Abstract
The first record of transgenic cotton cultivation in Brazil was in 2005, of that of the cultivar MON 531, possessing the cry1Ac gene. Since then, no evaluation has been performed to understand whether the cultivation of Bt cotton has caused any interference with the soil microbiota, including bacteria. In this context, our research was aimed to assess whether the cultivation of Bt cotton negatively affects the community of soil bacteria, through quantitative and metagenomic analyses (marker gene 16S rRNA) for phylum identification. Samples of bacterial populations obtained from the soil cultivated with Bt cotton expressing the Cry1Ac toxin were compared with soil samples from the area cultivated with conventional cotton. Significant differences were not observed in the measure of colony-forming units of bacteria between the soils cultivated with Bt and non-Bt cotton; however, differences were detected only when comparing samples from different collection times of the Bt treatment. Cultivation of Bt cotton did not affect the diversity of the soil bacterial population. Overall, our study shows that, similar to most of the works that have been reported worldwide, cultivation of transgenic cotton does not seem to affect the quantity and diversity of natural soil bacteria.
Highlights
Modified plants (GMPs) or transgenic plants originate from recombinant DNA technology
The structural diversity of bacterial communities has been studied using methods based on the investigation of a part of their DNA sequence, such as the 16S rDNA. These methods involve the amplification of the 16S rDNA by PCR and posterior characterization through cloning and sequencing, or analysis by electrophoresis, using techniques such as amplified ribosomal DNA restriction analysis (ARDRA), terminal restriction fragment length polymorphism (T-RFLP), random amplified polymorphic DNA (RAPD), ribosomal intergenic spacer analysis (RISA), denaturing gradient gel electrophoresis (DGGE)/temperature gradient gel electrophoresis (TGGE), and single-strand conformation polymorphism (SSCP)
Significant differences were not observed concerning the number of colony-forming units (CFUs) of bacteria between the soils cultivated with Bt or non-Bt cotton (F = 2.12; df = 1, 34; P = 0.16; Table 1)
Summary
Modified plants (GMPs) or transgenic plants originate from recombinant DNA technology. These methods involve the amplification of the 16S rDNA by PCR and posterior characterization through cloning and sequencing, or analysis by electrophoresis, using techniques such as amplified ribosomal DNA restriction analysis (ARDRA), terminal restriction fragment length polymorphism (T-RFLP), random amplified polymorphic DNA (RAPD), ribosomal intergenic spacer analysis (RISA), denaturing gradient gel electrophoresis (DGGE)/temperature gradient gel electrophoresis (TGGE), and single-strand conformation polymorphism (SSCP) This results in obtaining data regarding the relatedness of the bacterial species that constitute the microbial community (Ranjard et al, 2000; Kozdrój & Van Elsas, 2001). Molecular methods for the analysis of the structure and diversity of microbes have been developed in the past that utilize the genomic DNA directly extracted from environmental samples Such developments have allowed considerable advances to be made in the study of microbial ecology (O’Donnell & Göres, 1999; Ranjard et al, 2000). To the best of our knowledge, this is the first report on the effects of Bt transgenic cotton on the soil bacterial community in Brazil
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