Artificial modification of Bacillus thuringiensis (Bt) proteins can effectively improve their resistance to target pests, but the effect of such modification on the diversity of rhizosphere microorganisms remains unclear. Transgenic maize 2A-7 contains two artificially modified Bt proteins, mCry1Ab and mCry2Ab. These proteins can enter soil and pose a potential threat to soil microbial diversity. To assess their impacts on rhizosphere bacteria communities, the contents of the two Bt proteins and changes in bacterial community diversity in the rhizosphere soils of transgenic maize 2A-7 and its control variety were analyzed at different growth stages in 2020. The results showed that the two Bt proteins were detected at low levels in the rhizosphere soils of 2A-7 plants. No significant differences in soil bacterial diversity were detected between 2A-7 and its control variety at any of the growth stages. Bioinformatics analysis indicated that the growth stage, rather than the cultivar, was the main factor causing changes in bacterial communities. This research provides valuable data for understanding the impact of Bt crops on the soil microbiome, and establishes a theoretical basis for evaluation of their safety.

Transgenic maize 2A-7 expressing mCry1Ab and mCry2Ab has excellent resistance to lepidopteran pests. Previous studies have investigated the effects of several Bacillus thuringiensis (Bt) proteins on the soil. However, the effects of artificially modified Bt proteins on soil ecosystems are still unclear. To evaluate the effects of transgenic maize 2A-7 on soil, the physicochemical properties, enzyme activities and functional diversities of the microbial communities in rhizosphere soils from 2A-7 and its near-isogenic non-transgenic control Dongdan 6531 were analyzed at different developmental stages under field conditions. The alteration of six physicochemical properties (pH, total nitrogen, total phosphorus, organic matter, available phosphorus and alkali-hydrolyzed nitrogen) and six functional enzymes (catalase, alkaline phosphatase, sucrase, acid phosphatase, urease and alkaline protease) activities in the rhizosphere soils between the two maize cultivars were drastically correlated with plant growth stage, but not affected by the artificially modified Bt transgenes. An analysis of time-course Biolog data revealed that the functional diversity of microbial communities in the rhizosphere soil of 2A-7 and its control were similar at each developmental stage. The results suggest that transgenic maize 2A-7 has no significant impact on the soil ecosystem and provide valuable information on scientific safety assessments of 2A-7 and its commercial applications.

The rhizosphere microbiota plays a vital role in plant stress resistance and pathogen suppression. Bacterial wilt, caused by Ralstonia solanacearum, leads to significant economic losses in a wide variety of crops. The utilization of native microbial consortia has emerged as a promising strategy for combating this disease. In this study, we assembled a synthetic microbial consortium (Co-4) from rhizosphere bacteria with demonstrated antagonistic activity, comprising four strains of Bacillus sp., Heyndrickxia sp., Franconibacter sp., and Pseudomonas sp. Transcriptome analysis of tomato plants treated with Co-4 revealed significant alterations in gene expression, particularly in carbohydrate and energy metabolism, as well as translation processes. These changes correlated with enhancements in various plant growth traits, including height, stem thickness, biomass, leaf area, photosynthetic rate, and root development. Furthermore, two simplified consortia, SynCom1 (Bacillus, Heyndrickxia, Franconibacter) and SynCom2 (Franconibacter, Pseudomonas), exhibited augmented antagonistic properties against R. solanacearum compared to their individual constituent strains. Using SynCom2 as a model, we demonstrated that its synergistic interactions resulted in increased biofilm formation, motility, biomass production, cross-feeding interactions, and volatile organic compounds (VOC) emissions, all of which likely contribute to disease suppression and enhanced plant defense. This study highlights the potential of simplified synthetic consortia for managing bacterial wilt through cooperative microbial functions, presenting an effective and environmentally sustainable biocontrol strategy.