Bt Research 2025, Vol.16, No.2, 47-54 http://microbescipublisher.com/index.php/bt 52 addition, the recombination of the Bt genome and the emergence of new toxin genes may also bring about unpredictable ecological consequences. Therefore, in the process of screening, application and supervision of Bt, special attention should be paid to the assessment and management of ecological risks related to plasmid diversity (Nair et al., 2018). 8 Concluding Remarks Plasmids are important mobile genetic elements of bacteria and play a core role in the adaptive evolution of bacteria such as Bt. The diversity of plasmids enables them to carry genes related to resistance, virulence, metabolism and environmental adaptation, thereby enhancing the survival ability of host bacteria in response to environmental changes. Plasmids not only promote genomic recombination but also accelerate the spread of beneficial traits in the population through horizontal gene transfer. This enables the Bt strain to respond to environmental stress more quickly. In addition, the insertion sequence on the plasmid can also promote gene inactivation and rapid adaptation, accelerating the evolution of the strain. Plasmid engineering provides an effective tool for enhancing the function of Bt strains and their application in biological control. By regulating the copy number of plasmids, optimizing vector design, and applying synthetic biology methods, precise control over the expression of target genes can be achieved, thereby enhancing toxin production, metabolic efficiency, and environmental adaptability. The latest research shows that combining the replication mechanisms of different plasmids or adjusting their copy numbers can not only reduce the metabolic burden on strains but also enable the microbiota to respond more flexibly to environmental changes. This provides support for the stability and functional performance of Bt strains in complex ecosystems. The future research directions can focus on the following three aspects: First, it is necessary to more systematically analyze the plasmidome diversity of Bt and related bacteria, especially the ecological functions and evolutionary roles of linear plasmids; Second, it is necessary to develop higher-throughput and more precise plasmidomics tools to reveal the interactions between plasmids and host genomes as well as environmental factors. Thirdly, plasmidomics should be integrated with biological control strategies to achieve targeted optimization of the functions of Bt strains and assess their ecological safety. At the same time, it is necessary to pay attention to the balance between the metabolic burden brought by plasmids and their adaptability, and explore engineering methods that can reduce the burden and enhance the stability of plasmids. Acknowledgments The authors appreciate the comments from Professor Lian on the manuscript of this study. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. References Bravo A., Likitvivatanavong S., Gill S.S., and Soberón M., 2011, Bacillus thuringiensis: a story of a successful bioinsecticide, Insect Biochemistry and Molecular Biology, 41(7): 423-431. https://doi.org/10.1016/j.ibmb.2011.02.006 Chelliah R., Wei S., Park B., Park J., Park Y., Kim S., Jin Y., and Oh D., 2019, New perspectives on Mega plasmid sequence (poh1) in Bacillus thuringiensis ATCC 10792 harbouring antimicrobial, insecticidal and antibiotic resistance genes, Microbial Pathogenesis, 126: 14-18. https://doi.org/10.1016/j.micpath.2018.10.013 Chen S., Huang K., He Z., and Zhao F., 2025, Ampicillin exposure and glutathione deficiency synergistically promote conjugative transfer of plasmid-borne antibiotic resistance genes, Environmental Microbiology, 27(5): e70106. https://doi.org/10.1111/1462-2920.70106 Ciok A., Budzik K., Zdanowski M., Gawor J., Grzesiak J., Decewicz P., Gromadka R., Bartosik D., and Dziewit L., 2018, Plasmids of Psychrotolerant Polaromonas spp. isolated from arctic and antarctic glaciers- diversity and role in adaptation to polar environments, Frontiers in Microbiology, 9: 1285. https://doi.org/10.3389/fmicb.2018.01285 Das J., and Dangar T., 2007, Diversity of Bacillus thuringiensis in the rice field soils of different ecologies in India, Indian Journal of Microbiology, 47: 364-368. https://doi.org/10.1007/s12088-007-0065-z
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