| Cow dung is rich in organic matter,cellulose,nitrogen,phosphorus and potassium and other nutrients needed by plants,but direct application without treatment not only has low fertilizer efficiency and utilization rate,but also easily causes adverse effects such as burning seedlings and pests and diseases.At present,aerobic composting technology is mostly used in China to process solid cow dung.The cellulose,lignin and nitrogen-containing compounds in cow dung are decomposed by the degradation of microorganisms to make them easily absorbed by plants.At the same time,the heat generated during the composting process can kill pathogenic bacteria and eggs of disease and insects to achieve harmless treatment.The effect of the treatment,the microbial population plays a decisive role in the aerobic composting process.At present,most of the existing researches use cow dung and crop residue mixed composting,and few use cow dung solid direct aerobic composting,and most of the previous studies only focus on bacteria.In this study,16 s DNA and ITS sequencing technologies were used to reveal the evolution of bacterial and fungal community structures in the process of direct composting after solid-liquid separation of cow dung,and to analyze the predictions of the major populations and functions,and to combine the environment that may have an impact.factor correlation analysis.In order to provide theoretical guidance for the subsequent research and development of new and efficient composting fermentation bacteria.The results of the study are as follows:(1)The composting process lasted for 54 days,the high temperature above 55°C was maintained for 9 days,and the p H value of the material reached below 8.5,which met the requirements of harmless treatment.After fermentation,the moisture content,organic matter,total nitrogen and ammonia nitrogen of the material decreased,but the content of total phosphorus and total potassium increased compared with that before composting.(2)Bacteria: 19 samples at different stages of composting were sequenced by16 S,and reads were assembled.On average,80,127 tags were measured per sample,and 79,459 valid data were obtained on average after quality control.The sequences were clustered into OTUs with 97% identity.By aligning with the database Silva138,there were a total of 3747 OTUs,of which the number of OTUs that could be annotated to the database was 3740(99.81%).In the initial period(20-30℃),the dominant species were Proteobacteria and Bacteroidota.The temperature rise period(30-45 ℃)is for Proteobacteria,Bacteroidota and Fibrobacterota,and the high temperature period(above 55℃)is for Proteobacteria,Actinobacteria,Chloroflexi,Gemmatimonadota,and Fibrobacterota.The cooling period(40-50 ℃)is Proteobacteria,Bacteroidota and unidentified-Bacteria.The mature stage(30-40 ℃)is Bacteroidota and Proteobacteria.The Wilcoxon rank-sum test for Shannon’s index found that there were significant differences in species diversity and evenness between CS-FS,CS-GW,CS-JW,FS-JW,GW-SW,and JW-SW groups(p < 0.05),the diversity of bacteria was most significant in the initial period and the warming period,with the increase of temperature,the species diversity increased,but the compost entered the high temperature stage,and the species diversity decreased significantly.The analysis of community composition by NMDS analysis showed that the initial period and the warming period had similar bacterial community structure between and within the group,the decomposing period and the cooling period had similar bacterial community structure between and within the group,while the high temperature period had similar bacterial community structure.The between-group and within-group is the stage with the greatest difference.The significant correlations between the combined environmental factors and the abundance of microorganisms at the genus level were mainly concentrated in p H,WAF,TN,NH4 N and OM.The order of correlation is WAF>OM>p H>NH4H>TN.The combination of p H and OM had the greatest impact on the microbial community.PICRUST was used to predict the function of the flora,and the functional information with the largest abundance in the top 10 at each annotation level at each temperature stage was selected.A total of 6 functional types were predicted in the first-level function prediction,and their relative abundances were metabolism>genetic information processing>environmental information processing>cellular transformation>human pathogenicity>organic system.The main functional advantages in the initial stage and the heating stage are the transformation of cells and human pathogenicity,in the high temperature stage,it becomes environmental information processing and genetic information processing,and the cooling stage and the decomposing stage are mainly organic systems,genetic information processing and metabolism.In secondary function prediction,the top 10 relative abundances of functions are amino acid metabolism > membrane transport > carbohydrate metabolism > replication and repair > energy metabolism > poorly characterized >translation function > metabolic cofactor vitamins > cellular process signaling > lipid quality metabolism.(3)Fungi;species annotation was performed by comparing with the database UNITE,and there were 2,582 OTUs,of which 1,746(67.62%)could be annotated into the database,and the dominant population in the initial period(20-30°C)was Ascomycota,Basidiomycota,Mortierellomycota and Mucoromycota.Warming period(30-45 ℃)for Ascomycota and Basidiomycota.The high temperature period(above 55 ℃)is the Ascomycota.The cooling period(40-50 ℃)includes Ascomycota,Mortierellomycota,Aphelidiomycota and Monoblepharomycota.The mature stage(30-40 ℃)is Ascomycota and Basidiomycota.The Wilcoxon rank sum test of Shannon index showed that there was a significant difference in CS-FS group(P=0.0323),indicating that the species diversity in the initial stage was significantly higher than that in the mature stage.Using the NMDS analysis method to analyze the community composition,we found that the samples in the initial period and the samples in the high temperature period,the cooling period and the decomposing period had the greatest differences in community structure,while the decomposing period and the cooling period had similar community structures.The combined environmental factors took the genus level as an example.Among the top 35 genera in abundance,there were significant correlations with p H,WAF,TN,NH4 N,TK(total potassium),and OM environmental factors,and TP(total phosphorus)was associated with fungi.Community abundance was not significantly affected.Variation in TK against unidentified-Rozellomycota,unidentified-Boletales,Neocucurbitaria,unidentified-GS16,Humicola The species abundance of the genera Humicola and Myriococcum had a significant effect.Based on the species classification of fungi,using Fun Guild’s ecological function and trophic type annotation of fungi,it was found that in the entire composting stage,except for the unknown flora,saprophytic functional flora occupied the second largest abundance of all floras,and at the initial stage the most abundant in the samples.Among the top 10 functional types annotated in abundance,the main force of the flora is saprophytic-symbiotic trophic type,and various trophic types and functional abundances are mainly concentrated in the initial stage.(4)In this experiment,56 strains of bacteria,34 strains of actinomycetes,and 19 strains of fungi were isolated from the five periods of composting,and the strains were preserved by glycerol cryopreservation. |
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