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Cao J.,China Agricultural University | Cao J.,Beijing Key Laboratory of Biodiversity and Organic Farming | Ji D.,China Agricultural University | Ji D.,Beijing Key Laboratory of Biodiversity and Organic Farming | And 2 more authors.
Soil Biology and Biochemistry | Year: 2015

The interactive impact of earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Rhizophagus intraradices, AM fungi) on the degradation of oxytetracycline (OTC) in soils was studied under greenhouse conditions. Treatments included maize plants inoculated vs. not inoculated with AM fungi and treated with or without earthworms at low (1 mg kg-1 soil DM) or high (100 mg kg-1 soil DM) OTC rates. The root colonization rate, the hyphal density of mycorrhizae, the residual OTC concentration in soils, catalase, dehydrogenase, urease, soil microbial biomass C, Shannon-Wiener index (H) for microbial communities from T-RFLP profiles were measured at harvest. The results indicated that earthworms and AM fungi would individually or interactively enhance OTC decomposition and significantly decreased the residual OTC concentration at both high and low OTC rates. Both earthworms and AM fungi could promote the degradation of OTC by increasing soil microbial biomass C at both high and low OTC rates. The effect of soil enzyme activity and soil microbial diversity on OTC decomposition was different between high and low OTC rates. Hyphomicrobium and Bacillus cereus were dominant bacteria, and Thielavia and Chaetomium were dominant phyla of fungi at all occasions. Earthworm activity stimulated the growth of Hyphomicrobium and Thielavia, while AM fungi may stimulate B. cereus, Thielavia and Chaetomium, resulting in greater OTC decomposition. The interaction between earthworms and AM fungi in affecting the degradation of OTC may be attributed to different mechanisms, depending on soil microbial biomass, function (enzyme activity) and communities (the abundance of Hyphomicrobium, B. cereus, Thielavia and Chaetomium) in the soil. © 2015 Elsevier Ltd. Source


Cao J.,China Agricultural University | Cao J.,Beijing Key Laboratory of Biodiversity and Organic Farming | Wang C.,China Agricultural University | Wang C.,Beijing Key Laboratory of Biodiversity and Organic Farming | And 3 more authors.
Soil Biology and Biochemistry | Year: 2016

The common practice of field-spreading animal manure on agricultural land contributes to the dissemination of antibiotics and antibiotic-resistant pathogens, which may disrupt important soil microbial functions. In this study, the potential independent and combined effects of oxytetracycline (OTC) and antibiotic-resistant Escherichia coli O157:H7 (E. coli O157:H7) on soil microbial activity and partial nitrification processes were investigated by testing the abundance of 16S rRNA and 18S rRNA, ammonia-oxidizing bacteria (AOB) and archaea (AOA). Treatments included manure-amended soil inoculated vs. not inoculated with E. coli O157:H7, treated or not treated with OTC at environmentally releant concentration. Results indicated that OTC did not affect soil bacterial diversity or abundance but increased the abundance of 18S rRNA, the AOB amoA gene, and the activity of urease. The invasion of E. coli O157:H7 significantly decreased the abundance of 16S rRNA, the AOA amoA gene, and soil microbial diversity from 1 to 14 days, while there was no significant impact of E. coli O157:H7 on soil microbial activity and function from 14 to 28 days. The dual treatment with OTC and E. coli O157:H7 significantly increased the abundance of AOB at day 14 and 28, which resulted in higher concentrations of NO3 -N in the soil. The interaction between OTC and E. coli O157:H7 on decreasing the abundance of 16S rRNA and microbial diversity was statistically significant after 1 day of incubation. Additionally, OTC and E. coli O157:H7 had significant interactive effects on urease activity, which may be also attributed to the impact on the partial nitrification process. © 2016 Elsevier Ltd. Source


Zhang W.,China Agricultural University | Zhang W.,Beijing Key Laboratory of Biodiversity and Organic Farming | Cao J.,China Agricultural University | Cao J.,Beijing Key Laboratory of Biodiversity and Organic Farming | And 4 more authors.
Applied Soil Ecology | Year: 2016

The aim of this study was to investigate the independent and interactive effectiveness of epigeic earthworms and arbuscular mycorrhizal (AM) fungi as soil conditioners in modifying the properties of salt-affected soil and increasing maize productivity. Treatments included maize plants inoculated vs. not inoculated with AM fungi and treated with or without earthworms. The mycorrhizal colonization, soil pH, electric conductivity (EC), nutrient availabilities and uptakes, catalase, soil microbial biomass C, and Shannon-Wiener index (H) for microbial communities from T-RFLP profiles were measured at harvest. The results showed that erthworms and AM fungi interactively decreased soil pH and EC, and increased the N, P and K content of maize shoot and root and their biomass. Earthworms and AM fungi interactively increased soil organic C, catalase activity and microbial biomass C in the saline alkali soil. Earthworms significantly decreased bacterial diversity, while earthworms and AM fungi interaction significantly increased fungal diversity. Pontibacter and Methylobacteriu were dominant bacteria, and Stachybotrys and Trichoderma were dominant fungi for all treatments. Earthworm addition significantly improved the abundance of Pontibacter and decreased the abundance of Methylobacteriu, which might result in higher soil P availablity and N absorption, respectively. Earthworms, AM fungi and their interaction increased the abundance of Trichoderma but decreased the abundance of Stachybotrys. Maize biomass and nutrient uptakes correlated significantly with the abundance of Trichoderma and Stachybotrys. In conclusion, earthworms, mycorrhiza and their interaction may have a potential role in elevating the chemical and biological properties to alleviate salinity and improve crop productivity in salt-affected soils. © 2016 Elsevier B.V. Source


Cao J.,China Agricultural University | Cao J.,Beijing Key Laboratory of Biodiversity and Organic Farming | Wang C.,China Agricultural University | Wang C.,Beijing Key Laboratory of Biodiversity and Organic Farming | And 6 more authors.
Chinese Journal of Applied Ecology | Year: 2015

Earthworms are considered as 'ecosystem engineers', as they affect soil microbial community and function by improving micro-habitat, increasing surface area of organic compound, feeding, and transporting microorganisms. Multi-scale cavities created through earthworm movements help improve soil porosity and aeration, thus supporting microbial growth and reproduction. Earthworms also break down complex organic compounds into microbe-accessible nutrients by means of feeding on, crushing, and mixing soil. This results in elevated mineralization and improvement of cycling of key soil nutrients including carbon, nitrogen, and phosphorus, overall enhancing the soil biological fertility. ©, 2015, Editorial Board of Chinese Journal of Applied Ecology. All right reserved. Source

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