Department of Civil and Environmental Engineering, Duke University, Durham, NC, 27708, USA.
Department of Civil and Environmental Engineering, Duke University, Durham, NC, 27708, USA.
Chemosphere. 2017 May;175:45-51. doi: 10.1016/j.chemosphere.2017.02.030. Epub 2017 Feb 5.
The cultivation and consumption of transgenic crops continues to be a widely debated topic, as the potential ecological impacts are not fully understood. In particular, because antibiotic resistance genes (ARGs) have historically been used as selectable markers in the genetic engineering of transgenic crops, it is important to determine if the genetic constructs found in decomposing transgenic crops persist long enough in the environment and if they can be transferred horizontally to indigenous microorganisms. In the present study, we address the question of persistence. Others have also estimated the DNA adsorption capacity of various clays, but have done so by manipulating the surface charge and size of particles tested which may overestimate sorption and underestimate the DNA available for horizontal transfer. In the present study, isotherms were generated using model Calf Thymus DNA and transgenic maize DNA without surface modification. Montmorillonite, kaolinite, and 3 soil mixtures with varying clay content were used in this study. The adsorption capacity of pure montmorillonite and kaolinite minerals was found to be one to two orders of magnitude less than previously estimated likely due to the distribution of clay particle sizes and heteroionic particle surface charge. However, it appears that a substantial amount of DNA is still able to adsorb onto these matrices (up to 200 mg DNA per gram of clay) suggesting the potential availability of free transgenic DNA in the environment may still be significant. Future studies should be conducted to determine the fate of these genes in agricultural soils.
转基因作物的种植和使用仍然是一个备受争议的话题，因为其潜在的生态影响尚未完全了解。特别是，由于抗生素抗性基因（ARGs）在转基因作物的遗传工程中一直被用作选择性标记，因此确定在分解的转基因作物中发现的基因构建体在环境中是否能够长时间存在，以及它们是否可以水平转移到土著微生物中，这一点非常重要。在本研究中，我们解决了持久性的问题。其他人也已经估计了各种粘土的 DNA 吸附能力，但他们通过操纵测试颗粒的表面电荷和大小来做到这一点，这可能会高估吸附并低估可用于水平转移的 DNA。在本研究中，使用未经过表面修饰的模型小牛胸腺 DNA 和转基因玉米 DNA 生成等温线。本研究使用蒙脱石、高岭石和 3 种具有不同粘土含量的土壤混合物。纯蒙脱石和高岭石矿物质的吸附能力发现比以前估计的要低一到两个数量级，这可能是由于粘土颗粒大小的分布和异质粒子表面电荷的影响。然而，似乎仍然有大量的 DNA 能够吸附到这些基质上（每克粘土高达 200 毫克 DNA），这表明环境中可能仍然存在大量自由转基因 DNA。未来的研究应该确定这些基因在农业土壤中的命运。
