Abstract: Soil collembolans play an important role in cropland ecosystems. The homeostasis of gut microbial communities in soil collembolans can reflect the impact of environmental changes on the host. The application of organic fertilizers has become an important measure to promote high-quality agricultural development. However, how it affects the gut microbiota of soil collembolans in cropland remain largely unknown. In this study, high-throughput sequencing and bioinformatics technologies were used to explore the dynamics (10, 40 and 80 days) of gut bacterial communities in soil collembolan (Entomobrya proxima Folsom) under different application rates (1%, 6%, and 10%) of organic fertilizer. The results showed that the addition of organic fertilizer disturbed the diversity, structure, composition, and function of gut bacterial communities in E. proxima. The duration of organic fertilizer addition had a stronger impact on the richness and evenness of gut bacterial communities than the application rate, and the effects of both factors showed a downward trend with the increase in addition duration. The structure of gut bacterial communities was significantly affected by the duration of organic fertilizer addition. The addition of organic fertilizer perturbed the composition of the gut bacterial communities. G_unclassified_f__Enterobacteriaceae, which is involved in multiple functions, was highly sensitive to the input of organic fertilizer, and its relative abundance decreased sharply in the initial stage of organic fertilizer addition. This led to a significant reduction in the relative abundance of facultatively anaerobic, potentially pathogenic, biofilm-forming, mobile element, and oxidative stress tolerant functional bacterial groups in the gut. However, with the increases in the duration of organic fertilizer addition, the functional bacterial groups in the gut tended to be stable, and their relative abundances did not change.

Key words: organic fertilizer, Entomobrya proxima, gut bacterial community, diversity, structure, composition, function