Bacterial communities in various conditions of the composting reactor revealed by 16S rDNA clone analysis and DGGE

Abstract

Composting is an efficient and cost-effective process for organic waste treatment. In order to expand our knowledge regarding microorganisms in the composting reactor, bacterial community structures in a variety of composting processes were examined by 16S rRNA gene (rDNA) clone analysis including denaturing gradient gel electrophoresis (DGGE), as a case study. As previously reported, the dominant bacteria consist of members of the order Bacillales in a typical composting condition with woodchips as the bulking agent. However, these aerobic bacteria decreased to 14%, and anaerobes or facultative anaerobes arose when the decomposition rate of organic compounds dropped following aggregation of the contents. In the composting reactor operated with plastic bottle flakes as bulking agent, the order Lactobacillales co-dominated with the Bacillales, regardless of reactor size, accounting for about 70% of the detected organisms during first week of the operation, gradually decreasing to about 30% with maturation of the composting process. Most species detected by clone analysis have not been cultivated, and may be VBNC (viable but non-culturable) species, implying symbiotic interactions among the microorganisms. In addition, the 16S rDNA-clone and DGGE methods are also introduced in this chapter. © 2010 Springer Science+Business Media B.V.