# Investigation into the Active Substance of Bacillus velezensis TRM82367 for Killing Aphis gossypii

## TL;DR

Researchers found a desert bacteria that produces a natural insecticide effective against cotton aphids, offering a greener pest control solution.

## Contribution

Identification of surfactin-like lipopeptides from Bacillus velezensis TRM82367 as potent insecticidal agents against Aphis gossypii.

## Key findings

- Bacillus velezensis TRM82367 produces surfactin-like lipopeptides that cause high mortality in cotton aphids.
- The crude extract of the bacteria achieved up to 88.67% aphid mortality at 500 mg/L concentration.
- The median lethal concentration (LC50) of the extract was determined to be 207.616 mg/L.

## Abstract

The cotton aphid (Aphis gossypii) is a major pest that severely reduces cotton yield and quality by sucking sap, transmitting plant pathogens, and reproducing rapidly. Although chemical insecticides are widely used for control, they lead to resistance and environmental pollution, creating an urgent need for greener alternatives. In this study, we isolated a bacterial strain, TRM82367, from the extreme environment of the Taklimakan Desert, which exhibits strong activity against cotton aphids. The strain was identified as Bacillus velezensis. Genomic and chemical analyses revealed that it produces surfactin-like lipopeptides, which were confirmed to be the key active components causing high mortality in aphids. Our results suggest that B. velezensis TRM82367 and its surfactin compounds are promising candidates for developing bio-insecticides, especially suitable for cotton-growing regions in arid areas. This work supports the development of sustainable pest management strategies.

A total of 304 bacterial strains were isolated from the Taklamakan Desert. Through screening, strain TRM82367 exhibited potent insecticidal activity against cotton aphids (Aphis gossypii) and was identified as Bacillus velezensis. To explore the primary insecticidal active components of this strain, lipopeptide substances in the fermentation broth were extracted via hydrochloric acid precipitation. The main active components were analyzed using activity-guided fractionation combined with liquid chromatography–mass spectrometry (LC-MS). Our results demonstrated that Bacillus velezensis TRM82367 possessed strong lethal activity against cotton aphids. The crude extract obtained by means of hydrochloric acid precipitation and methanol dissolution showed high insecticidal efficacy. At concentrations of 100, 150, 200, 250, 300, 400, and 500 mg/L, the 48 h corrected mortality rates of cotton aphids were 25.14%, 38.05%, 50.09%, 53.03%, 57.96%, 74.68%, and 88.67%, respectively. The toxicity regression equation was Y = 2.47X − 5.72, with a median lethal concentration (LC50) of 207.616 mg/L and a 95% lethal concentration (LC95) of 1004.673 mg/L. After separation by an ODS chromatographic column and identification by means of mass spectrometry, the main active components were confirmed to be C12–C16 surfactin homologs.