| Antibiotic resistance gene(ARG)is a new type of environmental pollutant,which can be transmitted between microorganisms by moving gene element(MGE)by horizontal gene transfer.ARGs pollution may lead to the increase of resistance of human pathogenic bacteria to antibiotics and seriously threaten human life and health.With the intensive development of aquaculture,antibiotics are widely used as feed additives in livestock and poultry breeding.Excessive antibiotics are not absorbed by animal intestines and discharged out of the body with feces.Therefore,livestock and poultry faeces have become an important ARGs storage.In this experiment,the macroporous adsorption resin(MAR),a new material with adsorption properties,was selected as composting additive.The effects of 0(CK),5%(L)and 15%(H)MAR on the physical and chemical properties,abundance of available copper,available zinc,ARGs and MGEs,as well as microbial community during aerobic composting of pig manure were studied,and the relationship between ARGs and environmental factors and microbial community was analyzed.The main findings and conclusions are as follows:(1)the reactor temperature of the three treatments reached 50°C and lasted for more than 6 days,which reached the innocuous standard of compost products,and the highest temperature was 68 ℃.The p H value of the heap decreased at the beginning of composting,then increased,and the recovery rate of p H in L and H treatments slowed down.The addition of MAR significantly decreased the trend of DTPA-Cu and DTPA-Zn,but had no significant effect on the C/N.(2)A total of 11 kinds of ARGs,were detected,of which 9 ARGs decreased their relative abundance after composting.After composting,the widespread sul1 and sul2 genes decreased by 79.60%?86.35% and 94.38%?96.31%,respectively.Among the four MGEs detected,ISCR1 and Tn916/1545 decreased by 98.80% ? 99.48% and 97.06% ? 99.21% respectively after composting.In the treatment of adding MAR,the decrease of int I1 and Tn916/1545 was more significant than that of the treatment without MAR.(3)Firmicutes,Proteobacteria,Actinobacteria,and Bacteroidetes are the dominant phyla in composting samples.The addition of MAR can alter the community structure of microorganisms by affecting specific microorganisms.RDA analysis showed that MGEs had the highest interpretations of ARGs during composting,and the composting process was the main driving force to promote microbial community succession.Network analysis found 14 ARGs,MGEs with decreased abundance,12 genera and 2 ARGs with increasing abundance.A decrease in the abundance of potential host bacteria during composting may result in a decrease in the abundance of ARGs carried by it.The co-existence of multiple ARGs with MGEs indicates that these ARGs may coexist with MGEs on the same gene fragment and transfer and propagate with MGEs in the environment. |
