Bt Research 2024, Vol.15, No.3, 118-130 http://microbescipublisher.com/index.php/bt 125 Similarly, Bt X022, a novel strain isolated from Chinese soil, was found to possess seven plasmids. Genomic and proteomic analyses revealed the presence of multiple Cry proteins and a vegetative insecticidal protein (Vip3A), which are crucial for its insecticidal activity. The study also uncovered a metabolic regulation mechanism influenced by Cu2+ treatment, which enhances the production of insecticidal crystal proteins (ICPs) (Quan et al., 2016). In Brazil, Bt isolates from various ecosystems, including the Amazon, Caatinga, and Cerrado biomes, were characterized for their pathogenicity against mosquito larvae. The study identified 400 Bt strains, with a significant number showing larvicidal activity. Plasmid analysis and gene profiling revealed the presence of multiple cry and cyt genes, which are essential for the insecticidal properties of these isolates (Soares-da-Silva et al., 2017). 7.2 Aquatic-derived Bt isolates Aquatic environments also serve as a source of diverse Bt isolates with unique plasmid profiles. Although specific studies focusing solely on aquatic-derived Bt isolates are limited, the genetic diversity observed in soil and insect-derived isolates suggests that aquatic habitats could harbor equally diverse Bt strains. The presence of various cry and cyt genes in these isolates indicates their potential for controlling aquatic insect pests, such as mosquito larvae, which are vectors for diseases like malaria and dengue (Soares-da-Silva et al., 2017). 7.3 Insect-derived Bt isolates Insect-derived Bt isolates exhibit distinct plasmid profiles and insecticidal properties, making them valuable for biopesticide development. In Bangladesh, Bt isolates were oBtained from insect guts, phylloplanes, and soil. The study identified 57 Bt isolates with diverse parasporal crystal proteins and plasmid profiles. These isolates showed significant insecticidal activity against pulse beetles, demonstrating their potential for biopesticide production (Shishir et al., 2012). In Turkey, Bt isolates from soil, fig leaves, and fruits were characterized for their insecticidal activity and Cry protein composition. The study identified several isolates with high toxicity against lepidopteran species, surpassing the reference strain HD1. Plasmid analysis revealed the presence of vip3 genes, which encode for Vip3 proteins with significant insecticidal properties (Şahin et al., 2012). In the Andaman and Nicobar Islands, Bt isolates from soil were characterized for their protein and cry gene profiles. The study identified a diverse range of Cry proteins, including novel cry genes potentially active against Coleoptera insects. This genetic diversity is attributed to the unique ecological factors and spatial separation of the islands, which influence the evolution of Bt strains (Swamy et al., 2011). The comparative analysis of plasmid profiles in Bt isolates from different habitats reveals significant genetic diversity and potential for biopesticide development. Soil-derived isolates exhibit a wide range of plasmid profiles and insecticidal properties, while insect-derived isolates show unique plasmid compositions and high toxicity against specific insect pests. Although studies on aquatic-derived isolates are limited, the genetic diversity observed in other habitats suggests that aquatic environments could also be a valuable source of novel Bt strains. 8 Technological Advances in Plasmid Research 8.1 High-throughput sequencing technologies High-throughput sequencing technologies have revolutionized plasmid research by enabling the rapid and comprehensive analysis of plasmid genomes. These technologies allow for the sequencing of entire plasmidomes, providing insights into the diversity, structure, and function of plasmids within various bacterial communities. For instance, the use of high-throughput sequencing in a biopurification system (BPS) facilitated the identification of high-molecular-weight plasmids, revealing a large diversity of plasmid replicons and horizontal gene transfer events within the habitat (Martini et al., 2016). Similarly, the metaplasmidSPAdes tool has been developed to assemble plasmids from metagenomic data sets, significantly reducing the false positive rate of plasmid detection and uncovering thousands of previously undetected plasmids (Antipov et al., 2019). These advancements
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