Effects Of Different Inoculants And Ventilation Methods On The Evolution Of ARGs In Chicken Manure Compost And Their Biological Mechanism

With the rapid development of China’s livestock and poultry breeding industry,the problem of fecal pollution brought by it is particularly prominent.Aerobic composting is an important way to resource and harmless treatment of livestock and poultry manure,but it has the disadvantages of low efficiency,poor compost product quality and low efficiency of antibiotic resistance genes(ARGs)reduction.In this study,chicken manure and rapeseed straw were used as raw materials,and the effects of different treatments on the fermentation dynamics of chicken manure and organic fertilizer quality were studied by setting up carbon-nitrogen ratio(C/N25 and 35),microbial agents(Trichoderma harzica and Bacillus)and ventilation mode(through 15-45 and 30-30).High-throughput sequencing and real-time PCR were used to analyze the effects of different treatments on bacterial communities and ARGs in the process of chicken manure composting,and the biological mechanism of the gene regression of drug resistance in different treatments was revealed,which provided a theoretical basis for improving the composting efficiency of livestock and poultry breeding wastes and more effectively reducing ARGs from livestock and poultry breeding wastes.The main results are as follows:1.The carbon-nitrogen ratio and T value ranges of different treated materials with CN of 25 after decay were 12.79～15.43 and 0.48～0.58,respectively,and the carbon-nitrogen ratio and T value of CN35 materials after decomposition were 23.81 and 0.64,respectively,indicating that different treated materials with CN of 25 could meet the requirements of decay after composting,but CN35 materials could not achieve decay.Compared with the control(CN)25 material),the inoculation of Bacillus under "pass 15-batch 45" and Trichoderma harzianum under "pass 30-interval 30" ventilation mode have a promoting effect on improving the microbial activity of the reactor and the quality of the decayed materials.2.The compost was effective in removing ARGs from the material,and the removal effect was more pronounced in CN35 material;sul2,ermC and tetM were the dominant ARGs in the material,with 92.20%,86.38%and 99.49%removal rates in CN35 material respectively.Compared to the control,inoculation with Trichoderma harzianum was more favourable to the removal of ARGs from the compost material than inoculation with Bacillus,but the "through 30-between 30" aeration method weakened this removal efficiency;in contrast to the Bacillus treatment,inoculation with Trichoderma harzianum promoted the removal of sul2 and ermC and weakened the removal of tetM.In contrast to the Bacillus inoculation treatment,inoculation with richoderma Trichoderma harzianum promoted sul2 and ermC removal and weakened tetM removal;compared to the aeration method of"through 15-between 45",the aeration method of "through 30-between 30" inhibited ermC removal in the Trichoderma harzianum inoculation treatment and sull and ermC removal in the Bacillus inoculation treatment,but had no effect on sull and Bacillus inoculated tetM removal.In addition,composting significantly promoted sull enrichment,but inoculation inhibited sull formation and was more pronounced in the "through 15-between 45" aeration treatment.3.Composting led to a significant decrease in species richness and diversity of the material bacterial community and significant changes in community structure.Compared with the control,the bacterial community species richness increased but diversity decreased after high CN material decomposition;inoculation with bacterium increased the bacterial community species richness and diversity,among which inoculation with Bacillus increased the species richness more significantly and inoculation with Trichoderma harzianum increased the diversity more prominently.The effect of the "through 30-between 30"aeration method on the increase of diversity by inoculation with mycorrhizal agents was significant,but weakened the effect of Bacillus inoculation on the increase of bacterial community richness.Compared to the control,the bacterial community structure was significantly altered by inoculation,but the effect of inoculation on the bacterial community was weakened by the through 30-between 30’ aeration method.These effects were mainly manifested at the phylum level by changes in the relative abundance of the phyla Proteobacteria,Bacteroidetes,Firmicutes,Actinobacteria and Tenericutes.4.Co-occurrence network analysis showed that the relative abundance of sul2,ermC and tetM potential hosts in each treatment material ranged from 0.06%to 13.84%,0.13%to 29.48%and 1.05%to 47.98%,respectively.sul2 relative abundance changes were similar to those of Bacteroidaceae,Promicromonosporaceae,Micrococcaceae,etc.ermC relative abundance changes were closely related to those of Enterobacteriaceae,Streptomycetaceae etc.tetM relative abundance changes were closely related to those of Enterobacteriaceae,Xanthomonadaceae,etc.In conclusion,the inoculation of Trichoderma harzianum with the "through 30between 30" aeration method is a composting model that takes into account the quality of C/N25 after decomposition and the removal of ARGs.