title: Field studies on the environmental fate of the Cry1Ab Bt-toxin produced by transgenic maize (MON810) and its effect on bacterial communities in the maize rhizosphere.
abstract: Field studies were done to assess how much of the transgenic, insecticidal protein, Cry1Ab, encoded by a truncated cry1Ab gene from Bacillus thuringiensis (Bt), was released from Bt-maize MON810 into soil and whether bacterial communities inhabiting the rhizosphere of MON810 maize were different from those of the rhizosphere of nontransgenic maize cultivars. Bacterial community structure was investigated by SSCP (single-strand conformation polymorphism) of PCR-amplified 16S rRNA genes from community DNA. Using an improved extraction and detection protocol based on a commercially available ELISA, it was possible to detect Cry1Ab protein extracted from soils to a threshold concentration of 0.07 ng/g soil. From 100 ng of purified Cry1Ab protein added per gram of soil, only an average of 37% was extractable. At both field sites investigated, the amount of Cry1Ab protein in bulk soil of MON810 field plots was always lower than in the rhizosphere, the latter ranging from 0.1 to 10 ng/g soil. Immunoreactive Cry1Ab protein was also detected at 0.21 ng/g bulk soil 7 months after harvesting, i.e. in April of the following year. At this time, however, higher values were found in residues of leaves (21 ng/g) and of roots (183 ng/g), the latter corresponding to 12% of the Cry1Ab protein present in intact roots. A sampling 2 months later indicated further degradation of the protein. Despite the detection of Cry1Ab protein in the rhizosphere of MON810 maize, the bacterial community structure was less affected by the Cry1Ab protein than by other environmental factors, i.e. the age of the plants or field heterogeneities. The persistence of Cry1Ab protein emphasizes the importance of considering post-harvest effects on nontarget organisms.
authors.affiliation: Institut für Agrarökologie, Bundesforschungsanstalt für Landwirtschaft (FAL), Bundesallee 50, 38116 Braunschweig, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Baumgarte
authors.forename: Christoph C
authors.initials: CC
authors.lastname: Tebbe
mesh_terms: D000704:Analysis of Variance; D000083722:Bacillus thuringiensis Toxins; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity; D001427:Bacterial Toxins / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity; D016000:Cluster Analysis; D004731:Endotoxins / Q000378:metabolism* / Q000493:pharmacokinetics / Q000633:toxicity; D004777:Environment; D004797:Enzyme-Linked Immunosorbent Assay; D005858:Germany; D006460:Hemolysin Proteins; D030821:Plants, Genetically Modified / Q000378:metabolism*; D018807:Polymorphism, Single-Stranded Conformational; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D003313:Zea mays / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D012336:RNA, Ribosomal, 16S; D012987:Soil; C030956:insecticidal crystal protein, Bacillus Thuringiensis