Phylogenetic profiling of culturable bacteria associated with early phase of mushroom composting assessed by amplified rDNA restriction analysis

The edible mushroom Agaricus bisporus is grown commercially on composted manure/straw mixtures. Mushroom composting is a fermentation process in which various groups of microorganisms play important roles at different stages of composting. The present study was conducted to explore the mesophilic bacterial diversity in the early phase of mushroom composting. Morphologically all the isolated bacteria were either Gram-positive rods, cocci or Gram-negative rods. The functional diversity of the bacterial isolates was examined by plate enzyme assays, siderophore production and antagonistic property. Good enzymatic activity for amylase, cellulase, xylanase and protease was reported for different bacterial isolates. Nine bacterial isolates showed siderophore production activity. During antibiosis assay, most of the isolates inhibited growth of Verticillium fungicola and Mycogone perniciosa. However, a consortium of selected bacterial isolates produced good amounts of lytic enzymes (amylase, cellulase, xylanase and protease) in solid state fermentation experiments that might help in enhancing the composting process. Amplified 16S-rDNA restriction analysis (ARDRA) of bacterial isolates indicated that four groups of nine bacterial isolates had 100% similarity in all the restriction profiles. However, other isolates exhibited discriminatory relationships with each other. The present study reveals culturable mesophilic bacterial diversity and community succession in the early phase of mushroom composting process as well as emphasizing the application of a bacterial consortium to enhance the composting process.