Succession of the Bacterial Communities and Functional Characteristics in Sheep Manure Composting

SIMPLE SUMMARY: The conversion of livestock manure into organic fertilizer through composting is an effective way to harmlessly and resourcefully utilize manure. The bacterial communities change rapidly during the composting process, and there is a synergistic effect of various bacteria, which realizes the dynamic fermentation of composting. However, the succession of bacterial communities and its relationship with the physicochemical properties of the material during sheep manure composting remain unclear. In this study, high-throughput sequencing technology and bioinformatics tools were used to analyze the succession and to explore the metabolic functions of bacterial communities during sheep manure composting. The results will help to further improve the sheep manure composting process, improve the quality of compost products, and promote fertilizer utilization of sheep manure. ABSTRACT: Bacterial community is a key factor affecting aerobic composting, and understanding bacterial community succession is important to revealing the mechanism of organic matter degradation. In this study, the succession and metabolic characteristics of bacterial communities were explored in 45 days composting of sheep manure and wheat straw by using high-throughput sequencing technology and bioinformatics tools, respectively. Results showed that the alpha diversity of bacterial community significantly decreased in the thermophilic (T2) phase and then recovered gradually in the bio-oxidative (T3) and the maturation (T4) phases. Bacterial communities varied at different stages, but there were 158 genera in common bacterial species. Unclassified_f_Bacillaceae, Oceanobacillus, Bacillus, Pseudogracilibacillus, and Nocardiopsis were identified as keystone bacterial genera. Eleven genera were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical factors. Redundancy analysis (RDA) showed that changes of bacterial community diversity correlated with physicochemical factors. The highest relative abundances were amino acid and carbohydrate metabolism among the metabolic groups in the compost. These results will provide theoretical support for further optimizing sheep manure composting conditions and improving the quality of organic fertilizers.