Study On The Bacterial Communities In The Phase â…¡ Agaricus Bisporus Compost

Phase II is indispensable for the preparing of a successful mushroom (Agaricus bisporus) culture, manipulating the succession of microorganism in the compost by means of indoor pasteurisation, which shape the substrate into a selective medium. The"selective"means an environment that favours the development of the mushroom mycelium and discourages the development of the competing moulds and bacteria. PCR-denaturing gradient gel electrophoresis(DGGE) and amplified rDNA restriction analysis(ARDRA) were used to track the rapidly changing bacterial community in the mushroom compost during phase II:1. Composts contain high levels of organic matter and pose a particular challenge in obtaining high quality total DNA, then a gentle method base on chemical-enzymatic extraction was adapted. This method consists of high salt/PVPP buffer for cell lysis, PEG-8000 for DNA precipitation. The extracted DNA were sufficiently free of contaminants to allow PCR amplification and restriction enzyme digestion.2.A total of seven compost samples taken from different stages of phase II were PCR amplified to get the V3 regions of the 16S ribosomal DNA for DGGE analysis. The DGGE profile showed a dramatic change of bacterial communities which related to the process of phase II and can be divided into four stages. Bacterial population, revealed by the full-length 16S rDNA clone libraries of the above four stages, was shown to undergo the same succession as the DGGE pattern. This result proved that DGGE profile and ARDRA analysis can be highly useful for monitoring of bacterial community structure and dynamics in the process of composting.3. DNA sequencing of the dominant bands of DGGE profile and the predominant ARDRA OUT( Operational Taxonomic Units) indicated that the bacterial diversity in the phase II was much higher than that studied by traditional, cultured-based approach. Not only the genus of Bacillus, commonly believed to dominate high temperature compost, but also some new groups belonged in the class of Bacilli such as Trichococcus, Planococcus, Caryophanon and even the γ—subgroup Proteobacteria were detected. At the same time, some sequences were related to the genus of Thermus thermophilus and α —subdivision Proteobacteria which were only recently reported in the hot compost. And the most interesting thing is that several sequences display extremely low similarity with the cultivated species in the Gen Bank, indicating high diversity of uncultivated bacteria in the compost. Admittedly, such molecular ecology methods broaden and deepen our knowledge about the environmental microbes.The study about the structure and succession of microbial communities during the composting is directly linked to the optimization of composting process. The methods of PCR-DGGE and ARDRA are of benefit to our knowing well about the mechanism of composting and the detailed function of microbes, then the DGGE pattern of the microbes has the potential to be the genetic fingerprinting of the compost quality.