Gut Bacterial Diversity of Insecticide-Susceptible and Insecticide-Resistant Megalurothrips usitatus (Thysanoptera: Thripidae) and Elucidation of Their Putative Functional Roles

SIMPLE SUMMARY: In this study, the researchers investigated the role of gut bacteria in an insect pest called Megalurothrips usitatus and its resistance to an insecticide and an entomopathogenic fungus. They compared the gut bacterial communities of an insecticide-susceptible population and an insecticide-resistant population of Megalurothrips usitatus. Through High-throughput sequencing, they found that the insecticide-resistant population exhibited significantly higher resistance to the insecticide and the Beauveria brongniartii. The sequencing also revealed changes in the abundance of specific bacterial species in response to the insecticide and the Beauveria brongniartii. The researchers observed that the gut bacteria of Megalurothrips usitatus are primarily involved in various metabolic activities, including the degradation of the Beauveria brongniartii. Some of these bacteria may even reduce the virulence of the fungus, thereby weakening its biocontrol ability. The results of this study provide a basis for future elucidation of the role of intestinal bacteria in the symbiotic relationship of insecticide resistance and the design of new management strategies for Megalurothrips usitatus using Beauveria brongniartii for biological control. ABSTRACT: The gut bacterial microbiota of insects plays a crucial role in physiological, metabolic, and innate immune processes. In the current study, the gut bacterial communities of an insecticide-susceptible (IS), and a resistant (IR) population of a major legume pest, Megalurothrips usitatus (Bagnall), were evaluated. The 16S rDNA V3 + V4 regions of M. usitatus infected with Beauveria brongniartii along with the intestinal flora of both populations were sequenced based on a High-throughput sequencing platform. Toxicological bioassays revealed that the IR population exhibited resistance to acetamiprid and B. brongniartii isolate SB010 at levels of 138.0-fold and 55.6-fold higher, respectively, compared to the IS population. Through 16S High-throughput sequencing, the results indicate that both resistant populations, as well as B. brongniartii infestation, reduce the number of species of M. usitatus gut microbes. Using KEGG function prediction, it was found that most intestinal bacteria were involved in various metabolic activities, and the abundance of resistant populations was higher than that of sensitive populations. The bacteria in the gut of M. usitatus are mainly involved in various metabolic activities to achieve the degradation of B. brongniartii. This study provides valuable insights into the interaction between gut bacteria, insecticide resistance, and Beauveria. brongniartii infection in Megalurothrips usitatus, which can help inform future pest control strategies.