Gut bacteria of field-collected larvae of Spodoptera frugiperda undergo selection and are more diverse and active in metabolizing multiple insecticides than laboratory-selected resistant strains

Bacterial symbiosis affects the physiology and development of insects, facilitating their adaptation to new environmental conditions. Insects and their associated microbiota acquire phenotypic features that guarantee survival in the face of biotic and abiotic stress factors. We used Spodoptera frugiperda (Lepidoptera: Noctuidae) to investigate the effect of selection pressures on the structure, diversity, and capacity of the gut microbiota to metabolize pesticides. We compared the composition of the gut microbiota of susceptible and insecticide-resistant strains of S. frugiperda, as well as the gut microbiota from larvae sampled in cornfields in five Brazilian states. The experiments were conducted through metagenomic analysis of the V3-V4 regions of the 16S ribosomal gene (16S rRNA), isolation, and culture of bacteria in selective minimal medium, and analysis of the growth of isolates using multiple insecticides as the only source of carbon. Field exposure to a range of xenobiotics affected the composition of the gut microbiota of S. frugiperda. Moreover, bacteria from field-collected larvae grew better and showed potential to metabolize more insecticides than the bacteria isolated from laboratory-selected resistant strains. In addition, most of the phylotypes isolated in insecticide-based media were fixed in the gut microbiota of natural populations of S. frugiperda. The higher diversity and capability of gut microbes to metabolize insecticides in field populations of S. frugiperda demonstrate the need for increased investigation of the role of gut microbes in the detoxification of insecticides in the host and their impact on the successful use of pesticides in pest control.