Mite gut microbiome and resistome exhibited species-specific and dose-dependent effect in response to oxytetracycline exposure

Potential of lavender essential oil to inhibit tetracycline resistance and modulate gut microbiota in black soldier fly larvae

The misuse of tetracycline in livestock farming leads to environmental residues that promote the proliferation of antibiotic resistance genes (ARGs), particularly tetracycline resistance (tet) genes. Black soldier fly (BSF) larvae, used for organic waste bioconversion, may carry tetracycline residues in their guts, raising concerns about ARG spread. To address this issue, plant-derived additives such as lavender essential oil (LEO) have been explored as alternative antibiotics. This study investigated the effects of LEO on tet gene suppression and gut microbiota modulation in BSF larvae. Results showed that oxytetracycline treatment increased tet gene relative abundance threefold compared to the control, reaching 1.13 ± 0.29 and enriched pathogens Klebsiella oxytoca and Enterobacter hormaechei. Conversely, LEO treatment (100 mg/kg) reduced tet gene abundance by 46.67 %, from 0.15 ± 0.02 to 0.08 ± 0.02, and enhanced beneficial microorganisms like Leuconostoc pseudomesenteroides. Furthermore, LEO reduced tet gene relative abundance in oxytetracycline-treated larvae from 1.13 ± 0.29 to 0.49 ± 0.19 and 0.70 ± 0.11 in separate treatments. LEO modified fungal composition and nutrient pathways. Network analysis revealed that LEO promoted a more integrated and modular gut microbiota, enhancing functional specialization and resilience. These findings suggest LEO can mitigate ARGs in BSF larvae, offering a sustainable approach for antibiotic resistance management in organic waste recycling and livestock farming.

Exposure to spaceflight enhances the virulence of Purpureocillium lilacinum against Tetranychus cinnabarinus: modulation of the host's enzyme activities and microbiome

Multiple studies have been conducted to investigate the impact of space conditions on human, plant, and microbial life. This research investigated the virulence of spaceflight mutants of the entomopathogenic fungus Purpureocillium lilacinum (HP7, HP36, HP52) and its original strain (SP535) against Tetranychus cinnabarinus as well as examination of the T. cinnabarinus immune response, including alterations in enzyme profiles and microbiome composition post fungal application. Our observations revealed contrasting, time-specific differences in pathogenicity and tissue infection between the ground-based isolate and spaceflight mutant isolates. Analysis of detoxifying and antioxidant enzymes showed a significant reduction in enzyme activities T. cinnabarinus infected with the most virulent spaceflight mutants at 36 h post-fungal infection, compared to ground-based isolates. Additionally, the microbiota was reduced due to a fungal infection, partly due to decreased antioxidant enzyme activities. Our findings indicate that changes in the microbiota of T. cinnabarinus following infection with P. lilacinum (both ground-based and spaceflight mutant isolates) resulted in variations in metabolism and genetic information-related KEGG pathways. This data can help identify potential changes in the host immune system that drive increased virulence after spaceflight mutation.

Increased Transmission of Antibiotic Resistance Occurs in a Soil Food Chain under Pesticide Stress

The rising spread of antibiotic resistance is a global concern, but the pathways of dissemination within soil ecosystems remain poorly understood. Here, we quantified the occurrence of antibiotic resistance genes (ARGs) in gut microbiomes of soil collembolans (Folsomia candida) under pesticide stress (zinc thiazole, ZT) and analyzed the trophic transfer of ARGs to the microbiomes of predatory mites (Hypoaspis aculeifer), natural predators of collembolans. High throughput quantitative PCR was used to quantify ARGs, whereas gut microbiomes of collembolans and mites were characterized using 16S rRNA gene amplicon sequencing, and potential pathogens were identified. Our results revealed that ZT exposure significantly elevated the abundance of ARGs (e.g., AAC(6')-Ir) in soil collembolan microbiomes. With the increase of ARGs in prey collembolan microbiomes, an increase of ARGs in predatory mite microbiomes was observed through trophic transfer. Mobile genetic elements (MGEs) significantly contribute to the transmission of ARGs within this food chain. Additionally, co-occurrence analysis indicated a strong association between gut resistomes and pathogens, such as Brevundimonas diminuta, in the collembolans and predatory mites. Overall, our study provides evidence for the dissemination of ARGs through the collembolan-predatory mite food chain following pesticide exposure, which is important for understanding the broader dynamics of antibiotic resistance spreading in soil ecosystems.

Effect of microplastics on oxytetracycline trophic transfer: Immune, gut microbiota and antibiotic resistance gene responses

Microplastics and antibiotics are prevalent and emerging pollutants in aquatic ecosystems, but their interactions in aquatic food chains remain largely unexplored. This study investigated the impact of polypropylene microplastics (PP-MPs) on oxytetracycline (OTC) trophic transfer from the shrimp (Neocaridina denticulate) to crucian carp (Carassius auratus) by metagenomic sequencing. The carrier effects of PP-MPs promoted OTC bioaccumulation and trophic transfer, which exacerbated enterocyte vacuolation and hepatocyte eosinophilic necrosis. PP-MPs enhanced the inhibitory effect of OTC on intestinal lysozyme activities and complement C3 levels in shrimp and fish, and hepatic immunoglobulin M levels in fish (p < 0.05). Co-exposure of MPs and OTC markedly increased the abundance of Actinobacteria in shrimp and Firmicutes in fish, which caused disturbances in carbohydrate, amino acid, and energy metabolism. Moreover, OTC exacerbated the enrichment of antibiotic resistance genes (ARGs) in aquatic animals, and PP-MPs significantly increased the diversity and abundance of ARGs and facilitated the trophic transfer of teta and tetm. Our findings disclosed the impacts of PP-MPs on the mechanism of antibiotic toxicity in aquatic food chains and emphasized the importance of gut microbiota for ARGs trophic transfer, which contributed to a deeper understanding of potential risks posed by complex pollutants on aquatic ecosystems.

Does Plant Identity Affect the Dispersal of Resistomes Above and Below Ground?

Resistomes are ubiquitous in natural environments. Previous studies have shown that both the plant phyllosphere and soil-borne nematodes were reservoirs of above- and below-ground resistomes, respectively. However, the influence of plant identity on soil, nematode, and phyllosphere resistomes remains unclear. Here, a microcosm experiment was used to explore the characteristics of bacterial communities and resistomes in soil, nematode, and phyllosphere associated with six different plant identities (Lactuca sativa, Cichorium endivia, Allium fistulosum, Coriandrum sativum, Raphanus sativus, and Mesembryanthemum crystallinum). A total of 222 antibiotic resistance genes (ARGs) and 7 mobile genetic elements (MGEs) were detected by high-throughput quantitative PCR from all samples. Plant identity not only significantly affected the diversity of resistomes in soil, nematode, and phyllosphere but also influenced the abundance of resistomes in nematodes. Shared bacteria and resistomes indicated a possible pathway of resistomes transfer through the soil-nematode-phyllosphere system. Structural equation models revealed that plant identity had no direct effect on phyllosphere ARGs, but altered indirectly through complex above- and below-ground interactions (soil-plant-nematode trophic transfer). Results also showed that bacteria and MGEs were key factors driving the above- and below-ground flow of resistomes. The study extends our knowledge about the top-down and bottom-up dispersal patterns of resistomes.