Thünen-Institut für Biodiversität, Bundesforschungsinstitut für Ländliche Räume, Wald und Fischerei, Bundesallee 50, 38116, Braunschweig, Germany.
Appl Microbiol Biotechnol. 2015 Sep;99(17):7333-41. doi: 10.1007/s00253-015-6655-5. Epub 2015 May 13.
Insecticidal delta-endotoxins of Bacillus thuringiensis are among the most abundant recombinant proteins released by genetically modified (GM) crops into agricultural soils worldwide. However, there is still controversy about their degradation and accumulation in soils. In this study, (14)C-labelled Cry1Ab protein was applied to soil microcosms at two concentrations (14 and 50 μg g(-1) soil) to quantify the mineralization of Cry1Ab, its incorporation into the soil microbial biomass, and its persistence in two soils which strongly differed in their texture but not in silt or pH. Furthermore, ELISA was used to quantify Cry1Ab and its potential immunoreactive breakdown products in aqueous soil extracts. In both soils, (14)CO2-production was initially very high and then declined during a total monitoring period of up to 135 days. A total of 16 to 23 % of the (14)C activity was incorporated after 29 to 37 days into the soil microbial biomass, indicating that Cry1Ab protein was utilized by microorganisms as a growth substrate. Adsorption in the clay-rich soil was the most important factor limiting microbial degradation; as indicated by higher degradation rates in the more sandy soil, extremely low concentrations of immunoreactive Cry1Ab molecules in the soils' aqueous extracts and a higher amount of (14)C activity bound to the soil with more clay. Ecological risk assessments of Bt-crops should therefore consider that the very low concentrations of extractable Cry1Ab do not reflect the actual elimination of the protein from soils but that, on the other hand, desorbed proteins mineralize quickly due to efficient microbial degradation.
苏云金芽孢杆菌的杀虫δ-内毒素是全球转基因（GM）作物向农业土壤中释放的最丰富的重组蛋白之一。然而，关于其在土壤中的降解和积累仍存在争议。在这项研究中，（14）C 标记的 Cry1Ab 蛋白以两种浓度（14 和 50 μg g（-1）土壤）应用于土壤微宇宙，以量化 Cry1Ab 的矿化、其掺入土壤微生物生物量以及在两种土壤中的持久性，这两种土壤在质地方面存在差异，但在淤泥或 pH 值方面没有差异。此外，还使用 ELISA 定量测定土壤水提物中 Cry1Ab 及其潜在免疫反应性降解产物的含量。在两种土壤中，（14）CO2 的产生最初非常高，然后在长达 135 天的总监测期内下降。在 29 至 37 天后，总共 16 至 23%的（14）C 活性被掺入土壤微生物生物量中，这表明 Cry1Ab 蛋白被微生物用作生长底物。在富含粘土的土壤中，吸附是限制微生物降解的最重要因素；由于更沙质土壤中的降解速率更高，土壤水提物中免疫反应性 Cry1Ab 分子的浓度极低，以及更多粘土结合的（14）C 活性更高，这表明这一点。Bt 作物的生态风险评估因此应考虑到可提取的 Cry1Ab 浓度非常低并不能反映该蛋白实际上已从土壤中消除，但另一方面，由于微生物降解效率高，解吸的蛋白会迅速矿化。
