Microbial community analysis of thermophilic contact oxidation process by using ribosomal RNA approaches and the quinone profile method

Microbial community structure of a lab scale thermophilic aerobic wastewater treatment reactor was analyzed by a combination of culture-independent methods. Quinone profile method provides for chemical analysis of respiratory quinone molecular species, which corresponds to bacterial groups. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA partial sequences (PCR-DGGE) clarifies community changes at species level, as DGGE can separate DNA fragments of different sequences. Certain phylogenetic groups of bacterial cells can be labeled by fluorescence in situ hybridization (FISH). Quinone profile showed a predominant presence of MK-7. PCR-DGGE revealed that constituents of the community were unchanged during the stable phase. FISH demonstrated the existence of the relatives of Bacillus lentus and B. thermocloacae in considerable proportions. The community was mainly composed of Bacillaceae, and obligate thermophilic and mesophilic Bacillus appeared in spite of the temperature fluctuation from 35°C to 60°C. The combination of these culture-independent methods revealed the community precisely enough to evaluate the reactor performance.