DRP005489
Eukaryotic community structures in anaerobic granular sludge based on 18S rRNA gene sequencing
Eukaryotes are important components of ecosystems in wastewater treatment processes. Although eukaryotic communities are well characterized in aerobic wastewater treatment processes, little is known in anaerobic treatment systems. In this study, eukaryotic community in the upflow anaerobic sludge blanket (UASB) reactor treating domestic sewage were investigated by V4 and V9 region of 18S rRNA gene amplicon sequencing. Sludge samples were collected from the UASB reactor during 2 years of operational period, activated sludge, and influent sewage, and analyzed and compared to characterize anaerobic eukaryotes. For the UASB reactor, V4 amplicon libraries were more specifically detected eukaryotic sequences than that of V9 amplicon library. The V9 amplicon library could detect different taxonomic group from V4 amplicon libraries, suggesting that commonly used V4 and V9 primer pairs produce a bias for eukaryotic community in the UASB reactor. Eukaryotic community structures in the UASB reactor were influenced by immigration of eukaryotic via influent sewage, but clearly different from influent sewage and activated sludge. The multivariate statistics indicated that some protist genus correlated with chemical oxygen demand and suspended solid concentration, suggested that they could be used as bioindicator of treatment performance in the UASB reactor. In addition, uncultured eukaryotes such as members of phylum Icthyosporea and Perkinsozoa in protist and LKM11 and LKM15 group in fungi were dominant in the UASB reactor.