Bt Research 2024, Vol.15, No.1, 20-29 http://microbescipublisher.com/index.php/bt 21 2 Overview of Bacillus thuringiensis 2.1 General characteristics of Bt strains Bt strains are characterized by their ability to form parasporal crystals during sporulation. These crystals contain insecticidal proteins that target specific insect orders, such as Lepidoptera, Coleoptera, and Diptera. The genome of Bt typically includes a circular chromosome and multiple plasmids, which harbor genes encoding for these toxins and other virulence factors. For instance, the genome of Bt strain HD521 contains a circular chromosome and six plasmids, encoding various virulence proteins such as Immune Inhibitor A, Hemolytic Enterotoxin, and Chitinase (Sun et al., 2021). Similarly, Bt strain GR007 has a circular chromosome and three megaplasmids, with multiple pesticidal protein genes (Figure 1) (Pacheco et al., 2021). Figure 1 Genome of B. thuringiensis strain GR007 (Adopted from Pacheco et al., 2021) Image caption: (A) Circular maps of chromosome and plasmids. (B) Representation of PAIs. Pesticidal proteins are represented in green arrows, transposases in blue arrows and additional ORF into the PAIs with purple arrows (Adapted from Pacheco et al., 2021) 2.2 Biological functions and applications The primary biological function of Bt is its role as a biopesticide. Bt produces a variety of insecticidal proteins, including Cry and Cyt toxins, which are effective against a wide range of insect pests. These proteins disrupt the gut cells of insects, leading to their death. Bt strains are also known for their potential in controlling plant diseases and promoting plant growth. For example, Bt strain SY49.1 exhibits significant activity against plant fungal infections and promotes plant growth through the production of bioactive compounds such as thuricin and bacillibactin (Yılmaz et al., 2022). Additionally, Bt strains have been explored for their antifungal potential, as seen in the case of Bt strain MORWBS1.1, which shows antagonistic activity against Fusariumspecies (Adeniji et al., 2021). 2.3 Genetic diversity among Bt strains Bt strains exhibit considerable genetic diversity, which is reflected in their genomic composition and the variety of
RkJQdWJsaXNoZXIy MjQ4ODYzNA==