Lateral gene transfer, also known as horizontal gene transfer (HGT) affects variation by moving genes across species boundaries, introducing new genes into existing genomes particularly in prokaryotes. HGT is defined as the acquisition of foreign genes by organisms. It only affects organisms that readily exchange genes. HGT is believed to be responsible for the rapid spreading and acquiring of new traits or characteristics across some types of bacteria. One such trait or characteristic is that of bacteria becoming resistant to antibiotics.