Eukaryotic Community in UASB Reactor Treating Domestic Sewage Based on 18S rRNA Gene Sequencing
Microbial eukaryotes play important roles in sewage treatment systems. In an up-flow anaerobic sludge blanket (UASB) reactor fed with domestic sewage, anaerobic bacteria, archaea, and microbial eukaryotes (protist and fungi) coexist. To date, bacterial and archaeal communities in the UASB reactor have been widely studied. However, little is known about the eukaryotic community structure and function in most of anaerobic treatment systems. In this study, we analyzed eukaryotic community in the UASB reactor treating domestic sewage over 2 years operational period based on 18S rRNA gene sequences. In addition, multivariate statistics were applied to elucidate the correlation between eukaryotic community and operational conditions of the UASB reactor. The dominant protist groups observed were from phylum Ciliophora, Apicomplexa, Perkisea and Amoebozoa in the UASB reactor. Followings were flagellate protist such as Cercozoa, Sulcozoa, Bicosoecida, Choanomonada, Dinoflagellata and Metamonada. The result showed protist phylum and water temperature were not correlated. Only phylum Sulcozoa positively correlated with COD and suspended solid (SS), whereas other protist showed low correlation. The dominant fungi groups were LKM11, LKM15 and phylum Ascomycota. Uncultured LKM15 correlated with sulfide whereas phylum Discicristoidea and Chytridiomycota showed negative correlation. Phylum Ascomycota seemed most abundant when sulfide was low, but their association with environmental variables remained unclear. These results suggested that some protist and fungi groups could be used as indicator of environmental parameters in the UASB reactor.
KeywordsEukaryotic community Anaerobic treatment Domestic sewage
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