Effects of Copper Addition on Copper Resistance, Antibiotic Resistance Genes, and intl1 during Swine Manure Composting.

Yanan Yin,Kaiyu Zhang,Xin Zhang,Jie Gu,Haichao Li,Xiaojuan Wang,Wen Song,Yajun Zhang,Wei Sun

doi:10.3389/fmicb.2017.00344

Yanan Yin, Kaiyu Zhang + Show 7 more

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https://doi.org/10.3389/fmicb.2017.00344

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Abstract

Copper is one of the most abundant heavy metals present in swine manure. In this study, a laboratory-scale aerobic composting system was amended with Cu at three levels (0, 200, and 2000 mg kg-1, i.e., control, Cu200, and Cu2000 treatments, respectively) to determine its effect on the fate of copper resistance genes [copper resistance genes (CRGs): pcoA, cusA, copA, and tcrB], antibiotic resistance genes [antibiotic resistance genes (ARGs): erm(A) and erm(B)], and intl1. The results showed that the absolute abundances of pcoA, tcrB, erm(A), erm(B), and intl1 were reduced, whereas those of copA and cusA increased after swine manure composting. Redundancy analysis showed that temperature significantly affected the variations in CRGs, ARGs, and intl1. The decreases in CRGs, ARGs, and intI1 were positively correlated with the exchangeable Cu levels. The bacterial community could be grouped according to the composting time under different treatments, where the high concentration of copper had a more persistent effect on the bacterial community. Network analysis determined that the co-occurrence of CRGs, ARGs, and intI1, and the bacterial community were the main contributors to the changes in CRGs, ARG, and intl1. Thus, temperature, copper, and changes in the bacterial community composition had important effects on the variations in CRGs, ARGs, and intl1 during manure composting in the presence of added copper.

Highlights

Poultry and livestock feeds are frequently supplemented with trace elements such as copper to promote optimum growth due to their antimicrobial properties (Xiong et al, 2010)
We investigated the changes in copper resistance genes (CRGs), antibiotic resistance genes (ARGs), and intl1 using quantitative PCR (qPCR), and we employed 16S rRNA highthroughput sequencing to determine the changes in the bacterial community
The co-occurrence relationships determined by network analysis in the present study need to be validated further using other approaches. This is the first study to investigate the fate of CRGs, ARGs [erm(A) and erm(B)], and intI1 during the composting of swine manure with added copper

Summary

Introduction

Poultry and livestock feeds are frequently supplemented with trace elements such as copper to promote optimum growth due to their antimicrobial properties (Xiong et al, 2010). Poultry and livestock absorb these additives at low rates and they excrete up to 95% in their dung and urine, which often contain high concentrations of heavy metals such as copper (Xiong et al, 2010). Copper can impose selective pressures on the bacterial community’s tolerance of copper during composting (Li et al, 2014), which may be attributable to bacteria carrying copper resistance gene (CRGs) in the bacterial community. CRGs may reflect the actual responses of bacteria to the selective pressure imposed by copper, but the effects of copper on the evolution of CRGs during swine composting are still unclear. The bacteria that carry these genes may be transferred from human and animal sources into the environment, thereby leading to disease. In E. faecium, tcrB belongs to the CPx-type ATPase family, and human homologs of the human CPx-type ATPase are related to Menkes and Wilson disease (Trenor et al, 1994)

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