. In this study the hypothesis that bacteria during introgrssion might regulate aquisition of foreign DNA by non-selected sequence by recombination was examined. The thesis contribute to earlier (Ray 2007)and ongoing projects investigating the fate of non-selected DNA during introgression of a choromsomal antibiotic resistance gene (nptII) in the bacterium A. baylyi. Hybrid transormants f A.baylyi ADP17021 contained a kanamycin resistance gene ande a mutS-gene deletion and an undeteramined amount of the donor strain A.sp.62A1. In this study DNA sequencing technologies and the Acinetobacter baylyi BD413 (ADP1) published geneome sequence was used to achive important results as identifying putative recombination junctions in ten back-transformants among the 10th and first generation and the effect of methyl-directet mismatch repair (mutS-deletion) on flanking DNA aquired by the recipient. The generation of the initial heterogamic transformation and ten subsequent backcross transformants were performed in a previous study (Ray, 2007). The aim of this study was identifying recombination junctins and the insert size of flanking DNA. It was clear that back-cross transformants harboured a significantly shorter donor sequence when compared to the initial genration. This indicates that during introgression, the non selected sequence will be gradually eliminated.