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 <i>S. frugiperda</i> 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 <i>S. frugiperda</i> 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 <i>S. frugiperda</i>. These isolates were identified using 16S rDNA sequencing as <i>Klebsiella quasipneumoniae</i> strain 60D (PP504878), <i>Klebsiella pneumoniae</i> strain 64D (PP504879), <i>Klebsiella pneumoniae</i> strain 66D (PP504880), and <i>Klebsiella pneumoniae</i> strain 71D (PP504881). In vitro chlorpyrifos degradation assays revealed that all isolates exhibited strong degradative capacities, with <i>Klebsiella pneumoniae</i> 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 <i>Klebsiella pneumoniae</i> strain 66D exhibited the most pronounced reduction in mortality by 19.16-fold compared to antibiotic-treated larvae following exposure to chlorpyrifos suspension.