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

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.