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Earthworm gut played an important role in the transformation of various contaminants in the soil environments. With the increasing application of organic fertilizer recently, the ingestion of antibiotics, antibiotic resistance bacteria (ARB), and antibiotic resistance genes (ARGs) made the earthworm gut a potential favorable micro-environment for the transmission of ARGs in the soil. In this work, the conventional plate incubation and high-throughput sequencing methods were both employed to investigate the composition of the cultivable and overall ARB/ARGs in the Metaphire guillelmi earthworm gut. A total of 87 cultivable isolates that resisted tetracycline (TC) and/or sulfadiazine (SD) were obtained, most of which belonged to phylum Firmicutes, genus Bacillus. Meanwhile, the counts of isolates with TC-SD dual resistance were higher than those with sole SD or TC resistance. Moreover, higher ARB counts and diversity were detected in the earthworm gut by high-throughput sequencing technique than those by the classical plate cultivation. Overall, the combination of conventional cultivable bacteria isolation and high-throughput sequencing methods provided a comprehensive understanding of the ARB composition in the earthworm gut. The results demonstrate that the earthworm gut is a hospitable micro-environment for ARB colonization. The potential role of earthworm intestinal ARB and ARGs proliferation in soil environments warrants further research.

Increasing evidence demonstrated the critical role the earthworm gut played in sustaining earthworm's metabolism and transformation of nutrients and pollutants in the environment. Being rich in nutrients, the earthworm gut is favorable for the colonization of (facultative) anaerobic bacteria, which bridge the host earthworm gut with adjacent terrestrial environment. Therefore, the status quo of earthworm gut research was primarily reviewed in this work. It was found that most studies focused on the bacterial composition and diversity of the earthworm gut, and their potential application in nutrient element and pollutant transformation, such as nitrification, methanogens, heavy metal detoxification, etc. Yet limited information was available about the specific mechanism of intestinal bacteria in nutrient and pollutant transformation. Therefore, in this work we highlighted the current problems and concluded the future prospect of worm's intestinal bacteria research. On one hand, high throughput sequencing and bioinformatics tools are critical to break the bottleneck in the intestinal bacteria research via clarifying the molecular mechanism involved in the transformation processes described above. In addition, a global dataset concerning worm gut bacteria will be needed to provide comprehensive information about intestinal bacteria pool, and act as a communication platform to further encourage the progress of worm gut research.

Due to the abusive usage of antibiotics in animal husbandry, a large amount of residual antibiotics has been released into the environment, therein posing great threat against both environment security and public health. Therefore, it is of great significance to investigate the toxicity of antibiotics on the widely-applied bioindicator-earthworm. In this work, the physiological parameters and the intestinal bacteria community of Metaphire guillelmi were monitored simultaneously to evaluate their sensitivity to the tetracycline (TC) exposure. As expected, the antioxidant enzyme activity and coelomocyte apoptosis acted fairly well as biomarkers for the TC toxicity. In contrast, the intestinal bacteria of Metaphire guillelmi responded varyingly to different TC doses. When TC concentration increased from 0 to 35.7 μg cm−2, the percentage of the Proteobacteria phylum declined significantly from 85.5% to 34.4%, while the proportions of the Firmicutes, Planctomycetes and Atinomycete phyla clearly increased (p

Antibiotic resistant pathogenic bacteria (ARPB) residual in soil-plant system has caused serious threat against public health and environmental safety. Being capable of targeted lysing host bacteria, phage therapy has been proposed as promising method to control the ARPB contamination in environments. In this study, microcosm trials were performed to investigate the impact of various phage treatments on the dissipation of tetracycline resistant Escherichia coli K-12 and chloramphenicol resistant Pseudomonas aeruginosa PAO1 in soil-carrot system. After 70 days of incubation, all the four phage treatments significantly decreased the abundance of the pathogenic bacteria and the corresponding antibiotic resistance genes (tetW and cmlA) in the soil-carrot system (p 0.05), following the order of the cocktail phage treatment (phages ΦYSZ1 + ΦYSZ2) the polyvalent phage (ΦYSZ3 phage with broad host range) treatment host-specific phage (ΦYSZ2 and ΦYSZ1) treatments the control. In addition, the polyvalent phage treatment also exerted positive impact on the diversity and stability of the bacterial community in the system, suggesting that this is an environmentally friendly technique with broad applications in the biocontrol of ARPB/ARGs in soil-plant system.

Coexistence of antibiotics/heavy metals and the overexpression of resistance genes in the vermicompost has become an emerging environmental issue. Little is known about the interaction and correlation between chemical pollutants and biological macromolecular compounds. In this study, three typical vermicompost samples were selected from the Yangtze River Delta region in China to investigate the antibiotic, heavy metal and corresponding antibiotic resistance genes (ARGs) and heavy metal resistance genes (HRGs). The results indicated the prevalence of tetracycline (TC), copper (Cu), zinc (Zn), cadmium (Cd), corresponding TC-resistance genes (tetA, tetC, tetW, tetM, tetO, and tetS) and HRGs (copA, pcoA, cusA, czcA, czcB, and czcR) in the three vermicompost samples. In addition, the ARG level was positively associated with the water-soluble TC fraction in the vermicompost, and it was same between the HRG abundance and exchangeable heavy metal content (p