| Widespread cultivation of glyphosate-resistant (GR) crops and the agricultural revolution on the ecological environment have received considerable attentions. Impacts of glyphosate and glyphosate-resistant crops on rhizosphere microorganisms have been reviewed based on field and green house projects.Here, we analyzed the effects of glyphosate-resistant rice (EP3) and glyphosate on the physiological profile and community structure of the rhizosphere microorganisms by combining Biolog and denaturing gradient gel electrophoresis (DGGE). We also described the impact of glyphosate shock to the microbial communities by metatranscriptomic analysis.The glyphosate sensitive rice varieties were Minghui 86 (parent of EP3), Kefeng 6 (transgenic Bt rice), II-YOU Minghui 86 and Shanyou 63 (two hybrid rice varieties). Soil samples were taken at the rice seedling period, tillering period, and maturity period, respectively. We did not observe the changes in carbon utilization abilities of the microorganisms in the rhizosphere soil of different rice varieties (P>0.05). The result is consistent with DGGE profiles. Hence, we concluded that community structure of the rhizosphere microorganisms were robust to changes in rice variety; however, community structure was more sensitive to seasonality than to rice varieties.Cultivation of GR crops has led to an enormous increase of glyphosate application, which might make great change to the agricultural ecological system. To measure the effect of glyphosate application on ecological systems, we analyzed the community level physiological profile and community structure of the mainly rhizosphere microorganisms in a greenhouse condition using Biolog and DGGE methods. Two GR-rice groups were treated with glyphosate at the concentrations of 27 mg·kg-1 (a field normal concentration) and 270 mg·kg-1 (10-fold increase), respectively. The control group was treated with water. Three replicate samples were taken on days 7, 14 and 30 after glyphosate treatment. Significant effects (P<0.05) on the physiological activity of the microbial community were found both at the normal concentration and the 10-fold increased concentration of glyphosate, but the abundance and diversity of the microbial communities remains unchanged. Within 30 days after glyphosate application, the microorganisms of the soil significantly reduced the utilization of several carbon sources, those are D-glucuronic acid,β-methyl-D-glucoside, D, L-α-glycerophosphate, L-arginine, and sitimuous significantly enhanced the utilization of 4-hydroxy benzoic acid. In addition to that, the DGGE profile showed although glyphosate application with normal field concentration did not significantly influence the microbial communities, the 10-fold glyphosate concentration altered the rhizosphere community structure ofα-proteobacteria, actinomycetes and azotobacter.In order to reveal the situ diversity, taxonomic, distribution and abundance of the rhizosphere microorganisms after glyphosate application at normal field concentration, we analyzed the metatranscriptomics by using high-throughput sequencing platform. Application of glyphosate at recommended rate to soil resulted notable changes in the population of microbial community. Glyphosate application with 27 mg kg-1 can change the abundance of prominent microbial communities. The population of proteobacteria and Achaea increased; Abundance of eukaryotes were seriously inhibited with the glyphosate shocked. Metatranscriptomics analysis offers an unprecedented opportunity to detect the organisms those cannot be detected by traditional methods, such as Deferribacteres, Lentisphaerae, Fibrobacteres, Thaumarchaeota, Blastocladiomycota, Glomeromycota, Rotifera, Ctenophora, Chordata, Bacillariophyta, Microsporidia and Haplosporidia. In this study, these microorganisms are inhibited by glyphosate shock. In a summary, glyphosate can cause significant changes on major microbial communities of rhizosphere soil after glyphosate shock and application. |
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