Abstract

In this study, the microbial characteristics of the anaerobic reactor of a sugar industry wastewater treatment plant were analyzed using cloning, FISH (Fluoresan in situ hybridization) and metagenomic analysis. Samples were obtained from seven different ports of the reactor on the 148th day of operation. The temperature was maintained at mesophilic conditions. The system’s pH range was operated at 6.8. The cloning results showed that most of the bacterial clones belonged to uncultured members of the Bacteria domain. Many archaeal clones were related to uncultured Archaea and Methanosarcina. The FISH method was applied to determine the microbial composition of the samples, which showed that bacterial and archaeal species had nearly equal rates. Rod-shaped cells, long bacilli, coccus and long chains were detected in the samples. After metagenomic analysis, in all samples, Archaea domain members ranged between 60- 36% and Bacteria domain members ranged between 58-31%. At the phylum level, in all samples, Euryarchaeota was the most dominant phylum. Proteobacteria (14.8-21.97%) and Actinobacteria (5.53-15.94%) phyla were high in rate. Furthermore, members of Spirochaeotes (0.63-4.82%) and Bacteroidetes (1.72-2.38%) were analyzed in the samples. This study revealed both bacterial and archaeal populations in the reactor of highconcentration organic sugar wastewater. These results will help in the development of more efficient anaerobic treatment systems.