Isolation of toxic bacteria for the Drosophila melanogaster fruit fly model

Abstract

The development of clean and green agriculture, aimed at promoting sustainable farming worldwide, increasingly focuses on finding new, safe insect-resistant materials. This is particularly important in light of growing concerns about pest resistance to pesticides, which has become more prevalent due to climate change and natural selection from native bacterial strains. In a study conducted in Vinh Long and Hau Giang provinces, 55 bacterial strains were isolated from garden soil and insect samples, all capable of thriving in LB (Luria-Bertani) medium. The collection included 31 Gram-positive bacteria and 24 Gram-negative bacteria. Toxicity tests revealed that the centrifuged solution of two bacterial strains, I3 and I4, along with the cells of two others, MT1 and MT2, demonstrated effective insecticidal properties. Moreover, the centrifuged solution of I4, the bacterial cells of MT2, and a combination of both sources were found to kill insects effectively after a 7-day period. Additionally, bacterial growth was influenced by incubation time and pH levels, with I4 showing a steady increase in optical density from pH 5 to pH 7, while MT2 showed a decrease. Both strains exhibited the highest biomass at 48 hours of incubation. Based on 16S-rRNA sequencing and biochemical analysis, the bacterial strains MT2 and I4 were identified as Bacillus subtilis and Proteus mirabilis, respectively, and classified as Bacillus sp. MT2 and Proteus sp. I4.