Spatial Heterogeneity of Bacteria: Evidence from Hot Composts by Culture-independent Analysis

The phylogenetic diversity of the bacteria in hot composting samples collected from three spatial locations was investigated by molecular tools in order to determine the influence of gradient effect on bacterial communities during the thermophilic phase of composting swine manure with rice straw. Total microbial DNA was extracted and bacterial near full-length 16S rRNA genes were subsequently amplified, cloned, restriction fragment length polymorphism-screened and sequenced. The superstratum sample had the highest microbial diversity among the three samples which was possibly related to the surrounding conditions of the sample resulting from the location. The results showed that the sequences related to Bacillus sp. were most common in the composts. In superstratum sample, 45 clones (33%) and 36 clones (27%) were affiliated with the Bacillus sp. and Clostridium sp., respectively; 74 clones (58%) were affiliated with the Clostridium sp. in the middle-level sample; 52 clones (40%) and 29 clones (23%) were affiliated with the Clostridium sp. and Bacillus sp. in substrate sample, respectively. It indicated that the microbial diversity and community in the samples were different for each sampling site, and different locations of the same pile often contained distinct and different microbial communities.