Diversity of Culturable Gut Bacteria in Natural Aphid Populations and Their Contribution to Insecticide Degradation

Microorganisms in insects play pivotal roles in various aspects, including nutrition, development, protection, physiology, and behavior. Aphids, a distinct group of insects that feed on plant sap, have been the focus of research exploring the intricate relationships between microbes and insects. While extensive investigations have delved into the obligate endosymbionts in aphids, there remains a gap in understanding the diversity of gut microbes and other associated microorganisms. This study employed culture-dependent methods to isolate microorganisms from diverse aphid species (Aphis gossypii, A. nerii, A. craccivora, Hysteroneura setariae, and Myzus persicae). The results identified three bacterial phyla (Firmicutes, Proteobacteria, Actinobacteria), belonging to families such as Bacillaceae, Corynebacteriaceae, Micrococcaceae, Morganellaceae, Staphylococcaceae, and Xanthomonadaceae. Bacillus emerged as the predominant taxon, with Aphis craccivora exhibiting both high abundance and an even distribution of bacteria. Both A. craccivora and A. gossypii displayed a diverse array of bacterial species, with A. gossypii exhibiting the highest dominance index. Hysteroneura setariae showcased a diverse dominance of bacteria among aphids. Notably, the microorganisms Exiguobacterium indicum MPB-2 and Pseudomonas hibiscicola CCF 2-2 demonstrated the ability to degrade imidacloprid at a rate of 18-22%. This finding emphasizes their capacity to utilize insecticides as sole sources of carbon and nitrogen, ultimately benefiting the fitness of the insects. This study contributes to our understanding of the microorganisms presented in aphids. Highlighting the efficacy of culture-dependent methods in unveiling the diversity of these microscopic organisms.