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. 2008 Mar 11;105(10):3957-62.
doi: 10.1073/pnas.0800072105. Epub 2008 Feb 21.

Antibiotic-resistant Soil Bacteria in Transgenic Plant Fields

Free PMC article

Antibiotic-resistant Soil Bacteria in Transgenic Plant Fields

Sandrine Demanèche et al. Proc Natl Acad Sci U S A. .
Free PMC article


Understanding the prevalence and polymorphism of antibiotic resistance genes in soil bacteria and their potential to be transferred horizontally is required to evaluate the likelihood and ecological (and possibly clinical) consequences of the transfer of these genes from transgenic plants to soil bacteria. In this study, we combined culture-dependent and -independent approaches to study the prevalence and diversity of bla genes in soil bacteria and the potential impact that a 10-successive-year culture of the transgenic Bt176 corn, which has a blaTEM marker gene, could have had on the soil bacterial community. The bla gene encoding resistance to ampicillin belongs to the beta-lactam antibiotic family, which is widely used in medicine but is readily compromised by bacterial antibiotic resistance. Our results indicate that soil bacteria are naturally resistant to a broad spectrum of beta-lactam antibiotics, including the third cephalosporin generation, which has a slightly stronger discriminating effect on soil isolates than other cephalosporins. These high resistance levels for a wide range of antibiotics are partly due to the polymorphism of bla genes, which occur frequently among soil bacteria. The blaTEM116 gene of the transgenic corn Bt176 investigated here is among those frequently found, thus reducing any risk of introducing a new bacterial resistance trait from the transgenic material. In addition, no significant differences were observed in bacterial antibiotic-resistance levels between transgenic and nontransgenic corn fields, although the bacterial populations were different.

Conflict of interest statement

The authors declare no conflict of interest.


Fig. 1.
Fig. 1.
Phylogenic relationship of blaTEM sequences isolated from medical origin and amplified from a transgenic corn field (Bt), a traditional corn field (M), and a prairie soil (S). Green shading identifies blaTEM sequences from the transgenic corn field. Black shading identifies blaTEM sequences from other origins. Red shading identifies the two blaTEM medical sequences that might originate from the environment.

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