Succession and phylogenetic composition of bacterial communities responsible for the composting process of rice straw estimated by PCR-DGGE analysis

PCR-DGGE analysis followed by sequencing of 16S rDNA was applied to reveal the succession and the phylogenetic composition of the bacterial communities responsible for the composting process of rice straw (RS). RS under the composting process exhibited more complex DGGE band patterns with more numerous bands and more diversification in intensity than the initial RS materials. The DGGE patterns of the bacterial communities in the initial RS materials and RS under the composting process were statistically divided into four groups, namely those characterizing the communities associated with the pre-composting stage, and thermophilic, middle, and curing stages of the compost, which corresponded exactly to the same grouping obtained from the PLFA pattern analysis for the same samples (Cahyani et al. 2002: Soil Sci. Plant Nutr., 48, 735-743). Different bacterial members characterized the respective stages as follows: alpha-Proteobacteria for the initial RS materials, thermophilic Bacillus spp. and actinomycetes at the thermophilic stage, and Cytophaga and clostridial members at the middle and curing stages, respectively. In addition, mesophilic Bacillus members were always present throughout the composting process. Temperature and substrates available to bacteria seemed mainly to determine the composition of the bacterial members at the respective stages.