Enhancing the insecticidal activity of new Bacillus thuringiensis X023 by copper ions

Abstract

Background A new Bacillus thuringiensis X023 (BtX023) with high insecticidal activity was isolated in Hunan Province, China. The addition of metals (Cu, Fe, Mg and Mn) to the medium could influence the formation of spores and/or insecticidal crystal proteins (ICPs). In previous studies, Cu ions considerably increased the synthesis of ICPs by enhancing the synthesis of poly-β-hydroxy butyrate. However, the present study could provide new insights into the function of Cu ions in ICPs. Results Bioassay results showed that wild strain BtX023 exhibited high insecticidal activity against Plutella xylostella. The addition of 1 × 10−5 M Cu2+ could considerably increase the expression of cry1Ac and vip3Aa, and the insecticidal activity was enhanced. Quantitative real-time polymerase chain reaction (qRT-PCR) and proteomic analyses revealed that the upregulated proteins included amino acid synthesis, the glyoxylate pathway, oxidative phosphorylation, and poly-β-hydroxy butyrate synthesis. The Cu ions enhanced energy metabolism and primary amino acid synthesis, will providing abundant raw material accumulation for ICP synthesis. Conclusion The new strain BtX023 exerted a strong insecticidal effect on P. xylostella by producing ICPs. The addition of 1 × 10−5 M Cu2+ in the medium could considerably enhance the expression of the cry1Ac and vip3Aa genes, thereby further increasing the toxicity of BtX023 to Helicoverpa armigera and P. xylostella by enhancing energy synthesis, the glyoxylate cycle, and branched-chain amino acids synthesis, but not poly-β-hydroxy butyrate synthesis.

Multiple cry Genes in Bacillus thuringiensis Strain BTG Suggest a Broad-Spectrum Insecticidal Activity

“…Berliner , while the strain BTG was clustered with B. thuringiensis subsp. galleriae , and B. thuringiensis X023 ( Bt X023), a strain with high insecticidal activity isolated in Hunan Province, China [ 19 ]. Strains 38 and PL20 fell into separate clusters.…”

“…A comparison of the BTG genome with the NCBI database shows 94.77% homology with the genomes of bacteria of the genus Bacillus and 5.23% homology with the genus Pseudomonas . The closest genome is that of B. thuringiensis X023 (GenBank GCA_021651035.1) [ 19 , 35 ], with a homology of 99.6% (92.9% alignment coverage). In silico DNA-DNA hybridization (DDH) with B. thuringiensis subsp.…”

“…Crystals are synthesized after the second stage of sporulation and accumulate in the cell, where they can represent up to 30% of the dry weight of sporulated cells [ 18 ]. The shapes of the parasporal crystals can be bipyramidal, pyramidal, cubic, flat rhombic, spherical, or rectangular [ 19 , 20 , 21 , 22 ] and may include one or more endotoxins, with a molecular weight between 60 kDa and 140 kDa [ 13 ].…”

Harnessing the Potential of Bacillus altitudinis MT422188 for Copper Bioremediation

“…demonstrated remarkable growth pattern in the absence of Cu, but the overall growth was observed to be decreased in the presence of increasing Cu concentrations ( Khan et al, 2017 ), which was also evident from the findings of our study. Cu ions did not affect growth of B. thuringiensis cells greatly, indicating that they survived and grew in low concentrations of the metal ( Liu et al, 2020 ). The half maximal effective concentration (EC 50 ) is considered to be the initial concentration of the metal ions at which the activity of the bacterial cells in the presence of metal is comparable to that of 50% of the control culture in the absence of the metal.…”