Exploring the dynamics of symbiont Enterobacter aerogenes expressing Cry1Ac for potential biocontrol of Helicoverpa armigera

Abstract

Paratransgenesis, the use of genetically modified symbiotic microbes to deliver bioactive molecules, offers a promising strategy for sustainable pest management. However, the colonization dynamics and ecological interactions of such engineered microbes remain insufficiently understood. This study evaluated the potential of Enterobacter aerogenes , a gut symbiont of Helicoverpa armigera, as a paratransgenic vector for delivering the Bacillus thuringiensis Cry1Ac toxin. Two plasmid constructs were introduced into E. aerogenes : one encoding Cry1Ac (construct 2: cry1Ac - KmR -pUC18) and another encoding green fluorescent protein (GFP) (construct 3: KmR -pGFP). GFP-expressing E. aerogenes (construct 3) successfully colonized the gut of H. armigera larvae within 48 h (SE ± 0.051) and the tomato phyllosphere within 24 h (SE ± 0.026), demonstrating its ability to establish in both insect and plant environments. The insecticidal activity of Cry1Ac-producing Escherichia coli (K12) and engineered E. aerogenes was evaluated using diet incorporation and leaf-dip bioassays. E. coli (K12) served as the control expression host for comparison. Feeding assays with diets containing 10 5 –10⁹ transformed cells produced larval mortality of 86% to 100% (SE ± 0.962–1.354) for E. coli (K12) and 79% to 100% (SE ± 0.959–2.348) for E. aerogenes . Foliar application of Cry1Ac-producing E. aerogenes at 1.0 × 10 8 cells per leaf resulted in 100% larval mortality within 192 h (SE ± 0.540). These findings establish a foundation for the development of E. aerogenes as a paratransgenic vector for integrated pest management. Further studies are required to evaluate its environmental persistence, transmission, and biosafety under field conditions and environmentally relevant stressors.