Dynamic Of Ammonia Oxidizing Bacteria And Anammox Bacteria In Cow Manure Composting

Composting is one of the most cost-effective ways to deal with agricultural waste.During the composting process,nitrogen conversion is an important biochemical process,driven by microorganisms,which affects the process of composting and the quality of compost products.Therefore,it is very important to study the transformation of nitrogen and related microbial communities during composting.Ammonia oxidation reaction is a key link in the nitrogen cycle,but the current research on the dynamics of ammonia-oxidizing bacteria(AOB)and its correlation with environmental factors in cow manure composting is not enough,and the dynamics of anaerobic ammonium oxide bacteria(ANAMMOX)and its correlation with environmental factors is rarely reported.In this study,the dynamic of ammonia oxidizing bacteria and anammox community structure were detected using polymerase chain reaction denaturing gradient gel electrophoresis(PCR-DGGE),clone library and fluorescence quantitative PCR and other molecular biology techniques,redundancy analysis is used to analyze the correlation between microbial community structure and environmental factors in composting.This study provides a theoretical basis for further analysis of nitrogen loss mechanism in composting and guidance of compost productions.The main results are as follows:(1)Compost was carried out for a total of 36 days.In the composting process,the p H value maintained in alkaline condition;water content decreased in the whole process,and dropped to 48.8% in the end of composting;the content changes of NH4+-N and NO3--N showed the opposite trend,NH4+-N first increased and then decreased,and reached the maximum(1308.4 mg/kg)in the high temperature period,then gradually decreased;NO3--N increased slowly in the initial stage of compost,the rapid rise in the high temperature period,maturity period reaches the maximum value(475.2 mg/kg).The seed germination rate index rose constantly during composting,the germination rate had reached more than 85% till the end of composting,which had been basically confirmed the compost maturity.(2)Using PCR-DGGE and cloning techniques to detect AOB and anammox bacteria.In composting,two types of AOB : Nitrosomonas and Nitrosospira were detected,Nitrosospira was in a dominant;and 3 types of anammox bacteria : Candidatus Scalindua,Candidatus Kuenenia and Candidatus Brocadia were detected,Candidatus Scalindua was predominant anammox bacteria genus.(3)During the composting process,the diversity index of AOB community ranged from 1.9192 to 2.6718,the diversity index of AOB community changed with temperature and.The diversity index of anammox bacterial community diversity ranged from 0.677 to 2.019,the diversity index of anammox bacteria community decreased at the beginning of composting(0 ~ 3d),and then reached the maximum on 17 day.(4)Redundancy analysis showed that environmental factors affected the changes of AOB and anammox bacteria community structure during composting.The correlations between environmental factors and community structure of AOB were nitrate nitrogen > ammonium nitrogen > temperature > p H,temperature and ammonium nitrogen(p<0.05)significantly influenced community structure of AOB;correlations between environmental factors and community structure of anammox bacteria were nitrate nitrogen > ammonium nitrogen > temperature > p H,temperature and ammonium nitrogen(p<0.05)significantly influenced community structure of anammox bacteria.(5)Quantitative PCR of AOB and anammox bacteria 16 S rRNA gene showed that the copy number change of AOB 16 S rRNA gene in various compost samples ranged from 2.96×106 to 1.10×107 copies·g-1,the number of AOB reached maximum on 14 day;the copy number of anammox 16 S rRNA gene changes from 2.10×106 to 7.15×108 copies·g-1,the largest number was found on 19 day.