Bacillus thuringiensis strain QBT220 pBtoxis plasmid structural instability enhances δ-endotoxins synthesis and bioinsecticidal activity

<p dir="ltr"><i>Bacillus thuringiensis</i> subsp. <i>israelensis</i> (<i>Bti</i>) spherical parasporal crystal contains several insecticidal proteins used as environmentally safe alternative to toxic chemical pesticides. The exploration of a <i>Bti</i> strain isolated from Qatar QBT220 genes encoding the δ-endotoxins responsible of the insecticidal activities revealed the alteration of a 14-kb DNA region including the δ-endotoxins <i>cry10A</i> and <i>cyt1C</i> genes of pBtoxis plasmid. The presence of all the insecticidal genes except <i>cry10A</i> and <i>cyt1C</i> was explained by a structural instability of the plasmid pBtoxis. However, when compared with the <i>Bti</i> reference strains H14 and QBT217 that carry all δ-endotoxins coding genes, it was found that QBT220, has a significantly higher insecticidal activity against the dipteran insect <i>Aedes aegypti</i> larvae despite of the plasmid pBtoxis structural instability due to the alteration of <i>cry10A</i> and <i>cyt1C</i> genes. In addition, QBT220 showed the highest δ-endotoxin synthesis per spore, compared with that of the wildtype strains. These findings confirm that the altered genes <i>cry10A</i> and <i>cyt1C</i> are not mandatory for <i>Bti</i> insecticidal activities and on the other hand show a possible inhibitory effect played by the 2 proteins Cry10A and Cyt1C on the insecticidal activities of the other insecticidal proteins. In addition, the QBT220 increased δ-endotoxins synthesis per cell, makes this strain a good candidate for possible applications in the industrial production of bioinsecticides.</p><h2>Other Information</h2><p dir="ltr">Published in: Ecotoxicology and Environmental Safety<br>License: <a href="http://creativecommons.org/licenses/by/4.0/" target="_blank">http://creativecommons.org/licenses/by/4.0/</a><br>See article on publisher's website: <a href="https://dx.doi.org/10.1016/j.ecoenv.2021.112975" target="_blank">https://dx.doi.org/10.1016/j.ecoenv.2021.112975</a></p>