The intestinal Stenotrophomonas maltophilia ZG-GX enhances the resistance of Spodoptera frugiperda to beta-cypermethrin and decreases the amino acid levels.

Spodoptera frugiperda is an invasive agricultural pest with a high tolerance for chemical insecticides. An increasing number of studies have reported that intestinal microbes of insects can affect host resistance to insecticides. Therefore, in this study, to explore the relationship between Spodoptera frugiperda intestinal microbiota and their resistance to pesticides, Spodoptera frugiperda was treated with beta-cypermethrin for analysis. The results showed that the abundance of Stenotrophomonas, which has the potential to degrade pyrethroid, significantly increased in the intestine. Among them, Stenotrophomonas maltophilia ZG-GX was isolated from the intestine. After being fed with ZG-GX, the resistance of Spodoptera frugiperda progeny to beta-cypermethrin was significantly increased. In addition, a significant shift occurred in the intestinal microbial community structure and metabolic functions, marked by an increase in the abundance of microbes related to pesticide resistance with ZG-GX treatment. Amino acid levels significantly decreased in Spodoptera frugiperda feces after ZG-GX treatment; however, the antioxidant enzyme activities and physiological adaptability remained unchanged. Further, the study revealed that the enhanced resistance of ZG-GX-treated Spodoptera frugiperda to beta-cypermethrin might be associated with the capability of ZG-GX to reduce beta-cypermethrin concentration. The study provided an important foundation for a deeper understanding of the resistance mechanisms of Spodoptera frugiperda to beta-cypermethrin. IMPORTANCE: Spodoptera frugiperda is an invasive organism that is highly tolerant to chemical pesticides and causes severe losses to agriculture. Studying the mechanism behind which Spodoptera frugiperda gains resistance to pesticides is important for agricultural production. Among the mechanisms discussed, the relationship between gut microorganisms of Spodoptera frugiperda and their resistance to pesticides is largely elusive. In this study, we demonstrated that Stenotrophomonas maltophilia ZG-GX isolated from the intestine of Spodoptera frugiperda increased the resistance of Spodoptera frugiperda to beta-cypermethrin and has strong potential to degrade beta-cypermethrin. Further, we compared the difference in its mechanism with beta-cypermethrin-induced resistance. It is of great significance for the protection of the ecological environment. The study lays the foundation for a better understanding of the mechanism of insect resistance to pesticides and provides clues for the development of new control strategies.