GMO bacterial pathogens

Field-testing Bacterial Pathogens with Antibiotic Resistance Genes

Prof. Joe Cummins

The University of Wisconsin is preparing to release genetically modified (GM) Erwinia carotovora bacteria containing antibiotic resistance marker genes in environmental field tests. The United States department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has prepared a docket with background information on the release and there is a public comment period ending 15 September 2005 [1]. The tests are to be conducted at the University of Wisconsin Experiment Station near Hancock, Wisconsin. The environmental release of bacterial strains each containing a different antibiotic should be a matter of grave concern and a strong public response is in order.

The purpose of the field trial seems to be simply experimental with no potential commercial application of the genetically modified bacteria. Erwinia carotovora causes a rotting disease in potatoes. The experiment is designed to test the fitness of bacteria that have genes known to be associated with pathogenesis disrupted by inserting into those genes the antibiotic resistance genes. The antibiotic resistance genes not only eliminate the function of the pathogenesis genes but also serve as selectable markers for the modified bacteria. The antibiotic resistance genes are precisely inserted into the target pathogenesis gene by adding short DNA tails to the resistance genes that are homologous to the target pathogenesis gene. The pathogenesis gene targeted is hrp, which controls secretion of virulence proteins into the host plant. Green fluorescence protein was inserted as a visual marker to identify potatoes with the modified bacteria