Effects Of Parameters On Bacterial Community Structure In Agricultural Waste Composting

Only 0.1% to 10% of the microbes from natural habitats can be cultured, so it can't well reflect the microbial diversity in the natural environment of the original state. With the development of molecular biology and phylogenetic analysis, based on 16S rDNA gene molecular biology methods such as polymerase chain reaction- denaturing gradient gel electrophoresis (PCR-DGGE) are gradually being widely used to analyze micrbial communities of different complex ecosystems. In this paper, the total DNA was amplified with PCR using the GC-338F/518R primers to obtain the bacterial 16S rDNA genes. The amplified products were separated and identified by DGGE, which could examine the bacterial composition differences and similarities of agricultural waste composting.Redundancy analysis (RDA) was applied to explore the relationship between bacterial species and composting parameters: pile and ambient temperature, moisture content, pH, C/N ratio, water soluable carbon (WSC), NH₄⁺-N and NO₃^--N by using QuantityOne2.0 and Canoco4.5 to determine which combination of variables could explain the species composition differences. The relationship between the ecological distribution of bacterial species and communities with the 8 parameters were clearly revealed on the RDA biplots. The purpose of the redundancy analyses was to determine which combination of parameters explained the most, if any, of the species composition differences of our compost samples. Establishing the identity of bacterial species and composting parameters will greatly enhance our understanding and management of agricultural waste biological treatment systems.The sample,species and parameters biplots were drawn on the results of RDA, and the relationships between the ecological distribution of the bacterial species and communities with the 8 parameters were clearly revealed on these biplots. The composting process could be divided into four phases: mesophilic phase (days 0²), thermophilic phase (days 3¹1), temperature falling phase (days 12²8) and maturation phase (days 19³6). Parameters that affect bacterial distribution and dynamic successions are listed as the following order: NO₃^--N> pile temperature> WSC> C/N> NH₄⁺-N> moisture content> pH> ambient temperature. It was found that pile temperature, WSC, NO₃^--N and NH₄⁺-N (P<0.01) and C/N, pH (P<0.05) were the most important parameters significantly affecting the variation of bacterial species in agricultural waste composting. Establishing the correlation between species data and composting performance will greatly enhance the understanding and optimization of agricultural waste composting system.