Ten years of Bt maize cultivation: Horizontal gene transfer of no significance
Scientists in France and Switzerland are working to show soil bacteria from Bt maize fields do not cause antibiotic-resistance. This topic has been very controversial in the past, but it appears these scientists may have been able to show that antibiotic-resistant genes don’t transfer from the transgenic plants to bacteria.
C.S. Prakash
Ten years of Bt maize cultivation: Horizontal gene transfer of no significance
GMO Safety
May 30, 2008
Scientists from France and Switzerland have been studying soil bacteria from a field where genetically modified Bt maize has been growing for 10 years. They wanted to find out whether controversial antibiotic-resistance genes can in fact transfer from transgenic plants to bacteria, as is widely feared. They have concluded that transgenic plants play no part in the spread of antibiotic resistances.
Bacteria have special mechanisms which enable them to exchange genetic information directly without sexual reproduction. For this reason it is feared that antibiotic‑resistance genes that are used as marker genes in transgenic plants could be absorbed by pathogenic bacteria and so reduce the effectiveness of important antibiotic drugs. Antibiotics are widely used in human and veterinary medicine and for a long time they were also added to animal food to promote animal growth and performance. This has led to the emergence of bacterial resistances to antibiotics used in medicine. The question is, do genetically modified plants also help spread this kind of antibiotic resistance?
Gene transfer from plant DNA to bacteria is considered to be highly unlikely because a whole series of conditions are required before it can occur at all. As yet, this type of horizontal gene transfer has not been detected under field conditions. Even in the laboratory, it could only be provoked with the help of specially constructed recipient bacteria.
To assess the likelihood and the significance of a possible transfer of antibiotic- resistance genes from transgenic plants to bacteria, scientists from France and Switzerland have studied soil bacteria from a field in south western France where genetically modified Bt176 maize has been growing for 10 years. By way of comparison, soil samples from a conventional maize field and from uncultivated land (prairie soil) were also investigated.
