Study On Correlation Between Nitrogentransforming Microbial Community And Physic-chemical Parameters In Composting

Composting is the main technology to deal with agricultural waste, but in the process of composting, the production of gaseous nitrogen may cause nitrogen loss and environmental pollution. At present, studies on the composting of nitrogen transformation have focused on the microbial community structure and law of succession. Fewer efforts have been made to investigate relationship between environmental factors and nitrogen transformation bacteria, which is not conducive to deeper understanding of the biological mechanism of the loss gaseous nitrogen and the development of the technology of controlling nitrogen loss in composting.The community structures and diversities of AOB?AOA and denitrifying bacteria were analyzed by polymerase chain reaction –denaturing gradient gel electrophoresis(PCR-DGGE) during the composting process based on the amo A and nos Z genes. Canoco4.5 and SPSS19.0 software were used to analysis the relationship between the community structure and diversity and physic-chemical parameters. This study provides the theoretical basis for revealing the mechanism of gaseous nitrogen loss and putting forward the technology of controlling nitrogen loss during the composting process. The following are the main results of the study:(1) During the composting process, 3 genera of AOB were detected: Nitrosomonas, Nitrosospira and Uncultured bacterium, and the dominant species of AOB was Nitrosomonas; 3 genera of AOA were detected: Uncultured crenarchaeote ? Uncultured archaeon and Candidatus Nitrososphaera gargensis, and the dominant species of AOA were Uncultured crenarchaeote and Uncultured archaeon; 6 genera of denitrifying bacteria were detected: Paracoccus ? Achromobacter ?Alcaligenes?Pseudomonas?Uncultured bacterium and Azospirillum, and the dominant species of denitrifying bacteria were Pseudomonas and Azospirillum.(2) During the composting process, the AOB community diversity index changed from 2.072 to2.220, it decreased during 0~7d and increased during 13~29d of the composting; the AOA community index changed from 1.936~2.177, it decreased during 0~7d and increased during13~29d of the composting; the denitrifying bacteria diversity index changed from 1.801~2.536, it increased during 0~4 d and decreased during 7~29d of the composting.(3) The redundancy analysis of AOB community structure and physic-chemical parameters showed that AOB community structure changed little during the beginning of composting(0~1d)and high temperature stage(4~7d), while it changed dramatically in the later stage of composting(13~29d). The correlation between NH4+-N and T and AOB community strtunture changes was relative large.(4) The redundancy analysis of AOA community structure and physic-chemical parameters showed that AOA community structure changed little in the later stage of composting(13~29d),while it changed more rapidly in the early stage of composting(0~7d), especially in the high temperature stage of composting. The correlation between T and NH4+-N and AOA community strtunture changes was relative large.(5) The redundancy analysis of denitrifying bacteria community structure and physic-chemical parameters showed that the denitrifying bacteria community structure changed little in the early stage of composting(0~1d), while it changed dramatically in high temperature stage(4~7d) and the later stage(13~29d) of composting, especially in the later stage of composting. The correlation between T and p H and denitrifying bacteria community strtunture changes was relative large.(6) During the composting process, Pearson correlation analysis showed that AOB community diversity was significantly negatively correlated with p H(P ? 0.05, r=-0.938), and was significantly positively correlated with water content(P ? 0.05, r=0.765); AOA community diversity was extremely significantly negatively correlated with NH4+-N(P ? 0.01, r=-0.901);denitrifying bacteria community diversity was significantly positively correlated with temperature(P?0.05,r=0.768), and was extremely significantly positively correlated with water content(P?0.01,r=0.864).