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| Effects of continuous thermophilic phase on removal of multidrug-resistant bacteria, its conjugative plasmids and antibiotic resistance genes during chicken-manure composting |
| Received:May 26, 2023 Revised:July 13, 2023 |
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| KeyWord:composting;multi-drug resistant bacteria;antibiotic resistance gene;continuous thermophilic phase |
| Author Name | Affiliation | E-mail | | YIN Tianqi | College of Forestry, Northeast Forestry University, Harbin 150040, China
Institute of Biotechnology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | | | SUN Xingbin | College of Forestry, Northeast Forestry University, Harbin 150040, China | sunxingbin1025@163.com | | GAO Haoze | Institute of Biotechnology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | | | SHEN Lei | Langfang Normal University, Langfang 065000, China | | | JIANG Xinran | College of Forestry, Northeast Forestry University, Harbin 150040, China | | | GUO Yajie | Institute of Biotechnology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | | | WANG Xuming | Institute of Biotechnology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | | | QIU Tianlei | Institute of Biotechnology, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China | qiutianlei@babrc.ac.cn |
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| Abstract: |
| To investigate the effect of continuous thermophilic phase on multidrug-resistant(MDR) Escherichia coli, its conjugative plasmid, and its antibiotic resistance genes(ARGs)during composting, MDR E. coli was inoculated into chicken-manure-composting raw material. Two treatments, namely normal thermophilic(NT) and continuous thermophilic(CT) composting treatments, were set up. Selective cultivation of MDR bacteria and 16S rRNA gene amplicon sequencing were used to monitor the variations in MDR bacteria. Digital droplet PCR was used to quantify the relative abundance of 16S rRNA genes of E. coli, namely the mobility proteins(MOBP), aminoglycoside resistance gene(APH(3) -Ib), sulfonamide resistance gene(sul2), and class I integrase gene(intl1). The effects of the CT treatment on MDR bacteria and the ARG reduction rate were obtained by comparison. According to the results, high-temperature composting could inhibit MDR bacteria growth significantly, and the inhibitory effect of the CT treatment was superior to that of the NT treatment. After composting, the reduction rate of the five detected genes in CT treatment was from 79.82% to 99.99%, however, the relative abundance of APH(3)-Ib, sul2, intl1 in NT treatment after ripening period was greater than that in the raw material. Reduction kinetics analysis of ARGs showed that the reduction of MDR E. coli and its conjugative plasmids conformed to the first-order reaction kinetics; however, the reduction kinetics of APH(3)- Ib, sul2, and intl1 showed obvious two -stage characteristics. Prolonging the thermophilic phase could inhibit the rebound of ARGs(CT treatment)significantly and restrain the rebound in the maturing period. Finally, shifts in bacterial community structure during composting were analyzed. The increase in relative abundance of ARGs in the NT treatment was related to the enrichment of specific genera, such as Moheibacter and Halomonas. The results show that during composting, prolonging the thermophilic phase could reduce the abundance of bacteria, which could be potential hosts to drug resistance genes; inhibit the vertical transmission of ARGs; and finally reduce ARG abundance in the finished fertilizer. |
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