In the production of genetically modified (GM) plants, genes conferring 'desirable' traits are identified and are then assembled in bacteria before delivery into the target plants. The assembly of genes in bacteria is made simple by including antibiotic resistance marker genes. The presence of a gene that codes for resistance to an antibiotic in a single bacterial cell means that, by adding the appropriate antibiotic to a culture, the single cell can be isolated from millions or even billions of bacteria lacking the resistance gene present in the same culture. By linking a gene that confers antibiotic resistance on its host bacterium to the genes that are to be inserted into plants, sufficient quantities of DNA can be harvested from a bacterial culture to allow the novel DNA to be delivered easily to the plant. One marker gene commonly used in the early days of GM crop development, called blaTEM, confers resistance to antibiotics such as ampicillin and amoxycillin. This gene causes the production of an enzyme, known as a â-lactamase, which breaks down the structure of these antibiotics, rendering them ineffective against bacteria. Although the bacteria that live in animal and human guts frequently carry blaTEM, which occurs naturally at a high frequency, this project is designed to examine the risk that blaTEM from GM maize can pass from the modified plant tissues into microbes in animals that are fed GM maize.