Bt Research 2025, Vol.16, No.6, 269-277 http://microbescipublisher.com/index.php/bt 269 Feature Review Open Access The Role of Plasmids in the Metabolic Diversity of Bt Chengxi Wang 1, Qiangsheng Qian 1, Danyan Ding 2 1 Modern Agricultural Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China 2 Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding email: danyan.ding@jicat.org Bt Research, 2025, Vol.16, No.6 doi: 10.5376/bt.2025.16.0030 Received: 25 Oct., 2025 Accepted: 15 Nov., 2025 Published: 26 Dec., 2025 Copyright © 2025 Wang et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Wang C.X., Qian Q.S., and Ding D.Y., 2025, The role of plasmids in the metabolic diversity of Bt, Bt Research, 16(6): 269-277 (doi: 10.5376/bt.2025.16.0029) Abstract Bacillus thuringiensis (Bt) is a widely used insect pathogenic bacterium, renowned for its synthesis of insecticidal crystal proteins. In addition to its insecticidal function, Bt also exhibits a high degree of metabolic diversity, and this diversity is largely related to the plasmids it carries. This study systematically explored the structural characteristics, functional roles of plasmids in Bt and their influence on the regulation of metabolic pathways, summarized the common types of plasmids in Bt strains and their interrelationships with chromosome genomes, and then focused on analyzing how plasmid-coding genes are involved in regulating carbon source metabolism, energy conversion and the synthesis of secondary metabolites. The role of plasmids in environmental adaptability was also discussed, including resistance to adverse conditions such as high salt and high temperature, biofilm formation ability, and the potential for horizontal gene transfer. Through case studies of typical Bt strains (such as Bt kurstaki and Bt israelensis), this study reveals the plasmid-driven metabolic characteristics and their value in agricultural and environmental applications. This study highlights the core position of plasmids in the functional evolution and ecological adaptability formation of Bt, providing theoretical support and application references for the improvement of Bt biopesticides and the enhancement of their environmental adaptability. Keywords Bacillus thuringiensis; Plasmid; Metabolic diversity; Toxin gene; Environmental adaptability 1 Introduction Bacillus thurningiensis (Bt) was first known because it can produce Cr-like insecticidal toxins, which are used to deal with some pests in farmlands. This Gram-positive bacterium can form spores and is often classified as a safe and green biopesticide. However, if you only focus on its insecticidal ability, you are underestimating it. The metabolic diversity of Bt is actually quite astonishing. This characteristic enables it to adapt to different ecological environments, exert pathogenic effects in specific insects, and also affects its own life cycle, developmental rhythm and survival strategy (Gillis et al., 2018; Fazion et al., 2018). In other words, the Cry toxin is only a superficial part. To truly understand the biological control potential of Bt, one must start from its complex metabolic adaptability. This also explains its wide presence and evolutionary advantage in the Bacillus cereus group. As for how the metabolic capacity of Bt comes about, plasmids might be the key. Unlike the core genes that stably exist on chromosomes, these mobile genetic elements are like "external modules". Some carry Cry toxin genes, while others control processes such as quorum sensing and spore formation (Cardoso et al., 2020). A Bt strain often has more than one plasmid, each with distinct functions. When combined, it's like equipping the strain with multiple toolkits. Interestingly, plasmids can be transferred, and this horizontal gene exchange enables different Bt strains to acquire new characteristics in a short period of time (Meric et al., 2018). It is precisely for this reason that Bt can always "activate the appropriate functions" when facing environmental changes or new hosts. This is the confidence that enables it to take root in various ecological niches. This study, by analyzing the genetic composition, mobility of plasmids and their functional impacts on bacterial physiology and ecology, clarifies the role of plasmids in the metabolic diversity of Bacillus thurningiensis (Bt), characterizes the plasmid diversity of different Bt strains, and understands how the plasmid coding system
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