# Isolation and Characterization of Chlorpyrifos-Degrading Gut Bacteria from Field-Collected Larvae of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

## TL;DR

Scientists found bacteria in the gut of a destructive pest that can break down a common pesticide, which could lead to new ways to control pests without relying on chemicals.

## Contribution

The study isolates and characterizes pesticide-degrading gut bacteria from field-collected fall armyworm larvae for the first time.

## Key findings

- Four gut bacteria capable of degrading chlorpyrifos were isolated from Spodoptera frugiperda larvae.
- Klebsiella pneumoniae strain 64D achieved 80.38% chlorpyrifos degradation in vitro within one day.
- Larvae colonized with Klebsiella pneumoniae strain 66D showed a 19.16-fold reduction in mortality after pesticide exposure.

## Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a highly invasive and economically important pest that inflicts significant damage on a wide range of host crops, particularly maize. One of the most challenging aspects of managing S. frugiperda populations is their capacity to develop resistance rapidly to various classes of chemical insecticides. Symbiotic microbes play vital roles in insect physiology and behavior, contributing to fundamental processes such as food digestion, nutrient acquisition, immune defense against pathogens, and even mating preferences, as well as insecticide resistance. In this study, four bacterial isolates capable of degrading chlorpyrifos were isolated from the gut of a field-collected population of S. frugiperda. These findings substantiate the concept of “detoxifying symbiosis,” wherein insect gut microbiota strengthen host survival in toxic environments. Harnessing such pesticide-degrading symbionts could pioneer innovative, microbe-based pest-management strategies that minimize reliance on synthetic chemicals.

Exploration of new niches for microorganisms capable of degrading recalcitrant molecules is still required. We hypothesized that the gut microbiota associated with the field S. frugiperda population carries pesticide-degrading bacteria that would enhance the host’s ability to metabolize pesticides. Three strategies were implemented to address this principle: (i) isolation and identification of chlorpyrifos-degrading gut bacteria from field-collected S. frugiperda larvae; (ii) evaluation of chlorpyrifos biodegradation capacity through in vitro assays; and (iii) assessment of the impact of specific bacterial taxa capable of degrading chlorpyrifos directly within the gut. In this study, we successfully isolated four chlorpyrifos-degrading gut bacterial isolates from a field-collected population of S. frugiperda. These isolates were identified using 16S rDNA sequencing as Klebsiella quasipneumoniae strain 60D (PP504878), Klebsiella pneumoniae strain 64D (PP504879), Klebsiella pneumoniae strain 66D (PP504880), and Klebsiella pneumoniae strain 71D (PP504881). In vitro chlorpyrifos degradation assays revealed that all isolates exhibited strong degradative capacities, with Klebsiella pneumoniae strain 64D achieving the highest degradation rate, 80.38%, after one day of inoculation. In contrast, in vivo chlorpyrifos biodegradation assessment demonstrated a clear protective effect of gut bacteria on host survival. Among the mono-associated groups, larvae colonized with Klebsiella pneumoniae strain 66D exhibited the most pronounced reduction in mortality by 19.16-fold compared to antibiotic-treated larvae following exposure to chlorpyrifos suspension.