Multiplication of upon Exposure to a Beta-Lactam Antibiotic Results in a Transferable Transposon in .

Plasmids play a crucial role in spreading antimicrobial resistance genes. Plasmids have many ways to incorporate various genes. By inducing amoxicillin resistance in , followed by horizontal gene transfer experiments and sequencing, we show that the chromosomal beta-lactamase gene is multiplied and results in an 8-13 kb contig. This contig is comparable to a transposon, showing similarities to variable regions found in environmental plasmids, and can be transferred between cells. As in eight out of nine replicate strains an almost completely identical transposon was isolated, we conclude that this process is under strict control by the cell. The single transposon that differed was shortened at both ends, but otherwise identical. The outcome of this study indicates that as a result of exposure to beta-lactam antibiotics, can form a transposon containing that can subsequently be integrated into plasmids or genomes. This observation offers an explanation for the large diversity of genes in plasmids found in nature and proposes mechanisms by which the dynamics of plasmids are maintained.