Bt Research 2024, Vol.15, No.3, 141-153 http://microbescipublisher.com/index.php/bt 146 Figure 1 Topological comparison between trees and their relevance to serological classification (Adopted from Shikov et al., 2021) Image caption: Red, blue, and green represent the proteins of different Bt strains, with red for strain 800/3, blue for strain 109/25, and green for strain 800/15. The overlapping of proteins labeled with different fluorescent colors on the 2D-DIGE image reveals the presence of protein differences among the strains during the sporulation phase. Although all strains form crystal inclusions, three-domain Cry toxins were not detected in any of the strains. Analyzing these differences allows for a better understanding of the virulence characteristics and classification relationships of different Bt serotypes (Adapted from Shikov et al., 2021). Whole-genome sequencing (WGS) is another powerful tool that offers comprehensive insights into the genetic relationships of Bt strains. Lechuga et al. (2020) utilized WGS to analyze the complete genome of Bt HER1410, revealing its close genetic relationship with B. thuringiensis serovar thuringiensis and other serovars, thus highlighting the intermingled taxonomy within the B. cereus group. By employing these advanced genomic techniques, researchers can accurately identify genetic relationships, trace evolutionary histories, and classify Bt strains more effectively (Figure 2). 6.2 Analysis of genetic divergence Genetic divergence among Bt strains is analyzed to understand how genetic variations contribute to the evolution and adaptation of these bacteria. Genetic divergence can be quantified by comparing genetic sequences and identifying differences that have accumulated over time. Techniques such as MLST, WGS, and comparative genomics are used to study genetic divergence. For instance, a study on Bt strains from Kuwait using random amplified polymorphic DNA (RAPD) analysis showed significant genetic divergence among the isolates, which were grouped into distinct clusters based on their genetic patterns (Qasem et al., 2015). Comparative genomic studies also provide insights into genetic divergence by identifying unique genomic features and variations among strains. In their study, Rabha et al. (2018) conducted a comparative analysis of Bt isolates from Assam soil, revealing substantial genetic divergence and the presence of unique vegetative insecticidal protein (vip) genes in different strains. The transfer of plasmids carrying toxin genes contributes to genetic divergence and adaptation to new hosts. Zheng et al. (2017) demonstrated that the acquisition of plasmids
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