Effects of 5 strains of exogenous thermophilic nitrogen-fixing bacteria on carbon and nitrogen losses and bacterial community in composting
[Objective]To reduce the loss of carbon and nitrogen during composting and improve the quality of the compost.[Method]This study investigated the effects of 5 strains of exogenous thermophilic nitrogen-fixing bacteria on carbon and nitrogen losses,nutrient content and the bacterial microbial commu-nity of composting using 6 treatments:CK(without exogenous nitrogen-fixing bacteria),A1(Allorhizobium tumefaciens),A2(Leucobacter sp.4J7B1),A3(Staphylococcus capitis),B1(Serratia liquefaciens)and B2(Ba-cillus cereus).[Result]5 strains of exogenous thermophilic nitrogen-fixing bacteria reduced the carbon and nitrogen losses in compost and increased the nutrient content.A1,A2,A3,B1,B2 compared with the control,the losses of carbon and nitrogen decreased by 38.74%,26.99%,33.09,28.75,32.25%and 25.33%,11.20%,22.25%,20.77%,20.51%,respectively;the nitrogen content increased by 279.15%,42.74%,344.31%,277.51%,1.42%;phosphorus increased by 49.21%,16.19%,51.33%,242.26%,58.90%;potassium increased by 27.76%,17.14%,15.36%,11.80%,29.12%;and organic matter increased by 31.41%,20.56%,27.15%,30.19%,25.61%.In general,A1>A3>B1>A2>B2.The succession of the bacterial community showed that the abundance of A1 and B1 strains was always higher than that of the con-trol.Exogenous nitrogen-fixing bacterial agents significantly increased the relative abundance of indigenous nitrogen-fixing bacteria in composting,such as Pseudomonas,Sphingobacterium,Saccharomonospora,Pl-anifilum and Bacillus,and decreased the relative abundance of denitrifying bacteria,such as Acinetobacter,Corynebacterium and Halomonas.KEGG analysis showed that exogenous nitrogen-fixing bacteria affected functional genes involved in amino acid metabolism,carbohydrate metabolism and biosynthesis of secondary metabolite biosynthesis.[Conclusion]It can be seen that A1 and B1 strains can colonize well in composting,which has the potential to develop nitrogen-fixing bacteria as bioorganic fertilizer.The addition of exog-enous nitrogen-fixing bacteria can inhibit carbon and nitrogen metabolism during composting by influencing dominant microbial communities and functional genes such as amino acid metabolism and carbohydrate me-tabolism,improve nutrient content and reduce carbon and nitrogen loss during composting.
compostingexogenous thermophilic nitrogen-fixing bacteriaC and N lossesbacterial com-munity
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